Brigitte Gille

1

Like an Indian God Hinduisation of the cult of Saint Anthony of Padua in Tamil Nadu 1

Brigitte Sébastia

1-Introduction

The shrine of Puliyampatti is located near Tirunelveli, in the south of Tamil Nadu. Dedicated to saint Anthony of Padua, he has a double identity: it is a pilgrimage centre and a "hospital". Pilgrims who attend it belong mostly to two castes: paravar which are the fishermen of the Fishery coast and nāt ̣ār 2 which traditionally collect fruits of coconut trees and borassus palmyra to make wine, alcohol and sugar with the sap. While the devotion of paravar to Saint Anthony is inherited from the missionaries who evangelized the region, that of nāt ̣ār is the consequence of the foundation of the village and the church by two families. Patients, quite often accompanied by one or more members of their families, suffer of ailments belonging to three main categories: 1-serious psychiatric illnesses such as schizophrenia, bi-or mono-polar disorder, mental retardation; 2-somatic and depressive disorders due to traumas; 3-organic diseases. The patients of the third category, who are taken to the shrine after to be discharged from hospitals due to the incapacity to cure of them, quite often die few days following their arrival. The two first categories of patients distinguish themselves not only by their illnesses, but also by the manner they express it: patients with psychotic behavior are never possessed, while those who experienced high traumatic events are subject to frequent possession symptoms.

Indians, like many other societies over the world, hold witchcraft and /or evil spirits responsible of psychiatric and mental disturbance as the result of transgression of a social or divine order. In the way to identify the cause of the disorder and to rectify the situation, they invoke Hindu deities or sufi saints (pīr) who are lying in the dargā who have the reputation to defeat the evil spirits or to overpower the effect of sorcery. Some Catholic icons have also this quality so that they were promoted by missionaries of India to perform exorcisms. However, the correspondence of missionaries which exposes many detail on the Indian life, rarely mentions Saint Anthony of Padua to perform exorcisms and one can wonder why this saint has this specificity in Tamil Nadu, and more specifically, at Puliyampatti. This question is all the more relevant as, in western Catholicism, although his cult is very important, he is never invoked to drive away demoniac entities.

Based on the ethnographic study of the shrine of Puliyampatti, the objectives of this article are to show how Saint Anthony of Padua and its cult have been absorbed into the Indian pantheistic universe. The saint holds a function similar to that of deities which, in popular Hinduism of this south region of Tamil Nadu, assures protection against various life hazards and provides help and relief to people, notably women who are the first victims of this society undergoing social, economic and structural transformation (marital violence, escalation of dowry, polygamy, male descendents, alcoholism, work and economic insecurity) In Puliyampatti, devotees perform specific rituals which are not possible in the famous shrine of Velankanni Virgin, the place of her apparition in India. The acceptability of practices is based on the quality of the icons defined by the Church. Virgin, considered as pure must be protected from "superstitious rituals" which, in opposite, are possible for Saint Anthony. In other words, Virgin is treated as the Great Devī while Saint Anthony as a minor god. By this difference, his cult is rich of a great variety of Hindu practices and conceptions.

2-Foundation of the shrine of Puliyampatti

Susaikanninadar, a nonagenarian, is the owner of the largest hotel of Puliyampatti, today managed by his three daughters. He is the descendant of Antoninadar, the founder of the Saint Anthony shrine. He tolds:

In the village of Kilavipatti, near Sivakasi, there were two brothers, Ramanadar and Lakshmananadar. Both nāt ̣ār were Hindus. One day, they left their village to go in search of a good job. They arrived at Naraikkinaru (village at 6 km of Puliyampatti) where the ūrttalaivar (chief of the village) who was tēvar gave them some job. But they got trouble with him and went to the jamīntār3 of Maniyacchi who hired them for cultivating his lands. He gave them a small plot of land to build their hut. This was the beginning of the hamlet of Pulliyampatti. Later, Antoninadar Puliyampatti, my ancestor came. He came from Puntapanai, a small village near Eral. He was also a nāt ̣ār but Catholic. The jamīntār of Maniyacchi hired him and put him at Puliyampatti with Ramananadar and Lakshmananadar families. Ramananadar who had a daughter, gave in marriage to him, who thereby became a Catholic. Antoninadar founded a small chapel in coconut leaves and put a statue of Saint Anthony. He took care of the shrine until the Jesuits discovered Puliyampatti and succeeded to capture the chapel by dint of trials. They demolished the chapel and build a new church with brick walls. My ancestors continued to manage the chapel as catechists (upatēci) until a permanent priest was located here.

The author of the booklet on the shrine Punita Antōniyār tiruttalam (1973) states the 17th century as its edification time. But, it is invalidated by the list of Susaikanninadar"s ancestors who served the church until 1954. This list which mentions six generations suggested that the shrine was not very old when the Jesuits appropriated it in the early 19th century. This dating is confirmed by the origin and identity of the founders of the village and the sanctuary. Robert L. Hardgrave (1969) and Dennis [START_REF] Templeman | The Northern Nadars of Tamil Nadu. An Indian Caste in the Process of Change[END_REF] who studied nāt ̣ār caste, considered that it emigrated from the former kingdom of Travancore (south part of Tamil Nadu) to six cities of the North Tamil Nadu during 19th century; Sivakasi was their first location. Regarding Antoninadar, he came from a region which knew a strong evangelic activism by protestant and catholic missions in the mid-18th and 19th centuries. Thus, as he was a Catholic, the edification of the shrine is more recent than the 17 th century. If the dating of the shrine foundation is uncertain, that of the church of Saint Antony is well known. The Directory of the Diocese of Palaiyamkottai (1973) mentions it was built by the French Jesuits of the New Mission of Madurai4 . It is based on the records in the diary of Father Gregory, Jesuit missionary from 1849 to 1853, which recounted: "The September 14, 1851, leaving Sivalaperi, I had to go Puliyampatti to visit the church of Saint Anthony which is building -the brick kiln is ready."

The church of Jesuits has been enlarged by keeping entirely the altar of Saint Anthony and it reopened in 1961. Many infrastructures has been added in its compound which allow to accommodate numerous of pilgrims and patients and their families, and especially, favour long stays from few days to months, and even, years.

3-A shrine organized for pilgrims and patients needs

Some infrastructures were built by priests who administered the parish and by some laymen. French Jesuits have erected ecclesial buildings (priests" residence, shelter for the procession carts) while diocesan priests have built lodges, a small maṇṭapam (hall) and a small clinic in the Mary Immaculate convent at Savalaperi, a small hamlet nearby Puliyampatti. Some devotees have offered a large maṇṭapam, two cattiram, the koṭimaram and a small chapel called Mātā Kōvil. The present maṇṭapam consists in a large hall with an altar where masses are said during pilgrimage days and where people, pilgrims as well as patients and families, find protection from sun or rain. They also sleep there during the night, the head oriented towards the altar, in order to favour incubatory dreams in which Saint Anthony is expected to come and give his instructions for improving or getting healing5 . Excepted the maṇṭapam which was built with political objectives, the four other edifications were offered by paravar families of Tuticorin, and are related to some attributes of Saint Anthony resulting from his hagiography or belonging to the pan-Indian context in which the cult was developed.

The cattirańkal are pilgrim shelters located in the part of the village where nāt ̣ār are located. The pilgrims, mostly paravar, occupy these shelters when they organize a visit to Saint Anthony for fulfilling a vow or performing the ear-piercing ceremony for a child. The first cattiram was built in 1942 by Pullavarayar to thank for his daughter"s healing who suddenly began dumb. Saint Anthony is celebrated for his talents of preaching, a quality that he acquires after his tongue was discovered in perfect conservation state at the moment of the translation of his body. According to the custom of thanksgivings established in some Catholic pilgrim centres in South India, Pullavarayar offered a golden ex-voto in the form of tongue. This form of exvotos which symbolizes the subject of the vow on a plate of metal (part of the body; child; couple) was very popular in western Catholicism, but its adoption in Indian context has been facilitated by this pre-existing expression. In Hinduism, the common ex-votos are the shape of animals (horse, naga) and deities in pottery or in stone settled in front of the temple, of cradles or winnowing baskets for child vows or of tāli6 for marriage arrangement. Tāli as well as cradle has been incorporated among the ex-voto used by Indian Catholics.

The second cattiram was offered by Marchiado for the protection of his last child who escaped of the death after he lost each of his newborns. As it will see later, this miracle mirrors the history of the founding of Saint Anthony cult at Puliyampatti, as it was after the death of his twelve children that Antoninadar has accepted to recognize the power of the saint and to put him in the shrine.

The koṭimaram was offered by the great grand-father of Dasan. This structure is a pole to the summit of which is erected the flag of Saint Anthony at the beginning of his annual festival. The annual flag is offered by Dasan who performs the ritual of its erection every year. This ritual is based on Hindu temple festival and means that the flag, embodying the power of the deity (exteriorized form of the deity), protects all the devotees residing in the village. The pole is situated in front of the deity shrine. The ritual of flag erection is performed by the dominant caste which holds the precedence, but at Puliyampatti, nāt ̣ār who hold precedence as descendants of the founder"shrine, do not participate to the annual festival due to conflicts with the clergy (Jesuits, diocesan priests). Dasan"s great grand-father offered a wood pole when he got a child after praying Saint Anthony; the first celebration of the flag took place in 1919. Fifty years ago, Dasan fell ill, he was seized with convulsions (valippu) and his mental state was not very good (putti cariyāka illai "son intelligence n"était pas bonne"). Suspecting a spell (ceyvinai), his parents decided to take him to Puliyampatti for a period of thirteen days7 . During a night under the old mandapam, her mother had a dream in which somebody told her that if they replace the badly damaged wood pole by a new one in iron8 , her son will be cure. Since the cure of Dasan, the family perpetuated the celebrations of the flag started by their ancestors.

The last structure, Mātā Kōvil (chapel of Virgin), does not result from a vow. This building was erected on a land bought by a paravar from Susaikanninadar for constructing a family vault. But the priest did not agree this project which would have aroused indignation from devotees due to impurity related to the death, and thus the paravar converted the building into a chapel. Despite of its name, the chapel does not possesses any statue of the virgin, but a Descent from the cross; Marie Magdalene who prays at the foot of the cross is likened by devotees as Virgin. The place that was chosen for erecting the vault is interesting because the entrance should be situated just in front of Saint Anthony altar so that the people buried at this place might beneficiated from the power of the saint. This idea is based on the concept of darśan (sk.; tm: taricanam "vision"), a Hindu devotional ritual which consists in "seeing" the deity and "be seeing" by it in order to get its power and protection. This concept is central at Puliyampatti because the middle of Mātā Kōvil and the koṭimaram, both erected at the east, in front of the Saint Anthony altar (like in Hindu temple, the deity faced up east) corresponds to the statue of the saint. These three places are very frequented by devotees, patients and their families who circumambulate around the three structures. While state of possession is rarely manifested inside the church, it is intensively expressed at the koṭimaram where patients have talks with Saint Anthony and at Mātā Kōvil where they beseech Saint Anthony and Mātā for relief.

