A C C Mateus

A F D C Varajão

Sabine Petit
email: sabine.petit@univ-poitiers.fr

F S Oliveira

C E G R Schaefer
email: carlos.schaefer@ufv.br

Ana Carolina

Campos Mateus

Mineralogical and geochemical signatures of Quaternary pyroclasts alterations at the volcanic Trindade Island, South Atlantic

Keywords: Palagonite, Halloysite, Zeolites, Infrared

published or not. The documents may come

Introduction

The Trindade Island is a small Brazilian island of ~13 km 2 and located in the South Atlantic (Fig. 1). The Island is part of an extensive east-west-oriented underwater volcanic chain, called Vitória-Trindade, and constitutes the upper portion of a volcanic building of ~5.2 km high. The Vitória-Trindade Chain corresponds to the western extension of the Trindade Victory Fracture Zone, located at 18°40' in the Mid Atlantic Ridge [START_REF] Alves | Zona de Fratura de Vitória-Trindade no oceano atlântico sudeste e suas implicações tectônicas[END_REF]. The Island is formed by five different volcanic episodes of lava flows and intrusions of poor silica rocks with accentuated sodium-alkaline content [START_REF] Almeida | Geologia e petrologia da Ilha de Trindade. er i o ráfico do Instituto Brasileiro de Geografia e Estatística[END_REF]. These volcanic episodes were described by [START_REF] Almeida | Geologia e petrologia da Ilha de Trindade. er i o ráfico do Instituto Brasileiro de Geografia e Estatística[END_REF] from bottom to top as: Trindade complex, Desejado sequence, Morro Vermelho Formation (MV), Valado Formation and Vulcão do Paredão Formation (VP) (Fig. 1). The volcanic spills are overlain by the Holocene deposits that represent a small portion of the stratigraphic units occurring on the island [START_REF] Castro | Geologia das ilhas oceânicas brasileiras[END_REF]) (Fig. 1).

Particularly in MV and VP formations, there are several pyroclasts such as lapilli and ash tuffs containing rotational lumps, blocks, aggregates and agglutinates of melanefelintic, basanite and tephrytic lava. [START_REF] Cordani | Idade do vulcanismo do Oceano Atlântico Sul[END_REF] suggested an eruption age by potassium-argon dating method of 0.17 Ma for the MV deposits. However, [START_REF] Pires | New 40 Ar/ 39 Ar ages and revised 40 K/ 40 Ar* data from nephelinitic-phonolitic volcanic successions of the Trindade Island (South Atlantic Ocean)[END_REF] a recorded a 0.25 Ma age for the VP volcanic deposits and suggests that this volcanism represents the most recent volcanic activity of the Brazilian territory.

Studies of volcano stratigraphy and eruption geological models in the area of the Paredão Volcano [START_REF] Pasqualon | Estratigrafia, petrologia e padrões de porosidade dos depósitos do Vulcão do Paredão, Ilha da Trindade, Brasil[END_REF] and Morro Vermelho Formation [START_REF] Luz | Estudo do Vulcanismo da Ilha da Trindade: estratigrafia e petrologia da Formação Morro Vermelho[END_REF] showed intercalation of nephelinitic flows and pyroclastic deposits, leading to the interpretation of heterogeneous volcanism characterized by an early stage of the Hawaiian style eruption [START_REF] Sumner | Spatter[END_REF][START_REF] Parcheta | Hawaiian fissure fountains 1: decoding deposits-episode 1 of the 1969-1974 Mauna Ulu eruption[END_REF][START_REF] Rader | Eruption conditions of spatter deposits[END_REF], and a final phase of the Strombolian style. According to [START_REF] Pasqualon | Estratigrafia, petrologia e padrões de porosidade dos depósitos do Vulcão do Paredão, Ilha da Trindade, Brasil[END_REF] and [START_REF] Luz | Estudo do Vulcanismo da Ilha da Trindade: estratigrafia e petrologia da Formação Morro Vermelho[END_REF], the Hawaiian style is represented, in the study area, exclusively by a'a flows but without describing the a´a morphotypes [START_REF] Murcia | Late Holocene lava flow morphotypes of northern Harrat Rahat, Kingdom of Saudi Arabia; implications for the description of continental la a fields[END_REF]. The Strombolian style is represented by pyroclasts deposits of tuff breccia and lapilli being composed mainly of basaltic scoria [START_REF] Pasqualon | Estratigrafia, petrologia e padrões de porosidade dos depósitos do Vulcão do Paredão, Ilha da Trindade, Brasil[END_REF][START_REF] Luz | Estudo do Vulcanismo da Ilha da Trindade: estratigrafia e petrologia da Formação Morro Vermelho[END_REF].

The petrological and geochemical studies of the olivine-nephelinites in the VP rocks showed strongly fractionated REE patterns in the melanephelinites and basanitestephrites, suggesting the presence of garnet as a probable residual phase and generation of melt at about 100 km depth [START_REF] Marques | Petrology, geochemistry and Sr-Nd isotopes of Trindade and Martin Vaz volcanic rocks (Southern Atlantic Ocean)[END_REF]. Bongiollo et al. (2015) recently used geochemical modeling to show that the nephelinites in Trindade Island were from magmas derived at a minimum of 1490 °C and 3 Gpa (>100 km depth).

Studies to date have focused on the petrogenesis and age of lava flows and intrusions on Trindade Island.

Except for studies of alteration of olivine crystals of the pyroclasts [START_REF] Mateus | Alteration of olivine in volcanic rocks from Trindade Island, South Atlantic[END_REF], there is still a deficiency of studies with emphasis on alteration of the rocks, that evolve specific factors like young volcanic parent materials, interaction with seawater and climate conditions. Detailed studies analyzing the features of palagonization and zeolitization, which are constantly found on oceanic islands with basic rocks consisting of sideromelane altered to palagonite (Wentworth, 1926;[START_REF] Stearns | Geology and ground-water resources of the island of Oahu, Hawaii[END_REF][START_REF] Nakamura | Stratigraphic studies of the pyroclastics of Oshima Volcano deposited during the last fifteen centuries. II. Activity of parasitic volcanoes[END_REF][START_REF] Einarsson | The ring-mountains Hverfiall, Lúdent, and Hrossaborg in northern Iceland. Vísindafélag Íslendinga[END_REF][START_REF] Thorseth | A textural and chemical study of Icelandic palagonite of varied composition and its bearing on the mechanism of the glass-palagonite transformation[END_REF] and to zeolite (Nayudu, 1964;[START_REF] Hay | Petrology of Palagonite Tufts of Koko Craters[END_REF][START_REF] Iijima | Authigenic zeolites in zeolitic palagonite tuffs on Oahu, Hawaii[END_REF][START_REF] Kristmannsdóttir | Zeolite zones in geothermal areas, Iceland[END_REF], can be used to understand the mechanisms involved in the transformations of pyroclatic rocks from the Trindade Island.

Therefore, this study used combined macromorphological, micromorphological, mineralogical and geochemical techniques to examine the composition, alteration products, and origin of the pyroclasts in MV and VP formations.

Methodology

The pyroclastic rocks were collected from the Holocene VP Formation (the latest event)

and the Late Quaternary MV formation. Macromorphologically, the coloration and the mineral constituents of the rocks were observed with the aid of a magnifying glass of 20x. The pyroclasts were measured and classified according to the systematic of the IUGS [START_REF] Le Maître | Igneous Rocks: A Classification and Glossary of terms[END_REF] taking into account the size of the clasts. The petrological description including mineralogy, texture, estimation of the percentage of minerals and photographic images were performed in polished thin sections using a Zeiss microscope coupled with a camera. More detailed mineralogical information was obtained on the samples using X-Ray Diffraction (XRD) technique. The samples were initially gently powdered in agate mortar and sieved with 250 mesh. The samples were analyzed at a scanning interval of 2 to 70 °2θ with a step size of 0.02 ° 2θ/s using a CuKα radiation and power 45KV and 40mA on a Panalytical diffractometer at the Universidade Federal de Ouro Preto (DEGEO/UFOP), Brazil. The diffractograms were interpreted with X'pert HighScore Plus software and compare with standards [START_REF] Brindley | Crystal Structures of Clay Minerals and Their Xray Identification[END_REF]. The Transform Fourier Thermo Nicolet, Nexus 5700 series infrared spectrometer coupled with Thermo Scientific Nicolet Continum microscope was used to complement the XRD mineralogical analyses at the IC2MP institute, Université de Poitiers, France. These analyses were performed on clay fractions and point analyses in thin sections. In microscope the near-infrared spectra (8000-4000 cm -1 ) were obtained using source of white light, beamsplitter CaF 2 , resolution of 4cm -1 , optical velocity of 0.3165 cm s -1 and 100 scans. The spectra of clay fraction were obtained with the same condition of acquisition in thin sections, but with velocity of 0.12659 cm s -1 .

Image analyses of the clay minerals were performed with a JEOL 2011 Bruker Esprit Transmission Electron Microscope (TEM) at CinaM-CNRS, Aix Marseille University.

The suspended clay separates were deposited onto carbon coated Formvar film Cu grids. The palagonitized regions were scraped and then deposited in resin to be made cuts in ultramicrotome. The cuts were deposited in grids.

The chemical analyses of the major and trace element compositions of the samples were measured in the ICP-OES Agilent Technologies 725 while the rare earth elements (REE) were performed in the ICP-MS Agilent Technologies 7700 at DEGEO/UFOP

LGqa Laboratory. For total digestion of 0.1g of each sample, 1ml of hydrogen peroxide, 3ml of HCl at 10mol/L, 6 ml of HNO 3 to 10mol/L, 20ml of HNO 3 to 2 mol/L and 4ml of HF concentrate were used. The percentage of SiO 2 was calculated in a relative way by the difference to 100% in the sum of the main elements and LOI.

Back-scattered electron images and semi-quantitative chemical analyses by Electron Dispersive X-ray (EDX) were made to analyze the habit and chemical compositions, respectively, of the volcanic glass and palagonite. These analyzes were made in Scanning Electron Microscope (SEM) coupled with EDX Jeol JSM-6510 with an operating voltage of 20KV.

