Giulia Bosio
email: giulia.bosio.giulia@gmail.com

Anna Gioncada
email: anna.gioncada@unipi.it

Claudio Di Celma
email: claudio.dicelma@unicam.it

Igor Maria Villa
email: igor.villa@unimib.it

Michel Pichavant
email: pichavan@cnrs-orleans.fr

Mario Urbina
email: mariourbina01@hotmail.com

Giovanni Bianucci
email: giovanni.bianucci@unipi.it

V S Kamenetsky

Two-mica rhyolitic tephra in the East Pisco Basin (Peru): new age and dispersion constraints for the eruptions of the Eastern Cordillera of Central Andes

Keywords: Strongly peraluminous tephra, 39 Ar-40 Ar ages, Miocene, Central Andes, Macusani

Two-mica-biotite and muscovite-volcanics are particularly rare in the geological record. One of the several dozen volcanic ash layers from Central Andes volcanoes found in the upper Miocene marine succession of the Pisco Formation (Ica Desert, Peru) contains juvenile biotite and muscovite, sillimanite/andalusite, feldspars, and rhyolitic glass. 39 Ar-40 Ar dating on biotite and muscovite concordantly constrain an age of 7.96 Ma for this two-mica ash layer. A second tephra in the Pisco Formation has a similar biotite composition and an age between 7.45 and 6.93 Ma. The peculiar mineral assemblage and the chemical composition of biotite indicate a strongly peraluminous composition of the erupted magmas and, together with the 39 Ar-40 Ar ages, suggest to consider a correlation of these ash layers to the eruptions of the Miocene Macusani (Peru) or Morococala (Bolivia) volcanic complexes in the Eastern Cordillera of Central Andes. The major and trace element composition of glass supports the correlation with Macusani. A prove-nance from Morococala seems less likely given the large distances involved. These results provide new data on the volcanic activity of the Eastern Cordillera revealing ash that dispersed to over 500 km to the west, in the forearc marine basins. This finding highlights that the exhumed forearc East Pisco Basin is highly promising as an archive of distal ash for the reconstruction of the volcanic activity of Central Andes during the Miocene silicic flare-ups.

Introduction

Strongly peraluminous (SP) volcanics (in the sense of Miller 1985: Al2SiO5-, two mica-, garnet-or cordierite-bearing "granitic" rocks) are particularly rare in the geological record. One of the largest peraluminous volcanic provinces is in the Eastern Cordillera of the Central Andes. Here, tectonomagmatic conditions responsible for generating crustal melts of strongly peraluminous composition prevailed for several million years in late Miocene [START_REF] Sandeman | Lithostratigraphy, petrology and 40Ar-39Ar geochronology of the Crucero Supergroup, Puno department, SE Peru[END_REF][START_REF] Caffe | Petrology of the Coyaguayma ignimbrite, northern Puna of Argentina: origin and evolution of a peraluminous high-SiO2 rhyolite magma[END_REF]. Although the Cenozoic marine sediments of the offshore and emerged forearc basins of southern Peru host many tuff layers representing distal volcanic ash of Central Andes eruptions, dispersed westwards by easterly winds [START_REF] Pouclet | Volcanic ash from leg 112 off Peru[END_REF][START_REF] Hart | Analysis and correlation of volcanic ash in marine sediments from the Peru margin, Ocean Drilling Program Leg 201: explosive volcanic cycles of the north-Central Andes[END_REF][START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF], no correlations with the Eastern Cordillera activity have been proposed up to now.

In the East Pisco Basin (southern Peru), the Miocene Pisco Formation hosts many undisturbed volcanic ash layers in diatomaceous sedimentary successions [START_REF] Celma | Sequence stratigraphy and palaeontology of the upper Miocene Pisco Formation along the western side of the lower Ica valley (Ica desert, Peru)[END_REF]Bosio et al. 2020b). Most of them, based on glass and biotite composition and mineral assemblage, are calc-alkaline dacites CC stays for Coastal Cordillera, PC for Pre-Cordillera, WC for Western Cordillera, A for Altipiano, EC for Eastern Cordillera, and SA for Subandean zone and rhyolites and subordinate andesites [START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF] representing the subduction-related activity of the Western Cordillera [START_REF] Mamani | Geochemical variations in igneous rocks of the central Andean orocline (13°S to 18°S): tracing crustal thickening and magma generation through time and space[END_REF]. A few, instead, show biotite composition pointing to the siderophyllite endmember, sug-gesting a peraluminous nature of the erupted magma [START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF]. One of these latter ash layers is a two-mica-biotite and muscovite-rhyolitic tephra.

In this paper, we provide field and petrochemical descriptions of volcanic ash and age determinations, and discuss the possible finding of Eastern Cordillera ash in the forearc East Pisco Basin. These results add new information about the volcanic activity of the Eastern Cordillera of Central Andes and reveal two major eruptions of strongly peraluminous magmas at 7-8 Ma that dispersed volcanic products up to hundreds of kilometers to the west, reaching the coastal forearc basins.

Geological and volcanological framework

Since the Mesozoic, the western margin of South America has been influenced by the subduction of the oceanic Nazca/ Farallon Plate underneath the continental South American Fig. 2 Geological map of the study area. Geological map of the studied localities in the western side of the Ica River and geographic position of SP tephra mentioned in this paper (red stars) modified from Di [START_REF] Celma | Intraformational unconformities as a record of Late Miocene eustatic falls of sea level in the Pisco Formation (southern Peru)[END_REF] and Bosio et al. (2020b) Fig. 3 Field photo of Cerros la Mama y la Hija. PE0.2 unconformity (i.e., the unconformity found at the base of the P2 allomember) (red continuous line) and MH-T4 tephra layer (yellow dashed line) at the locality of Cerros la Mama y la Hija Plate. In the Central Andes, this subduction was responsible for the production of calc-alkaline metaluminous magmas along the western magmatic arcs forming the Western Cordillera [START_REF] Baker | Upper Cenozoic volcanism in the Central Andes-ages and volumes[END_REF][START_REF] De Silva | Volcanoes of the Central Andes[END_REF][START_REF] Trumbull | The time-space distribution of Cenozoic volcanism in the South-Central Andes: a new data compilation and some tectonic implications[END_REF][START_REF] Mamani | Geochemical variations in igneous rocks of the central Andean orocline (13°S to 18°S): tracing crustal thickening and magma generation through time and space[END_REF]). On the eastern side of the Central Andes orogen, instead, the peraluminous and S-type volcanic and intrusive magmatic units emplaced since 25 Ma indicate that the Eastern Cordillera magmatism is not related to subduction and was the result of extensive crustal melting [START_REF] Trumbull | The time-space distribution of Cenozoic volcanism in the South-Central Andes: a new data compilation and some tectonic implications[END_REF]. Confirming this petrogenetic distinction, the extensive fractional crystallization of the Eastern Cordillera crustal-derived magmas led to Sn and W enrichment [START_REF] Mlynarczyk | The role of collisional tec-tonics in the metallogeny of the Central Andean tin belt[END_REF], while in the western Cordillera, predominantly mantle-derived, metaluminous magmas led to porphyry Cu-Au-Mo and epithermal ore deposits [START_REF] Rosenbaum | Subduction of the Nazca Ridge and the Inca Plateau: insights into the formation of ore deposits in Peru[END_REF]. Examples of the crustal-derived magmatic units of the Eastern Cordillera emplaced from 14°S to 26°S (see Fig. 1) are the Kari Kari ignimbrite [START_REF] Schneider | Eruptive processes, mineralization and isotopic evo-lution of the Los Frailes, Kari Kari region, Bolivia[END_REF], the Macusani volcanics [START_REF] Noble | Rare-element enriched, S-type ash-flow tuffs con-taining phenocrysts of muscovite, andalusite and sillimanite, south-eastern Peru[END_REF]Pichavant et al. 1988a, b), the Morococala Meseta ig-nimbrites [START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF], Revancha dyke [START_REF] Sandeman | Glass-rich, cordierite-biotite rhyodacite, Valle Ninahuisa, Puno, southeastern Peru: petrological evidence for hybridization of "Lachlan S-type" and potassic mafic magmas[END_REF], Cayconi volcanic field [START_REF] Sandeman | Commingling and mixing of S-type peraluminous, ultrapotassic and basalticmagmas in the Cayconi volcanic field, Cordillera de Carabaya[END_REF], and Los Frailes ignimbrites [START_REF] Kay | Regional chemical diversity, crustal and mantle sources and evolution of central Andean Puna plateau ignimbrites[END_REF].