4-Saint Anthony, the kulateyvam of paravar and natar

In the West, the devotion to Saint Anthony of Padua is very much alive. From the number of candles burning in front of his statue and his presence in the churches, his cult is as fervent as that of the Virgin. If he well-known specialty is to recover lost things, his worship is not confined to this only area. In her ethnographic study on the saint, Elisabeth Blanc (1991) has shown that devotees invoke him for mundane affairs, from child request to healing through success in examination, marriage etc. She states: he is "a saint to do everything", a confidant, a friend, almost a member of the family that we visit regularly."

Saint Bonaventure, in his Song, claimed (Petit trésor des amis de Saint Antoine de Padoue : 32):

If you want miracles, go to Saint Anthony! He has power over death, fault, disasters of any kind, demons, leprosy and all diseases. He breaks the chains, calms the waves and recovers lost things and limbs.

The cult of Saint Anthony has spread in India through missionaries who worked for the Padroado9 . The saint was native of Portugal and belonged to the Order of Friars Minor. In his iconographic study, Louis Réau points out that during the 16th century, Saint Anthony became "firstly the national saint of Portuguese who put their churches abroad in his name, and then, an universal saint" (1958 III: 117). Therefore, it is possible that his cult in southern Tamil Nadu was promoted by Franciscans, or by Jesuits as Francis Xavier distinguished himself by the christianization of paravar 10 . Put at the prow or on a small altar, the saint protected the vessels against sinking during the travels across the dangerous waters of Cape of Good Hope. The importance of Saint Anthony cult is remarkable along the Fishery coast by his numerous small chapels erected on the beach or in the villages. Having adopted the custom of the missionaries, paravar used to protect their fishing by a statue of the saint tied around the pole or drew on the hull. Finally, the miracle of Saint Anthony that paravar regard as the most important is the preaching to the fishes, a miracle quite often depicted in churches and altars dedicated to Saint Anthony.

Paravar make up the group of pilgrims the most important; the second community in size is nāt ̣ār due their involvement in the foundation of the shrine. For these two communities, Saint Anthony of Padua is the kulateyvam, family god or caste god11 . In Hindu devotion, the kulateyvam assures protection of the family/caste, and in compensation, it receives an annual cult organized by family and / or caste. Because of their function, they hold a privileged place within the domestic sphere for protection against difficulties of the daily life, and for performance of biographical ceremonies (naming ceremony, ear-piercing ceremony, marriage, ceremony of the 7th month of pregnancy) which integrate new members into the family; the child becomes a full member of the paternal line, and the bribe by joining her new family has to adopt its kulateyvam. These ceremonies are held preferentially in the temple of the kulateyvam. However, to celebrate the naming or the ear-piercing ceremony ((kātukuttu vīlā), people prefer to go to the main temple of their kulateyvam. Catholics have remained in large part these customs considered by the clergy as social practices and some churches, notably pilgrimage centres dedicated to the virgin such as Velankanni (Sébastia 1998), offer the services for the performance of devotional and biographical rituals.

4-1-Nērttikkat ̣an: a relation of obligation

The pilgrimage day of Puliyampatti is Tuesday which corresponds traditionally to the day of week when the Saint Anthony"s corpse was buried. But for important vows and ceremonies, pilgrims come the last Tuesday of each Tamil month. This choice is based on Hindu concepts on effectiveness and completeness of the vow. The end of the month is followed by the beginning of a new one which, implicitly, induces renewal and regeneration. Choosing the end of a month to thank the deity for its intercession, devotees put all chances on their side so that their afflictions cease completely. This time is also appropriated for the ear-piercing ceremony due to the fact that regeneration is in the heart of the ritual. Regeneration concept which is central in Indian devotion is expressed through some religious practices.

Thanking for the fulfillment of a vow is a devotional act performed in western Catholicism. However, at least in its present practice, thanks are rarely mentioned in the books of prayer intentions of the churches which have a miraculous statue. For example, the statistics by G. [START_REF] Herberich | Messages et prières des pèlerins de Thierenbach[END_REF] show that the "thanks" addressed to the Virgin of Thierenbach represent only 6.6% of prayer intentions and 3.4% when they are accompanied by a new request. Comparatively, the statistics I made from the thanksgivings written in the magazine Vailankanni Calling and exposed in the Velankanni ex-voto museum, show a very different devotional practice as 66% concern thanks and requests, and only 22% thanks and only 4% for requests. This difference is understandable by the conception of devotional expression of the bhakti in which the devotee, as aṭimai (subordinated person), kaṭavuḷḷukku kaṭṭuppaṭutal (god slave) interacts directly with his elected deity. The bhakti is a religion of emotion and communication in which the devotee is in contact with the divine through touch, vision, prayers, songs, spiritual exercises. As defined by Madeleine [START_REF] Biardeau | Hinduism. The anthropology of a civilisation[END_REF], bhakti involves a relationship of grace from the god to its creature and an entire devotion relationship from the creature to the god. In this relationship, the vow is central for its importance as well as by its formulation. A favour can not beg without promising any compensation. In Tamil, the word "vow" is translated by vēṇ t ̣utal "to wish", and more interesting, by nērttikkat ̣an, made of nērtti "which is equitable" and kaṭan "loan". This word gives an account of what is at stake in the prayers: maintain of the communication between the devotee and deity through a relationship of dependency. This relationship must never be interrupted; the devotee fulfils his promises to the deity and, again, begs it for other favours. The maintenance and quality of the relationship devotee / divinity does not focus on the content of the vow (request / promise) but on compliance with commitments and obligations. The manner to thank the deity for its favours is very various in India comparatively with western countries: to go to pilgrimage by foot which may take several weeks; to visit the deity"s shrine several times (for ex. to go to Puliyampatti thirteen successive Tuesdays); to circumambulate a certain number of times (3; 13; 108) around the shrine or the sanctum sanctorum by walking, by rolling on the floor, by laying all the body and walking a distance pertaining to the body length; to offer all kinds of things such as money, exvoto, written witness of the miracle, and also hair and an acanam, two important offerings which merit attention.

4-1-2 Hair: "a dominant symbol" Hair offering or shaving (moṭṭai) is a devotional practice and a part of the ritual of earpiercing ceremony. It symbolizes the regeneration. Shaving has been introduced into catholic practices because it is considered as a penance and is assimilated to the tonsure of some Catholic orders. If traditionally, moṭṭai means the complete removal of hair, at Puliyampatti, paravar adopt often the tonsure of Franciscans.

The ear-piercing ceremony is practised, in principle, when the child is young, seven, nine, eleven, etc., months12 . It consists to shave his head, to pierce his ears, to give him a bath and to dress him with new cloths. Shaving and ear-piercing are practised within the compound of the shrine by different specialists, some belonging to barber castes, the other to the caste of jeweller. The ritual involves the participation of the extended family, and notably of the mother"s brother who is, in the Dravidian kinship context, the person who finances the ceremony. The ritual is performed in the morning before the celebration of the mass at the maṇṭapam, and a meal, called acanam, ends the ceremony.

In the context of disease, moṭṭai is practised by way of thanks for a healing. This ritual corresponds to what Van Gennep called a "rite of passage", a rite performed to mark the beginning of a new life stage, here, to put an end to the period of illness and to start a new life. At Puliyampatti, many patients affected by mental disorders perform shaving to force Saint Anthony to cure them, i.e., to deliver them from "evil spirits harassment". The removal of hair seems inadequate if one considers the symbolism of hair in the Indian conception of mental illness. As mental illness is considered resulting from evil spirits, the possession manifestation is expressed by codified gesture, among them, by head whirling with untied hair. Untied hair is an expression of possession because evil spirits are supposed to enter into a person through hair and to leave the body through a hair lock located on the summit of the head. When after long negotiations the evil spirit agrees to come out, the exorcist pulls out the lock and nailed it down on the trunk of a pulimaram (tamarinier), a tree which is considered attracted evil spirits (Tarabout 1999).

The symbolism of hair is so rich in symbolism that it is a "dominant symbol" according to Victor Turner"s expression [START_REF] Nabokov | Religion against the Self. An Ethnography of Tamil Rituals[END_REF]. The different meanings attached to the same symbolism sometimes seem contradictory, but the meaning is defined by the context. We may state that two opposing ways of a same substance have a close symbolization, and even, identical. If the shaving is done for thanking or requesting of mundane things, it is also practiced to express a state of asceticism, a situation in which the person is temporarily or permanently cut off from mundane life. The body marking, for exemple, favours the separation of a deceased person from the living word and indicates the state of impurity which restricts them to take part in auspicious social celebrations. Shaving is also practised by people who choose a religious path (Jain, Buddhist) or who are assigned to religious duties (brahmins), activities which prevent or limit sexual practice, a central activity in human relationships. The congruence between adoption of the chastity and the obtaining of spiritual powers is a fact that Marine Carrin observes in her study of santal women (tribe) who become priestesses (1997). The Goddess manifests to them as she goes long matted locks of hair appear on their head and their psychology and physiology change with the cessation of menstruation. Marine Carrin analysis differs from the psychoanalytic theory in Medusa's hair (1984) by Gananath Obeyesekere who considers the bun of tangled hair locks (hindi jota) as an expression of the phallic shape and shaving as a principle of castration. From speeches and life stories of the priestesses, Marine Carrin notes that the appearance of jota coincides with the loss of sexual identity. The cessation of menstruation involves the stopping of reproductive function and, thereby, the disinterest in sex and the social world.

4-3 Āt ̣uvat ̣t ̣utal Adaptation of the goat sacrifice

Puliyampatti is well known for its offerings of animals. Each week, on average twenty goats and a few cocks are 'sacrificed' to Saint Anthony and the number reaches fifty the last Tuesday of Tamil months, and one hundred goats during the festival. The word used by people to define this offering is pali which means "sacrifice". This term refers to the worship of nonvegetarian Hindu deities, but the method adopted in Catholic context differs from that practised in temples. It is a symbolic pali authorized by the clergy who get advantages by selling goat skins. This practice is definitively forbidden at Velankanni as the purity of the virgin cannot be stained by the sacrifice blood. She is honored with coconuts, fruits and flowers which are offerings for vegetarian deities.

