Nature and Evolution of Primitive Vesuvius Magmas: an Experimental Study

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1 JOURNAL OF PETROLOGY VOLUME 55 NUMBER11 PAGES 2281^ doi: /petrology/egu057 Nature and Evolution of Primitive Vesuvius Magmas: an Experimental Study MICHEL PICHAVANT 1 *, BRUNO SCAILLET 1,ANNEPOMMIER 1,2, GIADA IACONO-MARZIANO 1 AND RAFFAELLO CIONI 3 1 INSTITUT DES SCIENCES DE LA TERRE D ORLEANS (ISTO), UMR 7327, UNIVERSITE D ORLEANS, ORLEANS, FRANCE AND ISTO, UMR 7327, CNRS, ORLEANS, FRANCE AND ISTO, UMR 7327, BRGM, BP ORLEANS, FRANCE 2 SCRIPPS INSTITUTION OF OCEANOGRAPHY, UC SAN DIEGO, 9500 GILMAN DRIVE, LA JOLLA, CA 92093, USA 3 DIPARTIMENTO DI SCIENZE DELLA TERRA, UNIVERSITA DEGLI STUDI FIRENZE, VIA LA PIRA 4, FIRENZE, ITALY RECEIVED DECEMBER 16, 2013; ACCEPTED SEPTEMBER 23, 2014 Two mafic eruptive products from Vesuvius, a tephrite and a trachybasalt, have been crystallized in the laboratory to constrain the nature of primitive Vesuvius magmas and their crustal evolution. Experiments were performed at high temperatures (from 1000 to 12008C)andbothat01MPa and at high pressures (from 50 to 200 MPa) under H 2 O-bearing fluid-absent and H 2 O- and CO 2 - bearing fluid-present conditions. Experiments started from glass except for a few that started from glass plus San Carlos olivine crystals to force olivine saturation. Melt H 2 O concentrations reached a maximum of 60 wt % and experimental fo 2 ranged from NNO ^ 01 to NNOþ 34 (where NNO is nickel^nickel oxide buffer). Clinopyroxene (Mg# up to 93) is the liquidus phase for the two investigated samples; it is followed by leucite for H 2 O in melt 53 wt %, and by phlogopite (Mg# up to 81) for H 2 O in melt 43 wt %. Olivine (Fo 85 ) crystallized spontaneously in only one experimental charge. Plagioclase was not found. Upon progressive crystallization of clinopyroxene, glass K 2 OandAl 2 O 3 contents strongly increase whereas MgO, CaO and CaO/Al 2 O 3 decrease; the residual melts follow the evolution of Vesuvius whole-rocks from trachybasalt to tephrite, phonotephrite and to tephriphonolite. Concentrations of H 2 OandCO 2 in near-liquidus 200 MPa glasses and primitive melt inclusions from the literature overlap. The earliest evolutionary stage, corresponding to the crystallization of Fo-rich olivine, was reconstructed by the olivine-added experiments. They show that the primitive Vesuvius melts are trachybasalts (K 2 O 45^55wt %, MgO ¼ 8^9 wt %, Mg# ¼ 75^80, CaO/Al 2 O 3 ¼ 09^095) that crystallize Fo-rich olivine (90^91) as the liquidus phase between 1150 and 12008C and from 300 to 5200 MPa. Primitive Vesuvius melts are volatile-rich (15^45wt % H 2 Oand600^ 4500 ppm CO 2 in primitive melt inclusions) and oxidized (from NNO þ 04 to NNOþ12). Assimilation of carbonate wall-rocks by ascending primitive magmas can account for the disappearance of olivine from crystallization sequences and explains the lack of rocks representative of olivine-crystallizing magmas. A correlation between carbonate assimilation and the type of feeding system is proposed: carbonate assimilation is promoted for primitive magma batches of small volumes. In contrast, for longer-lived, large-volume, less frequently recharged, hence more evolved, cooler reservoirs, magma^carbonate interaction is limited. Primitive magmas from Vesuvius and other Campanian volcanoes have similar redox states. However, the Cr# of Vesuvius spinels is distinctive and therefore the peridotitic component in the mantle source of Vesuvius differs from that of the other Campanian magmas. KEY WORDS: Vesuvius; experimental petrology; phase equilibria; primitive magmas; carbonate assimilation; magma reservoirs; potassic series INTRODUCTION Volcanic eruptions of Mt. Vesuvius (Italy) have been conveniently divided into two groups, open-conduit and closed-conduit (e.g. Santacroce et al., 1993; Marianelli *Corresponding author. pichavan@cnrs-orleans.fr ß The Author Published by Oxford University Press. All rights reserved. For Permissions, please journals.permissions@ oup.com

2 JOURNAL OF PETROLOGY VOLUME 55 NUMBER 11 NOVEMBER 2014 et al., 1995). Lava effusion and mixed effusive^explosive activity characterize the former group, which is best illustrated by the 1637^1944 period of activity (Santacroce et al., 1993; Marianelli et al., 1995, 1999, 2005; Scandone et al., 2008). The latter group involves either Plinian or sub-plinian eruptions with erupted volumes of a maximum of a few km 3, as illustrated by the Pompei (AD 79) and the Pollena (AD 472) eruptions (Rosi & Santacroce, 1983; Cioni et al.,1995). Mafic compositions (tephrite to phonotephrite) typically characterize open-conduit eruptions, and more evolved compositions (tephriphonolite to phonolite) closed-conduit eruptions. Despite this fundamental subdivision, there is an overall consensus that volcanic activity at Vesuvius is driven by the periodic arrival of primitive mafic magma batches at shallow crustal levels (e.g. Santacroce et al., 1993; Scandone et al., 2008). Mafic magmas are directly emitted together with more evolved, generally crystal-rich, products, during violent Strombolian activity, as for example during the 1794, 1822, 1872, 1906 and 1944 eruptions (Marianelli et al., 1995, 1999, 2005; Scandone et al., 2008). In contrast, eruption of mafic magma is not observed in Plinian events. However, Plinian magma reservoirs such as that of the AD 79 eruption are periodically recharged by primitive magma batches that contribute energy and mass to the reservoir and mix with the resident differentiates (Cioni