Volcanic ash layers linked to the activity of the Central Andes (Central Volcanic Zone) have been found along the Peruvian and Chilean coast [START_REF] Pouclet | Volcanic ash from leg 112 off Peru[END_REF][START_REF] Hart | Analysis and correlation of volcanic ash in marine sediments from the Peru margin, Ocean Drilling Program Leg 201: explosive volcanic cycles of the north-Central Andes[END_REF][START_REF] Breitkreuz | Neogene to quaternary ash deposits in the Coastal Cordillera in northern Chile: distal ashes from supereruptions in Central Andes[END_REF][START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF], in the Coastal Cordillera and in the forearc basins formed during the Cenozoic [START_REF] Travis | Hydrocarbon potential of coastal basins of Peru[END_REF][START_REF] Thornburg | Sedimentary basins of the Peru continental margin: Structure, stratigraphy, and Cenozoic tectonics from 6°S to 16°S latitude[END_REF]. These products represent the distal ash of large explosive erup-tions, which may have been dispersed westwards by south-southeasterly winds, similar to the products of the Huaynaputina eruption, the largest explosive event in historical times (1600 AD) in Peru [START_REF] Thouret | Largest explosive eruption in historical times in the Andes at Huaynaputina volcano, AD 1600, southern Peru[END_REF][START_REF] De Silva | Global influence of the AD 1600 erup-tion of Huaynaputina, Peru[END_REF].

One of the forearc basins, the East Pisco Basin now exposed in the Ica Desert of Peru, hosts one of the most world-renowned marine vertebrate Fossil-Lagerstätte [START_REF] Esperante | Taphonomy and paleoenvironmental conditions of deposition of fossil whales in the diatomaceous sediments of the Miocene/Pliocene Pisco Formation, southern Perua new fossil-lagerstätte[END_REF]Bianucci et al. 2016aBianucci et al. , b, 2018)).

The Miocene Pisco Formation is the youngest unit of the East Pisco Basin marine fill and is mainly composed of diatomaceous siltstones and sandstones, interposed by frequent tephra layers [START_REF] Dunbar | Cenozoic marine sedimentation in the Sechura and Pisco basins, Peru[END_REF]). Di [START_REF] Celma | Sequence stratigraphy and palaeontology of the upper Miocene Pisco Formation along the western side of the lower Ica valley (Ica desert, Peru)[END_REF] divided this formation in three main allomembers, P0, P1, and P2, from the oldest to the youngest, bounded by regionally extensive intraformational unconformities. P1 and P2 allomembers are composed of yellow sandstones at the base and white diatomaceous siltstone at the top. Along the western side of the Ica River, the P0 allomember was deposited in between 14.8 and 12.4 Ma (Bosio et al. 2020a), the P1 allomember between 9.5 and 8.6 Ma, whereas the P2 allomember was deposited from 8.4 to at least 6.7 Ma (Bosio et al. 2020b). Volcanic ash layers are mainly preserved in the diatomaceous mudstone portions of the marine succes-sions of the P1 and P2 allomembers.

Methods

Among more than 200 samples of volcanic ash layers collect-ed in the East Pisco Basin succession during the fieldwork from 2014 to 2016, this work focuses on three ash samples from the localities of Cerros la Mama y la Hija, Cerro los Quesos, and Cerro la Bruja (Fig. 2). Samples were collected at the base of the ash layer in order to avoid any possible reworking and bioturbation affecting the top of the layer. The surface of the outcrop was discarded to avoid weathered or extraneous grains. Before compositional and 39 Ar-40 Ar dating analyses, the samples were inspected under a stereomicroscope, and smear slides were studied under an optical microscope for petrographic features. The ash layers were considered as the primary deposition of tephra on the basis of a percentage of volcanic components (glass shards and juvenile loose crystals) greater than 95 vol% [START_REF] Griggs | Optimising the use of marine tephrochronology in the North Atlantic: a detailed investigation of the Faroe Marine Ash Zones II, III and IV[END_REF][START_REF] Tada | Methods[END_REF].

Grain-size analyses were performed with the Malvern Mastersizer 2000E™ Laser Granulometer and processed with the grain-size analysis program GRADISTAT [START_REF] Blott | Gradistat: a grain size distribution and statistics package for the analysis of unconsolidated sediments[END_REF] at the Università di Milano-Bicocca (Dipartimento di Scienze dell'Ambiente e della Terra, Milano, Italy). The ash samples were wet sieved with meshes of 500, 250, 125, and 63 μm, and the 125-250 μm and 250-500 μm fractions were mounted in resin and polished for compositional analyses. SEM-EDS (Scanning Electron Microscope equipped with Electron Dispersion Spectroscopy) microanalysis was carried out at the Università di Pisa (Dipartimento di Scienze della Terra, Pisa, Italy) with a Philips™ XL30 scanning electron microscope equipped with an Edax Genesis microanalytical device, with 20-kV filament voltage, 5-nA beam current, and ZAF correction. EPMA (Electron Probe Micro-Analysis) analyses for major elements were performed on glass shards, Al-Si minerals, and biotite and muscovite phenocrysts with a JEOL 8200 Superprobe™ at the Università di Milano (Dipartimento di Scienze della Terra "Ardito Desio," Milano, Italy) (15-kV accelerating voltage, 5-nA beam The first number is the crystal and the second one represents the core (1) or the rim (2). X is K + Na + Ba and Y is AlVI+Mg + Fe + Mn + Ti. Abbreviations: "na" stands for "not analyzed" and "bd" stands for "below detection" The first number is the crystal and the second one represents the core (1) or the rim (2). Comparison with the Macusani and Morococala mean biotite compositions from literature. "AR" is the abbreviation for andalusite-bearing rhyolites in [START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]. X is K + Na + Ba and Y is AlVI+Mg + Fe + Mn + Ti. Abbreviations: "na" stands for "not analyzed" and "bd" stands for "below detection" Comparison with the SP Macusani feldspar fields current) with counting time of 30 s on the elemental peak and 10 s on the background. The beam diameter was 3 μm for phenocrysts and 10 μm for glass shards, i.e., enlarged in order to avoid Na migration under the beam. EPMA analyses were also performed for major elements, plus zinc and fluorine, at the Institut des Sciences de la Terre d'Orleans (ISTO) (Orléans, France) facilities with a SX Five CAMECA instrument, with 15-kVaccelerating voltage and 5-nA beam current. The counting time was 10 s on peak and 5 s on background; the spot size was defocused to 10 μm on glasses and focused to 1-2 μm on minerals.