The protocol of goats offering follows partially Hindu practice. The animal is bathed for purification, adorned with a garland of flowers, and presented to the deity by circumambulating three times around his sanctum sanctorum. Then, the animal is beheaded outside the church area, in a cattiram or in lodge compound, while in Hinduism the sacrifice is performed in front of the deity. The slaughter of the goat and then, the cari cooked with it is done by a specialist hired through the shrine administration or by cooks who are attached traditionally to the family. Once the "sacrificial" goat is cut up, the pilgrims offer its skin to the church. This practice differs from the Hindu one in which the deity receives the first part of the food (pataippu "food offering on a banana leaf". The second part of the food is consumed as the piracātam, the sacred "leftovers" of the deity. The skin of the goat donated to the shrine, implicitly, represents the offering of food prepared with the "sacrificial" goat for which devotees receive from the church a poster of Saint Anthony regarded as a piracātam. Food offerings are a part of Saint Anthony cult as it represents the "Saint Anthony bread for the poor", a practice born from one of thirteen miracles of Saint Anthony 13 . A large part of food is offered to other people, in principle for thirteen people, as acanam, a term use in Tamil Catholicism. In some acanam organized by or for a recovered patient, the ex-patient serves the thirteen people by taking a sample of food from each portion and swallowing it. By this process, the food is invested with the qualities of piracatām, the divine leftovers. People who beneficiate of the food offerings, are mostly patients and their families. This distribution is an important source of food for them as they are often completely impoverished due to their long stay.

5-Saint Anthony, the saint for patients and possessed

Unlike pilgrims, patients and their caregivers belong to the various castes of the region (paḷḷar, kōnār, nāt ̣ār, tēvar, paravar etc.) and are predominantly Hindu (55-65%), Christians shared between Catholics (25-35%) and Protestants (5-10%); Muslims do not frequent the shrine, preferring to go to pīr14 in dargā which have a very good reputation to expel evil spirits. The most famous among the dargā is that of Ervadi, sadly known since the tragedy in 2001, where 28 patients, charred by a fire in a mental home, died. While the venue of pilgrims at Puliyampatti is based on the particular relationship they maintain with the saint, patients and their families come for the healing and exorcist qualities of the saint. This shrine is also the most famous for exorcism located within one hundred kilometers.

5-1-The construction of the exorcist vocation of Saint Anthony

By its hagiography, Saint Michael is certainly among all the saints, that who is capable to fight the devil. His specificity is present at Puliyampatti where, perched above the entrance of the sacristy located in the back of the church, he kills the demon. Unlike Saint Michael"s martial attitude, nothing in the iconography of Saint Anthony of Padua suggests his exorcist function. Carrying Jesus child who is sitting on a book, he is the embodiment of gentleness and paternal affection. Nevertheless, his representation at Puliyampatti is different from that in the west as, like Saint Francis Xavier, he brandishes a cross in his right hand, symbol of evangelization. This gesture reminds the technique used by the priests to expel the demon. This specific iconography of the saint at Puliyampatti is very little widespread outside Tirunelveli region and Fishery coast, 13 The miracle concerns Miss Bouffier who could not open her shop, the lock being broken. She called a locksmith but the man did not succeed and went out to look for another worker. She thought: "if you promise to offer bread to Saint Anthony"s poor, may be he will help you to open the door." When the locksmith came back with another employee, the door opened without any resistance. From this moment, Miss Bouffier institutionalized the "bread of Saint Anthony for the poor" (Petit trésor des amis de saint as he is commonly represented under his sulpician icon. Nevertheless, in the whole Tamil Nadu, he is venerated as exorcist and healer.

How Saint Anthony gets his reputation of exorcist and healer in Tamil Nadu, and specifically at Puliyampatti? It is difficult to answer as the missionary correspondence is hardly informative on the cult of saints in India. If one considers Saint Anthony"s hagiography, the second of his thirteen miracles (or Tuesdays) is based on his ability to fight the demon. This second miracle, which follows the first one dedicated to the protection of children, means that this ability was recognized to him and held a central position in his worship. One can suppose that this function has been spread through missionaries, but through Jesuits or Franciscans? According the French Jesuits correspondence, they practiced exorcism by invoking either the Virgin, the Christ [START_REF] Guchen | Cinquante ans au Maduré 1837-1887. Récits et souvenirs[END_REF] or sometimes Saint Benedict (Lacombe 1892) while Portuguese Jesuits invoked Ignace Lloyala, Saint Francis Xavier or the Virgin, but both never referred to Saint Anthony of Padua. This suggests that this specialty was developed by Franciscans. Jesuits often denounced Franciscans for their lack of harshness to forbidden the superstitious practices and the hinduisation of rituals. If these criticisms are rooted in a period of intense rivalry between Padroado and Propaganda Fide for the jurisdiction of Fishery and Coromandel coasts, they provide valuable information on the practices of the converts. Among examples, many concern Oriyur, a martyr village of Saint John de Britto that David F. Mosse (1986) had studied in his thesis.

From ethnography of Tamil shrines dedicated to Saint John de Britto, Saint James and Saint Anthony the Desert, David F. Mosse highlights the special qualities of the saints that are sought by pilgrims and patients. These three saints hold the characteristic to be associated with the savage, unorganized, and asocial world. This world is that of Hindu deities who receive animal sacrifices. They protect the frontiers of the village, the lineage and caste. By their functions, they endow the devotees with well-being, but this protection can be reversed into affliction when devotees commit transgressions.

The ambivalent character of Saint Anthony of Padua, and the theme of wilderness are recurrent in the history of the founding of Puliyampatti shrine that Susaikaninadar told me. This story is also published in the booklet Punita Antōniyār tiruttalam (1973). I mention here the main facts which occur in continuation of the foundation story.

As said previously, Antoninadar married Ramanadar"s daughter. The couple had thirteen children. At this time, there was no church at Puliyampatti and the family used to go to the small portuguese Saint Francis-Xavier church at Sendapettai (near Sivalaperi) located at six kilometers. The family was happy, but suddenly, their life was stricken by the disease which affected twelve of their children. At each child affected by the disease, Saint Anthony visited Antoninadar and asked him to be install in a shrine. But Antoninadar was too poor for answering the request and finally lost twelve of his children. Badly hit by these series of affliction, he shut himself off into prayers and loneliness. Once again Saint Anthony came to him for requesting him a cult. He went to Sendapettai and confined in Saint Francis-Xavier his distress. During the night, Saint Anthony came and told him to visit the jamīntār of Maniyacchi for requesting a piece of land. He followed this advice and on the way to Maniyacchi, he met the jamīntār and described him his misfortunes and his dreams. The jamīntār informed him that, during the night, a saint person came in his dreams and asked him to offer a piece of his lands for building a shrine. Considering the convergence of the dreams as a sign of the Providence, he invited Antoninadar to choose a land at Puliyampatti. Antoninatar inspected the lands for an ideal place, when suddenly, he discovered a cańkucet ̣i (a shrub with blue conch-shape flower) which branches formed a cross.

Seeing it as a sign of Saint Anthony"s choice, he selected this land. Few days later, while he began the church foundations he dug up a golden cross. From this holy place, he built the altar and put up the small statue of Saint Anthony which was in the cemetery of Sengapettai.

This story shows several interesting features to understand the qualities devoted to Saint Anthony. The first one is the ambivalence of his character which is symbolized by the death of Anthony"s children until Antoninadar accepted to establish him a shrine. The series of deaths suggest an act of witchcraft. In popular interpretation, the repetition of misfortunes that falls upon innocent victims is considered as a sign of sorcery resulting from transgression or faults. In this story, the twelve children were subjected to saint"s vengeance provoke by the fault of their father, implicitly, his lack of faith and confidence. Such reactions are well known from certain categories of Hindu deities, notably of minor gods. However, if this story highlights the ambivalent character of Saint Anthony, he is also perceived by devotes as much more tolerant and kinder than Hindu gods which are susceptible and very difficult to satisfy. The moderation in the ambivalent character of Saint Anthony as well as of Catholic figures in general, are often expressed by patients who accuse Hindu deities to be responsible for their suffering (tunpam).

The second factor that shows a parallel between Saint Anthony and the Hindu minor deities is the wilderness and asocial space, as this space is that of ambivalent deities which possess exorcist qualities. Nearly Iraiyur in Villupuram district, there are two small shrines of Saint Anthony of Padua, established by devotees, which are located in desert places called kaṭu ('forest', 'jungle', 'uncultivated land'). One of them is erected at the edge of the forest while the second is built under a grove of banyan trees. Both informal shrines are kept by upatēci (catechists) who organize prayer sessions for devotees and patients and practise exorcisms. At Puliyampatti today, Saint Anthony shrine is close to houses, but according to the history, the hamlet was funded by two nāṭār families, from one Antoninadar married the daughter. This suggests that the number of houses was limited.

The story of Susaikaninadar refers twice to universe of the wildness through the details of the chapel location and the origin of Saint Anthony"s statue. The place of the chapel was chosen among jamīntār"s lands, at the spot where a golden cross was dug up. This detail calls for comments. The discovery of a sacred object is a recurrent feature in the foundation myths of Portuguese (and Spanish) chapels as well as of Hindu temples (Tarabout 1999; Reiniche 1979). David F. Mosse in his thesis on Ramnad district gives an interesting example (1986) of a small temple foundation. Its foundation results from the discover of a buried goddess statue close to a well (ūruṇ i) after villagers dug at the place of a stone on which a shepherd woman often tripped over when she crossed the land (kaṭu). The two terms ūruṇ i and kaṭu refer to wild space, that of the auto-manifested (cuvāyampū from sk. svāyambhū "self-existent") deities"s seats (pīt ̣am). These deities have an ambivalent, versatile and unexpected disposition.

Saint Anthony statue would come from the cemetery of Saint Francis Xavier church at Sendapettai. The church, very damaged, still exists and is managed by a mother and her son who organize Friday masses. The son who was healed from evil spirits affliction by Saint Francis Xavier, performs exorcism. The church is located in a very wild space near Tambraparni river where some graves are scattered. The nearest houses are located at one kilometer from the church; they are entirely abandoned today. The cemetery, the place where Antoninadar took Saint Anthony"s statue to put it in his shrine, gives to the statue a power as huge as dangerous. Funeral areas in India are places where danger and impurity are correlative to regeneration and transcendence. This polarity is symbolized by Shiva-Rudra, the ascetic and the terrible who, covered with ashes collected at the cremation place, has the power to destroy and regenerate the world. As Isabelle [START_REF] Nabokov | Religion against the Self. An Ethnography of Tamil Rituals[END_REF] has shown in her analysis of exorcism rituals, the fact that the cremation areas are selected to perform exorcist rituals derives from this double symbolization destruction/regeneration because these rituals portray the separation of evil spirits from body and then the reintegration of the possessed in the social world. The cemetery as the place of origin of Saint Anthony"s statue is often mentioned by the devotees when they emphasized the destructive and exorcist powers of the saint.

Lastly, another significant dimension that explains the exorcist function of Saint Anthony of Padua is the superposition of his cult with that of Saint Anthony of the Desert. This cult overlap is not specific to Indian Catholicism and is often reported in iconographical and ethnographical studies in the west [START_REF] Reau | Iconographie de l'art chrétien, Tome III "Iconographie des Saints[END_REF]Blanc 1991). One of the hagiographical particularity of Saint Anthony of the Desert called "the temptation of Saint Anthony" refers to his numerous battles against the devil and the forces of evil [START_REF] Reau | Iconographie de l'art chrétien, Tome III "Iconographie des Saints[END_REF]Guerin 1878). In India, while the cult of Saint Anthony of Padua is spread among fishing castes, that of Saint Anthony of the Desert is well established among agricultural castes. During the Hindu ritual Pońkal, a feast of new rice celebration, in some churches devoted to Saint Anthony of the Desert, the priest uses to bless the cattle the day of māṭu pońkal "cow pońkal", as this saint has the quality to protect animals, specifically pigs. According to the records in the diaries written by Father Arulanandan who worked at Puliyampatti between 1953 and 1973, his celebration was practiced at Puliyampatti, that seems testify a certain superposition of cults.