et al., 1995). Therefore, it is critical for our understanding of the volcanic activity of Vesuvius to gain a better knowledge of the physical and chemical properties of these primitive magma batches. So far, information on primitive magma batches at Vesuvius has been elusive. Indeed, the absence of primitive products is typical of the activity of Vesuvius (e.g. Dallai et al., 2011). Geochemical studies have stressed the importance of magma mixing in crustal magma reservoirs; most Vesuvius eruption products represent mixtures between mafic and more evolved magmas (e.g. Belkin et al., 1993; Santacroce et al. 1993; Villemant et al., 1993; Marianelli et al., 1999). Until now, only detailed mineralogical studies have provided clues on Vesuvius primitive magmas. Studies of primitive phenocrysts (Fo-rich olivine and diopside) and of their melt inclusions have documented the occurrence of trachybasaltic to tephritic glasses (MgO ¼ 8^10 wt %; CaO/Al 2 O 3 ¼10^11), proposed to be representative of primitive Vesuvius melts (Marianelli et al., 1995, 1999, 2005; Cioni et al., 1998; Cioni, 2000). Volatile concentrations in these melt inclusions (H 2 O ¼15^45wt %, CO 2 ¼ 600^4500 ppm; Marianelli et al., 1995, 1999, 2005; Cioni, 2000) have been used to determine depths of magma crystallization (Marianelli et al., 1999, 2005). Another approach to constrain the nature of Vesuvius primitive magma is experimental. For Vesuvius, previous high-pressure experimental work has concentrated on evolved phonotephritic to phonolitic rocks (Dolfi & Trigila, 1978; Scaillet et al., 2008). One relatively primitive tephrite sample has been experimentally investigated at 01MPa (Trigila & De Benedetti, 1993). Here we report the results of an experimental study on Vesuvius mafic products, as an extension of our earlier work on Vesuvius phonolites (Scaillet et al., 2008). The data constrain the nature and physical conditions (major element composition, crystallization pressures and temperatures, melt volatile concentrations and redox state) of primitive Vesuvius magmas. New arguments for interaction between the primitive magmas and carbonate wall-rocks are provided. A correlation between the extent of carbonate assimilation and the type of feeding system is proposed. On a broader perspective, this study contributes to the experimental characterization of mafic K-rich magmas, which include rock-types such as lamproites, lamprophyres and minettes (Barton & Hamilton, 1978; Esperanc a & Holloway, 1987; Wallace & Carmichael, 1989; Righter & Carmichael, 1996). EXPERIMENTAL APPROACH AND SELECTION OF STARTING SAMPLES In this study natural mafic products from Vesuvius were equilibrated under controlled laboratory conditions. Most experiments were carried out at high pressures (between 50 and 200 MPa), both under hydrous but H 2 O-undersaturated conditions (hereafter designated as fluid-absent; i.e. the melt H 2 O content is less than the solubility) and in the presence of an H 2 O- and CO 2 -bearing fluid phase (hereafter designated as fluid-present; i.e. addition of CO 2 imposes the presence of a fluid phase). In addition, volatile-free experiments were performed at 01MPa. Experimental products were systematically compared with phenocryst assemblages and phenocryst and glass inclusion compositions from the eruptive products. In this study, eruptions younger than Avellino (39 ka BP) have been considered, in particular Pompei (AD 79), Pollena (AD 472), 1631, the 1637^1944 period and 1906 and One major concern at the beginning of this study was the choice of appropriate starting materials because, as emphasized above, primitive eruptive products are basically lacking at Vesuvius. Another issue is that few mafic Vesuvius products actually represent magmatic liquids, because of magma mixing and phenocryst accumulation or removal (e.g. Marianelli et al., 1999). With these difficulties in mind, two samples were selected, a tephrite () from a subplinian medieval (8th century) eruption and a trachybasalt () from the 1944 eruption (Table 1; Fig. 1). originates from a lava fountaining episode and is made of fallout crystal-rich (40% crystals) lapilli. 2282

3 PICHAVANT et al. PRIMITIVE VESUVIUS MAGMAS Table 1: Major element composition of primitive Vesuvius samples VS whole-rock* glassy whole-rock* glassy whole-rock* SiO 2 (wt%) (5) (5) 4891 TiO (6) (8) 100 Al 2 O (2) (2) 1384 FeO t (34) (38) 705 MnO (8) (8) 014 MgO (34) (37) 752 CaO (2) (2) 1239 Na 2 O (8) (9) 189 K 2 O (12) (13) 572 P 2 O (8) (8) 076 LOI 074 Total Na 2 O þ K 2 O CaO/Al 2 O Mg# *Whole-rock data:, ICP-AES analysis (CRPG, Vandoeuvre-lès-Nancy, France);, analysis from Marianelli et al. (1999); VS97-718, analysis from R. Cioni (unpublished). yaverage of five electron microprobe analyses; numbers in parentheses are standard deviations in terms of least unit cited. Mg# ¼ 100 molar MgO/(MgO þ FeO) with total Fe as FeO. FeO t, all Fe as FeO. Phenocrysts of clinopyroxene (cpx, Fs 5^18 En 34^49 Wo 46^50, calculated with total Fe as Fe 2þ ), leucite [K/ (K þ Na) ¼ 0903^0943] and rare plagioclase (plag, Ab 20^53 An 40^80 Or 1^7 ) are present, together with a few magnetite (TiO 2 ¼117 wt %) and apatite inclusions (Table 2). comes from the main layer of the 1944 lava fountain deposits (Marianelli et al., 1999). The sample is porphyritic (45% crystals). It hosts two distinct phenocryst assemblages, the first comprising diopside (Fs 5 En 48 Wo 47 ) and Fo-rich olivine (ol, Fo up to 90) and the second salite (Fs 9^15 En 36^43 Wo 48^50 ), less Fo-rich olivine (Fo 50^73 ), plagioclase (Ab 11^16 An 80^87 Or 2^5 ) and minor leucite [K/(K þ Na) ¼ 0907^0914; Table 2; Marianelli et al., 1999]. (K 2 O ¼ 555 wt %, Table 1; Fig. 1) is compositionally close to the parental mafic magma batch B of Santacroce et al. (1993), being slightly more primitive than the V36 tephrite investigated by Trigila & De Benedetti (1993). MgO (673 wt %) and CaO/Al 2 O 3 (088) are in the middle of the range of primitive melt inclusions from the 1637^1944 period (Marianelli et al., 1995, 1999, 2005). Compared with, has higher MgO (797 wt %) and CaO/Al 2 O 3 (104, Table 1), approaching the most primitive 1637^1944 inclusions (Marianelli et al., 1995, 1999, 2005). However, it is less potassic (K 2 O ¼ 429 wt %) and more calcic (CaO ¼1396 wt %) than and the primitive melt inclusion group, suggesting some clinopyroxene accumulation (Marianelli et al., 1999). Other starting products were considered during the course of the study, but none with clearly superior characteristics was found. In particular, a tephrite^phonotephrite (VS97-718) from a peripheral eruption of pre-medieval age (Table 1; Fig. 1) was examined in detail. This porphyritic sample contains phenocrysts of diopside (Fs 4^5 En 48^ 49Wo 47^48 ), salite (Fs 10^17 En 32^44 Wo 46^51 ), Fo-rich (Fo up to 90) olivine with Cr-rich (Cr# up to 81) spinel inclusions, and leucite [K/(K þ Na) ¼ 0916^0930, Table 2]. Geochemically, VS is close to (Fig. 1), being only slightly more magnesian (Table 1). Mineralogically, it is similar to (coexistence of two distinct phenocryst assemblages). Moreover, olivine in VS is too Fo-rich to be in equilibrium with the bulk-rock. Therefore, it was not subjected to specific experimental investigations. However, olivines, diopsides and Cr-spinels in VS are among the most primitive in Vesuvius products and their compositions are given in Table 2. EXPERIMENTAL METHODS Starting materials and were ground in an agate mortar to 50 mm and fused in air at 14008C, 01MPa in a Pt crucible. For each sample, two cycles of melting of 2^4 h each (with grinding between) were performed, yielding a homogeneous glass whose composition was checked by electron microprobe (Table 1). The glass was then crushed to 50 mm and stored in an oven. Most experiments used these two glasses directly as starting materials. A few experiments were conducted with glass (either or ) plus San Carlos olivine crystals (Fo 905, sieved to 50^100 mm) to force saturation of the melt with a Fo-rich olivine under the specific experimental conditions. High-pressure experiments Noble metal capsules, either Au 90 Pd 10 or Au 70 Pd 30 (more rarely Ag 70 Pd 30 )at410508c andau10508c, were used as containers (length 15 mm, internal diameter 25 mm, wall thickness 02 mm). For hydrous but H 2 O-undersaturated experiments, amounts of distilled water between 06 and 2 ml and about 30 mg of glass powder (i.e. less water than expected solubilities) were loaded in the capsule. For hydrous but fluid-saturated experiments performed with H 2 O^CO 2 mixtures, Ag 2 C 2 O 4 was introduced in the capsule as the source of CO 2, together with distilled 2283

4 JOURNAL OF PETROLOGY VOLUME 55 NUMBER 11 NOVEMBER 2014 wt% K2O + Na2O Eruption products AD 472 AD 79 tephrite trachybasalt phonolite wt% SiO 2 Experimental glasses phonotephrite tephriphonolite trachybasalt 70 + Ol + Ol phonolite tephriphonolite phonotephrite Dolfi & Trigila 1978 Trigila & De Benedetti 1993 Scaillet et al Table 2: Representative electron microprobe analyses of phenocrysts in primitive Vesuvius samples this work VS Fig. 1. Total alkalis^silica (TAS) diagram for Vesuvius starting materials, experimental glasses and eruption products. Inset shows the composition of the starting materials: trachybasalt () and tephrites (, VS97-718). Shown for comparison are the V36 tephrite composition of Trigila & De Benedetti (1993), phonotephrite V 1 of Dolfi & Trigila (1978) and four phonolites studied by Scaillet et al. (2008). Shaded fields represent whole-rock compositions of the AD 79 (Pompei), AD 472 (Pollena), 1631, 1637^1944 period, 1906 and 1944 eruptions from Rosi & Santacroce (1983), Rosi et al. (1993), Santacroce et al. (1993), Cioni et al. (1995, 1998) and Marianelli et al. (1999, 2005). Sample Phase SiO 2 TiO 2 Al 2 O 3 Cr 2 O 3 FeO MnO MgO CaO Na 2 O K 2 O NiO Total Composition Lc Ne 3 Ks 46 Qz 51 Cpx Fs 8 En 44 Wo 48 Plag An 35 Ab 62 Or 3 Lc Ne 4 Ks 45 Qz 51 Cpx Fs 5 En 48 Wo 47 Cpx Fs 12 En 40 Wo 48 Ol Fo 886 Ol Fo 734 Plag An 11 Ab 87 Or 2 VS Lc Ne 4 Ks 46 Qz 50 Cpx Fs 4 En 49 Wo 48 Cpx Fs 12 En 38 Wo 50 Ol Fo 90 Sp Cr#81 Lc, leucite; Cpx, clinopyroxene; Plag, plagioclase; Ol, olivine; Sp, Cr Al spinel; Ne ¼ 100 atomic (at.) Na/Si; Ks ¼ 100 at. K/Si; Qz ¼ 100(Si Na K)/Si in leucite; Fs ¼ 100 at. Fe/(Mg þ Fe þ Ca); En ¼ 100 at. Mg/ (Mg þ Fe þ Ca); Wo ¼ 100 at. Ca/(Mg þ Fe þ Ca) in pyroxene (total Fe as Fe 2þ ); Fo ¼ 100 at. Mg/(Mg þ Fe) in olivine; An ¼ 100 at. Ca/(Ca þ Na þ K), Ab ¼ 100 at. Na/(Ca þ Na þ K); Or ¼ 100 at. K/(Ca þ Na þ K) in plagioclase; Cr# ¼ 100 at. Cr/(Cr þ Al) in spinel. water and the glass powder (about 30 mg). H 2 O and Ag 2 C 2 O 4 were weighed so as to generate charges with variable XH 2 O in. [initial molar H 2 O/(H 2 O þ CO 2 )] while the (H 2 O þ CO 2 )/(H 2 O þ CO 2 þ glass) mass ratio was kept constant at 10%. All capsules were sealed by arc welding, keeping them in a liquid nitrogen bath to prevent water loss. They were then put in an oven for several hours and reweighted to check for leaks. 2284