The microanalyses of the olivines, pyroxenes, zeolites, spinels, sideromelane and palagonite were performed with electron microprobe JEOL JXA-8230 at the Microanalysis Laboratory of the DEGEO/UFOP. The acceleration and current conditions were 15 kV and 20 nA, and corrections of the common ZAF matrix were applied. The counting time in the peaks/background were 10/5s for all elements except the sodium that was 20/10s (Na, Si, Al, Mg, Fe, Cr, Ti, Ca, Ni, K, Mn). The punctual analyses were calibrated with jadeite-TAP, rutile-LIF, sanidine-PETJ, magnesium-TAP oxide, chromium-LIF oxide, AN100-PETJ, corindon-TAP, rodonite-LIF, quartz-TAP, magnetite-LIF. The FeO was considered as the amount of total iron obtained through the microprobe.

Results

The pyroclastic rocks collected in the VP (pyroclast 1) and MV formations (pyroclasts 2 and 3) were classified according to their sizes [START_REF] Le Maître | Igneous Rocks: A Classification and Glossary of terms[END_REF]. The pyroclasts 1 and 2 are classified as tuff breccia deposit according to diagram of [START_REF] Németh | Practical volcanology -Lecture notes for understanding volcanic rocks from field based studies[END_REF].

The pyroclasts 1 and 2 contain more than 75% of angular and subangular fragments larger than 64.0mm (blocks) (Figs. 2A,C). In addition, pyroclast 1 contains fragments between 2.0 and 64.0mm (lapilli; [START_REF] Fisher | Rocks composed of volcanic fragments[END_REF] in smaller proportions (Fig. 2B). The pyroclast 3 belongs to a lapilli deposit containing more than 75% of 2.00 to 64.00mm (lapilli) fragments (Figs. 2D,E). Macroscopically, all the pyroclasts have dark gray color with some brownish to reddish regions, and vesicular and amygdaloid structures (Fig. 2). The matrix of the pyroclasts contain scattered small green crystals (~2.0 mm).

Owing to the fine-grained size (<1.0 mm) of the matrix constituents, it is difficult to distinguish their mineral composition in macroscopic view.

Microscopically the pyroclast 1 are altered and show reddish brown vitreous matrix (Fig. 3A) that is attributed to exposure to intense alteration. Some regions of pyroclasts 2 have grayish stains because of the presence of unaltered portions of the rock (Fig. 3E).

However, fragments in pyroclast 3 are yellowish brown in color (Fig. 3J). All the pyroclasts have vesicular and amygdaloid structures and hypocrystalline textures (Figs. 3A,D,J). The pyroclasts are composed of a pale brown vitreous mass in 50% of thin section area, which are isotropic in crossed polarized light and occurs around olivine, pyroxene and spinel crystals. Bulk rock XRD analyses show that the matrix of these pyroclasts are essentially composed of biotite, goethite, ilmenite, anatase, magnetite, hematite, pyroxene and olivine [START_REF] Mateus | Alteration of olivine in volcanic rocks from Trindade Island, South Atlantic[END_REF].

Glass -The vitreous mass (glass) is classified as sideromelane due to the basaltic composition of the pyroclasts (Table 1; Figs. 4B,C). The sideromelane changes to a reddish brown (Fig. 3B) and yellowish brown (Fig. 3K) materials identified as palagonites. In pyroclast 1, the glass is totally palagonitized and it is possible to find only sideromelane in pyroclasts 2 and 3. The reddish colorations are due to a high degree of alteration and high Fe content. In some portions, palagonite is whitish (Fig. 3K) due to leaching of Fe in the reddish brown and yellowish brown palagonite. This process is similar to what was observed in palagonites of Iceland [START_REF] Thorseth | A textural and chemical study of Icelandic palagonite of varied composition and its bearing on the mechanism of the glass-palagonite transformation[END_REF].

Chemical analyses of the palagonite showed a loss of alkali and alkaline-earth elements (Na, Ca, Mg) and enrichment of Fe and water in relation to the sideromelane (Table 1) in the reddish and yellowed regions. This composition is similar to those found in palagonites from previous studies such as Peacock (1926[START_REF] Peacock | Chlorophaeite, sideromelane, and palagonite from the Columbia River Plateau[END_REF], [START_REF] Thorseth | A textural and chemical study of Icelandic palagonite of varied composition and its bearing on the mechanism of the glass-palagonite transformation[END_REF], Stroncik andSchmincke (2001, 2002) and Pauly et al. (2011). The infrared analyses in the palagonitized regions of pyroclasts 1 and 2 showed the presence of halloysite (Fig. 5). Notably, the characteristic bands of halloysite are observed at about 7070, 7200, and 4530 cm -1 . The two former bands are attributed to the first overtones of the Al 2 OH stretching vibrations and the latter band to the Al 2 OH stretching plus bending combination mode [START_REF] Madejová | Application of vibrational spectroscopy to the characterization of phyllosilicates and other industrial minerals[END_REF]. Images of TEM confirm the presence of tubular halloysite in the clay fraction of the altered and palagonitized portions of the pyroclasts. The diameter of the tubes ranges from 0.1 to 0.2m (Fig. 6). Figure 6B shows a halloysite crystal and a fragment of volcanic glass.

Olivine -Olivine is euhedral, forsterite (Fo 80 ) in composition [START_REF] Mateus | Alteration of olivine in volcanic rocks from Trindade Island, South Atlantic[END_REF] and makes up 20% of the rock in all the pyroclasts. The olivine phenocrysts in pyroclast 1 are essentially altered and fractured with axis sizes greater than 1mm (Fig. 3A). The fractures and edges of these altered and fractured olivine phenocrysts in pyroclasts 1 are filled and corroded with reddish dark brown colored iddingsite (Fig. 3A). However, well preserved olivine phenocrysts with sizes ranging from 0.5mm to 3mm dominate pyroclasts 2 and 3 (Figs. 3D,L).

Pyroxene -The pyroxenes were observed as very small crystals about of 70 µm in the form of microliths in the vitreous matrix and present in trace amount (5 %) in pyroclast 1 (Fig. 3B). Pyroxenes in pyroclast 2 are mostly tiny (20 µm), dispersed in the matrix and surround the olivine phenocrysts with high interference colors, and are present in small amount (15 %). However, largest crystals of ⁓120 mm are rarely found (Fig. 3F).

In the pyroclast 3, prismatic pyroxenes, constituting about 25 %, are tiny (⁓20 µm) and occur within the microlytic matrix and surrounding the olivine phenocrysts (Fig. 3L).

Electron microprobe micro-chemical analyses show that the pyroxene in pyroclasts 1 and 2 are diopside (Table 2; Fig. 7). TEM analyses also show occurrence of fragments of pyroxene in clay fraction (Fig. 6D). Spinels -Spinels are commonly observed dispersed in the matrix of the pyroclasts, and within the fractures and edges of olivine phenocrysts in varying trace amounts (5 -10 %; Fig. 3C). The crystals are anhedral and are about 0.05mm in size. Electron microprobe analyses shows that the spinels are titaniferous magnetites, and some crystals display Cr-rich and Cr-poor zones (Table 3; Figs . 4E,G,H). Due to the degree of alteration of the spinels, it was difficult and nearly impossible to determine their chemical composition as none of the analysis was close to 100 %.

Zeolite -In pyroclast 2, amygdales and microfractures are partially to completely fill by zeolites (Figs. 3D,E,H). The zeolites are small pseudorhombohedral crystals (Fig. 3E), mostly less than 20 µm, with low interference colors, and constitute about 10% in thin section observations. The zeolites filled microfractures sometimes crosscut the olivine crystals (Figs. 3G,I) and vesicles (Fig. 3I), suggesting their latter and secondary crystallization. The zeolites also crystallize in the walls of the palagonitized portions (Fig. 4F).

Electron microprobe analyses of the zeolites in pyroclast 2 shows that they are predominantly heulandite-Ca and chabazite-Ca (Table 4; Figs. 4F,G). Both the heulandite-Ca and chabazite-Ca are found in the amygdales filled zeolites while those in the microstructure veins are essentially chabazite-Ca. The average calculated structural formula is (Ca 3.17 Na 0.85 K 4.28 ) for the heulandite-Ca and chabazite-Ca, respectively. The Si:Al ratios are relatively low in the heulandite-Ca (2.08) and chabazite-Ca (1.74).

Geochemical of pyroclasts -

The pyroclasts are undersaturated with silica (~37 %). Na 2 O content is higher than K 2 O in pyroclasts 1 and 2 but lower in pyroclast 3 (Table 5). All the pyroclasts plot in the ultrabasic rocks and foidites fields on the Na 2 O + K 2 O vs SiO 2 TAS classification diagram (Fig. 8; Les [START_REF] Bas | A chemical classification of volcanic rocks based on the total alkali-silica diagram[END_REF]. The high FeOt, MgO, TiO 2 and CaO contents in all the pyroclasts (Table 5) are probably due to the presence of ferromagnesian minerals such as magnetites, olivines, ilmenites and clinopyroxene.

The pyroclasts are also enriched in trace elements, such Ba, Cr, Sr, V, Zr, Zn and Ce (Table 5). The elevated trace elements contents are related to the presence of pyroxenes as shown by [START_REF] Panina | Silicate-carbonate-salt liquid immiscibility and origin of the sodalite-haüyne rocks: study of melt inclusions in olivine foidite from Vulture volcano, S. Italy[END_REF] who documented the enrichments of trace elements in clinopyroxenes in foidian olivine in southern Italy. Moreover, the pyroclasts display strong enrichments of light rare earth elements (LREE) over the heavy rare earth elements (HREE) (∑LREE/∑HREE = 12.38 to 13.71; La/Yb= 33.55 to 40.85, Table 5.5 and Fig. 9).