work 1-1 1-2 2-1 2-2 3-1 3-2 4-1 4-2 5-1 5-2 6-1 6-2 7-1 7-2 8-1
Trace element concentrations in the MH-T4 matrix glass were analyzed by LA-ICP-MS (Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry) at Orléans (joint ISTO-IRAMAT facility). A RESOlution ArF excimer laser (LA; λ = 193 nm) coupled to an Agilent TripleQuad ICPMS was used. Ablation was per-formed at a frequency of 10 Hz and an energy of 2. 5 J.cm -2 . A beam diameter of 10 μm was used. NIST610 was used as external standard and obsidian glass JV2 [START_REF] Pichavant | The Macusani glasses, SE Peru: evidence of chemical fractionation in peraluminous magmas[END_REF]) as secondary standard. Since small spot sizes were necessary, systematic analyses were performed on JV2 at different spot sizes between 100 and 10 μm to check that decreasing spot sizes had no significant effect on element concentrations. A total of three successful analyses were obtained. The raw data were processed off-line using the Glitter software [START_REF] Griffin | GLITTER: data reduction software for laser ablation ICP-MS[END_REF] where time-resolved signals were examined one by one.

For 39 Ar-40 Ar analysis, biotite and muscovite phenocrysts were carefully handpicked under a stereomicroscope, making particular care to avoid any contamination, following Bosio et al. (2020b). 39 Ar-40 Ar dating were performed with the NuInstruments™ Noblesse® noble gas mass spectrometer at the Università di Milano-Bicocca using the step-heating procedure described by Bosio et al. (2020b).

Results

Field and petrographic description

The sample MH-T4 was collected from an ash layer outcrop-ping at Cerros la Mama y la Hija (Figs. 2,3), at the base of the P2 allomember, 3 m above the PE0.2 unconformity (Fig. 3). The layer is a 5-cm-thick white ash with visible fine-grained biotite, which can be traced laterally for several tens of meters in sandstones. The CLQ-T23 and LB-T19 ash layers were sampled at Cerro los Quesos and Cerro la Bruja localities, re-spectively (Fig. 2). These ash layers were described and correlat-ed based on stratigraphy, grain-size, shard morphology, and glass and biotite composition by [START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF], and they will be referred to as CLQ-T23/LB-T19 tephra herein after. Under the optical microscope, the MH-T4 ash consists of highly vesiculated, colorless glass shards and of loose crystals of juvenile biotite, feldspars, and minor Comparison with the Macusani and Morococala matrix glass analyses from literature. "CR" is the abbreviation for cordierite-bearing rhyolites in [START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]. Concentrations are normalized to 100 and the original EPMA total of MH-T4 is shown. Abbreviations: "na" stands for "not analyzed" and "bd" stands for "below detection" muscovite. An Al2SiO5 mineral phase, andalusite or sillimanite, was also detected inspecting the sample with SEM-EDS (Fig. 4). Biotite, muscovite, feldspar, and andalusite/sillimanite are coated by juvenile rhyolitic glass (Fig. 4). The CLQ-T23/LB-T19 tephra consists of colorless glass shards with a bubble-wall morphology and only a very few small phenocrysts of biotite. Through grain-size analysis, we find that both tephra samples are unimodal and poorly sorted (see Fig. 4e), and they are composed by extremely fine ash (˂ 1/ 16 mm) following the classification of [START_REF] White | Primary volcaniclastic rocks[END_REF].

Mineral and glass composition

Biotite phenocrysts of both tephra layers (MH-T4 and CLQ-T23/LB-T19) show a rather homogeneous major element composition from core to rim (Tables 1 and2, and [START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF]. From the point of view of the biotite classification in an Al IV vs Fe/Fe + Mg diagram, they are on the siderophyllite-rich side of the field representing the composition of biotite found in the P2 allomember tephra (Fig. 5a). Biotite compo-sition, for both tephra layers, can be distinguished from the rest of the P2 tephra in Ti vs Fe/Fe + Mg (Fig. 5b). Moreover, biotite phenocrysts are richer in Al2O3 wt% with respect to the rest of P2 tephra (Fig. 5c) and fall within the field of the micas found in peraluminous granite in the discrimination diagrams of Abdel-Rahman (1994) (Fig. 5c,d). They show detectable ZnO contents, while F is mostly below detection (Tables 1 and2).

The peculiarity of the MH-T4 tephra is the presence of muscovite crystals, which are juvenile phenocrysts as indicated by the coating of rhyolitic glass (Fig. 4c). Muscovite contains significant amounts of Ti, Fe, and Mg, detectable ZnO, and high F, similarly to muscovite in SP rocks (Table 3). Feldspar phenocrysts coated by rhyolitic glass are both plagioclase (oligoclase) and sanidine (Table 4, Fig. 5e). MH-T4 tephra shows, also, the presence of Al2SiO5 minerals in rhyolitic glass, probably andalusite or sillimanite (Table 5).

The composition of the matrix glass is rhyolitic and, on the basis of K2O vs SiO2 diagram, corresponds to magmas belonging to the high-K calc-alkaline series (Table 6, Fig. 6a). When normalized to 100, the silica and CaO content is slightly higher and the Al2O3 is slightly lower for MH-T4 than for CLQ-T23/LB-T19 (Fig. 6b,c). The low microprobe analysis totals may indicate a high concentration of magmatic water or that hydration of glass occurred following the subaqueous deposition of ash. Since the removal of mobile cations follow-ing interaction with an aqueous fluid may cause an increase of the A/CNK (molar Al2O3/CaO + Na2O + K2O) ratio of glass, the analyses showing at the same time low K2O, low micro-probe total, and high A/CNK were discarded. The obtained A/CNK ratio of (mean value) 1.18 in MH-T4 and 1.28 in CLQ-T23/LB-T19 indicates a peraluminous composition (Fig. 6d).

The concentration of fluorine and of several trace elements was determined for MH-T4 matrix glasses. Fluorine is rather high (mean value of 2700 ppm, Table 6). The trace element composition of the matrix glass normalized to upper continental crust exhibits high B, Be, Rb, Cs, and Sn and low Li, Zr, Sr, Ba, and La (Table 7, Fig. 6e).