5 PICHAVANT et al. PRIMITIVE VESUVIUS MAGMAS High-pressure experiments were all carried out in the same internally heated pressure vessel, working vertically and pressurized with Ar^H 2 mixtures obtained by sequential loading of H 2 and Ar at room temperature (Scaillet et al., 1992). Initial H 2 pressures ranged from zero (no H 2 initially loaded) to 5 bar. This yielded experimental fh 2 (measured by Ni^Pd^O sensors; see below), from 01to12 bar (Tables 3 and 4). Total pressure was recorded by a transducer calibrated against a Heise Bourdon tube gauge (uncertainty 20 bar). A double winding Mo furnace was used, allowing near-isothermal conditions in the 2^3 cm long hot-spot (gradient 52^38C cm 1 ). Temperature was measured by three thermocouples (either type S or K) and was recorded continuously (total uncertainty 58C). Run durations were longer for the fluid-absent (145^23 h) than for the fluid-present (2^75 h) experiments. All runs were drop-quenched, resulting in nearly isobaric quench rates of 1008C s 1 (Di Carlo et al., 2006). A majority of runs included a Ni^Pd^O sensor capsule, which served to determine the experimental fh 2 (Taylor et al., 1992; Di Carlo et al., 2006; Pichavant et al., 2009). Analysis of the composition of the NiPd alloy after the experiment allows the fo 2 of the sensor capsule to be determined (Pownceby & O Neill, 1994). The fh 2 of the sensor (and by inference of the experiment, as fh 2 is identical for all capsules) is then obtained from the water dissociation equilibrium using the fo 2 determined above, the dissociation constant of water (Robie et al., 1979) and the fugacity of pure water at the experimental P and T (Holloway, 1987). NiPd alloy compositions and the corresponding fh 2 are listed in Tables 3 and 4. For runs performed without a sensor, experimental fh 2 were estimated from the H 2 initially loaded into the vessel, the procedure being calibrated from experiments that included a sensor. For a given experiment (constant P^T^fH 2 ), the fo 2 of each charge varies along with ah 2 O(orfH 2 O). The latter was determined for each charge from the H 2 O content of the quenched glass, using the thermodynamic model for H 2 O solution in multicomponent melts of Burnham (1979). The oxygen fugacity of each charge is then calculated from the water dissociation equilibrium, using the fh 2 and fh 2 O determined above, and the dissociation constant of water (Robie et al., 1979). Typical uncertainties on log fo 2 are less than 025 log units (e.g. Scaillet et al., 1995; Martel et al., 1999; Scaillet & Evans, 1999; Costa et al., 2004). In this study, fo 2 values are expressed as deviations from the NNO (nickel^nickel oxide) buffer (NNO values), calculated at the P and Tof interest (Tables 3 and 4). At the end of the experiment, the capsules were weighed to check for leaks and then opened. For each capsule, fragments of the run product were mounted in epoxy and polished for scanning electron microscope (SEM) observations and electron microprobe analyses. Glass chips from selected charges were prepared for Fouriertransform infrared spectrometry (FTIR) measurements. The metallic pellets in the sensor capsule were recovered, mounted in epoxy and then analyzed by electron microprobe. 01 MPa experiments These were carried out in two vertical gas-mixing furnaces using the wire-loop method. Redox conditions were controlled with CO^CO 2 gas mixtures and the fo 2 (from NNO to NNO þ 05) was directly read using a ZrO 2 electrochemical cell. Temperature was monitored from Pt^ PtRh thermocouples. Considerable experimental difficulties were encountered, especially with K 2 O volatilization. To minimize K 2 O volatilization and, at the same time, Fe loss from the charge to the suspension wire, experiments were repeated under constant T^fO 2 conditions during 2^ 3 cycles of relatively short durations (3 h, each starting with fresh glass) to progressively saturate the same suspension wire with Fe. Intermediate charges were quenched, then dissolved in HF, and the charge from the last cycle was retained for detailed study (Pichavant et al., 2009). Both Re and Pt suspension wires were tested but Re was found to enhance K 2 O volatilization and its use was subsequently avoided. ANALYTICAL METHODS All charges were systematically examined by SEM under back-scattered electron mode (JEOL WINSET JSM 6400 instrument, University of Orle ans) to assist in the identification of the phases and to evaluate the importance of quench crystallization. Electron microprobe analyses of natural and experimental phases were performed with a Cameca Camebax, Cameca SX-50 or Cameca SX Five at the joint BRGM^CNRS^UO facility at Orle ans. Analyses were carried out under an acceleration voltage of 15 kv, counting times of 10 and 5 s on peak and background respectively, and a sample current of 6 na, except for metallic sensor phases, which were analyzed under 20 kv and 20 na. For glasses, a slightly defocused beam of about 5 mm was used, and for minerals a focused beam of 1^2 mm. Silicate minerals were used as standards. For the various oxides, the relative analytical errors are 1% (SiO 2,Al 2 O 3, CaO), 3% (FeO, MgO, TiO 2 ) and 5% (MnO, Na 2 O, K 2 O, P 2 O 5 ). Phase proportions and FeO and K 2 O losses were calculated for each charge using a least-squares mass-balance routine computed after Albare' de (1995), using the electron microprobe compositions of the glass starting material and of phases coexisting in the charge. The regression was based on eight major oxides, excluding MnO, P 2 O 5 and H 2 O. One near-liquidus (charge 5-4) experimental glass was analyzed for dissolved H 2 O by Karl-Fischer titration, using equipment and procedures identical to those 2285