Discussions

The eruption type and the alteration process of pyroclasts

According to [START_REF] Walker | veins and vesicles partially and totally filled by zeolites. (e) PPL photomicrograph from the rhombohedral zeolites with low relief and glass volcanic grayish. (f) XPL photomicrograph from the pyroxenes intercrossed. (g) PPL photomicrograph showing vein of zeolite cutting olivine crystal. (h) PPL photomicrograph showing hypocrystalline structure and partial vesicles and fully filled by zeolites. (i) XPL photomicrograph from vein of zeolite cutting vesicles filled by zeolite. Pyroclast 3: (j) XPL photomicrograph from the fragments of 2mm pyroclasts with vesicles structure. (k) PPL photomicrograph showing fully palagonitized glass and region with white palagonite. (l) XPL photomicrograph from the hypocrystalline matrix with vesicles and small crystals of pyroxenes around phenocrystals of fractured olivines. Some olivine crystals are euhedral. XPL = cross polarized light; PPL = plane polarized light[END_REF], the eruptions during the formation of pyroclastic deposits can be regarded as Strombolian-type by producing initially coarse materials, with a restricted range of sizes. This affirmation is attested in this study by the presence of blocks and lapilli. Additionally, the high vesicularity and fluidal shape presented by the fragments, that indicate degassing and magmatic fragmentation, are characteristic of Strombolian-type eruption (Vergniolle and Brandeis, 1996;Vergniolle et al., 1996;[START_REF] Houghton | Shallow-seated controls on styles of explosive basaltic volcanism: a case study from New Zealand[END_REF]. The Strombolian-type eruption is supported by studies of [START_REF] Pasqualon | Estratigrafia, petrologia e padrões de porosidade dos depósitos do Vulcão do Paredão, Ilha da Trindade, Brasil[END_REF] and [START_REF] Luz | Estudo do Vulcanismo da Ilha da Trindade: estratigrafia e petrologia da Formação Morro Vermelho[END_REF] on pyroclasts deposits in the areas of this study.

The main alteration products of pyroclasts are: palagonite, iddingsites, halloysite and zeolites.

The palagonite is an alteration product of volcanic glass (like sideromelane) and its presence is characterized by regions with reddish and yellowish color due to the relative concentration of iron due to the loss of more mobile chemical elements such as Na, K, Mg [START_REF] Stroncik | Palagonite-a review[END_REF]. Several authors consider that the palagonite is the first stable product of aquatic mafic glass alteration (Peacock, 1926;[START_REF] Hay | Petrology of Palagonite Tufts of Koko Craters[END_REF][START_REF] Staudigel | Alteration of basaltic glass: mechanisms and significance for the oceanic crust-sea water budget[END_REF][START_REF] Furnes | Chemical-changes during progressive subaerial palagonitization of a subglacial olivine tholeiite hyaloclastitea microprobe study[END_REF][START_REF] Thorseth | A textural and chemical study of Icelandic palagonite of varied composition and its bearing on the mechanism of the glass-palagonite transformation[END_REF]. [START_REF] Bunsen | Beitrag zur Kenntnis des isländischen Tuffgebirges[END_REF] and [START_REF] Correns | Über einen Basalt vom Boden des atlantischen Ozeans und seine Zersetzungsrinde[END_REF] were the first to observe that the alteration of sideromelane to palagonite results in loss of some elements. An explanation for the formation of palagonite would be a hydrovolcanic eruption that occurred when the ascending magma came into contact with sea water at high tide [START_REF] Stroncik | The evolution of palagonite: crystallization, chemical changes, and element budget[END_REF]. The process of palagonitization by the hydrovolcanic eruption [START_REF] Németh | Review of Explosive Hydrovolcanism[END_REF] has been previously described in volcanic islands, such as the Azores, Hawaii (Wentworth, 1926;[START_REF] Stearns | Geology and ground-water resources of the island of Oahu, Hawaii[END_REF] and Oshima [START_REF] Nakamura | Stratigraphic studies of the pyroclastics of Oshima Volcano deposited during the last fifteen centuries. II. Activity of parasitic volcanoes[END_REF]; and in lakes or low ground with a high groundwater in Auckland [START_REF] Searle | Auckland volcanic district in New Zealand volcanology[END_REF], Idaho [START_REF] Hamilton | Menan Buttes, cones of glassy basalt tuff in the Snake River Plain, Idaho[END_REF] and Iceland [START_REF] Einarsson | The ring-mountains Hverfiall, Lúdent, and Hrossaborg in northern Iceland. Vísindafélag Íslendinga[END_REF]. According to Bonati (1965), hydration of the lava is probably faster at higher temperatures when the lava is still in a molten state. During this phase, the hydrous lava forms directly hydrated glass (palagonite). This process seems to have occurred in the pyroclast 2 because there is a large amount of yellowish brown palagonite with little sideromelane. Following the complete consolidation of magma and the alteration of volcanic glass as a result of seawater interaction, the pyroclasts underwent a second phase of alteration due to exposure to meteoric water. The presence of halloysite in the palagonitized sideromelane attested by infrared and MET analyses; the crystals of olivine and amigdals cut by zeolites veins, the presence of zeolites crystallized in palagonitized regions; and the presence of iddingsitized olivines (see [START_REF] Mateus | Alteration of olivine in volcanic rocks from Trindade Island, South Atlantic[END_REF] corroborate this proposition.

Alterations of sideromelane to zeolites have been described in palagonite tuffs from Oahu, Hawaii [START_REF] Hay | Petrology of Palagonite Tufts of Koko Craters[END_REF][START_REF] Iijima | Authigenic zeolites in zeolitic palagonite tuffs on Oahu, Hawaii[END_REF] and Iceland (Nayudu, 1964). The probable formation of zeolites in pyroclast 2 would to be the reaction of sideromelane with meteoric fluid in temperature around of 100°C. According to [START_REF] Kristmannsdóttir | Zeolite zones in geothermal areas, Iceland[END_REF], heulandite, stilbite and analcime may form at temperatures below 100°C. [START_REF] Barrows | Zeolitization of Miocene volcanoclastic rocks, southern Desatoya Mountains, Nevada[END_REF] In this study, the meteoric water reacted with the vitreous matrix of the rock to form the palagonite and precipitated the Si, Al, Ca, Na, and K in the form of zeolites in the adjacencies of the palagonite, similar to the one described by [START_REF] Hay | Petrology of Palagonite Tufts of Koko Craters[END_REF] and [START_REF] Iijima | Authigenic zeolites in zeolitic palagonite tuffs on Oahu, Hawaii[END_REF] in zeolithic palagonite tuffs. The occurrence of zeolites impoverished in silica is due to the low silica contents in the pyroclasts and primary basaltic magma.

In all pyroclasts occur olivines iddingsitized by meteoric water. The difference in the degree of preservation or alteration of olivine phenocrysts between VP (pyroclast 1) and MV (pyroclasts 2 and 3) is related to their position on the sampling profile [START_REF] Mateus | Alteration of olivine in volcanic rocks from Trindade Island, South Atlantic[END_REF]. The pyroclast 1 was collected at higher altitude and in a more humid region, exposing it to greater leaching and alteration processes compared to pyroclasts 2 and 3 that were collected from much lower altitude with less exposure to alterations. [START_REF] Mateus | Alteration of olivine in volcanic rocks from Trindade Island, South Atlantic[END_REF] argue that the presence of iddingsite in the high altitude and humid region indicates an advanced alteration stage of the olivine crystals during weathering.

Geochemical considerations

The presence of spinels enriched with chromium and the LREE enrichment indicate that the magma has a mantelic origin [START_REF] Irvine | Chromian spinel as a petrogenetic indicator[END_REF].

The strongly fractionated REE patterns suggest the presence of garnet as a probable residual phase, implying that melt generation occurred at depths of about 100 km. This interpretation is corroborated by the earlier work of [START_REF] Marques | Petrology, geochemistry and Sr-Nd isotopes of Trindade and Martin Vaz volcanic rocks (Southern Atlantic Ocean)[END_REF], who suggested a garnet magma source at deeper depth (~100 km) for the olivine-nephelinites in the VP Formation and proven by Bongiollo et al. (2015) through geochemical modeling.

Conclusions

The Quaternary pyroclastic rocks of the Vulcão do Paredão (Holocene) and Morro Vermelho (Pleistocene) showed the following products of alteration:

1-sideromelane palagonitized through the interaction of magma with the sea water and subsequently with meteoric water; 2-particularly in the pyroclast 2, the palagonite alters to form zeolite and halloysite through the passage of hydrothermal fluids and meteoric water during weathering.

The main factors justifying this assertion are:

1-in the palagonitized regions there is a loss of bases (Na, Ca, Mg) and an enrichment of Fe and water in relation to the sideromelane; 2.1-the chemical analysis by microprobe showed the presence of zeolites alongside the palagonite; 2.2-the point-source analyses of infrared allow to identify halloysite in the palagonite of pyroclast with totally altered sideromelane; 2.3-TEM observations confirm the presence of halloysite in the palagonitized regions.

In addition, the presence of palagonite may indicate a hydrovolcanic eruption for these deposits. 54.86 63.53 60.28 77.24 89.11 90.91 86.68 90.06 89.68 37.28 62.56 74.00 64.06 99.24 98.55 98.41 63.25 80.68 77.29

CNRS -Aix Marseille

  described heulandite, clinoptilolite, mordenite, analcime, thomsonite, erionite and chabazite in thick Miocene volcaniclastic sequences in Nevada attributed to a process involving the circulation of low temperature meteoric fluid in an open hydrologic system. Höller and Wirsching (1980) observed the formation of chabazite, phillipsite, and analcime in the reaction of nephelinite with a solution of 0.01 N NaOH at 150°C in open system.

  University) for assistance in the TEM observations, the Microanalysis Laboratory of the Universidade Federal de Ouro Preto, member of the Microscopy and Microanalysis Network of Minas Gerais State/Brazil/FAPEMIG and to the Laboratory of Microanalysis and Electronic Microscopy of the Microscopy Center of the Universidade Federal de Minas Gerais for the mineral chemical analyses. Lastly, we would like to show our appreciation to the Laboratory of X-Ray Diffraction of DEGEO/UFOP DRX and laboratory IC2MP, Université de Poitiers for the mineralogical analyses. The authors would like to thank the reviewers Karoly Nemeth and Sorin C. Barzoi, who greatly improved our manuscript.