39 Ar-40 Ar dating of the two-mica tephra

The composition of MH-T4 biotite indicates a relatively high alkali site occupancy from 1.83 to 1.95 apfu, i.e., it is only slightly altered, which makes it suitable for 39 Ar-40 Ar dating. The K concentration calculated from the 39 Ar release is substoichiometric. As discussed in more detail by Bosio et al. (2020b), slight alteration affects micas from marine tephra.

The age spectrum of MH-T4 biotite shows a clear plateau (Fig. 7a). We consider only the isochemical steps (sensu [START_REF] Villa | Geochronology and isotope transport systematics in a subsurface granite from the Larderello-Travale geothermal system (Italy)[END_REF], i.e., steps 2-6 having Ca/K < 0.005 and/or steps 3-6 with Ca/K < 0.003 (see Fig. 7b). Both choices yield isochrons with an atmospheric intercept and a slightly elevated MSWD = 3. The weighted average age of steps 2-6 is 7.98 ± 0.03 Ma.

The muscovite phenocrysts show a high alkali site occupancy, between 1.83 and 1.99 apfu, reflecting a very slight alteration. The age spectrum of MH-T4 mus-covite shows a plateau around 8 Ma (Fig. 7a). We chose the isochemical steps 3-9 with Ca/K < 0.005 and Cl/K < 0.00016 (Fig. 7b,c). The isochron has an atmospheric intercept; therefore, it is valid to consider the weighted average age of steps 3-9, i.e., 7.95 ± 0.03 Ma. All the 39 Ar-40 Ar data for both the biotite and muscovite separates are shown in Tables 8 and9, respectively.

Discussion

The East Pisco Basin tephra of the P2 allomember are prevalently rhyolitic for what concerns the composition of glass shards [START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF]. The biotite composition of these tephra straddles the phlogopite and biotite fields, with a trend pointing to the siderophyllite end-member (see Fig. 5a). When plotted in the discrimination diagrams for granitic rocks based on biotite composition (Fig. 5c,d), they mostly fall in the field corresponding to mica in calc-alkaline rocks, except for a few falling in the field of mica in peraluminous rocks. Among these last tephra, one contains juvenile muscovite, biotite, and Al2SiO5 silicates, revealing a strongly peraluminous composition of the erupted magma. The presence of this peculiar mineral association, unusual in subduction-related arc system, leads to discuss the possible volcanic source for the ash. Two-mica volcanic rocks are rare in the geological record, and examples in upper Miocene can be found in the Eastern Cordillera, which host one of the largest peraluminous provinces in the world [START_REF] Sandeman | Lithostratigraphy, petrology and 40Ar-39Ar geochronology of the Crucero Supergroup, Puno department, SE Peru[END_REF]). In the Eastern Cordillera, the presence of volcanic muscovite has only been reported in the Macusani and Morococala SP volcanic products [START_REF] Noble | Rare-element enriched, S-type ash-flow tuffs con-taining phenocrysts of muscovite, andalusite and sillimanite, south-eastern Peru[END_REF][START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]. The Miocene-Pliocene Macusani ignimbrite field is the largest SP volcanic unit in southern Peru [START_REF] Noble | Rare-element enriched, S-type ash-flow tuffs con-taining phenocrysts of muscovite, andalusite and sillimanite, south-eastern Peru[END_REF]Pichavant et al. 1988a, b;[START_REF] Cheilletz | Volcano-stratigraphy and 40Ar/39Ar geochronology of the Macusani ignimbrite field: monitor of the Miocene geodynamic evolution of the Andes of Southeast Peru[END_REF]. This field comprises crystalrich ash-flow tuffs and rare obsidian glasses, with an unusual mineralogy similar to two-mica peraluminous leucogranites [START_REF] Pichavant | The Macusani glasses, SE Peru: evidence of chemical fractionation in peraluminous magmas[END_REF](Pichavant et al. , 1988a)). The Macusani Formation consists of a 500-m-thick package of ash flows of variable thickness, comprising six major cooling units, which emplaced into two volcanic cycles, giving origin to a Lower and an Upper Member of the formation [START_REF] Cheilletz | Volcano-stratigraphy and 40Ar/39Ar geochronology of the Macusani ignimbrite field: monitor of the Miocene geodynamic evolution of the Andes of Southeast Peru[END_REF]). In the Eastern Cordillera of Bolivia, the late Miocene Morococala volcanic field is composed of andalusite-, biotite-, and muscovite-bearing rhyolite tuffs at the base, cordierite-and biotite-bearing rhyolite tuffs, and biotite-bearing quartz latite tuffs and lavas at the top [START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF].

A correlation with these Eastern Cordillera volcanics can be discussed on the basis of the mineral assemblage and chem-istry, glass composition, and age determinations. The chemi-cal composition of biotite, which has been demonstrated to be a useful tool for tephra correlations [START_REF] Shane | Biotite composition as a tool for the identification of quaternary tephra beds[END_REF][START_REF] Lebti | Neogene and quater-nary ignimbrites in the area of Arequipa, southern Peru: Stratigraphical and petrological correlations[END_REF][START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF], allows discriminating among the peraluminous Central Andes volcanics [START_REF] Caffe | Petrology of the Coyaguayma ignimbrite, northern Puna of Argentina: origin and evolution of a peraluminous high-SiO2 rhyolite magma[END_REF].

The biotite composition of the MH-T4 and CLQ-T23/LB-T19 tephra layers corresponds well with analyses of mica of the Macusani and Morococala SP volcanic units from previous work (i.e., [START_REF] Noble | Rare-element enriched, S-type ash-flow tuffs con-taining phenocrysts of muscovite, andalusite and sillimanite, south-eastern Peru[END_REF]Pichavant et al. 1988a, b;[START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF], except for the low fluorine content (see Tables 1 and2; Fig. 5). In the case of MH-T4 ash layer, the correlation is supported by the high F and the major and minor element composition of muscovite and by the composition of feldspar and Al-silicate minerals (Tables 3, 4, and5).

To compare the glass composition of the Pisco tephra with the Macusani and Morococala volcanics, the available data for matrix glasses and obsidian glasses (macusanite) from previ-ous work [START_REF] Pichavant | The Macusani glasses, SE Peru: evidence of chemical fractionation in peraluminous magmas[END_REF][START_REF] London | Melt-vapor solubilities and elemental partitioning in peraluminous granite-pegmatite systems: experimental results with Macusani glass at 200 MPa[END_REF][START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]) are reported in Table 6 and Fig. 6. A correlation with Macusani and Morococala volcanic regions is supported by the major element composition of matrix glass and by the high F content measured the MH-T4 glass shards. The trace element composition of the ash glasses, with particularly high B, shows a striking correspondence with the Macusani matrix glasses and a rather similar pattern with the Morococala glass inclusions. The major discrepancy is shown by Li, which is very low in the East Pisco Basin tephra (Table 7, Fig. 6e). Lithium, however, is a highly mobile ele-ment, and volcanic glass may be depleted in Li during post-depositional processes, as recently reported in several studies (e.g., [START_REF] Misra | Lithium isotope history of Cenozoic seawa-ter: changes in silicate weathering and reverse weathering[END_REF][START_REF] Hofstra | Silicate Melt Inclusion Evidence for Extreme Pre-eruptive Enrichment and Post-eruptive Depletion of Lithium in Silicic Volcanic Rocks of the Western United States: Implications for the Origin of Lithium-Rich Brines[END_REF][START_REF] Ellis | Post-eruptive mobility of lithium in volcanic rocks[END_REF].