6 JOURNAL OF PETROLOGY VOLUME 55 NUMBER 11 NOVEMBER 2014 Table 3: H 2 O-bearing fluid-absent experiments Charge WBD 1 (wt %) H 2 O melt (wt %) ah 2 O NNO 2 Phase assemblage 3 P R 2 FeO 4 (%) K d Fe Mg cpx liq K d Fe Mg ol liq Run 3, 2141 MPa, 11508C, 15 h, X Ni ¼ 042, fh 2 ¼ 065 MPa / þ10 Gl(100) n.d þ06 Gl(94), Cpx(6), qu þ03 Gl(93), Cpx(7), qu þ03 Gl(83), Cpx(17), qu Run 5, 2105 MPa, 11508C, 10 h, X Ni ¼ 027, fh 2 ¼ 028 MPa VS96-54þOl þ15 Gl, Ol, Cpx, qu þ14 Gl, Ol, Cpx, qu þ Ol / þ13 Gl, Ol 037 Run 1, 2101 MPa, 11008C, 145h, X Ni ¼ , fh 2 ¼ MPa þ09 Gl(69), Cpx(31), qu þ14 Gl(81), Cpx(19), qu þ06 Gl(55), Cpx(45) Run 2, 2135 MPa, 11008C, 19 h, X Ni ¼ 014, fh 2 ¼ 009 MPa þ25 Gl(75), Cpx(25), qu 053 þ þ24 Gl(67), Cpx(33), qu 025 þ þ21 Gl(64), Cpx(36), qu Run 1b, 2138 MPa, 11008C, 17 h, X Ni ¼ 028, fh 2 ¼ 028 MPa 1b þ14 Gl(91), Cpx(9), qu b þ11 Gl(87), Cpx(13), qu b þ06 Gl(78), Cpx(21), qu Run 4, 2081 MPa, 10508C, 205h, X Ni ¼ 041, fh 2 ¼ 051 MPa þ10 Gl(60), Cpx(36), Phl(4), qu þ09 Gl(49), Cpx(41), Phl(10), qu þ08 Gl(54), Cpx(41), Phl(5), qu Run 8, 2026 MPa, 10508C, 21 h, fh 2 ¼ 061 MPa þ08 Gl(63), Cpx(29), Phl(8), qu Run 9, 2062 MPa, 10008C, 19 h, fh 2 ¼ 61 MPa þ07 Gl(58), Cpx(34), Phl(8), qu Run 6, 1045 MPa, 11008C, 23 h, X Ni ¼ 026, fh 2 ¼ 012 MPa þ17 Gl(75), Cpx(25), qu þ17 Gl(88), Cpx(12), qu Run 10, 1014 MPa, 10508C, 215h, fh 2 ¼ 065 MPa þ02 Gl(61), Cpx(33), Phl(6) 202 þ6 035 (continued) 2286

7 PICHAVANT et al. PRIMITIVE VESUVIUS MAGMAS Table 3: Continued Charge WBD 1 (wt %) H 2 O melt (wt %) ah 2 O NNO 2 Phase assemblage 3 P R 2 FeO 4 (%) K d Fe Mg cpx liq K d Fe Mg ol liq Run 11, 1054 MPa, 10008C, 22 h, fh 2 ¼ 061 MPa Gl(50), Cpx(41), Phl(9), qu Run 7, 55 MPa, 11008C, 165h, X Ni ¼ 062, fh 2 ¼ 030 MPa þ04 Gl(68), Ol(1), Cpx(31), qu 008 þ þ04 Gl(86), Cpx(14) H 2 O in glass estimated with the by-difference method. H 2 O melt in charges 3-1, 5-1 and 5-2 analyzed by FTIR and in charge 5-4 analyzed both by Karl-Fischer titration and FTIR. For charge 3-1 the two numbers given are duplicate FTIR measurements, and for charge 5-4, the first is the Karl-Fischer titration and the second the FTIR measurement. ah 2 O calculated from Burnham (1979) with WBD taken as the wt % dissolved H 2 O and melt composition from Table 6. 2 NNO ¼ log fo 2 log fo 2 of the NNO buffer calculated at experimental P and T (Pownceby & O Neill, 1994). For run 1, NNO is the average calculated for fh 2 ¼ 01 MPa and fh 2 ¼ 05 MPa. 3 Phase proportions calculated by mass balance; Gl, glass; Cpx, clinopyroxene; Ol, olivine; Phl, phlogopite; qu, quench phases identified by SEM. 4 Apparent loss or gain of FeO (Fe ¼ FeO t ) calculated as 100(FeOcalc FeOstarting sample)/feostarting sample. FeOcalc and R 2 are obtained from the mass-balance calculations. 5 Olivine-added charge, mass-balance calculations not performed. K d Fe Mg cpx liq ¼ (Fe/Mg in cpx)/(fe/mg in melt) calculated with FeO ¼ FeO t in both cpx and melt. K d Fe Mg ol liq ¼ (Fe/Mg in ol)/(fe/mg in melt) calculated with FeO ¼ FeO in olivine and melt. (See text for the calculation of melt FeO.) X Ni, mole fraction Ni in the alloy phase of the sensor. described by Behrens et al. (1996). This glass was also analyzed for H 2 O by FTIR, together with glasses 3-1, 5-1 and 5-2 (fluid-absent experiments), whereas glasses 18-1, 17-2 and 5-3 (fluid-present experiments) were analyzed for both H 2 O and CO 2. To do so, a Thermo Fisher FTIR instrument comprising a Nicolet 6700 spectrometer attached to a Continuum microscope was used. Spectra were acquired between 650 and 7000 cm 1 on doubly polished glass wafers mostly 550 mm thick using an IR light source, a KBr beamsplitter and a liquid nitrogen cooled MCT/A detector. Between two and six spots (aperture mostly 50 mm) were analyzed on each sample. Concentrations of H 2 O and CO 2 were determined from the Beer^Lambert law. Densities of the experimental glasses were calculated from the densities of the starting glasses measured at room conditions (VS96-54 A: ; : ) and using a partial molar volume of H 2 O of 12cm 3 mol 1 (Richet et al., 2000). H 2 O concentrations were obtained from the absorbance of the 3510^3530 cm 1 band, with a linear baseline drawn between 3800 and 2500 cm 1.Anextinction coefficient (e 3530 ) of 67 L mol 1 cm 1 was used (Marianelli et al., 1999). For CO 2, the absorbance of the 1515 cm 1 band was measured on backgroundsubtracted spectra (Dixon et al., 1995). An extinction coefficient (e 1515 )of365lmol 1 cm 1 (Marianelli et al., 1999) was used. Most charges had too many crystals to allow analysis of their glass volatile concentrations by FTIR. Therefore, we had to resort to the by-difference method to estimate the concentration of dissolved volatiles (e.g. Devine et al., 1995). In each electron microprobe session, the difference from 100% of glass electron microprobe analyses was calibrated against the dissolved H 2 O content, using glasses of known H 2 O concentrations (those analyzed by Karl- Fischer titration and FTIR) as secondary standards. For the fluid-absent (CO 2 -free) charges, the calibration is straightforward and glass H 2 O concentrations with this method are estimated to within 05 wt %. For the fluidpresent (CO 2 -bearing) charges, glass H 2 O concentrations are overestimated, as CO 2 dissolved in glass increases the difference from 100%. However, in this study, CO 2 concentrations in glasses are 502 wt %. Therefore, the overestimation remains small and the by-difference method was also applied to estimate glass H 2 O concentrations in CO 2 -bearing charges. EXPERIMENTAL RESULTS The experiments are divided into three groups, corresponding respectively to the fluid-absent, fluid-present and 01MPa charges. Experimental conditions and results for each group are detailed in Tables 3^5, and experimental compositions are given intable 6. In total,19 high-pressure 2287