5-2-The clergy and the patients: ambiguous discourses and pressure

Therapeutic rituals are fully organized by patients" caregivers or by patients themselves when their stay at Puliyampatti is old or when they are alone. These rituals are informal and take place outside the church compound, at the koṭimaram and Mātā kōvil. Possession state is rarely manifested inside the church, and when it occurs, caregivers oblige the possessed to go out the church. This situation results from the rules imposed by the clergy, aware to maintain order and orthodoxy inside the shrine. The priest considers that possessed are rarely affected by "demonic attack", "bad evil" as people think, they are mentally ill people. He interprets evil spirit conception of people by their ignorance and therapeutic rituals by an expression of "folk therapy". By this way, he justifies his refusal to practise exorcism rituals. If the priest gives little credit to "demonic attacks" in the possession, however, his sermons abound of references to the "bad power" (tīya cakti) of Satan. Patients are particularly sensitive to these repetitive speeches because, by hearing concepts with which they are familiar, they are reinforced in their interpretation of the illness. In some ways, the ambiguous attitude of Indian diocesan clergy differs very little from that of French Jesuit missionaries who had in charge this shrine. Through their correspondence, the phenomenon of possession is tackled differently according to the period, the end of the 19 th century being the transitional period. Before the end of the 19 th century, the possession narratives were contextualized in a culture where the magical power was well recognized and where people who practised magic were perceived by missionaries as dreadful practitioners. Firmly convinced of the damaging effects of magic, missionaries adhered to the conception of possessed. They rarely refused to perform exorcisms, and even, imposed themselves for this liturgical task. Methods and rhetoric they used, which were defined by western Catholicism, differed little from those of Hindu exorcists. To expel the "devil", missionaries invoked some saints or the Virgin, gave a holy medal or a Scapular to the patient, and they sprinkled holy water on them. All these acts had an effect on malevolent spirits which, according to the common concept in many religions, violently reacted when they faced up to holy objects and ask for escaping. Unlike Hindu exorcism which metaphorizes the departure of spirits by cutting a lock of hair and nailing up it on a tree trunk, Jesuits did not perform any ritual of separation. However, this separation is done by conversion to Catholicism. Proposed more or less explicitly by missionaries or desired by the patients as a guaranty of their gratitude, the conversion involved a separation between the world of human and that of "demons". While the term "demon" refers to Satan, the missionaries used it to define all the Hindu deities whatever their status.

The first evidences on the practice of exorcism at Puliyampatti are reported in two articles in the French Jesuit journal Caritas published in English respectively in 1951 and 1962. They are interesting because they testify the change in possession concepts.

Puliyampatti is well known in the south as a popular pilgrim resort in honor of St Anthony of Padua. (…). It is known that among the clients of St Anthony there are not a few non-Christians and that at their investigation what goes by the name of "devil dance" is sometimes practiced. This has been severely tabooed. (Caritas 1951: 160) A good many pilgrims go to this shrine of St Anthony of Padua. There are always crowds there, but at once a monththe last Tuesday of the month about five to eight hundred pilgrims can be seen there. Among the sick that come there, many of those who are suffering from hysteria and falsely think that it is possession. I saw this year a number of such patients relieved of their sickness. One young woman lost her husband and a few days after she lost her child also -No wonder she got off her head. Her parents took her to Puliyampatti and stayed there for bout one month. She got much better. The girl"s father had some sense in thanksgiving wanted to become a Catholic. The father, the mother and the girl -all Hindus-began to study catechism and they were baptised. (Caritas 1962: 138-139) These two excerpts show that French Jesuits conception does not differ from that of the present clergy. They condemned the "demonic dance" that they described as superstitious practice, and rejected the supernatural interpretation to the benefit of mental disturbances. They used a terminology which did not belong to magic, witchcraft, demoniac universe, but which belonged to the alienism/psychiatry vocabulary: "hysteria", "insane", "to get off the head". This change in the interpretation of possession mirrors that of the Church which accepts to abandon a part of its competence to the benefit of medicine. Analyzed in the west by Giordana Charuty (1985), this conceptual transformation began in the second half of the 19th century and came from the alliance of church and the alienist medicine This alliance is based on a new division of therapeutic interventions: the Church abandons to the mental medicine a domain that it considered until now as an area within its competence. Although it continues to recognize the demonic origin of some phenomena, the High clergy appears increasingly reluctant to authorize exorcism rituals that the village priests intend to use, especially in the possession epidemics which multiply during the second half of the century (Charuty: 180-181) (my translation).

However, strategic adherence to the alienist knowledge, including individual experimentation relationship to supernatural towards mental pathology, is not without difficulties. The Church can not, in fact, adhere to "the hateful doctrine" of these rationalist doctors for whom: "there is no revelation that is not a hallucination, miracle that be reduced ultimately to neurosis." So theologians work to demonstrate the existence of supernatural phenomena that are unexplainable by human psychological processes alone. But conversely, to retain control on beliefs, all the practices which infringe religious orthodoxy will be condemned not only as superstition, but as dangers for mental health, even as signs of madness (Charuty: 181-182)(my translation).

Ambiguities mentioned in this analysis are also in the narratives of French Jesuits. While they denounced the fallacy of interpretation of suffering to which they attribute a psychological or mental origin, they recognized the thaumaturgic power of Saint Anthony. This means that, although they were aware to prevent the shrine from certain "superstitious" practices, the "miraculous cure" allowed to testify the superiority of the Catholic religion on Hinduism, the omnipotence and benevolence of the thaumaturgic saints in comparison with the evil nature of Hindu deities. Moreover, the Jesuits did not ignore the limits of evangelization: a too high intolerance could result in the refusal to convert or to abandon Catholicism to the benefit of another religion more permissive.

These ambiguities and limitations in respect of orthodoxy are certainly the reasons for which the shrine of Puliyampatti does not lose its vocation to heal mental disorders. Furthermore, as Susaikaninadar told, Antoninadar and his descendants who hold the function of upatēci (catechist), took care of the shrine and its devotees until it was declared an independent parish in 1954:

After Antoninadar founded the shrine, miracles occurred. By using the lamp oil which was light in front of Saint Anthony statue, people realized that it possessed healing properties. And thus Antoninadar who was very sensitive to these miracles decided to take care of the shrine and its patients and began the upatēci. When patients came, he rubbed the sick body part with the lamp oil, chanted some prayers and pratised exorcism.

When Father Arunalandan was appointed to the shrine, he forbidden the exorcist practice and thus my ancestor refused to continue to work as catechist.

The difficult relationship between the nāt ̣ār community of Puliyampatti and parish priests who managed the shrine on which they are many references in the priest diaries, certainly results from the lost of status and power of the descendants of Antoninadar after the appointment of the permanent priest. It is very rare that a caste who holds precedence accepts to abandon its privileges to the benefit of another caste like in the case Puliyampatti where the organization of the annual festival is entirely in the hands of paravar. The unique privilege they retain is that the procession cars turn around the part of the village where they live, but it may be noticed that there is no paravar in the village and the other inhabitants of the village are Hindu paḷḷar, that that justifies the processional route.

6-Conclusion

Cults of Saint Anthony of Padua at Puliyampatti as well as of the Virgin of Velankanni are very interesting for their hinduisation features. Performance of biographical rituals performance, large variety of ex-voto and offerings such as coconut at Velankanni or goat "sacrifice" at Puliyampatti, devotional gestures and penances, particular rituals in festival celebration are specific to these places due to the fact that they are important pilgrim centres, Velankanni at the national level while Puliyampatti at the regional one. The difference of status between these two icons is expressed by the legitimation of practices by the clergy and thus comparison of these two famous shrines questions the elasticity of the term of "superstition" that the Indian clergy manipulates for tolerating or rejecting rituals. As these two centres gather many devotees, Catholics and also Hindus, the clergy is obliged to have an attitude more tolerant than that in the ministry of an ordinary parish. Nevertheless, a comparison with Catholic practice in the west shows that the hinduisation of Catholic cults has been favoured by the fact that Catholicism and Hinduism share many common features. Saint Anthony, the Virgin and many other Catholic icons have been easily assimilated to the Hindu pantheon due to their specific functions and their rich hiagiography which is comparable to the Hindu iconography and agama, stories of temple foundation and of god miracles. By playing on the similarity between the two religions, the missionaries are reached to impose their religion. But this type of evangelisation has induced cult confusion that the clergy attempts progressively to eradicate.

This article has been written from a thesis titled Les rondes de saint Antoine. Culte, affliction et possession à Puliyampatti (Inde du sud) defended in

and published by Aux lieux d"Etre in 2007 under the same title. The fieldwork of sixteen months was financially supported by the French Institute of Pondicherry through a fellowship.2 The transliteration used for Tamil words follows that defined by the Tamil Lexicon, Madras, 1982. The plurial of words is kaḷ which change according to the final letter: kkaḷ after a vowel; kaḷ after a consonant excepted "m"; ńkal ̣ where "ń" is the nasalization of the "m". The plural of caste communities is not marked. The Sanskrit words are specified by "sk.".

A jamīntār was a territory owner (jamīn) for which he had to pay land revenues thanks to the taxes collected from people who farmed his lands.

The Society of Jesus was broken up by the brief Dominus ac Redemptor by Clement XIV July 21, 1773, and this, until 1838. However, before this papal decision, Portugal in 1759 and France in 1764 had decreed the dismissal of the Jesuits established in India, in order to stop the famous quarrel on the Malabar Rites (see[START_REF] Meersman | The Ancient Franciscan Provinces in India 1500-1835[END_REF]. However, the French Jesuits stayed in India and worked under the jurisdiction of the Foreign Mission Society appointed in 1776 by Louis XVI and approved by Rome to replace the Jesuits(Launay, I, 1898).

Incubation is a therapeutic method very ancient. fort ancienne connue sous le terme d"incubation. It was known in Mesopotamia, in Egypt and especially in Greek where it was practised in 300 to 400 asklepiads, therapeutic shrines of the god of medicine Asklepios, in which patients stayed until their healing[START_REF] Sudhir | Shamans, Mystics and Doctors. A psychological inquiry into India and its healing traditions[END_REF][START_REF] Kostas | Des Asklepiades à Hippocrate : une rupture anthropocentrique à la conception de la santé et de la maladie (l"exemple du rêve)[END_REF][START_REF] Weatherhead | Psychology, Religion and Healing[END_REF]). This practice is also performed in Hinduism[START_REF] Morinis | Levels of culture in Hinduism. A case study of dream incubation at a Bengali pilgrimage centre[END_REF]

The tāli is a thin cord made of 108 threads and colored with curcuma (purifying and cooling substance) which is tied to the bride neck during marriage ceremony. In Catholicism, the jewel symbolizing a Hindu god which is hung up to the cord is replaced by a cross or icon of Virgin. The tāli as an ex-voto consists in the thin cord on which a piece of curcuma is hung up.