The age of the MH-T4 tephra eruption was determined on biotite and muscovite due to the fact that the consistent mineral assemblage and composition indicate that the ash layer represents deposition from a single eruption, with both muscovite and biotite as juvenile phenocrysts. The quantitative compositional data indicate that submarine alteration was not pervasive, allowing us to determine the age of the erup-tion.

The 39 Ar-40 Ar ages determined separately on the two micas are identical, 7.95 ± 0.03 Ma and 7.98 ± 0.03 Ma, and allow us to propose a weighted average age of 7.96 ± 0.02 Ma for this eruption. This age is more reliable and precise than the previous age of 8.05 ± 0.14 Ma obtained from biotite by Bosio et al. (2020b); biotite shows a lower Ca concentration than the previous sample, which indicates a reduced amount of Ca-rich impurities/alteration phases (Fig 7b).

The age of 7.96 ± 0.02 Ma falls within the literature age range of the Peruvian Macusani volcanics, between ca. 10 and 4 Ma (Pichavant et al. 1988a;[START_REF] Cheilletz | Volcano-stratigraphy and 40Ar/39Ar geochronology of the Macusani ignimbrite field: monitor of the Miocene geodynamic evolution of the Andes of Southeast Peru[END_REF][START_REF] Poupeau | Fission-track dating of 15 macusanite glass pebbles from the Macusani volcanic field (SE Peru)[END_REF]) and with the late Miocene ages of the Bolivian Morococala volcanic field [START_REF] Koeppen | The Morococala volcanics: highly peraluminous rhyolite ash flow magmatism in the Cordillera Oriental, Bolivia[END_REF][START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]. According to [START_REF] Cheilletz | Volcano-stratigraphy and 40Ar/39Ar geochronology of the Macusani ignimbrite field: monitor of the Miocene geodynamic evolution of the Andes of Southeast Peru[END_REF], the Macusani erup-tion ages (i.e., 10.0 ± 0.5 Ma, 7.8-8.0 ± 0.1 Ma, 7.5 ± 0.1 Ma, 7.3 ± 0.1 Ma, 6.8-7.0 ± 0.1 Ma, 6.7 ± 0.1 Ma) cluster in corre-spondence to two important Andean tectonic phases, with the second cluster being by far the most voluminous. These ages are in agreement with the K-Ar ages reported by Pichavant et al. (1988a), i.e., 10.5 ± 0.5 Ma, 7.6 ± 0.3 Ma, 7.1 ± 0.7 Ma, and 6.8 ± 0.2 Ma, and with those proposed by [START_REF] Poupeau | Fission-track dating of 15 macusanite glass pebbles from the Macusani volcanic field (SE Peru)[END_REF], i.e., 7 ± 1 Ma and late episodes at 5. 7-5.3 and 4.8-4.3 Ma. The late Miocene ages of 7.6-8 Ma for Macusani agree with the 7.96 Ma age of the two-mica tephra. MH-T4 age also overlaps with the Morococala late Miocene ages. According to 39 Ar-40 Ar dating, the andalusite-bearing rhyolites give an age of ca. 8.4 Ma, the cordierite-bearing rhyolites 6.8 Ma, and the quartz latites 6.4 Ma [START_REF] Koeppen | The Morococala volcanics: highly peraluminous rhyolite ash flow magmatism in the Cordillera Oriental, Bolivia[END_REF]. Since the twomica volcanic prod-ucts are only present in the andalusitebearing rhyolites, only the age of this unit should be taken into account for comparison with the Pisco tephra. This age is consistent with the 7.96 ± 0.02 Ma age of MH-T4.

The CLQ-T23/LB-T19 tephra can be traced and recognized by tephra fingerprinting and correlation for over 6 km at both the localities of Cerro los Quesos (CLQ-T23) and Cerro la Bruja (LB-T19) [START_REF] Bosio | Chemical and petrographic fingerprinting of volcanic ashes as a tool for high-resolution stratigraphy of the upper Miocene Pisco Formation (Peru)[END_REF]. The age, indi-rectly bracketed by 39 Ar-40 Ar dating of ash layers in the same stratigraphic sections [START_REF] Celma | Sequence stratigraphy and palaeontology of the upper Miocene Pisco Formation along the western side of the lower Ica valley (Ica desert, Peru)[END_REF][START_REF] Gariboldi | Biostratigraphy, geochronology and sedimentation rates of the upper Miocene Pisco Formation at two important marine vertebrate fossilbearing sites of southern Peru[END_REF], is between 7.45 ± 0.01 Ma and 6.93 ± 0.09 Ma. Direct age determination could not be achieved here because of the small size of biotite phenocrysts. This late Miocene age over-laps with the late Miocene eruptions of both the Macusani and Morococala volcanic fields [START_REF] Cheilletz | Volcano-stratigraphy and 40Ar/39Ar geochronology of the Macusani ignimbrite field: monitor of the Miocene geodynamic evolution of the Andes of Southeast Peru[END_REF][START_REF] Koeppen | The Morococala volcanics: highly peraluminous rhyolite ash flow magmatism in the Cordillera Oriental, Bolivia[END_REF].

The characteristics of the MH-T4 and CLQ-T23/LB-T19 tephra, such as the grain-size classification as extremely fine ash following [START_REF] White | Primary volcaniclastic rocks[END_REF], correspond to deposition of distal ash from fallout from Plinian plume-cloud systems or co-ignimbrite plumes rising above pyroclastic density currents. The good correspondence of the mineral assemblage, composition of mineral and glass phases, and the smaller from vents suggest to propose a correlation of MH-T4 tephra with the ignimbrites of Macusani. We suggest that a major eruption of the Macusani field occurred at 7.96 Ma and that the MH-T4 layer could correspond to one of the largest events of the Macusani region, with ash deposited at over 500 km of distance.

These results indicate that the coastal basins of Peru are highly promising as archives for distal ash from Central Andes eruptions and supereruptions, not only from the Western Cordillera and Altiplano but also from the Eastern Cordillera. Future studies may lead to a better reconstruction of the volcanic history of the Central Andes of Southern Peru.