8 JOURNAL OF PETROLOGY VOLUME 55 NUMBER 11 NOVEMBER 2014 Table 4: H 2 O-, CO 2 -bearing fluid-present experiments Charge XH 2 O in 1 VBD 2 H 2 O CO 2 ah 2 O NNO 3 Phase assemblage 4 P R 2 (%) FeO 5 K d Fe Mg cpx liq K d Fe Mg ol liq (wt %) (wt %) (ppm) Run 18, 2078 MPa, 12008C, 5 h, fh 2 ¼ 004 MPa þ Ol þ34 Gl, Ol 013 Run 17, 2138 MPa, 12008C, 65h, fh 2 ¼ 004 MPa VS96-54 þ Ol þ32 Gl, Ol 035 Run 5, 2105 MPa, 11508C, 10 h, X Ni ¼ 027, fh 2 ¼ 028 MPa VS96-54 þ Ol / þ12 Gl, Ol, Cpx, qu Run 13, 2004 MPa, 11508C, 2 h, fh 2 ¼ 004 MPa þ11 Gl(64), Cpx(36) þ07 Gl(77), Cpx(23) Run 15, 986 MPa, 11508C, 75h, X Ni ¼ 006, fh 2 ¼ 001 MPa þ25 Gl(73), Cpx(27) 070 þ þ 24 Gl(69), Cpx(31) 112 þ þ27 Gl(76), Cpx(24) þ26 Gl(69), Cpx(31) 097 þ þ23 Gl(86), Cpx(14) Run 12, 101 MPa, 11008C, 4 h, X Ni ¼ 007, fh 2 ¼ 001 MPa þ11 Gl(55), Cpx(37), Lc(7) þ23 Gl(56), Cpx(37), Lc(7) þ27 Gl(60), Cpx(36), Lc(4) Run 16, 493 MPa, 11508C, 35h, fh 2 ¼ 004 MPa þ14 Gl(81), Cpx(19), qu 097 þ þ14 Gl(79), Cpx(21), qu 132 þ þ10 Gl(73), Cpx(27) þ09 Gl(87), Cpx(13) XH 2 O in ¼ initial molar H 2 O/(H 2 O þ CO 2 ) in the charge. 2 Total volatiles (H 2 O þ CO 2 ) dissolved in melt estimated with the by-difference method. H 2 O and CO 2 concentrations in glasses 18-1, 17-2 and 5-3 determined by FTIR. Multiple numbers correspond to duplicate analyses. ah 2 O calculated from Burnham (1979) with VBD taken as the wt % dissolved H 2 O and melt composition from Table 6. 3 NNO ¼ log fo 2 log fo 2 of the NNO buffer calculated at experimental P and T (Pownceby & O Neill, 1994). 4 Phase proportions calculated by mass balance; Gl, glass; Cpx, clinopyroxene; Ol, olivine; Lc, leucite; qu, quench phases identified by SEM. 5 Apparent loss or gain of FeO (Fe ¼ FeO t ) calculated as 100(FeOcalc FeOstarting sample)/feostarting sample. FeOcalc and R 2 are obtained from the mass-balance calculations. 6 Olivine-added charge, mass-balance calculations not performed. K d Fe Mg cpx liq ¼ (Fe/Mg in cpx)/(fe/mg in melt) calculated with FeO ¼ FeO t in both cpx and melt. K d Fe Mg ol liq ¼ (Fe/Mg in ol)/(fe/mg in melt) calculated with FeO ¼ FeO in olivine and melt. (See text for the calculation of melt FeO.) X Ni, mole fraction Ni in the alloy phase of the sensor. 2288

9 PICHAVANT et al. PRIMITIVE VESUVIUS MAGMAS Table 5: 01 MPa experiments Charge T (8C) Log fo 2 1 (bar) NNO Phase assemblage 2 P R 2 FeO 3 (%) K 2 O 4 (%) K d Fe Mg cpx liq þ04 Gl(100) n.d þ04 Gl(97), Cpx(3) þ04 Gl(81), Cpx(19) þ04 Gl(80), Cpx(20), Lc(tr) þ01 Gl, Cpx, Lc n.d. n.d. n.d. n.d. VES þ00 Gl(100) n.d þ01 Gl(100), Cpx(tr) þ02 Gl(100), Cpx(tr) þ02 Gl(77), Cpx(18), Lc(5) þ01 Gl, Cpx, Lc n.d. n.d. n.d. n.d. 1 Log fo 2 calculated from EMF measured by the zirconia oxygen probe; NNO ¼ log fo 2 log fo 2 of the NNO buffer calculated at the experimental T (Pownceby & O Neill, 1994). 2 Phase proportions (wt %) calculated by mass balance; Gl, glass; Cpx, clinopyroxene; Lc, leucite; tr, trace (51%). 3 Apparent loss or gain of FeO (Fe ¼ FeO t ) calculated as 100(FeOcalc FeOstarting sample)/feostarting sample. FeOcalc and R 2 are obtained from the mass-balance calculations. 4 Apparent loss or gain of K 2 O calculated as 100(K 2 Ocalc K 2 Ostarting sample)/k 2 Ostarting sample. K 2 Ocalc is obtained from the mass-balance calculations. 5 K d Fe Mg cpx liq ¼ (Fe/Mg in cpx)/(fe/mg in melt) calculated with FeO ¼ FeO t in both cpx and melt. 6 Mass-balance calculations not performed, crystals too small for analysis. n.d., not determined. (corresponding to 44 charges) and 10 01MPa experiments are reported. All experimental charges were equilibrated under moderately to fairly oxidizing redox conditions. NNO range from 01 toþ34 in the high-pressure experiments, and the fluid-absent (NNO ¼ ^01 to þ25) and fluid-present (NNO¼þ07 to þ34) charges overlap. The 01MPa charges are more tightly grouped (NNO ¼ 0toþ04). Fe loss, quench crystallization and evaluation of equilibrium The importance of Fe loss (owing to Fe alloying with the metallic capsule) can be evaluated from the massbalance calculations (Tables 3^5). In the high-pressure experiments, five charges have 410% relative Fe loss, including three charges with 420% loss; none has more than 27% relative Fe loss. At temperatures 11008C, Fe losses or gains are 510% relative, except in charge 1-6 (Table 3). At temperatures C, Fe loss reaches 21 and 25% relative in charges 3-2 and 3-4 (Table 3). It should be noted, however, that the olivine-added charges were not mass-balanced (because the added olivine crystals were not precisely weighed) and so their Fe losses are unknown. In the 01MPa experiments, three charges have Fe losses 410% and none has more than 19% relative loss. Therefore, Fe loss was kept at relatively low levels in our experiments. No systematic change in phase assemblage or composition appears between charges with different Fe losses. K volatilization was limited to 10% relative in the 01MPa experiments (Table 5). Quench phases were commonly detected from SEM observations and their presence is rather systematic in the high-pressure fluid-absent charges (Table 3). In comparison, in the fluid-present charges, which are on average less H 2 O-rich, quench crystals are rare (Table 4). Quench