The number of thirteen refers to the specificity of Saint Anthony"s cult. According to the tradition, thirteen was the date of his death.

The replacement of the wood by iron is in relation with the opposite qualities of these materials. Iron is considered to repel the evil spirits while they are kept by the wood. The presence of a wood pole in Hindu temple is to protect the shrine from malevolent forces[START_REF] Reiniche | Les Dieux et les hommes: Etude des cultes d'un village du Tirunelveli, Inde du Sud[END_REF]).

The Padroado was fixed by the bull of Sixtus IV August 21, 1472. This signature confirms the bull of Nicolas V June 18, 1452, granting to King Alfonso V of Portugal privileges on trade and right to evangelize people discovered during their voyages.

For the christianisation of paravar, see Susan[START_REF] Bayly | Saints, Goddesses and Kings. Muslims and Christians in South Indian Society, 1700-1900[END_REF] Inès G. Županov (1999).

In south India, caste and family merge on due to the fact that the preferential marriage, according to the Dravidian kinship, is endogamous.

The symbolism of imparity belongs to conception on transaction that is expressed through the devotion toward the deity. While parity involves completeness, imparity means the continuity of transaction. It is well shown by money transaction in traditional area where the sum may be 101 or 1001 but never 100 or 1000.

Pīr are Muslim saints who died while they Islamized India. Dargā were erected where their bodies were buried. Their tombs are famous for exorcism rituals which are often carried out by a person who claims to be a descendant of the pīr.


Christophe Tournassat
email: c.tournassat@brgm.fr

Catherine Lerouge

Philippe Blanc

Jocelyne Brendle

Jean-Marc Greneche

Stéphane Touzelet

Eric C Gaucher

Jocelyne Brendlé

Cation exchanged Fe

Keywords: dolomite, strontianite, siderite, cation exchange, Callovian-Oxfordian, porewater composition

Introduction

The French National Radioactive Waste Management Agency (ANDRA) is building an underground research laboratory (URL) in Bure (north eastern France) in order to study the disposal of radioactive waste in a deep clay formation. The main gallery is located in a Callovian-Oxfordian formation (COX) at an approximate depth of 490 m. To assess the durability of materials (glass, stainless steel, concrete, engineered clay barrier, etc.) and determine the speciation and related mobility of the radionuclides in the host rock formation, it is necessary to define the chemistry of the COX porewater. A modelling work program has been dedicated to this topic for several years, based on thorough investigations of the mineralogical composition and physical properties of the COX formation [START_REF] Gaucher | ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovian-Oxfordian Formation by investigative drilling[END_REF] and has led to a first estimate of the COX clay rock porewater composition (Gaucher et al., 2006). This porewater composition model still has some deficiencies that need to be solved. Amongst them, the control of iron solute concentration and subsequent redox control in the formation needs to be improved in order to better simulate redox perturbation in the COX (redox sensitive radionuclide migration, mineral transformations due to the gallery opening to air atmosphere, nitrate plume coming from class B wastes, etc., see the ANDRA "Dossier 2005" report (ANDRA, 2005) for more details). For instance, the modelled Fe(II) porewater concentration and redox potential modelled by [START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF], leads to water compositions supersaturated related to Fe(III) oxi(hydr)oxides although none of these Fe(III) phases have been observed on COX samples preserved from oxidation [START_REF] Gaucher | ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovian-Oxfordian Formation by investigative drilling[END_REF]. This inconsistency could be linked to two main hypotheses: (1) a problem of sample observation where Fe(III) oxi(hydr)oxides could have been missed or (2) a problem with the model. Hypothesis (1) is unlikely, given the repeated observations made on a wide variety of samples by different laboratories and leading to the same conclusion (see data compiled in [START_REF] Michel | Report on meshing for the transport model in the Callovian-Oxfordian formation[END_REF], the COX database in Access© format is available upon request to the corresponding author of the present paper). Hypothesis (2) could be linked to a misunderstanding of the thermodynamic equilibrium governing the Fe and redox system or a problem originating from the thermodynamic database used for the calculations made in [START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF]. The same type of problem occurs for the Sr concentration in the model that should lead to an oversaturation of strontianite (SrCO 3 ), although this mineral has not been observed.

As a consequence, the sample preservation (1) and the thermodynamic database (2) hypotheses were tested in the present paper step by step:

(A) Firstly, a thorough examination of iron and strontium bearing mineral phases was performed using various microscopic and spectrometric techniques on very well preserved samples using a liquid N 2 sample preservation and transport procedure [START_REF] Gehin | Reversible surface-sorption-induced electron-transfer oxidation of Fe(II) at reactive sites on a synthetic clay mineral[END_REF].

(B) Secondly, it is shown how to use the clay exchanger composition and exchange equilibrium equations to constrain the thermodynamic solubility products of carbonate minerals in clay formations. Thus, an experimental method was developed to retrieve the cation exchanged Fe(II) in very well preserved COX samples in order to add constraints to the Fe(II) carbonate system.

(C) Given the broad range of solubility values available in the literature for strontianite (SrCO 3 ), dolomite ((Ca, Mg)(CO 3 ) 2 ) and siderite (FeCO 3 ), these theoretical and experimental approaches were combined to select appropriate thermodynamic solubility values for these minerals.

Materials and Methods

Callovian-Oxfordian rock samples

Samples used for the recovery of cation exchanged Fe(II) on clay minerals and Mössbauer analysis were taken directly from the drill-core performed for the PAC (water sampling for chemical and isotope analysis) experiments in the ANDRA URL (Bure, Meuse Haute-Marne, France) in December 2005 (borehole PAC-1002, sample EST 25687). The core was obtained by nitrogen drilling instead of oil-based mud drilling, thus reducing contact with atmospheric O 2 . As soon as the core was brought to the surface (~1 h after drilling), a hammer was used to sample rock fragments, which were immediately introduced into a Dewar flask containing liquid N 2 (77 K) to avoid any further oxidation with atmospheric O 2 . The samples were then stored in a Dewar flask. The claystone samples used in this study were taken from the centre and the periphery of the core. The liquid N 2 sample preservation towards oxidation has been successfully tested in a former study [START_REF] Gehin | Reversible surface-sorption-induced electron-transfer oxidation of Fe(II) at reactive sites on a synthetic clay mineral[END_REF].

Only a small part of the core could be stored in liquid nitrogen Dewar flasks. The remaining parts of the core were placed in Ar and He gas conditioning cells for preservation and further gas analysis [START_REF] Gaucher | ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovian-Oxfordian Formation by investigative drilling[END_REF][START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF][START_REF] Girard | Stable isotope composition of CO 2 outgassed from cores of argillites: a simple method to constrain δ 18 O of porewater and δ 13 C of dissolved carbon in mudrocks[END_REF]. These samples were used for mineralogical investigations by optical microscopy, SEM, TEM and electron microprobe. For these mineralogical investigations, Callovian-Oxfordian samples originating from other cores (namely samples EST 12436, EST 21400, EST 25380 and EST 20714) were also used.

Synthetic montmorillonite samples

The synthetic sample is the same as that used in the Gehin et al. Fe(II) adsorption study [START_REF] Gehin | Reversible surface-sorption-induced electron-transfer oxidation of Fe(II) at reactive sites on a synthetic clay mineral[END_REF]. The synthesis of montmorillonite having the theoretical formula: Na 0.30 [(Al 1.7 Mg 0.30 ) Si 4 O 10 (OH,F) 2 ], n H 2 O was performed in acidic and fluoride medium under hydrothermal conditions [START_REF] Reinholdt | Fluorine route synthesis of montmorillonites containing Mg or Zn and characterization by XRD, thermal analysis, MAS NMR, and EXAFS spectroscopy[END_REF]. A hydrogel having a 1 SiO 2 : 0.212 Al 2 O 3 : 0.075 MgO: 0.075 Na 2 O: 0.05 HF: 96 H 2 O molar composition was prepared starting from water, hydrofluoric acid, sodium and magnesium acetate, silica and aluminium oxide. This mixture was matured for 2 hours at room temperature before being hydrothermally treated in a PTFE lined stainless steel autoclave at 493 K for 72 hours under autogeneous water pressure. After crystallization, the product was separated by filtration and thoroughly washed with distilled water. The pH of the supernatant was 3.5 -4.5. After drying for one night at 338 K, the sample was placed in a controlled humidity chamber (P/P 0 = 80%, where P represents the saturated vapour pressure over the sample at 298 K and P 0 the saturated aqueous vapour pressure at 298 K). Ca-montmorillonite was obtained by saturation of the prepared Na-montmorillonite with a 0.05 M aqueous solution of CaCl 2 . After treatment, the solid suspension was N 2 -degassed, before being placed in a glove box.

Extraction of cation exchanged Fe(II) from the Callovian-Oxfordian samples

Two measurement campaigns were carried out: the first was performed on a sample representative of the centre of the core. The second one was performed on a sample localized originally on the periphery of the core. Claystone samples were transferred from the liquid N 2 Dewar directly into the glove box. Claystone samples were then crushed in an agate mortar in a <0.1 and 23 ppm O 2 atmosphere for the central and periphery sample respectively.

The following procedure was entirely performed under a <0.1 ppm O 2 atmosphere. A mass m sample (~0.3 -0.5 g) of sample was precisely weighed on a mg precision balance (Sartorius Basic BA310S) and deposited as a dry powder on a Millipore, Millex-VV, PVDF sterile 0.1 µm filter. 2.5 mL of a solution containing 4.18 mol L -1 acetic acid (purity grade > 99.5%), 2.45 mol L -1 sodium acetate (purity grade > 98%) and 1.64 mmol L -1 1,10-phenanthrolin hydrochloride (purity grade > 99%) were then added to the filter holder at 298 ± 1K. The resulting suspension was immediately filtered under vacuum using a hand-pump. 2.5 mL of the same solution was then immediately added and filtered identically. The resulting filtrate was orange-coloured, in agreement with the absorbance colour of the Fe(II)-phenanthrolin complex [START_REF] Rodier | L'Analyse de l'eau, eaux naturelles, eaux résiduaires[END_REF]. The total filtration time did not exceed one minute. The Fe(II) concentration in the filtrate was then measured by absorbance photometry (λ = 510 nm) using an ATI Unicam spectrometer. The above procedure was repeated for four sub-samples for each of the samples from the centre and the periphery of the core.