Conclusion

Few strongly peraluminous volcanic eruptions are reported in the Central Andes and, among these, two-mica volcanics are particularly rare. The mineral assemblage and the mineral and glass composition of the two-mica Pisco ash correspond to the Macusani volcanic complex, active between 10 and 4 Ma in the Eastern Cordillera of Peru, and to the late Miocene Morococala, in northern Bolivia. Concordant biotite and muscovite age determinations indicate an age of 7.96 Ma ± 0.02 Ma. This age, together with the petrographic correspon-dence and the smaller distance between source and sample, leads us to suggest a correlation with the Macusani volcanic field. These results provide new data on the volcanic activity of the Central Andes, suggesting that a major explosive erup-tion at 7.96 Ma, probably from the Macusani field. This re-sulted in the dispersal of co-ignimbrite ash to over 500 km to the west and into the forearc marine basins. This finding pos-sibly represents the farthest occurrence of Eastern Cordillera volcanics in the geological record and highlights the importance of the exhumed forearc basins as an archive of distal ash from Central Andes volcanoes.

Fig. 1

 1 Fig. 1 Geographical setting and Eastern Cordillera volcanism of the Central Andes. The orange star shows the East Pisco Basin (EPB) location. Blue stars show the main Eastern Cordillera volcanic fields (MAC = Macusani; MOR = Morococala).

Fig. 5

 5 Fig. 5 Biotite compositional diagrams. a Classification of MH-T4 and CLQ-T23/LB-T19 biotite in the Al IV vs Fe/Fe + Mg diagram of Clarke (1981). For MH-T4, open symbols represent analyses at the Institut des Sciences de la Terre d'Orleans (Orléans, France), and close symbols represent analyses at the Università di Milano (Dipartimento di Scienze della Terra "Ardito Desio," Milano, Italy). Comparison with biotite composition from tephra of the P2 allomember (gray field) and from SP Macusani and Morococala volcanic fields. b MH-T4 and CLQ-T23/LB-

Fig. 6

 6 Fig. 6 Composition of matrix glass. a Harker K2O vs SiO2 diagram of glass shards showing the glass composition of MH-T4 and CLQ-T23/LB-T19 tephra. Comparison with glass composition from tephra of the P2 allomember (gray field) and from SP Macusani and Morococala volcanic fields. Fields from Peccerillo and Taylor (1976). b CaO vs SiO2 diagram of glass shards showing the glass composition of MH-T4 and CLQ-T23/LB-T19 tephra. Comparison with glass composition from tephra of the P2 allomember (gray field) and from SP Macusani and Morococala volcanic fields. c Al2O3 vs SiO2 diagram of glass shards showing the glass composition of MH-T4 and CLQ-T23/LB-T19 tephra. Comparison with

Fig. 7

 7 Fig. 7 Age spectra, Ca/K vs age and Cl/K vs age diagrams. a MH-T4 age spectra of biotite (red) and muscovite (blue) separates. Uncertainties are shown as 2σ. The isochemical ages (i.e., weighted average age of isochemical steps) are 7.98 ± 0.03 Ma for biotite and 7.95 ± 0.03 Ma for muscovite. b MH-T4 Ca/K vs age diagram of biotite (red full circles), previous dated biotite (red empty circles) and muscovite (blue diamonds)

Table 1

 1 EPMA analyses on biotite phenocrysts of MH-T4 tephra

	Provenance of samples:	MH-T4 -Pisco Basin
	Source:	This

Table 2

 2 EPMA analyses on biotite phenocrysts of

	Provenance of samples: Source:	MH-T4 -Pisco Basin This work 16-1 16-2	17-1	17-2	18-1	18-2	19-1	19-2	20	21	22	23	24	25	26	42 Page 8 of 22
	SiO2 wt%	35.06	35.52	34.03	34.23	34.61	34.08	34.73	34.01	35.16	35.19	34.88	34.81	35.22	34.93	35.57
	TiO2	3.20	3.21	3.51	3.45	3.60	3.80		3.23	3.09	3.36	3.06	3.28	2.94	3.45	3.37	2.94
	Al2O3	19.11	18.99	18.00	18.59	18.99	18.52	18.98	18.94	19.85	20.30	20.07	20.11	19.13	19.18	19.91
	FeO	20.33	20.62	20.82	20.55	20.42	20.68	22.13	21.33	22.70	19.43	20.02	21.39	20.59	21.27	21.62
	MnO	0.20	0.16	0.17	0.13	0.14	0.10		0.21	0.22	0.11	0.15	0.23	0.34	0.24	0.17	0.21
	MgO	6.68	6.65	6.62	6.72	7.15	7.19		5.45	5.44	6.03	7.31	7.23	5.28	7.23	6.88	4.98
	CaO	0.01	bd	0.03	0.04	0.01	0.02		bd	0.01	0.01	bd	bd	bd	0.04	0.02	bd
	Na2O	0.30	0.30	0.33	0.39	0.33	0.35		0.36	0.42	0.38	0.36	0.31	0.29	0.32	0.31	0.37
	K2O	9.13	9.11	8.98	9.02	9.07	9.08		8.95	9.00	8.65	8.72	8.80	9.25	9.36	9.08	9.16
	F	na	na	na	na	na	na		na	na	na	na	na	bd	bd	bd	0.08
	Cl	0.05	0.05	0.10	0.11	0.16	0.15		0.13	0.15	0.14	0.08	0.06	na	na	na	na
	ZnO	na	na	na	na	na	na		na	na	na	na	na	0.14	bd	0.02	bd
	BaO	0.09	bd	0.04	0.10	0.02	0.16		0.09	0.06	bd	bd	bd	na	na	na	na
	Total	94.18	94.62	92.68	93.33	94.49	94.13	94.29	92.69	93.69	94.69	95.69	94.81	95.81	95.93	96.74
	Ions on the basis of 22 oxygens
	Si apfu	5.43	5.47	5.39	5.37	5.35	5.31		5.42	5.39	5.35	5.37	5.33	5.40	5.38	5.36	5.48
	Ti	0.37	0.37	0.42	0.41	0.42	0.45		0.38	0.37	0.38	0.35	0.38	0.34	0.40	0.39	0.34
	Al	3.49	3.45	3.36	3.44	3.46	3.40		3.49	3.54	3.56	3.65	3.62	3.67	3.44	3.47	3.62
	AlIV	2.57	2.53	2.61	2.63	2.65	2.69		2.58	2.61	2.65	2.63	2.67	2.60	2.62	2.64	2.52
	AlVI	0.92	0.91	0.75	0.81	0.80	0.72		0.91	0.94	0.90	1.02	0.95	1.07	0.82	0.84	1.09
	Fe	2.63	2.65	2.76	2.70	2.64	2.70		2.89	2.83	2.89	2.48	2.56	2.77	2.63	2.73	2.78
	Mn	0.03	0.02	0.02	0.02	0.02	0.01		0.03	0.03	0.01	0.02	0.03	0.04	0.03	0.02	0.03
	Mg	1.54	1.53	1.56	1.57	1.65	1.67		1.27	1.29	1.37	1.66	1.65	1.22	1.65	1.57	1.14
	Ca	bd	bd	0.01	0.01	bd	bd		bd	bd	bd	bd	bd	bd	0.01	bd	bd
	Na	0.09	0.09	0.10	0.12	0.10	0.11		0.11	0.13	0.11	0.11	0.09	0.09	0.10	0.09	0.11
	K	1.80	1.79	1.82	1.81	1.79	1.81		1.78	1.82	1.68	1.70	1.72	1.83	1.82	1.78	1.80
	Cl	0.01	0.01	0.03	0.03	0.04	0.04		0.03	0.04	0.04	0.02	0.02	na	na	na	na
	Zn	na	na	na	na	na	na		na	na	na	na	na	0.02	bd	bd	bd
	Ba	0.01	bd	bd	0.01	bd	0.01		0.01	bd	bd	bd	bd	bd	bd	bd	0.04
	sum	15.40	15.38	15.47	15.47	15.45	15.51	15.41	15.45	15.39	15.36	15.39	15.38	15.46	15.44	15.34
	X	1.90	1.88	1.92	1.94	1.89	1.92		1.90	1.95	1.79	1.80	1.81	1.92	1.93	1.87	1.95
	Y	5.49	5.48	5.52	5.50	5.52	5.54		5.47	5.45	5.56	5.53	5.56	5.45	5.52	5.55	5.39
	MgV Provenance of samples: MH-T4 -Pisco Basin 0.37 0.36 Source: This work	0.36 Macusani volcanic field 0.37 0.38 Noble et al. (1984)	0.38	0.31 Pichavant et al. (1988a) 0.31	0.32 Morococala volcanic field 0.40 0.39 Morgan et al. (1998)	0.31	0.39	0.37	0.29	Bull Volcanol
	SiO2 wt% TiO2 Al2O3	27 34.35 3.50 18.84	28 34.85 3.33 19.33	mean (6) mean (6) mean (10) 36.30 36.40 35.30 2.55 2.88 2.94 21.10 19.60 21.30	mean (15) 36.01 2.76 20.29	SD 0.71 0.96 0.94	AR mean (164) SD 34.79 0.49 2.88 0.26 20.30 0.76	AR mean (91) SD 35.24 0.44 2.89 0.28 20.60 0.86	AR mean (113) SD 34.91 1.02 2.91 0.21 20.12 0.92	(2020) 82:42
	FeO	21.04	21.02	21.40	23.00	22.80		21.46		1.48	23.84	0.97	22.25		1.70	23.31	1.66
	MnO	0.20	0.19	0.01	0.01	0.02		0.18		0.07	0.30	0.08	0.33		0.13	0.28	0.10
	MgO	6.20	6.60	4.71	5.03	4.71		4.96		1.07	4.92	0.89	5.22		1.23	5.12	0.63