crystallization is marked by the appearance of very thin needles (most certainly phlogopite) generally forming overgrowths on pre-existing crystals. Quench phases tend to concentrate in crystal-rich regions, and are typically absent from large glass pools. They are also less frequent in crystal-poor charges. Despite their common occurrence, quench phases are rarely abundant enough for their crystallization to have a measurable effect on the melt composition. K 2 O loss (which measures quench phlogopite crystallization in high-pressure experiments; Di Carlo et al., 2006) is 510% relative except in two charges (4-2: 12%; 4-3: 18%, Table 3). It is therefore concluded that quench crystallization is of negligible importance in this study. Most charges (48) were of crystallization type, whether fluid-absent, fluid-present or volatile-free. In the six 2289

10 JOURNAL OF PETROLOGY VOLUME 55 NUMBER 11 NOVEMBER 2014 Table 6: Compositions of experimental products (oxides in wt %) Charge Phase SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O Cr2O3 NiO P2O5 Total Composition Starting glasses Gl 1 (5) 2 489(2) 3 107(12) 127(2) 748(44) 014(6) 819(14) 148(2) 161(9) 420(13) 003(3) 002(3) 081(4) 978 Mg89 Gl(5) 497(5) 095(9) 141(2) 758(25) 013(8) 663(16) 128(24) 182(11) 54(16) 000(0) 001(3) 089(6) 981 Mg87 High-pressure H2O-bearing fluid-absent experiments 3-1 Gl(5) 498(4) 102(6) 129(1) 627(21) 011(6) 827(12) 150(3) 154(6) 415(6) 006(7) 000(0) 090(5) 932 Mg Gl(5) 498(4) 112(4) 138(1) 617(31) 020(12) 761(9) 141(1) 172(8) 454(8) 003(6) 000(0) 093(4) 943 Mg76 Cpx(4) 520(6) 041(6) 205(41) 308(37) 006(6) 166(2) 245(4) 011(2) 005(2) 007(6) 012(14) n.d. 990 En46Wo Gl(5) 497(2) 105(4) 138(2) 635(9) 016(7) 754(17) 141(3) 169(9) 456(4) 004(3) 002(5) 088(9) 950 Mg74 Cpx(3) 520(1) 041(16) 219(54) 299(40) 005(7) 169(3) 240(4) 013(6) 017(16) 023(2) 008(10) n.d. 991 En47Wo Gl(5) 497(2) 117(7) 151(2) 594(13) 009(8) 673(19) 132(2) 183(12) 511(13) 007(5) 004(4) 104(5) 949 Mg73 Cpx(5) 506(18) 059(21) 343(154) 459(146) 007(6) 154(14) 238(3) 017(8) 006(4) 013(6) 004(7) n.d. 989 En44Wo49 5-1(þOl) Gl(5) 491(2) 107(6) 127(2) 677(18) 014(9) 907(9) 1452(8) 15(10) 424(19) 001(3) 004(5) 084(4) 937 Mg79 Ol(5) 400(5) 001(1) 003(3) 835(36) 015(5) 491(2) 018(11) 000(1) 001(1) 006(3) 039(16) n.d. 983 Fo91 Cpx(3) 515(6) 033(10) 174(79) 311(41) 01(9) 171(6) 243(2) 013(7) 002(2) 03(14) 003(6) n.d. 987 En47Wo48 5-2(þOl) Gl(5) 492(2) 109(9) 133(2) 660(18) 015(7) 864(6) 1391(2) 176(6) 440(9) 002(3) 001(1) 086(4) 938 Mg79 Ol(2) 399(10) 001(2) 001(1) 870(32) 012(18) 491(5) 018(1) 001(1) 003(4) 000(0) 040(6) n.d. 985 Fo91 Cpx(2) 524(9) 033(12) 168(22) 319(7) 001(1) 169(3) 245(6) 016(0) 005(2) 026(2) 001(1) n.d. 995 En47Wo (þol) Gl(6) 496(2) 097(8) 138(1) 644(25) 014(11) 865(19) 125(3) 17(9) 520(16) 003(6) 005(6) 092(5) 949 Mg79 Ol(2) 400(0) 000(0) 000(0) 881(15) 011(4) 4954(5) 014(10) 002(2) 002(1) 004(1) 032(7) n.d. 990 Fo Gl(5) 485(3) 114(6) 169(2) 803(19) 016(8) 514(12) 106(1) 226(7) 61(21) 006(8) 004(5) Mg62 Cpx(1) n.d. 996 En43Wo Gl(5) 480(3) 110(11) 153(3) 800(27) 017(11) 622(8) 127(2) 195(8) 54(10) 005(5) 003(4) Mg69 Cpx(4) 514(9) 052(12) 269(53) 426(50) 012(5) 159(5) 246(4) 016(2) 010(4) 004(8) 004(8) n.d. 999 En44Wo Gl(5) 504(3) 111(10) 189(3) 530(49) 019(7) 385(10) 881(9) 280(10) 763(32) 001(3) 000(0) Mg65 Cpx(4) 490(13) 102(5) 611(92) 580(12) 007(8) 1383(7) 232(6) 032(5) 021(12) 013(8) 006(6) n.d. 998 En41Wo Gl(5) 492(7) 115(9) 156(2) 843(44) 018(9) 555(24) 114(3) 206(10) 527(18) 002(3) 004(6) Mg69 Cpx(5) 505(12) 047(9) 297(96) 523(65) 008(6) 152(6) 235(4) 017(4) 010(6) 003(5) 002(5) n.d. 983 En44Wo Gl(6) 494(6) 118(4) 164(2) 829(26) 021(5) 510(22) 103(4) 227(19) 586(14) 002(3) 002(6) Mg67 Cpx(1) n.d. 981 En40Wo49 (continued) 2290

11 PICHAVANT et al. PRIMITIVE VESUVIUS MAGMAS Table 6: Continued Charge Phase SiO 2 TiO 2 Al 2 O 3 FeO MnO MgO CaO Na 2 O K 2 O Cr 2 O 3 NiO P 2 O 5 Total Composition 2-3 Gl(7) 492(2) 113(8) 170(1) 840(41) 011(7) 486(19) 963(33) 227(10) 627(18) 004(4) 002(4) Mg65 Cpx(3) 492(20) 064(17) 433(198) 590(167) 017(6) 141(14) 232(3) 025(9) 023(13) 004(4) 002(3) n.d. 981 En41Wo49 1b-1 Gl(4) 488(7) 109(12) 155(3) 744(19) 025(9) 575(20) 120(2) 225(12) 579(16) 004(7) 003(6) Mg69 Cpx(2) 510(14) 051(25) 295(95) 467(141) 012(6) 153(10) 241(1) 014(9) 013(5) 004(6) 000(0) n.d. 990 En43Wo49 1b-2 Gl(4) 492(5) 100(7) 161(2) 750(30) 007(6) 539(9) 111(2) 220(15) 633(15) 006(6) 002(4) Mg66 Cpx(2) 515(0) 043(8) 276(64) 427(9) 004(5) 159(3) 237(2) 016(4) 014(1) 008(9) 004(5) n.d. 991 En45Wo48 1b-3 Gl(4) 493(5) 101(9) 170(1) 743(25) 013(14) 465(10) 983(28) 238(7) 712(9) 004(4) 011(8) Mg61 Cpx(4) 500(18) 085(35) 406(150) 556(126) 010(8) 149(9) 239(7) 022(5) 013(5) 014(6) 003(2) n.d. 998 En42Wo Gl(4) 496(2) 103(6) 175(2) 751(38) 021(7) 409(8) 104(9) 247(8) 610(8) 005(7) 001(2) Mg59 Cpx(4) 473(12) 096(24) 491(72) 665(57) 020(14) 134(6) 234(7) 024(6) 022(8) 005(7) 001(3) n.d. 973 En39Wo50 Phl(2) 366(4) 235(2) 157(1) 795(1) 005(7) 196(4) 015(13) 024(3) 985(3) 004(5) 003(5) n.d Phlog Gl(2) 517(11) 082(4) 192(8) 649(17) 015(5) 190(2) 955(13) 229(100) 661(126) 010(6) 009(11) Mg44 Cpx(1) n.d. 983 En37Wo51 Phl(1) n.d. 936 Phlog Gl3() 504(11) 092(7) 187(5) 731(68) 019(4) 296(40) 912(28) 240(81) 688(141) 003(4) 010(7) Mg51 Cpx(2) 484(11) 082(10) 490(55) 674(101) 027(11) 136(5) 236(2) 030(3) 016(6) 007(9) 007(0) n.d. 989 En40Wo49 Phl(4) 364(4) 296(18) 159(2) 932(50) 014(3) 188(4) 021(7) 032(5) 974(25) 005(4) 005(9) n.d. 938 Phlog Gl(3) 521(3) 098(7) 183(3) 666(34) 009(11) 22(31) 857(4) 272(21) 722(33) 002(3) 005(9) Mg46 Cpx(2) 493(8) 077(3) 455(2) 733(23) 020(7) 134(1) 239(0) 021(3) 005(2) 011(1) 004(2) n.d. 999 En39Wo50 Phl(2) 369(4) 256(9) 158(0) 101(0) 007(0) 181(3) 007(2) 024(5) 971(17) 001(1) 000(0) n.d. 935 Phlog Gl(3) 534(3) 075(6) 187(2) 610(5) 005(4) 193(9) 743(6) 289(12) 764(1) 001(2) 000(0) Mg45 Cpx(1) n.d. 989 En34Wo52 Phl(1) n.d. 949 Phlog Gl(5) 483(3) 115(12) 159(2) 801(22) 017(9) 576(25) 119(4) 202(10) 563(19) 001(3) 004(5) Mg69 Cpx(3) 509(6) 064(7) 314(14) 530(46) 013(11) 153(5) 232(4) 013(5) 010(3) 015(11) 002(2) n.d. 990 En44Wo Gl(5) 494(5) 103(7) 155(3) 764(30) 015(5) 539(15) 112(2) 210(7) 647(12) 001(1) 005(8) Mg69 Cpx(4) 507(15) 061(31) 346(124) 485(132) 010(9) 149(9) 241(4) 013(1) 007(4) 021(6) 004(5) n.d. 990 En43Wo50 (continued) 2291