Extraction of cation exchanged Fe(II) on synthetic smectite

As a control, the exchanged Fe(II) extraction procedure was applied to a synthetic montmorillonite, whose exchanger composition had been enriched in Fe(II). 0.5 mL of a 0.005 mol L -1 FeCl 2 (purity grade) solution was introduced into a 4.5 mL synthetic montmorillonite suspension (30 g L -1 ) previously equilibrated with a CaCl 2 0.05 mol L -1 solute background. The resulting 5 mL of Fe-Ca montmorillonite suspension were then filtered on a 0.1 µm filter. Subsequently, the same Fe(II) extraction procedure as that used for the Callovian-Oxfordian sample was applied.

Extraction of cation exchanged Na, Ca, Mg, K and Sr

Cation exchanged Na, Ca, Mg, K and Sr were extracted using the cobalthexamine method as described in [START_REF] Gaucher | ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovian-Oxfordian Formation by investigative drilling[END_REF], adapting the method from Ciesielski and Sterckeman, 1997.

Optical microscopic observations

Samples were observed on thin polished sections using a transmitted and reflected light optical microscope to identify transparent and opaque mineral phases.

Scanning electron microscopy

Observations, analyses and elemental mapping were performed with a JEOL JSM 6100 scanning electron microscope (SEM) coupled with an Energy Dispersive Spectrometer (Kevex Quantum) at 25 kV. Prior to analysis, a thin carbon layer was sputter-coated on the samples (Edwards Auto 306).

Transmission electron microscopy

Observations and analyses were performed at Orléans University (France), on a Philips CM20 with a CCD Gatan camera, at 200 kV. The TEM samples were prepared by dispersing the powdered samples in alcohol using ultrasonic treatment, dropping them onto a porous carbon film supported on a copper grid, and then drying them in air.

Electron microprobe

Spot analyses and elemental mapping were performed using a Camebax SX50 electron microprobe. Elemental mappings were recorded with a step of 4 µm, an acceleration voltage of 15 kV and a current beam of 14 nA. Spot analyses of silicates, carbonates, oxides and sulphates were performed with 15 kV acceleration voltage, a current beam of 12 nA and a 1-2 µm beam width. The counting time was 10 s for major elements and 20 s for trace elements.

Standards used included both well-characterized natural minerals and synthetic oxides. Matrix corrections were made with a ZAF computing program. Detection limits of elements were calculated for carbonates (Table 1).

Mössbauer spectrometry

The Mössbauer sample holder was filled with about 300 mg of powder, capped and sealed with an Araldite TM epoxy resin in the glove box with a <0.1 ppm O 2 atmosphere. The Mössbauer sample was kept overnight in the glove box so that the epoxy resin could dry, and was then taken out and immediately reintroduced into the liquid-N 2 -filled Dewar for transport to the Mössbauer facilities. The Mössbauer spectra were recorded at 77 K using a constant acceleration spectrometer and a 57 Co source diffusing into a rhodium matrix. Velocity calibrations were carried out using α-Fe foil at room temperature (RT, 295 K). All isomer shifts are reported relative to the α-Fe spectrum obtained at RT.

The hyperfine structure clearly revealed the presence of ferric and ferrous ions from the central part and the right part, respectively. The spectra were first fitted using a discrete number of independent quadrupolar doublets composed of Lorentzian lines where the line width at half-height Γ (mm s -1 ), the centre shift δ (mm s -1 ) and the quadrupole splitting ΔE Q (mm s -1 ) were refined using a least-squared fitting procedure. However, it is important to emphasize that numerous fitting models can be used to describe the hyperfine structure.

Experimental results

Extraction of exchanged Fe on synthetic montmorillonite

A Fe concentration of 9 × 10 -6 mol L -1 was recovered in the filtrate, corresponding to an exchanged content of 6.8 meq kg -1 , according to the following equation: 1where C filtrate is the Fe(II) concentration in the filtrate in mol L -1 , V is the volume of the filtrate (5 mL) and m clay is the mass of clay on the filtrate (0.135 g). This extracted Fe(II) content compares well with the expected content, 6.9 meq kg -1 , as given by the cation exchange capacity of the clay (0.63 eq kg -1 , [START_REF] Gehin | Reversible surface-sorption-induced electron-transfer oxidation of Fe(II) at reactive sites on a synthetic clay mineral[END_REF] and the Fe(II) cation exchange model by [START_REF] Charlet | Fe(II)-Na(I)-Ca(II) cation exchange on montmorillonite in chloride medium; evidence for preferential clay adsorption of chloride -metal ion pairs in seawater[END_REF]. We consider that this test validates our method of exchanged Fe extraction and that our protocol enables at least the exchanged Fe(II) content of the clay material to be recovered.

clay filtrate FeX m V C C × × = 2 2 Equation
Kinetics tests were also carried out and clearly showed a readsorption of the complex Fephenanthrolin with increasing reaction time (data not shown). The filtration duration conditions given in the Materials and Methods section aims at minimizing this effect.

Exchanged Fe(II) on Callovian-Oxfordian claystone samples

Table 2 shows the extracted Fe(II) content for the two samples, centre and periphery. It may be noted that the recovered amount in the centre is higher than in the periphery. There are two main hypotheses to explain this discrepancy:

• The mineralogical composition was enriched in clay in the core centre sample as compared to the periphery sample, leading to a greater extent of exchanged Fe in the centre sample;

• Oxidation occurred during drilling or during crushing of the periphery sample.

Whatever the cause of this discrepancy, the measured exchanged Fe is of the order of magnitude of 1 meq/kg rock in these samples. In the following, the centre sample with mean extracted Fe content of 1.2 ± 0.2 meq kg -1 will be considered. This extracted Fe(II) must be considered as the upper limit of cation exchanged Fe(II) concentration in the clay sample. It has already been shown that Fe(II) can sorb specifically on clay edges and that most of this sorbed Fe(II) is present as weakly bounded outer-sphere complexes at pH above ~7 [START_REF] Gehin | Reversible surface-sorption-induced electron-transfer oxidation of Fe(II) at reactive sites on a synthetic clay mineral[END_REF]. Given the near neutral pH of the porewater in the Callovian-Oxfordian samples [START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF], part of the extracted Fe(II) is then expected to originate from the clay edges.

Other exchanged cations in the samples

Table 3 shows the extracted exchanged Na, K, Ca, Mg and Sr contents for the two samples, centre and periphery. The exchanged contents of Na, K, Ca, Mg and Sr are very similar in the centre and periphery samples. The first hypothesis given above for the variability of exchanged Fe is then ruled out. The relative proportions between exchanged Na, K, Ca and Mg compare well with previously reported data on Callovian-Oxfordian samples [START_REF] Gaucher | ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovian-Oxfordian Formation by investigative drilling[END_REF], highlighting the homogeneity of the clay formation towards cation exchange processes.

Microscopic and spectrometric observations of Fe bearing minerals

Iron is distributed among numerous phases of the Callovian-Oxfordian clay samples: silicates, carbonates, sulphur phases and oxides (Table 4). Silicates include dominantly detrital clay minerals (illite, interstratified illite-smectite and chlorite), minor detrital micas (biotite, muscovite), scarce detrital tourmaline and local diagenetic glauconite (Figure 1). Carbonates include dominantly calcite with minor iron-bearing dolomite, ankerite and siderite (Figures 2 and3). Calcite constitutes a large part of the fine-grained matrix with clay minerals, but also occurs as rare euhedral 50-100 µm-sized grains. Dolomite and ankerite occur respectively as core and rims of euhedral 50-100 µm-sized grains in most of the samples of the Callovian-Oxfordian formation (Figure 2C). Siderite is present as rims of euhedral 50-100 µm-sized grains, growing after iron-rich calcite in the sample EST 25687 (Figure 2D).

Sulphides are syn-sedimentary to diagenetic, dominantly pyrite and scarce iron-bearing sphalerite. Iron can be found also in detrital ilmenite (Fe(II)TiO 3 ). It should be noted that diagenetic minerals are particular iron-rich mineral phases (glauconite, pyrite, ankerite and siderite).

Taking account of the distribution of the different mineral phases in the Callovian-Oxfordian rocks, the iron is mainly carried in decreasing order by detrital clay minerals, sedimentary to diagenetic pyrite and sedimentary calcite. Diagenetic siderite is one of the main iron carrier minerals in one observed sample (EST 25687). This iron distribution in the different mineral phases of the Callovian-Oxfordian claystone is further supported by the 77K Mössbauer spectrum of the EST 25687 sample (Figure 4, Table 5): the Mössbauer spectrum can be perfectly reproduced using only quadrupolar doublets parameters of the phases identified by the microscopic techniques. Mössbauer spectrometry results indicate that the redox state of Fe in the formation is mainly Fe(II). The reported 7% of Fe(III) is the maximum relative amount that can be introduced into the fitting model.

Microscopic and spectrometric observations of Sr bearing minerals

Strontium is a trace element in the Callovian-Oxfordian formations (0.025-0.12% wt % SrO, [START_REF] Gaucher | ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovian-Oxfordian Formation by investigative drilling[END_REF]. Contrary to iron, it is essentially carried by one phase, namely celestite (SrSO 4 ), and is present at only trace concentrations in carbonates. The celestite precipitated in late infilling of porosity and in veins, and is therefore a diagenetic mineral phase.

Compositions of iron-rich dolomite and ankerite were analyzed in the rims of euhedral grains disseminated in the rocks or associated with celestite, suggesting that iron-rich dolomite and ankerite are also diagenetic mineral phases. The strontium content in carbonate phases is low, generally below 0.09 wt % SrO, except late calcite overprinting celestite vein and some euhedral grains of dolomite that exhibit a strontium content up to 0.6 wt % SrO.

Discussion

Estimation of carbonate mineral solubility values with cation exchange composition

The exchanger composition of a clay rock provides information about the relative amount of exchanged cations, namely Na + , K + , Ca 2+ , Mg 2+ , but also Sr 2+ and Fe 2+ , in solution through exchange equilibrium reactions [START_REF] Tournassat | Two cation exchange models for direct and inverse modelling of solution major cation composition in equilibrium with illite surfaces[END_REF]. As already described in the literature, the exchanger composition is then an "image" of the porewater major cation composition [START_REF] Bradbury | A Physicochemical characterisation and geochemical modelling approach for determining porewater chemistries in argillaceous rocks[END_REF][START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF][START_REF] Pearson | Mont Terri project -Geochemistry of water in the Opalinus clay formation at the Mont Terri Rock Laboratory[END_REF].

This porewater composition is also in equilibrium with mineral phases. The consideration of these equilibria is the basis of porewater model development (e.g. [START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF].

Based on microscopic and spectrometric observations (this study, [START_REF] Gaucher | ANDRA underground research laboratory: Interpretation of the mineralogical and geochemical data acquired in the Callovian-Oxfordian Formation by investigative drilling[END_REF][START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF], it is likely that the COX porewater is in equilibrium with the following carbonate minerals: calcite, dolomite and ankerite/siderite, but not with strontianite (SrCO 3 ).

Hence, the following equilibria must apply:

• Calcite dissolution/precipitation:

CaCO 3 + H + ⇔ Ca 2+ + HCO 3 - Reaction 1 { }{ } { } + - + = H HCO Ca K calcite 3 2 Equation 2
where values in brackets are representative of solute species activities.