Table 3

 3 EPMA analyses on muscovite phenocrysts of MH-T4 tephra

	Provenance of samples:	MH-T4 -Pisco Basin
	Source:	This work
		12		13	14		1	2	3-1	3-2	4	5	6		7	8
	SiO2 wt%	48.86	48.00	48.12	45.44	45.61	45.63	46.10	44.96	45.68	45.52		45.44	45.59
	TiO2	0.94		0.94	1.36		1.29	0.94	0.77	1.23	0.88	1.07	0.82		1.20	1.19
	Al2O3 FeO T	34.82 2.44	36.64 1.75	36.97 1.32	35.53 1.25	35.69 1.59	33.93 2.30	33.57 2.05	34.97 1.78	35.54 1.44	35.51 1.60		34.79 1.52	35.20 1.47
	MnO	bd		bd	0.05		0.03	0.02	0.01	0.01	bd	0.01	bd		0.02	0.04
	MgO	1.29		0.78	0.71		0.72	0.70	1.18	1.12	0.76	0.77	0.76		0.93	0.89
	CaO	0.01		bd	bd		0.01	bd	bd	0.02	0.02	bd	bd		bd	bd
	Na2O	0.70		0.78	0.79		0.74	0.69	0.72	0.67	0.66	0.72	0.72		0.67	0.69
	K2O	10.92	11.08	10.64	10.22	9.78	9.80	9.82	9.81	9.81	9.71		9.72	9.75
	P2O5	0.02		0.04	0.03		na	na	na	na	na	na	na		na	na
	F	na		na	na		na	na	na	na	na	na	na		na	na
	Cl	na		na	na		bd	0.01	bd	bd	0.01	0.01	0.01		bd	bd
	ZnO	na		na	na		na	na	na	na	na	na	na		na	na
	BaO	na		na	na		bd	0.06	bd	0.10	bd	bd	0.01		0.05	bd
	Total	93.61	93.27	94.99	95.22	95.09	94.33	94.69	93.84	95.05	94.66		94.33	94.82
	Provenance of samples: MH-T4 -Pisco Basin		Macusani volcanic field			Morococala volcanic field
	Source:	This work			Noble et al. (1984)		Pichavant et al. (1988a)	Morgan et al. (1998)
		9	10	16	17	Mean	Mean	Mean (7)	Mean (5)	SD	AR	SD	AR	SD	AR	SD
						(10)	(4)				mean (102)		mean (62)		meam (23)
	SiO2 wt%	45.48	45.54	46.28	45.58	47.00	47.00	47.00	45.54	0.79	46.70	0.25	46.74	0.13	46.40	0.3
	TiO2	1.00	1.07	0.95	1.00	0.69	0.70	0.77	0.49	0.28	0.97	0.24	0.91	0.24	0.91	0.18
	Al2O3 FeO T	35.16 1.34	34.85 1.39	33.12 2.30	32.76 2.45	34.70 2.53	35.40 2.22	36.20 1.38	34.21 2.55	1.22 0.68	35.15 1.83	0.57 0.28	34.49 1.90	0.28 0.24	34.95 1.87	0.22 0.22
	MnO	0.06	0.03	0.05	0.09	bd	bd	bd	0.03	0.03	bd	bd	bd	bd	bd	bd
	MgO	0.77	0.80	1.40	1.36	1.06	0.92	0.72	1.05	0.08	0.87	0.07	0.87	0.04	0.83	0.08
	CaO	0.01	0.02	0.03	0.08	bd	bd	bd	bd	bd	bd	bd	bd	bd	bd	bd
	Na2O	0.73	0.66	0.73	0.68	0.71	0.70	0.74	0.65	0.05	0.61	0.03	0.68	0.04	0.65	0.04
	K2O	9.60	9.62	10.53	10.27	10.24	10.28	10.32	10.14	0.15	10.14	0.44	9.75	0.17	9.76	0.30
	P2O5	na	na	bd	0.01	na	na	na	na	na	na	na	na	na	na	na
	F	na	na	1.73	1.57	bd	bd	bd	1.49	0.60	2.19	0.92	3.65	0.41	3.72	0.26
	Cl	bd	bd	na	na	0.01	0.02	0.02	na	na	bd	bd	0.01	0.01	0.02	0.01
	ZnO	na	na	bd	0.23	na	na	na	0.08	0.10	bd	bd	bd	bd	bd	bd
	BaO	bd	bd	na	na	na	na	na	na	na	0.09	0.12	0.05	0.02	0.05	0.01
	Total	94.15	93.98	97.13	96.07	97.00	97.20	97.10	95.91	1.23	97.67	-	97.51	-	97.59	-