Figure 1 :

 1 Figure 1: Geological map of Trindade Island and the regions of collection of pyroclasts 1, 2 and 3. Modified of Patrício (2012).

Figure 2 :

 2 Figure 2: (a) Pyroclast 1 of Vulcão do Paredão formation showing reddish-colored alteration features. On the right, sample where the blade was made for the micromorphological description. (b) Image showing lapilli of different sizes in pyroclast 1. (c) Pyroclast 2 of the Morro Vermelho formation, with the altered edges of

Figure 3 :

 3 Figure 3: Pyroclast 1: (a) PPL photomicrograph from the euhedral olivine phenocrystals with altered borders for iddingsite wrapped by reddish brown matrix. (b) PPL photomicrograph from the prismatic pyroxene near vesicles wrapped in palagonite. (c) Reflected light photomicrograph showing the crystals of spinel in the matrix.

Figure 4 :

 4 Figure 4: SEM photomicrograph and point of microchemical analyses by micropobre of pyroclasts. Pyroclast 1: (a) Punctual analysis of the palagonite in the wall and around a vesicle, (e) Punctual analysis of two spinel crystals.

Figure 5 :

 5 Figure 5: (a) NIR analysis of clay and palagonitized portions of pyroclast 1 and 2 showing the presence of halloysite. The clay analysis was used to compare the positions of the signals between 7000 and 7230cm -1 , since the signal in the palagonitized region is weak due to thickness and resin of the slender section. The spectrum of resine and glass was obtained to show the regions when occurs signal of resine and glass in spectrum of thin section. b, c and d) XPL photomicrograph in regions palagonitized and points of the analysis of the pyr. 1 (b and c) and pyr. 2 (d). Pyr=pyroclasts.

Figure 6 :

 6 Figure 6: TEM images of halloysites in clay fraction of altered regions of the pyroclast 1 (a), 2 (c), and 3 (e) and halloysites in regions with palagonitization (pyroclast 1-b, 2-d and 3-f). In all figures the arrows indicate the tubular halloysite crystals. The figure b

Figure 7 :

 7 Figure 7: Morimoto diagram (1988) modified showing the composition of the clinopyroxene. The square indicates the pyroclasts 1 and 2.

Figure 8 :

 8 Figure 8: TAS diagram (Les Bas et al. 1986) for the pyroclasts 1 (circle) of the Vulcão do Paredão and, 2 (cross) and 3 (square), both of Morro Vermelho formation.

Figure 9 :

 9 Figure 9: Typical chondrite-normalized (McDonough and Sun,1995) rare-earth-element (REE) plots of pyroclasts.

  8.3 (Si 21.58 Al 10.34 )O 72 .26H 2 O and Ca 1.31 (A l4.42 Si 7.6 O 24 ).13H 2 O

Table 1 :

 1 EDX analyses of sideromelane and palagonitized regions. SiO 2 25.52 29.82 28.37 32.36 54.62 53.92 50.35 54.87 55.64 16.74 30.84 34.66 30.61 40.37 39.88 39.91 31.85 41.83 40.22 Al 2 O 314.76 17.79 14.05 15.67 25.01 23.70 23.28 24.62 24.87 16.24 15.05 20.60 21.95 13.18 13.05 13.03 23.33 8.71 7.64

			1-palagonite			2-sideromelane			2-palagonite		3-sideromelane		3-palagonite
			Figure 4A				Figure 4C				Figure 4D, F			Figure 4B			Figure 4B
	N°	1	2	3	4	1	2	3	4	5	1	2	3	4	1	2	3	4	5	6
										%
	Na 2 O	0.30 0.22 0.23 0.49 5.72 5.51 5.44 6.11 6.21 0.23	0.45	1.12	0.42 3.56 3.65 3.68 0.15 0.04 0.07
	MgO	1.34 1.86 1.65 3.05 0.11 0.69 0.66 0.14 0.17 0.41	2.24	1.27	0.74 5.04 4.99 5.02 0.72 0.86 0.73
	ZnO	0.00 0.02 0.00 0.19 0.07 0.04 0.00 0.04 0.02 0.00	0.00	0.00	0.00 0.09 0.01 0.00 0.03 0.07 0.00
	FeO	7.41 8.23 8.60 9.58 0.93 1.26 1.24 0.74 0.82 0.33	4.59	3.18	1.06 11.47 11.48 11.43 4.34 14.93 14.10
	SrO	0.00 0.00 0.00 0.00 0.01 0.04 0.05 0.04 0.01 0.02	0.16	2.60	0.30 0.00 0.00 0.00 0.00 0.00 0.00
	CaO	2.21 2.18 2.94 8.20 1.63 4.18 4.44 2.11 1.07 1.74	4.26	5.27	5.58 14.72 14.51 14.49 1.53 4.37 4.43
	Cr 2 O 3 0.00 0.00 0.00 0.30 0.00 0.09 0.14 0.00 0.06 0.11	0.00	0.00	0.08 0.00 0.04 0.05 0.03 0.00 0.04
	P 2 O 5	0.54 0.47 0.20 2.30 0.38 0.87 0.19 0.83 0.09 0.48	0.83	1.16	1.90 0.80 0.88 0.83 0.33 1.11 1.24
	NiO	0.05 0.02 0.00 0.01 0.00 0.02 0.00 0.00 0.02 0.00	0.01	0.03	0.02 0.00 0.00 0.00 0.04 0.00 0.03
	K 2 O	0.12 0.15 0.18 0.09 0.23 0.13 0.24 0.15 0.16 0.34	0.57	3.60	1.06 3.80 3.91 3.85 0.48 0.58 0.65
	MnO	0.07 0.06 0.08 0.09 0.03 0.00 0.06 0.00 0.02 0.00	0.07	0.18	0.00 0.19 0.15 0.17 0.00 0.00 0.00
	SO 3	0.04 0.06 0.02 0.13 0.02 0.06 0.07 0.01 0.02 0.47	0.02	0.04	0.07 0.19 0.18 0.16 0.13 0.01 0.00
	TiO 2	2.51 2.66 3.97 4.79 0.36 0.42 0.53 0.39 0.49 0.17	3.48	0.29	0.28 5.84 5.82 5.80 0.28 8.17 8.15
	Total

Table 2 :

 2 Micropobre analyses with ions calculated for clinopyroxene.

	497
		1-Diopsidie		2-Diopsidie		498
	Region	Core	499 Edge Interm. Edge Edge Edge
	SiO 2	41.33	% 42.79 47.36 47.41 47.30 46.41 500
	TiO 2	6.54	5.61	2.95	3.17 3.48	501 3.97
	Al 2 O 3 FeO	9.39 7.70	8.58 7.61	4.37 7.50	5.27 5.33 6.43 6.74	5.42 502 7.43
	MgO	10.93	503 11.72 16.87 13.67 13.42 13.08
	MnO	0.06	0.05	0.14	0.12 0.12	504 0.13
	CaO	23.56	23.87 21.62 23.30 23.73 23.76
	Na 2 O	0.43	0.46	0.29	0.29 0.32	0.35
	Cr 2 O 3	0.00	0.00	0.00	0.00 0.00	0.00
	NiO	0.00	0.00	0.00	0.00 0.00	0.00
	K 2 O	0.03	0.02	0.02	0.05 0.03	0.02
	Total	100.01	100.71 101.12 99.69 100.47 100.58
		Calculation based on 6 oxygens
	Si	1.57	1.61	1.76	1.78 1.77	1.74
	Ti	0.19	0.16	0.08	0.09 0.10	0.11
	Al	0.42	0.38	0.19	0.23 0.23	0.24
	Fe	0.25	0.24	0.23	0.20 0.21	0.23
	Mg	0.62	0.66	0.93	0,76 0.75	0.73
	Mn	0.00	0.00	0.00	0.00 0.00	0.00
	Ca	0.96	0.96	0.86	0.94 0.95	0.95
	Na	0.03	0.03	0.02	0.02 0.02	0.03
	Cr	0.00	0.00	0.00	0.00 0.00	0.00
	Ni	0.00	0.00	0.00	0.00 0.00	0.00
	K	0.00	0.00	0.00	0.00 0.00	0.00
	Ens	0.34	0.35	0.46	0.4	0.39	0.38
	Fs	0.13	0.13	0.12	0.11 0.11	0.12
	Wo	0.53	0.52	0.42	0.49 0.50	0.50

Table 3 :

 3 Chemical analysis by microprobe of the spinels of the pyroclasts 1, 2 and 3.

	1	2	3
	Fig. 4E	Fig.4G	Fig. 4H

Region Edge Core Edge Core Edge Edge Core Core Edge Core Edge

	No.	1	2	3	4	1	2	3	4	1	2	3
						%
	SiO 2	0.04 0.07 0.00 0.06	0.14	0.04 0.03 0.09 0.05	0.00 0.03
	Al 2 O 3 4.96 6.12 5.44 5.74	2.14	8.29 18.07 7.25 5.18 21.755 5.29
	MgO	5.63 9.52 8.09 7.26 1,267	3.83 11.67 4.40 8.01 10.789 8.15
	FeO 56.60 50.10 53.13 54.64 71.99 61.453 33.44 62.03 60.61 37.396 59.67
	Cr 2 O 3 0.88 6.88 6.28 2.48	3.19	5.47 2.96 8.69 1.97 20.434 3.10
	MnO	0.36 0.42 0.47 0.77	0.18	0.29 4.07 0.44 0.39	0.13 0.45
	TiO 2 21.77 16.70 17.74 20.18 10.392	9.12 2.30 5.34 18.94	4.65 17.93
	Total 90.30 89.80 91.15 91.13 89.307 88.501 93.55 88.24 95.75 9549 95.05
	Calculation based on 4 oxygens
	Si	0.001 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002
	Ti	0.622 0.561 0.561 0.561 0.561 0.561 0.561 0.561 0.561 0.561 0.561
	Al	0.222 0.250 0.250 0.250 0.250 0.250 0.250 0.250 0.250 0.250 0.250
	Cr	0.027 0.073 0.073 0.073 0.073 0.073 0.073 0.073 0.073 0.073 0.073
	Fe +2	0.506 0.550 0.550 0.550 0.550 0.550 0.550 0.550 0.550 0.550 0.550
	Fe +3	1.293 1.139 1.139 1.139 1.139 1.139 1.139 1.139 1.139 1.139 1.139
	Mn	0.012 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024
	Mg	0.319 0.400 0.400 0.400 0.400 0.400 0.400 0.400 0.400 0.400 0.400