• Dolomite dissolution/precipitation:

MgCa(CO 3 ) 2 + 2 H + ⇔ Ca 2+ + Mg 2+ + 2 HCO 3 - Reaction { }{ }{ } { } 2 2 3 2 2 + - + + = H HCO Mg Ca K dolomite Equation
• Siderite dissolution/precipitation:

FeCO 3 + H + ⇔ Fe 2+ + HCO 3 - Reaction { }{ } { } + - + = H HCO Fe K siderite 3 2 Equation
Combining Equation 2 with Equation 3, one obtains:

{ } { } + + = 2 2 2 Ca Mg K K calcite dolomite

Equation

The Mg/Ca solute activity ratio is also linked to cation exchange equilibrium:

CaX 2 + Mg 2+ ⇔ MgX 2 + Ca 2 + Reaction { } { } 2 2 2 2 / CaX MgX Mg Ca ex E E Mg Ca K × = + + Equation 6
where K ex is the exchange selectivity coefficient in the Gaines and Thomas convention [START_REF] Sposito | The thermodynamics of soil solution[END_REF], X -represents one mole of the exchanger and E i is the exchanged equivalent fraction of species i.

Combining Equations 5 and 6:

Mg Ca ex CaX MgX calcite dolomite K E E K K / 2 2 2 × × = Equation 7
With siderite, one obtains:

Fe Ca ex CaX FeX calcite siderite K E E K K / 2 2 × × = Equation 8
The exchanger composition is then directly related to the equilibrium constant of calcite, dolomite and siderite carbonate minerals. While the calcite equilibrium constant is well constrained, that is not the case for dolomite. The above equations are then useful for constraining the carbonate equilibrium constant in natural systems. For siderite, unfortunately, the value E FeX2 is not known exactly: the extracted Fe(II) measurements in the above experiments ( ) give only an indication of its maximum amount and then:

meas FeX E 2 Fe Ca ex CaX meas FeX calcite siderite K E E K K / 2 2 × × < Equation 9
Strontianite was never observed in fresh Callovian-Oxfordian samples. It means that the porewater is likely to be undersaturated towards this mineral phase. The equalities given above cannot be used to determine the strontianite solubility value. However, the absence of strontianite in the formation can be related in the equation form:

{ } { } + + × > 2 2 Ca Sr K K calcite te strontiani
Equation 10

Combining Equation 10 with the information from cation exchange:

Sr Ca ex CaX SrX calcite te strontiani K E E K K / 2 2 × × >
Equation 11

Dolomite, siderite and strontianite equilibrium constants

There is a good agreement between the thermodynamic databases available in the literature and provided with thermodynamic calculation codes for calcite thermodynamic parameters.

Most of these databases rely on the calcite data by [START_REF] Plummer | The solubilities of calcite, aragonite and vaterite in CO2-H2O solutions between 0 and 90[degree sign]C, and an evaluation of the aqueous model for the system CaCO3-CO2-H2O. Geochim[END_REF] For reaction 1, the calcite solubility value is log 10 K calcite = 1.85.

As a consequence, we used the log 10 K calcite = 1.85 as a reference point for the calculation of the solubility value of dolomite and siderite in the clay formation using the following formulas:

E K E K K - - + >
Equation 14

Ca and Mg are known to behave very similarly on smectite and illite exchanger with little preference for Ca over Mg (smectite exchanger, [START_REF] Charlet | Fe(II)-Na(I)-Ca(II) cation exchange on montmorillonite in chloride medium; evidence for preferential clay adsorption of chloride -metal ion pairs in seawater[END_REF]Sposito et al., 1983a;Sposito et al., 1983b) or little preference (illite exchanger, [START_REF] Tournassat | Two cation exchange models for direct and inverse modelling of solution major cation composition in equilibrium with illite surfaces[END_REF] for Mg over Ca. Hence, we assume a log 10 K ex Ca/Mg value of 0. Fe and Ca behave similarly towards cation exchange and we assume here a log 10 of the selectivity coefficient equal to 0 [START_REF] Charlet | Fe(II)-Na(I)-Ca(II) cation exchange on montmorillonite in chloride medium; evidence for preferential clay adsorption of chloride -metal ion pairs in seawater[END_REF][START_REF] Kamei | Fe(II)-Na ion exchange at interlayers of smectite: adsorption-desorption experiments and a natural analogue[END_REF][START_REF] Saeki | Ca 2+ -Fe 2+ and Ca 2+ -Mn 2+ exchange selectivity of kaolinite, montmorillonite, and illite[END_REF]. The same assumption is made for the Ca/Sr exchange selectivity coefficient [START_REF] Fletcher | The chemical modeling of clay/electrolyte interactions for montmorillonite[END_REF]. The obtained solubility values are compared in Table 6 to the one tabulated in various databases especially available with thermodynamic calculation codes.

In NAGRA/PSI, Minteq.v4 and Wateq4f (the one distributed with GWB, not with PHREEQC2), the original equilibrium constant value, 3.57, comes from the database published by Nordstrom et al. [START_REF] Nordstrom | Revised chemical equilibrium data for major water-mineral reactions and their limitations[END_REF]. In a more recent determination, Hemingway and Robie [START_REF] Hemingway | Enthalpy and Gibbs energy of formation of dolomite[END_REF] determined the Gibbs energy of formation by calorimetry, leading to the same value for the equilibrium constant, 3.57. The dolomite solubility value derived from the analysis of the cation exchange population of the Callovian-Oxfordian sample is about 3.3-3.4 in log 10 scale. This value compares well with the 3.57 value. The difference in value could be seen as ( 1) an effect of the error bands on cation exchange measurement or (2) an effect of temperature, the Callovian-Oxfordian formation temperature being below 298K, (3) an effect of the impurities in the dolomite structure (e.g.

Fe and Sr), or (4) the dissolution of calcite during the extraction procedure leading to an overestimation of Ca concentration on the exchanger phase (Dohrmann, 2006a;Dohrmann, 2006b;Dohrmann, 2006c). It should then be noted that the solubility value given in the Llnl.dat and derived database (e.g. Thermo.dat) cannot be applied to the clay media of the Callovian-Oxfordian (2 log K values depending on the crystallinity at values 2.51 and 4.06).

The 4.06 value would be obtained in the case of an exchanged Mg/Ca ratio value of 2.3 instead of 0.48 ± 0.12 and the 2.51 value in the case of a ratio value of 0.065. Clearly none of these ratio values is relevant even considering the source of uncertainties in the measured ratio. It is then considered that the dolomite solubility value given by Nordstrom et al. is the best estimate of the one that applies to the Callovian-Oxfordian formation.

With regards to strontianite, very different values can be found as a function of the databases given in Table 6. The only value compatible with the constraint of Equation 11is the solubility value of 1.06 that originates from the work of [START_REF] Busenberg | The solubility of strontianite (SrCO 3 ) in CO 2 -H 2 O solutions between 2 and 91°C, the association constants of SrHCO + 3 (aq) and SrCO 0 3 (aq) between 5 and 80°C, and an evaluation of the thermodynamic properties of Sr 2+ (aq) and SrCO 3 (cr) at 25°C and 1 atm total pressure[END_REF].

The maximum siderite solubility value computed from extracted exchanged Fe(II) is in agreement with all of the solubility values of all the databases given in Table 6 with the exception of the Minteq.v4 database, which gives a too high solubility value.

The composition of the Fe(II) carbonate in the COX formation is not a pure siderite (FeCO 3 ) but a sideroplesite having a composition of approximately Fe 0.7 Mg 0.2 Ca 0.1 CO 3 (see Figure 3) with a solubility product value of log K sid_COX . Using the same method as described above, one derives for this particular composition: The solubility product of a carbonate phase with the composition Fe 0.7 Mg 0.2 Ca 0.1 CO 3 was evaluated using a ternary solid-solution model and the following three end-members: calcite, siderite and magnesite (MgCO 3 ). The solubility of calcite was taken from [START_REF] Plummer | The solubilities of calcite, aragonite and vaterite in CO2-H2O solutions between 0 and 90[degree sign]C, and an evaluation of the aqueous model for the system CaCO3-CO2-H2O. Geochim[END_REF], that of siderite from Chivot, 2004, whereas that of magnesite was calculated from the ΔH°f and S° values tabulated in Robie and Hemingway, 1995 for a natural magnesite.

The calculation of the free energy of mixing at 298 K ( mix G Δ ) was obtained through the following relationships:

excess mix i i i mix G X X T R G Δ + = Δ ∑ = 3 1 ln . . Equation 16 123 3 2 1 23 3 2 13 3 1 12 2 1 W X X X W X X W X X W X X G excess mix + + + = Δ Equation 17
where R is the gas constant (8.314 J mol -1 K -1 ), T the temperature in K (298 K), X i is the molar fraction of end member i (1, 2, 3 representative of calcite, magnesite and siderite respectively), is the excess free energy of mixing and W ij(k) are interaction parameters. For reasons of simplicity, we used the Davies and Navrotsky formulation for regular solid-solution (Davies and Navrostsky, 1983, Eq. 26). The binary terms (W ij ) were estimated using the model given in [START_REF] Davies | Quantitative correlations of deviations from ideality in binary and pseudobinary solid solutions[END_REF]: W cs = 20.2 kJ mol -1 , W cm = 23.9 kJ mol -1 and W ms = 4.3 kJ mol -1 where subscripts c, s and m refer to calcite, siderite and magnesite respectively. The ternary term W cms was neglected owing to the lack of available parameters to estimate its value. W ms value is low and is in agreement with the continuous domain of miscibility between the magnesite and the siderite end-members at 25°C.

Furthermore, the estimated value is in close agreement with the value measured by Chai and Navrotsky, 1996, namely 4.44 ± 0.75 kJ mol -1 . W cm and W cs values are high in agreement with

excess mix G Δ
the presence of a large miscibility gap between calcite and magnesite or calcite and siderite end-members [START_REF] Ganguly | Mixtures and mineral reactions. Minerals and rocks[END_REF].

Considering these parameters, we could estimate the solubility of sideroplesite as . This value is in agreement with the constraint obtained with the clay cation exchanger composition. Nevertheless, several sources of uncertainties in this calculation need to be highlighted: (i) the model was performed with estimated and not measured W parameters, (ii) a regular solid-solution model was used, and (iii) the ternary mixing term was neglected. In addition, the considered composition is a "bulk" composition of the grain rim and could be non-representative of the composition in contact with the porewater. Further spectroscopic experiments are planned to refine this preliminary model.