Comparison with the Macusani and Morococala mean muscovite compositions from literature. "AR" is the abbreviation for andalusite-bearing rhyolites in

[START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]

. Abbreviations; "na" stands for "not analyzed" and "bd" stands for "below detection"

Table 4

 4 EPMA analyses on feldspar phenocrysts of MH-T4 tephra

	Provenance of MH-T4 -Pisco Basin				Macusani volcanic field	Morococala volcanic field
	samples:
	Source:	This work					Pichavant et al. (1988a)	Morgan et al. (1998)
	Type:	Sanidine		Plagioclase		Sanidine	Plagioclase	Plagioclase	Sanidine
		12	13	15	16	19	20	Mean SD Mean SD	AR mean SD AR mean SD AR mean SD
								(3)		(7)		(282)	(288)	(537)
	SiO2 wt%	64.44 59.60 64.36 61.67 63.18 62.55 65.06 0.27 62.34 3.12 62.89	1.46 63.53	1.05 64.50	0.32
	Al2O3	19.21 18.25 19.21 23.54 22.26 22.63 18.90 0.06 23.56 1.94 23.12	1.03 22.72	0.66 19.33	0.11
	FeO T	0.06 0.03 0.01 0.06 0.08 bd	na	na na	na	0.02	0.01 0.05	0.03 0.02	0.01
	CaO	0.05 0.07 0.10 4.11 2.85 3.29 bd	bd 4.58	2.58 3.58	1.15 3.13	0.81 0.05	0.02
	Na2O	2.67 2.81 2.65 8.51 9.41 9.15 3.40	0.13 8.42	1.40 8.89	0.62 9.14	0.47 3.05	0.23
	K2O	12.03 11.54 11.87 0.68 0.68 0.77 11.60 0.24 0.63	0.23 0.67	0.12 0.71	0.06 12.07	0.28
	BaO	0.22 0.38 0.13 bd	bd	0.01 0.07	0.08 na	na	na	na	na	na 0.12	0.06
	An	0.26 0.37 0.52 20.23 13.78 15.84 0.00	0.00 22.38 12.90 17.49	5.70 15.26	4.00 0.30	0.10
	Ab	25.05 26.71 25.14 75.80 82.33 79.71 30.78 1.29 73.96 11.67 78.61	5.20 80.62	3.80 27.62	2.00
	Or	74.69 72.92 74.34 3.97 3.89 4.45 69.22 1.29 3.66	1.31 3.90	0.70 4.12	0.40 71.90	1.90
	Total	98.72 92.69 98.36 98.57 98.50 98.46 99.00 0.36 99.54 1.04 99.32	-	99.43	-	99.35	-

Plagioclase and sanidine phenocrysts are compared with the Macusani and Morococala mean compositions from literature. "AR" is the abbreviation for andalusite-bearing rhyolites in

[START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]

. Abbreviations; "na" stands for "not analyzed" and "bd" stands for "below detection"

Table 5

 5 EPMA analyses on Al2SiO5 minerals of MH-T4 tephra

	Provenance of MH-T4 -Pisco Basin				Macusani volcanic field				Morococala volcanic field
	samples:
	Source:	This work					Noble et al. (1984)	Pichavant et al. (1988a)	Morgan et al. (1998)
	Type:	Al2SiO5 mineral				Sillimanite Andalusite Sillimanite Andalusite Andalusite Andalusite
		11	12	14	17	18	21	Range	Range	Mean SD Mean SD AR	SD AR	SD
										(2)	(3)		mean		mean
													(34)		(39)
	SiO2 wt%	38.25 36.16 36.20 35.60 36.88 36.07 na	na	36.40 0.37 37.25 0.80 36.84 0.19 36.99 0.07
	TiO2	bd	bd	0.01	0.06	bd	bd	0.01-0.11 0.01-0.34 0.03	0.04 0.04	0.04 0.10	0.03 bd	bd
	Al2O3	61.51 63.86 64.37 64.51 62.75 64.36 na	na	63.33 0.27 62.14 0.34 62.02 0.36 62.53 0.04
	FeO T	0.22 0.26	0.08	0.22	0.13 0.18	0.04-0.44 0.17-0.80 0.18	0.05 0.24	0.05 0.61	0.25 0.29	0.02
	MnO	bd	0.03	0.04	0.01	bd	0.04	na	na	0.05	0.07 0.03	0.03 bd	bd bd	bd
	MgO	0.02 bd	bd	bd	0.02 bd	na	na	0.02	0.03 0.04	0.02 0.05	0.03 bd	bd
	CaO	bd	0.03	bd	0.02	bd	bd	0.01-0.20 bd	0.02	0.03 0.01	0.01 bd	bd bd	bd
	Na2O	bd	0.03	bd	bd	0.02 bd	na	na	bd	bd bd	bd bd	bd bd	bd
	K2O	bd	0.03	bd	0.01	0.09 bd	na	na	bd	bd bd	bd bd	bd bd	bd
	Total	98.73 100.41 100.72 100.42 99.90 100.67 -	-	100.02 0.06 99.75 1.01 99.62 -	99.81 -

Comparison with the Macusani and Morococala mean compositions of sillimanite and andalusite from literature. "AR" is the abbreviation for andalusite-bearing rhyolites in

[START_REF] Morgan | Petrochemistry of late-Miocene peraluminous silicic volcanic rocks from the Morococala field, Bolivia[END_REF]

. Abbreviations; "na" stands for "not analyzed" and "bd" stands for "below detection"

Table 7

 7 Trace element LA-ICP-MS analysis of matrix glasses for

	MH-T4 tephra
		MH-T4 glass 1	MH-T4 glass 2	MH-T4 glass 3
	Li (ppm)	9.04	6.70	< 11.62
	Be	18.2	26.3	47.5
	B	865	873	803
	Rb	645	584	558
	Sr	15.1	16.2	25.1
	Zr	14.65	21.2	15.96
	Nb	21.0	21.6	19.24
	Sn	55.1	68.8	51.2
	Cs	166	167	162
	Ba	17.08	26.0	33.5
	La	1.24	1.71	2.25
	Ta	6.12	6.02	5.96
	W	26.2	19.1	22.0
	Pb	20.3	25.7	29.1
	U	19.3	24.9	23.4

Acknowledgments The authors are grateful to R. Varas-Malca and W. Aguirre for their assistance in the field and at the Natural History Museum in Lima. Special thanks to E. Malinverno for the support in the field and in laboratory analyses, to V. Barberini for the help in 39 Ar-40 Ar dating, and N. Fusi for grain-size analyses. The authors wish to thank A. Risplendente for the help with the microprobe analyses. Finally, the authors would like to thank two anonymous reviewers, V.S. Kamenetsky and the Executive Editor for their revisions and thorough support.

Funding This study was supported by grants from the Italian Ministero dell'Istruzione dell'Università e della Ricerca (PRIN Project 2012YJSBMK) and by the University of Pisa PRA_2015_0028 and PRA_2017_0032 grants.