Table 4 :

 4 Chemical analysis by microprobe of the zeolites of the pyroclast 2.

	Mineral	Heulandite-Ca	Chabazite-Ca	Chabazite-Ca	Chabazite-Ca
	Region	Amygdale filled Fig. 4G	Fracture Fig. 4G	Fracture Fig. 4F	Amygdale partially filled Fig. 4G
	N°	5	6	5	7
			%
	SiO 2	48.21	47.09	45.87	49.18
	TiO 2	0.09	0.05	0.00	0.00
	Al 2 O 3	19.60	23.25	24.02	23.92
	FeO	1.06	0.18	0.24	0.32
	MgO	0.13	0.20	0.05	0.30
	MnO	0.05	0.00	0.00	0.00
	CaO	6.60	7.57	8.74	7.52
	Na 2 O	0.49	0.13	0.36	0.31
	K 2 O	4.24	0.69	4.98	0.91
	Cr 2 O 3	0.03	0.04	0.00	0.00
	H 2 O	19.50	20.80	14.23	17.54
	Total	100.00	100.00	100.00	100.00
		Calculation based on 98	Calculation based on 36 oxygens
		oxygens
	Si	21.58	7.60	8.08	8.16
	Ti	0.00	0.00	0.00	0.00
	Al	10.34	4.42	4.99	4.68
	Fe	0.40	0.02	0.04	0.04
	Mg	0.09	0.05	0.01	0.08
	Mn	0.02	0.00	0.00	0.00
	Ca	3.17	1.31	1.65	1.34
	Na	0.85	0.08	0.25	0.20
	K	4.84	0.28	2.24	0.38
	Cr	0.00	0.00	0.00	0.00
	H	65.50	25.18	18.82	21.84

Table 5 :

 5 Chemical analyses of the major elements, trace and REE in representative samples of pyroclasts of the Vulcão do Paredão (1) and Morro Vermelho (2 and 3). LQ = Quantification Limit.

	Pyroclasts
	%

Acknowledgements

Special thanks to the Brazilian Navy for their logistical support and to the CNPq (306424/2016-9; 442730/2015-2), CAPES (scholarship) and FAPEMIG (PPM-00326-18) and the European Union (ERDF) and Région Nouvelle Aquitaine for their financial contribution. We would also like to express our gratitude to Olivier Grauby (CINam-

 Bulletin 30,Honolulu,Hawaii,121 p. 492


Baptiste Grard

Sophie Joimel

Laure Vieublé

Giulia Giacche

Anne-Cécile Daniel

Claire-Sophie Haudin

Apolline Auclerc

Sabine Houot

Antoine Lagneau

Geoffroy Séré

Giulia Giache

Nastaran Manouchehri

Valérie Camel

Jean-Noël Consalès

Patrick Stella

Christine Aubry

Claire Chenu

An evaluation of

come

• Test the hypothesis that soil organic matter plays a major role in ecosystem services delivery ;

• Propose how to optimize ecosystem services delivery.

Urban micro-farms (Daniel 2017; Chang and Morel 2018) are :

-small scale production units (<1.5 ha per farm),

-based on organic production, -multi-functional spaces that provide a diversity of activities (e.g., recreational, educational, or cultural)

Urban micro-farms?

Ecosystem services studied Acknowledgement : The authors would like to thanks ADEME agency for funding the project. They also would like to thanks all the farmers and stakeholders involved in the project and make it possible.

Introduction

  Investigations during two years on six micro farms in the Paris Metropolitan Area  Measurements on micro-farms will involve a participatory research (by stakeholders) in parallel to direct measurements by researchers.  The study will last 2 years with continuous and/or one-time measurements.  Study scales: soil, micro-farms and neighbourhood Aims of the project • Define an adapted framework for the quantitative assessment of ecosystem services ;



  Soil fertility (nutrients, soil structure)  Water infiltration and storage, water quality) Urban waste recycling  Local climate (T°)  Global climate (C storage)  Vision, perception and contribution for users (well-being, accessibility, education, aestheticism etc.)  Representation of city stakeholders (property value, urban planning document, co-visibility) Biodiversity


Anthony Quenehen
email: anthony.quenehen@ensam.eu

Jérôme Pocachard
email: jerome.pocachard@ecam.fr

Nathalie Klement

Process optimisation using collaborative robots -comparative case study

Keywords: collaborative robot, lean manufacturing, process improvement, integration method collaborative robot, lean manufacturing, process improvement, integration method collaborative robot, lean manufacturing, process improvement, integration method collaborative robot, lean manufacturing, process improvement, integration method collaborative robot, lean manufacturing, process improvement, integration method collaborative robot, lean manufacturing, process improvement, integration method

Human Robot Collaboration is seen as a significant feature of Industry 4.0 implementation. Collaborative robots (cobots) are supposed to deliver superior process performance, which was so far achieved through the application of Lean Manufacturing techniques. The following case study, built around the assembly process of a pneumatic cylinder, tends to analyse not only the actual benefits of cobot implementation, but also the success factors, in conjunction with Lean Manufacturing usage. Finally, this paper suggests a draft method towards the successful integration of cobot.

INTRODUCTION

For the past few years, there has been an emerging shift to the '4th industrial revolution', also called 'Industry 4.0', a term first used by the German government. In the structured literature reviews [START_REF] Liao | Past, present and future of industry 4.0-a systematic literature review and research agenda proposal[END_REF], [START_REF] Maghazei | Implementation of industry 4.0 technologies: What can we learn from the past[END_REF], [START_REF] Moeuf | The industrial management of SMEs in the era of industry 4.0[END_REF], robotics is listed as one of the technologies participating in this 4th industrial revolution. A collaborative robot -named cobot, is a robot which has been specifically designed to work simultaneously and safely with humans -without safety cages/fencingin shared workspaces. The objective is to improve the operations by delegating tasks to the cobot, and let the human operator carry out the tasks that cannot be handled by the cobot [START_REF] Petruck | Humanrobot collaboration in manual assembly-a collaborative workplace[END_REF]. Based on a German survey [START_REF] Bauer | Lightweight robots in manual assembly, best to start simply[END_REF], the top-3 reasons to choose to implement cobots are: 1-operational efficiency, 2-innovation and 3-ergonomics.

Concurrently, Lean Manufacturing has so far been recognised as a leading model to achieve a sustainable operations improvement, relying on limited investments and therefore a controlled level of automation.

Both similarities and contradictions can be seen between Industry 4.0 and Lean Manufacturing models. They both seek a higher efficiency in operations, and consider human as a key asset in this improvement process. Nevertheless, Industry 4.0 can be seen as 'technology centered', whereas Lean Manufacturing is rather methodology orientated for performance enhancement. At conceptual level, several potential interaction scenarios between those two models have emerged, ranging from: 'Industry 4.0 will make Lean obsolete to 'Industry 4.0 is a support for Lean Manufacturing', including also 'Lean Manufacturing is a prerequisite for Industry 4.0', or 'Industry 4.0 is an extension for Lean Manufacturing' [START_REF] Dombrowski | Interdependencies of industrie 4.0 & lean production systems: A use cases analysis[END_REF] [START_REF] Satoglu | Lean transformation integrated with industry 4.0 implementation methodology[END_REF] [START_REF] Kolberg | Lean automation enabled by industry 4.0 technologies[END_REF].

Such scenarios are still mainly theoretical and the use cases mostly described as 'to be' situations, offer little view for practitioners on how to shift from their current operations towards the integration of 4.0 technologies.

Through a case study, we suggest contributing to filling this gap by trying to answer the two following questions:

• How to assess the benefits of collaborative robot with figures? • Are there any success factors in relationship with Lean Manufacturing?

CONDITION OF RESEARCH

Case study

A case study was built around a simplified manual assembly process of a pneumatic cylinder, see fig . 1. This case offers some different types of tasks to be carried out, with different levels of complexity, see fig. 2. In order to mimic the integration process of a cobot into an existing production environment, it was decided to build first a fully manual process on which tentative optimisation loops will be implemented. The purpose is to compare different optimisation strategies and highlight potential success factors.

We selected Universal Robot TM UR5 cobot, for the ease of use and the availability of online self-training material (Universal Robots academy).

Initial Setup

In order to minimise the impact of operators' experience during the comparison process, 2 separate teams -A and B -were gathered, with limited communication opportunities. They were composed of some 4 th and 5 th year students

INTRODUCTION

For the past few years, there has been an emerging shift to the '4th industrial revolution', also called 'Industry 4.0', a term first used by the German government. In the structured literature reviews [START_REF] Liao | Past, present and future of industry 4.0-a systematic literature review and research agenda proposal[END_REF], [START_REF] Maghazei | Implementation of industry 4.0 technologies: What can we learn from the past[END_REF], [START_REF] Moeuf | The industrial management of SMEs in the era of industry 4.0[END_REF], robotics is listed as one of the technologies participating in this 4th industrial revolution. A collaborative robot -named cobot, is a robot which has been specifically designed to work simultaneously and safely with humans -without safety cages/fencingin shared workspaces. The objective is to improve the operations by delegating tasks to the cobot, and let the human operator carry out the tasks that cannot be handled by the cobot [START_REF] Petruck | Humanrobot collaboration in manual assembly-a collaborative workplace[END_REF]. Based on a German survey [START_REF] Bauer | Lightweight robots in manual assembly, best to start simply[END_REF], the top-3 reasons to choose to implement cobots are: 1-operational efficiency, 2-innovation and 3-ergonomics.