Conclusions

The microscopic and spectrometric investigations of Fe and Sr bearing phases and the relationship between cation exchanger composition and carbonate solubility products enabled the following conclusions to be drawn:

• The solubility product of dolomite in the COX formation is in agreement with the one determined by [START_REF] Hemingway | Enthalpy and Gibbs energy of formation of dolomite[END_REF] (log K dolomite = 3.57);

• The only solubility product of strontianite that agrees with the exchanger composition and the absence of this mineral phase from the Callovian-Oxfordian formation is the one determined by [START_REF] Busenberg | The solubility of strontianite (SrCO 3 ) in CO 2 -H 2 O solutions between 2 and 91°C, the association constants of SrHCO + 3 (aq) and SrCO 0 3 (aq) between 5 and 80°C, and an evaluation of the thermodynamic properties of Sr 2+ (aq) and SrCO 3 (cr) at 25°C and 1 atm total pressure[END_REF] (log K strontianite = 1.06);

• A preliminary solubility product has been estimated for the siderite like mineral present in the EST 25687 sample: Fe 0.7 Mg 0.2 Ca 0.1 CO 3 + H + ⇔ 0.7 Fe 2+ + 0.2 Mg 2+ + 0.1 Ca 2+ + HCO 3 -log K sid_COX = 0.23.

Furthermore, the very homogeneous cation exchange composition relative to Ca and Mg of the formation is completely linked to a homogeneous presence of calcite and dolomite minerals, whose equilibrium reactions control part of the porewater composition. Given the ubiquitous presence of siderite/ankerite minerals in the formation, we anticipate that the exchangeable Fe/Ca ratio of the sample EST 25687 is also valid in the whole COX formation.

Unfortunately, the value obtained in this paper must be considered only as an upper limit for this ratio, i.e. about 0.01.

With regards to Fe(III) oxi(hydr)oxide mineral phases, it is now clear that they are absent from the COX samples that were well preserved from oxidation by atmospheric O 2 .

The consideration of mineral-water and cation exchange equilibria is the basis of the porewater composition estimation models previously published in the literature [START_REF] Bradbury | A Physicochemical characterisation and geochemical modelling approach for determining porewater chemistries in argillaceous rocks[END_REF][START_REF] Coudrain-Ribstein | Quantitative study of geochemical processes in the Dogger aquifer, Paris Basin, France[END_REF][START_REF] Gaucher | Modelling the porewater chemistry of the Callovian-Oxfordian formation at a regional scale[END_REF][START_REF] Pearson | Mont Terri project -Geochemistry of water in the Opalinus clay formation at the Mont Terri Rock Laboratory[END_REF]. The present study, together with on-going URL experiments (Vinsot and Delay, 2007 (accepted)) and new data acquisitions, will help to refine these models, particularly for the redox control of the porewater. Future models and associated thermodynamic databases must, at least, lead to the following results: equilibrium with a sideroplesite or ankerite mineral, equilibrium with pyrite and overall undersaturation with regards to ferrihydrite, goethite, magnetite and hematite. (e) Provided with The Geochemist's Workbench (GWB), [START_REF] Bethke | Geochemical reaction modeling[END_REF], http://www.geology.uiuc.edu/Hydrogeology/hydro_thermo.htm.

(f) Provided with Visual Minteq, http://www.lwr.kth.se/English/OurSoftware/vminteq/. 5. The black curve is the sum of all of these contributions. (Intended for colour reproduction in print)

Figure captions Figure 1 .Figure 3 .

 captions13 Figure captions

Figure 4 .

 4 Figure 4. 77 K Mössbauer spectrum of sample EST 25687. Red, pink, green, light blue and

  Fig. 1

Figure 1 .Figure 2 Figure 3 .

 123 Figure 1. Optical microscopic observations using transmitted natural light. A, B and D: sample EST 25380; C: sample EST 25687. Glt: glauconite; Bt: biotite; Ms: muscovite; Chl: chlorite; Tur: tourmaline. (Intended for colour reproduction in print)

  Fig.4

Figure 4 .

 4 Figure 4. 77 K Mössbauer spectrum of sample EST 25687. Red, pink, green, light blue and dark blue curves refer to Mössbauer fitting components given in Table5. The black curve is the sum of all of these contributions. (Intended for colour reproduction in print)

Table 1 .

 1 Detection limits of Ba, Ca, Fe, Mg, Mn and Sr in carbonates using electron

	microprobe analysis.
	Elements	BaO	CaO	FeO	MgO	MnO	SrO
	Detection limits wt %
	oxides	0.11	0.08	0.07	0.02	0.07	0.02

Table 2 .

 2 Results of the extraction of Fe exchanged on COX samples (EST25687). The "centre" sample was very well preserved from oxidation by the air, whereas the "periphery" one was more subject to O 2 exposure.

	Location	of	the	Replicate	Exchanged
	sample in the core		number	Fe (meq/kg)
	Centre			#1	1.4
				#2	1.4
				#3	1.1
				#4	0.7
	Periphery			#1	0.9
				#2	0.3
				#3	0.4
				#4	0.4

Table 3 .

 3 Na, K, Ca, Mg and Sr contents exchanged by the cobalthexamine method[START_REF] Ciesielski | Determination of cation exchange capacity and exchangeable cations in soils by means of cobalt hexamine trichloride. Effects of experimental conditions[END_REF] on the "centre" and "periphery" samples (EST25687).

	Location of the	Replicate	Exchanged Cations (meq/kg)
	sample in the core	number
			Na	K	Ca	Mg	Sr
	Centre	#1	36	14	103	39	5
		#2	38	15	107	39	5
		#3	38	15	109	41	5
	Periphery	#1	37	14	106	42	5
		#2	35	13	98	40	5
		#3	38	14	109	44	5

Table 4 .

 4 List of Fe-bearing minerals in the Callovian-Oxfordian clay rocks, their formation, their percentage in the rock, their general chemical composition and their average iron content given in weight percent of FeO. The * indicates an exceptional high iron content analyzed in the calcite of only one sample of the Callovian-Oxfordian formations (EST 25687). n.d. = not determined (below quantification limit).

			Indicative
			% of
			phases in	Structural formulae	Eq. wt% FeO
			COX
			samples
	Silicates
	Biotite	detrital	traces	K 2 (Fe, Mg) 6-4 (Fe, Al, Ti) 0-2 (Si 6-5 Al 2-3 O 20 ) (OH, F) 4	13 -22
	Chlorite	detrital	~ 2 %	(Fe, Mg Al) 12 ((Si, Al) 8 O 20 ) (OH) 16	~ 20
	Muscovite/phengite detrital	traces	(K, Na) 2 (Fe, Mg, Fe, Al, Ti) (Si 6.4 Al 1.6 O 20 ) (OH) 4	1 -3
	Dioctahedral
	interlayer-deficient	detrital	36-71	(K, Na) x+y (Fe 2+ , Mg) x (Fe 3+ , Al) 2-x (Si 4-y Al y O 10 ) (OH) 2. nH 2 O 1.7 -5.7
	micas
	Glauconite	diagenetic	n.d.	(K) 0.8 (Fe 2+ , Fe 3+ , Mg, Al) 4 (Si 7-7.6 Al 1-0.4 O 20 ) (OH) 4. nH 2 O	9.3 -16.5
	Tourmaline	detrital	n.d. (<1 %)	(K, Na) (Fe, Mg, Li, Al) 3 Al 6 (Si 6 O 18 ) (BO 3 ) 3 (OH, F) 4	6.2-10.6
	Carbonates
	Calcite cement	sedimentary	15-95	CaCO 3	0.2 -0.8
	Core of euhedral calcite	detrital or sedimentary	n.d.		< 0.5 4 -6 *
	Calcite II	diagenetic	n.d.		0.1 -3.2
	Iron rich dolomite II/ankerite	diagenetic	< 10 %	Ca (Mg, Fe) (CO 3 ) 2	0.1 -6.0-14.4
	Siderite	diagenetic	< 5 %	FeCO 3	41
	Fe(II) -Ti-Oxide
	Ilmenite	detrital	n.d. (<1 %)	FeTiO 3	19 -29
	Sulphides				wt % Fe
	Pyrite	sedimentary to diagenetic	0.2-3	FeS 2	52 -53
	Sphalerite	sedimentary to diagenetic	n.d. (<1 %)	ZnS	0.8-10.9

Table 5 .

 5 Mössbauer parameters of sample EST 25687 at 77 K. I.S. = Isomer shift value relative to that of the α-Fe at 300 K; Γ = line width; Q.S. = quadrupolar splitting value; % =

	ratio of each component.
			I.S. mm s -1	Γ mm s -1	Q.S. mm s -1 %	Doublet structural attributions
		Doublet 1 (red)	0.40	0.34	0.61	39%	Fe(II) in pyrite
		Doublet 2 (light blue)	1.40	0.41	2.14	15%	Fe(II) in carbonates
	EST 25687 sample	Doublet 3 (dark (pink) Doublet 4 green)	1.20 1.31	0.27 0.28	3.02 3.02	19% 20%	sorbed iron) (structural and/or Fe(II) associated with clay minerals
		Doublet 5 (blue)	0.40	0.56	0.45	2%	Fe(III) associated
		Doublet 6 (green)	0.40	0.38	1.10	5%	with clay minerals

Table 6 .

 6 Comparison of computed dolomite, siderite and strontianite solubility values with tabulated values in databases available in the literature. Hummel et al., 2002, available at http ://les.web.psi.ch/TDBbook/index.htm. (d) Provided with PHREEQC2, http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/, Parkhurst and Appelo, 1999.

			Solubility value (log 10 )
	Dolomite (ordered)	Dolomite (disordered)	Siderite	FeCO 3 (pr) Strontianite
	This study, sample
	EST 25687, 6	3.29 ± 0.02	< -0.11 ± 0.10	> 0.55
	experimental points
	This study, data
	from (a), 29 experimental points	3.44 ± 0.04		N.A	N.A.
	at different depths
	This study, data
	from (b), 128 experimental points	3.36 ± 0.13		N.A	N.A.
	at different depths
	NAGRA-PSI (c)	3.57	4.12	-0.56	-0.12	1.06
	Llnl.dat (d)	2.51	4.06	-0.19		-0.31
	Minteq.v4.dat (d,e,f)	3.57	4.12	0.09		1.06
	Wateq4f.dat (d)		4.12	-0.56		1.06
	Wateq4f.dat (e)		3.57	-0.56	-0.12	1.06
	Thermo.dat (e)	2.52	4.06	-0.22		-1.08
	Chivot (g)			-0.47
	(a) Gaucher et al., 2004.
	(b) Michel et al., 2006
	(c)

Acknowledgements

This research has been financially supported by the 6 th PCRD Euratom FUNMIG program and the BRGM-ANDRA scientific partnership. Claire Beny, Fabian Delorme and Christian Gilles are acknowledged for their help with SEM, TEM and electron microprobe analyses.

We would like to thank Agnès Vinsot (ANDRA URL, Bure, PI of the PAC experiments) for providing access to core samples under good conditions with regard to oxidation preservation.

Consequently, different quadrupolar hyperfine parameters were chosen in a second stage amongst those available in the literature (e.g. in [START_REF] Stevens | Mössbauer Mineral Handbook[END_REF] for the identified phase by microscopic techniques in the samples and vice-versa. Finally, only the proportions of each Fe component were refined, thereby allowing a quantitative analysis of the sample.