Concurrently, Lean Manufacturing has so far been recognised as a leading model to achieve a sustainable operations improvement, relying on limited investments and therefore a controlled level of automation.

Both similarities and contradictions can be seen between Industry 4.0 and Lean Manufacturing models. They both seek a higher efficiency in operations, and consider human as a key asset in this improvement process. Nevertheless, Industry 4.0 can be seen as 'technology centered', whereas Lean Manufacturing is rather methodology orientated for performance enhancement. At conceptual level, several potential interaction scenarios between those two models have emerged, ranging from: 'Industry 4.0 will make Lean obsolete to 'Industry 4.0 is a support for Lean Manufacturing', including also 'Lean Manufacturing is a prerequisite for Industry 4.0', or 'Industry 4.0 is an extension for Lean Manufacturing' [START_REF] Dombrowski | Interdependencies of industrie 4.0 & lean production systems: A use cases analysis[END_REF]) [START_REF] Satoglu | Lean transformation integrated with industry 4.0 implementation methodology[END_REF]) [START_REF] Kolberg | Lean automation enabled by industry 4.0 technologies[END_REF].

Such scenarios are still mainly theoretical and the use cases mostly described as 'to be' situations, offer little view for practitioners on how to shift from their current operations towards the integration of 4.0 technologies.

Through a case study, we suggest contributing to filling this gap by trying to answer the two following questions:

• How to assess the benefits of collaborative robot with figures? • Are there any success factors in relationship with Lean Manufacturing?

CONDITION OF RESEARCH

Case study

A case study was built around a simplified manual assembly process of a pneumatic cylinder, see fig . 1. This case offers some different types of tasks to be carried out, with different levels of complexity, see fig. 2. In order to mimic the integration process of a cobot into an existing production environment, it was decided to build first a fully manual process on which tentative optimisation loops will be implemented. The purpose is to compare different optimisation strategies and highlight potential success factors.

We selected Universal Robot TM UR5 cobot, for the ease of use and the availability of online self-training material (Universal Robots academy).

Initial Setup

In order to minimise the impact of operators' experience during the comparison process, 2 separate teams -A and B -were gathered, with limited communication opportunities. They were composed of some 4 th and 5 th year students

INTRODUCTION

For the past few years, there has been an emerging shift to the '4th industrial revolution', also called 'Industry 4.0', a term first used by the German government. In the structured literature reviews [START_REF] Liao | Past, present and future of industry 4.0-a systematic literature review and research agenda proposal[END_REF], [START_REF] Maghazei | Implementation of industry 4.0 technologies: What can we learn from the past[END_REF], [START_REF] Moeuf | The industrial management of SMEs in the era of industry 4.0[END_REF], robotics is listed as one of the technologies participating in this 4th industrial revolution. A collaborative robot -named cobot, is a robot which has been specifically designed to work simultaneously and safely with humans -without safety cages/fencingin shared workspaces. The objective is to improve the operations by delegating tasks to the cobot, and let the human operator carry out the tasks that cannot be handled by the cobot [START_REF] Petruck | Humanrobot collaboration in manual assembly-a collaborative workplace[END_REF]. Based on a German survey [START_REF] Bauer | Lightweight robots in manual assembly, best to start simply[END_REF], the top-3 reasons to choose to implement cobots are: 1-operational efficiency, 2-innovation and 3-ergonomics.

Concurrently, Lean Manufacturing has so far been recognised as a leading model to achieve a sustainable operations improvement, relying on limited investments and therefore a controlled level of automation.

Both similarities and contradictions can be seen between Industry 4.0 and Lean Manufacturing models. They both seek a higher efficiency in operations, and consider human as a key asset in this improvement process. Nevertheless, Industry 4.0 can be seen as 'technology centered', whereas Lean Manufacturing is rather methodology orientated for performance enhancement. At conceptual level, several potential interaction scenarios between those two models have emerged, ranging from: 'Industry 4.0 will make Lean obsolete to 'Industry 4.0 is a support for Lean Manufacturing', including also 'Lean Manufacturing is a prerequisite for Industry 4.0', or 'Industry 4.0 is an extension for Lean Manufacturing' [START_REF] Dombrowski | Interdependencies of industrie 4.0 & lean production systems: A use cases analysis[END_REF]) [START_REF] Satoglu | Lean transformation integrated with industry 4.0 implementation methodology[END_REF]) [START_REF] Kolberg | Lean automation enabled by industry 4.0 technologies[END_REF].

Such scenarios are still mainly theoretical and the use cases mostly described as 'to be' situations, offer little view for practitioners on how to shift from their current operations towards the integration of 4.0 technologies.

Through a case study, we suggest contributing to filling this gap by trying to answer the two following questions:

• How to assess the benefits of collaborative robot with figures? • Are there any success factors in relationship with Lean Manufacturing?

CONDITION OF RESEARCH

Case study

A case study was built around a simplified manual assembly process of a pneumatic cylinder, see fig . 1. This case offers some different types of tasks to be carried out, with different levels of complexity, see fig. 2. In order to mimic the integration process of a cobot into an existing production environment, it was decided to build first a fully manual process on which tentative optimisation loops will be implemented. The purpose is to compare different optimisation strategies and highlight potential success factors.

We selected Universal Robot TM UR5 cobot, for the ease of use and the availability of online self-training material (Universal Robots academy).

Initial Setup

In order to minimise the impact of operators' experience during the comparison process, 2 separate teams -A and B -were gathered, with limited communication opportunities. They were composed of some 4 th and 5 th year students

INTRODUCTION

For the past few years, there has been an emerging shift to the '4th industrial revolution', also called 'Industry 4.0', a term first used by the German government. In the structured literature reviews [START_REF] Liao | Past, present and future of industry 4.0-a systematic literature review and research agenda proposal[END_REF], [START_REF] Maghazei | Implementation of industry 4.0 technologies: What can we learn from the past[END_REF], [START_REF] Moeuf | The industrial management of SMEs in the era of industry 4.0[END_REF], robotics is listed as one of the technologies participating in this 4th industrial revolution. A collaborative robot -named cobot, is a robot which has been specifically designed to work simultaneously and safely with humans -without safety cages/fencingin shared workspaces. The objective is to improve the operations by delegating tasks to the cobot, and let the human operator carry out the tasks that cannot be handled by the cobot [START_REF] Petruck | Humanrobot collaboration in manual assembly-a collaborative workplace[END_REF]. Based on a German survey [START_REF] Bauer | Lightweight robots in manual assembly, best to start simply[END_REF], the top-3 reasons to choose to implement cobots are: 1-operational efficiency, 2-innovation and 3-ergonomics.

Concurrently, Lean Manufacturing has so far been recognised as a leading model to achieve a sustainable operations improvement, relying on limited investments and therefore a controlled level of automation.

Both similarities and contradictions can be seen between Industry 4.0 and Lean Manufacturing models. They both seek a higher efficiency in operations, and consider human as a key asset in this improvement process. Nevertheless, Industry 4.0 can be seen as 'technology centered', whereas Lean Manufacturing is rather methodology orientated for performance enhancement. At conceptual level, several potential interaction scenarios between those two models have emerged, ranging from: 'Industry 4.0 will make Lean obsolete to 'Industry 4.0 is a support for Lean Manufacturing', including also 'Lean Manufacturing is a prerequisite for Industry 4.0', or 'Industry 4.0 is an extension for Lean Manufacturing' [START_REF] Dombrowski | Interdependencies of industrie 4.0 & lean production systems: A use cases analysis[END_REF]) [START_REF] Satoglu | Lean transformation integrated with industry 4.0 implementation methodology[END_REF]) [START_REF] Kolberg | Lean automation enabled by industry 4.0 technologies[END_REF].

Such scenarios are still mainly theoretical and the use cases mostly described as 'to be' situations, offer little view for practitioners on how to shift from their current operations towards the integration of 4.0 technologies.

Through a case study, we suggest contributing to filling this gap by trying to answer the two following questions:

• How to assess the benefits of collaborative robot with figures? • Are there any success factors in relationship with Lean Manufacturing?

CONDITION OF RESEARCH

Case study

A case study was built around a simplified manual assembly process of a pneumatic cylinder, see fig . 1. This case offers some different types of tasks to be carried out, with different levels of complexity, see fig. 2. In order to mimic the integration process of a cobot into an existing production environment, it was decided to build first a fully manual process on which tentative optimisation loops will be implemented. The purpose is to compare different optimisation strategies and highlight potential success factors.

We selected Universal Robot TM UR5 cobot, for the ease of use and the availability of online self-training material (Universal Robots academy).

Initial Setup

In order to minimise the impact of operators' experience during the comparison process, 2 separate teams -A and B -were gathered, with limited communication opportunities. They were composed of some 4 th and 5 th year students

INTRODUCTION

For the past few years, there has been an emerging shift to the '4th industrial revolution', also called 'Industry 4.0', a term first used by the German government. In the structured literature reviews [START_REF] Liao | Past, present and future of industry 4.0-a systematic literature review and research agenda proposal[END_REF], [START_REF] Maghazei | Implementation of industry 4.0 technologies: What can we learn from the past[END_REF], [START_REF] Moeuf | The industrial management of SMEs in the era of industry 4.0[END_REF], robotics is listed as one of the technologies participating in this 4th industrial revolution. A collaborative robot -named cobot, is a robot which has been specifically designed to work simultaneously and safely with humans -without safety cages/fencingin shared workspaces. The objective is to improve the operations by delegating tasks to the cobot, and let the human operator carry out the tasks that cannot be handled by the cobot [START_REF] Petruck | Humanrobot collaboration in manual assembly-a collaborative workplace[END_REF]. Based on a German survey [START_REF] Bauer | Lightweight robots in manual assembly, best to start simply[END_REF], the top-3 reasons to choose to implement cobots are: 1-operational efficiency, 2-innovation and 3-ergonomics.

Concurrently, Lean Manufacturing has so far been recognised as a leading model to achieve a sustainable operations improvement, relying on limited investments and therefore a controlled level of automation.

Both similarities and contradictions can be seen between Industry 4.0 and Lean Manufacturing models. They both seek a higher efficiency in operations, and consider human as a key asset in this improvement process. Nevertheless, Industry 4.0 can be seen as 'technology centered', whereas Lean Manufacturing is rather methodology orientated for performance enhancement. At conceptual level, several potential interaction scenarios between those two models have emerged, ranging from: 'Industry 4.0 will make Lean obsolete to 'Industry 4.0 is a support for Lean Manufacturing', including also 'Lean Manufacturing is a prerequisite for Industry 4.0', or 'Industry 4.0 is an extension for Lean Manufacturing' [START_REF] Dombrowski | Interdependencies of industrie 4.0 & lean production systems: A use cases analysis[END_REF]) [START_REF] Satoglu | Lean transformation integrated with industry 4.0 implementation methodology[END_REF]) [START_REF] Kolberg | Lean automation enabled by industry 4.0 technologies[END_REF].

Such scenarios are still mainly theoretical and the use cases mostly described as 'to be' situations, offer little view for practitioners on how to shift from their current operations towards the integration of 4.0 technologies.

Through a case study, we suggest contributing to filling this gap by trying to answer the two following questions:

• How to assess the benefits of collaborative robot with figures? • Are there any success factors in relationship with Lean Manufacturing?

CONDITION OF RESEARCH

Case study

A case study was built around a simplified manual assembly process of a pneumatic cylinder, see fig . 1. This case offers some different types of tasks to be carried out, with different levels of complexity, see fig. 2. In order to mimic the integration process of a cobot into an existing production environment, it was decided to build first a fully manual process on which tentative optimisation loops will be implemented. The purpose is to compare different optimisation strategies and highlight potential success factors.

We selected Universal Robot TM UR5 cobot, for the ease of use and the availability of online self-training material (Universal Robots academy).

Initial Setup

In order to minimise the impact of operators' experience during the comparison process, 2 separate teams -A and B -were gathered, with limited communication opportunities. They were composed of some 4 th and 5 th year students

INTRODUCTION

For the past few years, there has been an emerging shift to the '4th industrial revolution', also called 'Industry 4.0', a term first used by the German government. In the structured literature reviews [START_REF] Liao | Past, present and future of industry 4.0-a systematic literature review and research agenda proposal[END_REF], [START_REF] Maghazei | Implementation of industry 4.0 technologies: What can we learn from the past[END_REF], [START_REF] Moeuf | The industrial management of SMEs in the era of industry 4.0[END_REF], robotics is listed as one of the technologies participating in this 4th industrial revolution. A collaborative robot -named cobot, is a robot which has been specifically designed to work simultaneously and safely with humans -without safety cages/fencingin shared workspaces. The objective is to improve the operations by delegating tasks to the cobot, and let the human operator carry out the tasks that cannot be handled by the cobot [START_REF] Petruck | Humanrobot collaboration in manual assembly-a collaborative workplace[END_REF]. Based on a German survey [START_REF] Bauer | Lightweight robots in manual assembly, best to start simply[END_REF], the top-3 reasons to choose to implement cobots are: 1-operational efficiency, 2-innovation and 3-ergonomics.

Concurrently, Lean Manufacturing has so far been recognised as a leading model to achieve a sustainable operations improvement, relying on limited investments and therefore a controlled level of automation.

Both similarities and contradictions can be seen between Industry 4.0 and Lean Manufacturing models. They both seek a higher efficiency in operations, and consider human as a key asset in this improvement process. Nevertheless, Industry 4.0 can be seen as 'technology centered', whereas Lean Manufacturing is rather methodology orientated for performance enhancement. At conceptual level, several potential interaction scenarios between those two models have emerged, ranging from: 'Industry 4. Such scenarios are still mainly theoretical and the use cases mostly described as 'to be' situations, offer little view for practitioners on how to shift from their current operations towards the integration of 4.0 technologies.

Through a case study, we suggest contributing to filling this gap by trying to answer the two following questions:

• How to assess the benefits of collaborative robot with figures? • Are there any success factors in relationship with Lean Manufacturing?

CONDITION OF RESEARCH

Case study

A case study was built around a simplified manual assembly process of a pneumatic cylinder, see fig . 1. This case offers some different types of tasks to be carried out, with different levels of complexity, see fig. 2. In order to mimic the integration process of a cobot into an existing production environment, it was decided to build first a fully manual process on which tentative optimisation loops will be implemented. The purpose is to compare different optimisation strategies and highlight potential success factors.

We selected Universal Robot TM UR5 cobot, for the ease of use and the availability of online self-training material (Universal Robots academy).

Initial Setup

In order to minimise the impact of operators' experience during the comparison process, 2 separate teams -A and B -were gathered, with limited communication opportunities. They were composed of some 4 th and 5 th year students To ensure similar initial conditions, Team A developed a fully manual assembly process: M-1, which was replicated by Team B based on video analysis: M-1'. It was then checked Teams A and B achieved comparable Cycle Time (CT) on their respective processes, this is confirmation stage C1. From this point, both teams were given the same

Development of solution

Team A immediately started the engineering stage of collaborative solution: PA-1, whereas Team B was given the opportunity to study and propose some improvements prior to the start of the integration of the collaborative solution: M-2. The purpose of this intermediate step is twofold:

I. With limited time available, can we obtain, through the regular continuous improvement tools, some comparable benefits to collaborative automation? II. Prevent Team B from developing some similar types of collaborative solutions to team A's.

As a second control item -C2, Team B was asked to replicate the solution PA-1 from Team A, to confirm that the skills acquired during the self-training stage were comparable. This is process PA-1'. See fig. 4.

Finally, Team B was asked to develop their own collaborative process: PA-2. Videos of each process are available at the following URL (youtube): http://yt.vu/p/PLEUzN_ OcAg_lSzqMKHTwfzxxjpSOhJDTj 2019 IFAC MIM Berlin, Germany, August 28-30, 2019

Fig. 5. The 3 phases of cobotics development

Result analysis

The review conclusion by [START_REF] Maghazei | Implementation of industry 4.0 technologies: What can we learn from the past[END_REF] suggested examining the research alongside with the characteristics of the Advanced Manufacturing Technologies (AMT) in terms of: the technology evaluation before implementation, the implementation phase, the outcomes (operational, organisational, strategic, and social) and the contextual variables that can have an influence. Therefore we divide a cobotics project into 3 successive phases as described in fig. 5. A cobotics project is to deploy some cobots in manufacturing or logistics activities, either working jointly with humans or standing alone.

In order to assess the investment, or 'cost' related to a solution, the sum of 'Engineering' and 'Implementing' times spent by the students will be measured through the development process. The sum will be called 'Development Time' (DT). This may correspond to the resource effort spent by the process engineering and shop floor resources to optimise an existing process in an industrial environment.

The performance output will be measured by the reduction of the average Total Cycle Time (controlling standard deviation remains comparable to the initial). It will be called ΔCT. Since the aim of the study is to highlight the efficiency of the integration of collaborative robotics, the performance output cannot be considered alone, even though it is itself a significant parameter. Thus, we propose to visualise each solution with Development Time vs ΔCT, and compare them.

Analysis tool

Each production run has been video recorded for analysis.

The blocks and the tasks of the observed process were broken down into task elements in order to capture and quantify the detailed impacts of each solution. This work is visualised by using Standard Work Combination Table (SWCT), a Lean Manufacturing tool that highlights the manual and automated tasks, and their interaction under a timeline format. SWCT for each manual and partially automated process can be found in Appendix A.1, A.2, A.3.

Table 1. Manual process confirmation C1

Av. CT σ(n=8) Variation Coeff.

Team A (M1) 46.5s 6.1s 13% Team B (M1') 47.2s 4s 9%

Table 2. Collaborative process confirmation C2

Dvpt time

Av. CT σ(n=4) Variation Coeff.

Team A (PA-1) 14 hrs 53.5s 4.4s 8%

Team B (PA-1')

16 hrs 52.5s 3.4s 6% Fig. 6. Team A's result for PA-1 cycle time 3. RESULTS

Initial setup

The results table of initial confirmation of manual processes M-1 and M-1' show comparable achievement for both teams, see table 1. It was then decided to move to the next step and include a cobot for Team A -config. PA-1, while Team B would perform continuous improvement loop on the manual process : config. M-2.

As a second confirmation item, Team B replicated the team A's collaborative process regardless of their own improvements (config. PA-1'). The respective development times are then compared, see table 2.

Again, the results are comparable, and it was assumed that both teams acquired similar skill level in Robotics through their self-training stage.

Team A's collaborative process

No specific guidance was given to team A on how to integrate the cobot in the manual process, just only to try to transfer the operations towards the robot. Despite the cobot introduction, Cycle Time has not been improved overall. The main impacting factors were highlighted on fig. 6.

Transferred time to robot measures the amount of manual work that was removed from the operator's work content of the initial process. It is mainly the pick and place operations in this case study, as they are perceived as quickest to develop.

2019 IFAC MIM Berlin, Germany, August 28-30, 2019 Fig. 7. Team B's result for PA-2 cycle time

Additional handling measures the quantity of work added to the operator's work content, due to the introduction of a cobot. In our case study, it mainly consists in the activation of the robot through a touch panel and the movements related to the fixed delivery position of the cobot from its pick and place operations. In Team A case, this time alone -7s-is higher than the transferred time (5.4s), hence already cancelling at this stage the benefit from the automation.

Waiting time represents the total time during which the operator has to wait for the cobot to complete her/his own task. Due to the duration and the sequencing of automated operations versus manual ones, a total operator waiting time of 5.3s has been created.

The details of both manual and collaborative processes can be found in Appendix A.1 and A.2, where those times captured through video analysis have been highlighted.

Team B's collaborative process

Prior to developing their processes, Team B had been given a 4 hour course on Lean techniques, covering the following items: standardised work creation and kaizen, operation time reduction, jidoka (man and machine separation). From this point onwards, students worked in autonomy until their processes were finalised.

Step 1: manual process improvement Team B achieved a CT of 44.5s, i.e. 2s reduction through the improvement on the combination of tasks and the sub component relocation to minimise the motion distances. This step's purpose is also to trigger some new ideas for automation (configuration M2).

Step 2: collaborative process creation After a development time of 5 hours, Team B did set-up a process 2.4s shorter than the initial one, see fig. 7 The transferred time is comparable to the config. PA1, but the additional handling time was maintained at a lower value thanks to the single activation of the cobot per total cycle (versus 2 for previous config. PA-1). Finally, Team B controlled the task sequencing between the operator and the cobot during the process development to avoid generating some operator waiting time. The detailed image of the manual and the collaborative processes can be found in Appendix.

Summary results

In both team A and B cases, when incorporating cobot, the resulting robot working time was close to 6 times the corresponding manual work from the original process See table3. Although this first finding is based on a very limited number of trials, it may give an idea on opportunities entailed the cobot integration. Further work is required to better identify any correlations, including other types of operations than pick and place or simple assembly.

Nevertheless, based on both team strategies, an outline for a method appears, which could be sequenced as follows:

1. Run initial optimisation loop to avoid spending time automating some inefficient operations 2. Select the candidate tasks for the automation based on their complexity versus team skills: define target transfer time 3. Evaluate the subsequent cobot working time (consider transfer time x 6 for low complexity operations). Verify robot working time <(Initial CT -transfer time)

4. Simulate the process sequence and verify no generation of some operator waiting times 5. Implement the process. Stabilise the results 6. Check the resulting cobot waiting time 7. Run another loop from step 2., considering a target transfer time in accordance with the cobot waiting time identified in 6.

CONCLUSIONS

Cobot integration can have some positive impacts on operation performance, even with limited development time.

In some industrial applications, this may support a Takt time change without having to add under-utilised human resources, or limit the usage of overtime [START_REF] Gil-Vilda | Integration of a collaborative robot in a U-shaped production line: a real case study[END_REF]. To that extent, the collaborative robot may support flexibility of the Lean Manufacturing environment. This experiment also highlights Lean Manufacturing techniques -standardised work analysis, continuous improvement (Kaizen), Man and Machine separation -as some key success factors for effective introduction of cobots. Besides, students from Team A and B were given the opportunity to feedback freely on the skills they thought they gained during this project. This activity may give hints on additional success factors to be considered at organisational level. Results described in table 4 suggest that beyond expectable results for robotics related competencies, a number of Lean related skills have been acquired on top of guidance from supervising teacher. Interestingly, a set of soft skills including behaviour have been mentioned, such as teamwork and accountability, also in connexion with Lean process management [START_REF] Liker | The toyota way[END_REF].

LIMITATIONS AND FURTHER DEVELOPMENTS

An iterative method, showing similarities with Kaizen cycle -has been identified, but some further loops of process improvements will be necessary to test its validity, along with the exploration on how far collaborative robots can enhance the process efficiency, and whether additional skills may be required to unlock higher levels of performance. Such development may also open research on operator skill development, as well as roles and responsibilities entailed by cobot integration as a human centred project.

Besides, both teams had to carry out some adaptations of their part containers to enable cobot to conduct pick and place tasks. This will have some detrimental effects on box design cost and exchange frequency, which will have to be measured and considered in the final efficiency gain balance, in order to give a more realistic image of the production environment.

  0 will make Lean obsolete to 'Industry 4.0 is a support for Lean Manufacturing', including also 'Lean Manufacturing is a prerequisite for Industry 4.0', or 'Industry 4.0 is an extension for Lean Manufacturing'[START_REF] Dombrowski | Interdependencies of industrie 4.0 & lean production systems: A use cases analysis[END_REF] [START_REF] Satoglu | Lean transformation integrated with industry 4.0 implementation methodology[END_REF] [START_REF] Kolberg | Lean automation enabled by industry 4.0 technologies[END_REF].

Fig. 1 .

 1 Fig. 1. Pneumatic cylinder description -from manufacturer's catalogue

Fig. 3 .

 3 Fig. 3. The conditions of research

Fig

  Fig. A.1. SWCT for process M1

Table 3 .

 3 Result summary.

					Operator	Transfer-	Robot
		Team	Dvpt time	CT	work	wait	-red time	work	wait
			(hours)	(s)	(s)	(s)	(s)	(s)	(s)
	M1	A	-	46.5	46.5	N/A	N/A	N/A	N/A
	PA-1	A	14	53.2	47.9	5.3	5.4	32.6	20.6
	M2	B	5	44.5	44.5	N/A	N/A	N/A	N/A
	PA-2	B	5	42.1	42.1	N/A	5	28.8	13.3

Table 4 .

 4 Skills acquisition.

			Team A	Team B
	Technical skills	Robotics	Trajectory optimisation Programming Understanding of robot's ability	Trajectory optimisation Programming
		Process design	Layout optimisation Assembly task sequencing Task allocation	Layout optimisation Process video analysis Waiting time elimination
	Soft skills	Organisation Time and priority managment Behaviour Teamwork	Job and responsability sharing Accountability Teamwork

ACKNOWLEDGEMENTS

The authors are most grateful to the anonymous reviewers for their valuable comments on an earlier version of the article, which significantly helped to improve its content.

Appendix A. STANDARD WORK COMBINATION TABLES OF EACH PROCESS (SWCT)

2019 IFAC MIM Berlin, Germany, August 28-30, 2019


What is known on exposure of whey proteins to alkaline pH? Gelation at 4 and 20°C

  [protein]   rate gel   [protein]   G' 50h , G'' 50h  [protein]>120 g/L  G'>G''  3 apparent steps • 0-200 min tand  • tand  (G'' & ' ): thickening • tand and G'  (G" ): gelation  Final tand  0.1 1,E-02 1,E-01 1,E+00 1,E+01 1,E+02 1,E+03 1,E+04 1,E+05 1 10 100 G', G'' (
4°C 20°C G' G''  [WPI]   t gel  (power law)  Exponent 20°C > 4°C  t gel 4°C<t gel 20°C  [WPI]   G' 50h & G" 50h  (power law)  Exponent 20°C > 4°C
t gel = 2.6.10 10 .

[WPI] -3.25 t gel = 1.9.10 6 .

[WPI] -1.72 G'= 9.10 -18 .

[WPI] 8.5 G" = 8.10 -16 [WPI] 7.4

Results

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Storage at 20°C

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Conclusions

The results improve our understanding of -Lg polymerisation at alkaline pH values.

This understanding is useful for applications in food processes:

• To produce aggregates or gels to increase the texture of food matrices, • To induce denaturation of whey proteins to increase their functional properties such as foaming or emulsifying properties,

• To prevent denaturation/aggregation of whey proteins, for instance during the production of native whey proteins (for nutritional ingredient production) or polymer-free whey protein powders (for production of dairy beverages…), • For optimisation of the alkaline cleaning of membranes used in tangential filtration processes

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MERCI THANK YOU FOR YOUR ATTENTION

Thanks to my colleagues: Florence Rousseau and Pascaline Hamon for her help in electrophoresis

  proteins at pH > 6 (mainly -lactoglobulin): • pH 6-8: reversible, Tanford transition, exposure of a glutamate residue (Tanford et al.1959) • pH 9-13 (Roels et al.1971; Monahan et al. 1995; Partanen et al. 2011) o irreversible, slow, o partially unfolded monomers of -lactoglobulin, o exposure of buried SH groups, o  hydrophobicity, o polymerisation, probably by thiol oxidation + others crosslinks (such as lysinoalanine) • Gelation of whey proteins at pH 9.6 (Mercadé-Prieto & Chen, 2005) • At lower temperatures ? General effect of alkaline pH on proteins (Whitaker & Feeney 2015) -more intense with heating • Changes on solubility and aggregation: net negative charge   solvation and conformation changes, hydrophobic residues exposed, …aggregation • Hydrolysis: amide groups (asparagine, glutamine), peptide bonds, guanidino groups (arginine); • -Elimination reactions (side chains of cystine, threonine, serine)  dehydroalanine • Crosslinking reactions (as dehydroalanine + lysine  lysinoalanine…) • Racemization of amino acids   contents in D-amino acids



  At 100 g/L  a viscous liquid  At 120 g/L  G'>G'', crossing point at freq <= 10 -3 Hz  At 150-300 g/L, no crossing in the range of measured frequencies and G', G'' more or less independent 20°C: slope of log 10 (G'),log 10 (G'') = f(log(freq)) www6.rennes.inrae.fr/stlo/ Results Gelation at 4 and 20°C: slope of log(G',G'') = f(log(freq)) At high [WPI] tand is constant  Only the number of interactions increases with [WPI], but the nature of interactions is the same 0

100-300 g/L] (by OD280nm)

	Gelation at 4°C
	 Slow rate gel (t gel ~100-700 min
	~ 2-12 h)
	o + 0.02% sodium azide
	 Gelation experiments
	o Overnight solubilization with magnetic stirrer at [protein] > [protein] target ,
	o Adjustment at pH 9.5 and [protein] at t 0,
	o Transfer on rheometer: DHR2 (TA Instruments) -plate-cone (5 cm diameter), T=4°C
	or 20°C -paraffin oil
	o Kinetics (low amplitude oscillation, =0.1%; frequency=1 Hz; gap init =2.5 mm; cst
	normal force) o Frequency sweep (10-10 -3 Hz, 5 points/decade;=0.1 %)	T°C 50	t gel WPI 160 g/kg (min) 75
	 Type of interactions during gelation o SDS-PAGE electrophoresis (dissociant+reduction SS)	55 60	25 7
	https://www6.rennes.inrae.fr/stlo/		.04 .05

https://www6.rennes.inrae.fr/stlo/ M&M  Whey protein isolate o 890 g prot, 5.92 g lactose and 63 g water/kg powder o 93.5% is whey proteins (-lactoglobulin + -lactalbumin + bovine serum albumin + other minor ones) o 6.5% is a mixture of caseins  Concentration of whey proteins: o [