12 JOURNAL OF PETROLOGY VOLUME 55 NUMBER 11 NOVEMBER 2014 Table 6: Continued Charge Phase SiO 2 TiO 2 Al 2 O 3 FeO MnO MgO CaO Na 2 O K 2 O Cr 2 O 3 NiO P 2 O 5 Total Composition 10-1 Gl(1) Mg48 Cpx(1) n.d. 995 En32Wo51 Phl(1) n.d. 940 Phlog Gl(2) 544(3) 060(6) 195(2) 521(5) 012(4) 134(9) 572(6) 329(12) 865(1) 010(2) 007(0) Mg38 Cpx(1) n.d. 997 En33Wo51 Phl(1) n.d. 939 Phlog Gl(6) 481(3) 117(6) 161(2) 857(32) 017(14) 545(13) 114(2) 217(6) 572(11) 002(2) 005(6) Mg61 Ol(7) 403(5) 003(3) 003(3) 136(5) 028(9) 448(4) 029(18) 002(2) 002(2) 002(3) 019(13) n.d. 995 Fo86 Cpx(2) 497(1) 070(6) 569(19) 567(11) 020(4) 133(4) 223(6) 040(0) 078(11) 007(9) 003(4) n.d. 987 En41Wo Gl(5) 490(4) 110(4) 160(2) 795(34) 018(12) 524(15) 110(4) 215(9) 633(11) 003(4) 000(0) Mg62 Cpx(3) 522(5) 052(4) 229(21) 458(30) 014(8) 159(3) 240(2) 011(3) 010(2) 000(0) 010(9) n.d. 999 En45Wo48 High-pressure H2O-, CO2-bearing fluid-present experiments 18-1(þOl) Gl(10) 491(1) 088(10) 127(1) 807(17) 016(9) 113(3) 115(2) 146(7) 432(15) 001(5) 002(11) 050(12) 951 Mg85 Ol core Fo96 Ol rim Fo (þOl) Gl(9) 487(3) 096(16) 116(2) 813(33) 015(9) 113(2) 136(1) 143(6) 370(9) 002(3) 000(14) 045(13) 958 Mg85 Ol core Fo91 Ol rim Fo (þol) Gl(5) 493(4) 104(6) 138(1) 655(10) 013(8) 811(17) 136(1) 172(6) 468(11) 005(6) 002(2) 097(6) 941 Mg77 Ol(1) n.d. 985 Fo91 Cpx(3) 514(4) 039(13) 207(45) 306(42) 003(4) 170(2) 242(4) 012(4) 004(2) 021(12) 012(12) n.d. 987 En47Wo Gl(5) 489(3) 104(6) 169(1) 724(25) 016(7) 545(11) 101(2) 233(7) 663(19) 003(8) 001(1) 119(7) 972 Mg67 Cpx (1) En42Wo Gl(6) 496(4) 109(7) 170(2) 678(28) 012(9) 505(10) 960(17) 246(12) 706(15) 003(5) 004(6) 117(4) 975 Mg65 Cpx(1) En41Wo47 (continued) 2292

13 PICHAVANT et al. PRIMITIVE VESUVIUS MAGMAS Table 6: Continued Charge Phase SiO 2 TiO 2 Al 2 O 3 FeO MnO MgO CaO Na 2 O K 2 O Cr 2 O 3 NiO P 2 O 5 Total Composition 15-1 Gl(5) 486(2) 117(12) 158(2) 741(27) 012(7) 644(17) 118(3) 202(8) 548(16) 001(3) 005(8) 100(4) 966 Mg76 Cpx(1) En41Wo Gl(5) 489(1) 116(3) 159(2) 736(32) 016(9) 606(7) 113(2) 217(7) 587(7) 000(1) 001(2) 106(9) 968 Mg74 Cpx(1) En38Wo Gl(5) 483(2) 112(13) 155(1) 782(30) 013(4) 655(13) 117(1) 242(6) 537(12) 001(2) 003(4) 102(5) 964 Mg76 Cpx(1) En44Wo Gl(5) 485(2) 104(7) 159(2) 759(30) 011(7) 627(12) 113(2) 229(15) 577(12) 006(5) 004(4) 109(9) 965 Mg75 Cpx(1) En40Wo Gl(7) 493(4) 102(9) 159(2) 733(40) 011(5) 586(15) 108(3) 232(13) 629(15) 000(1) 002(3) 106(9) 968 Mg73 Cpx(3) 483(2) 072(15) 442(16) 626(33) 013(7) 154(3) 230(3) 023(2) 014(3) 030(4) 006(10) 009(16) 992 En44Wo Gl(4) 508(4) 101(5) 179(4) 739(20) 025(8) 353(5) 786(23) 317(12) 658(21) 000(0) 006(6) 137(4) 976 Mg56 Cpx(3) 459(9) 093(7) 756(9) 824(44) 014(4) 136(3) 225(2) 037(1) 019(17) 003(2) 004(7) 040(8) 998 En40Wo47 Lc(3) 548(2) 011(4) 220(3) 082(10) 001(1) 005(5) 007(10) 058(3) 201(1) 001(2) 003(5) 003(4) 986 Lc Gl(4) 505(4) 109(3) 177(1) 783(14) 015(13) 356(8) 795(15) 336(13) 644(13) 004(6) 000(0) 139(5) 965 Mg61 Cpx(2) 468(11) 094(3) 731(81) 765(84) 011(4) 135(4) 219(7) 038(0) 052(15) 000(0) 001(1) 031(16) 995 En40Wo47 Lc(2) 546(1) 007(2) 217(3) 073(15) 000(0) 028(29) 055(55) 058(2) 198(5) 007(2) 002(3) 001(1) 984 Lc Gl(5) 506(5) 107(5) 181(2) 703(16) 013(12) 372(11) 755(21) 303(12) 738(12) 005(6) 000(0) 127(11) 958 Mg66 Cpx(2) 447(4) 110(9) 783(23) 868(28) 012(0) 136(1) 228(6) 037(3) 019(0) 000(0) 010(5) 045(1) 1000 En39Wo47 Lc(2) 544(2) 008(2) 220(1) 078(1) 000(0) 003(2) 021(23) 048(1) 203(3) 000(0) 003(4) 017(22) 985 Lc Gl(5) 484(3) 107(10) 147(1) 785(29) 017(7) 732(11) 126(2) 193(8) 497(11) 001(1) 007(8) 091(9) 966 Mg73 Cpx(2) 464(9) 078(13) 638(103) 779(118) 013(14) 144(5) 227(4) 028(2) 027(21) 040(2) 023(29) 005(7) 998 En41Wo Gl(7) 481(3) 109(7) 149(2) 810(37) 012(7) 711(10) 124(2) 215(15) 505(13) 000(0) 002(3) 101(7) 966 Mg72 Cpx(1) En42Wo Gl(5) 488(2) 118(8) 157(1) 763(16) 017(8) 632(17) 114(4) 210(9) 565(20) 002(3) 004(4) 104(11) 969 Mg69 Cpx(1) En42Wo Gl(5) 493(3) 099(8) 158(2) 713(30) 009(7) 602(17) 110(2) 212(10) 642(14) 008(7) 004(4) 101(5) 970 Mg69 Cpx(1) En42Wo48 (continued) 2293

14 JOURNAL OF PETROLOGY VOLUME 55 NUMBER 11 NOVEMBER 2014 Table 6: Continued Charge Phase SiO 2 TiO 2 Al 2 O 3 FeO MnO MgO CaO Na 2 O K 2 O Cr 2 O 3 NiO P 2 O 5 Total Composition 01 MPa experiments 3 Gl(7) 491(4) 103(8) 130(2) 680(32) 019(4) 818(12) 154(3) 158(11) 376(12) 003(7) 006(6) 082(10) 985 Mg73 4 Gl(6) 495(3) 104(5) 136(2) 643(31) 014(7) 783(13) 148(3) 166(6) 420(12) 005(6) 002(5) 083(4) 988 Mg73 Cpx(3) 512(6) 047(5) 372(157) 384(12) 011(10) 176(14) 238(14) 016(24) 015(64) 046(16) 000(6) 000(9) 1015 En48Wo46 6 Gl(3) 493(2) 107(4) 147(0) 696(10) 008(7) 677(18) 132(1) 188(10) 508(19) 001(2) 003(5) 091(8) 982 Mg69 Cpx(8) 463(5) 082(10) 665(101) 775(45) 015(10) 149(9) 230(14) 016(20) 015(61) 009(5) 005(6) 036(8) 1004 En42Wo46 7 Gl(5) 484(3) 116(5) 157(1) 711(19) 016(6) 610(6) 129(3) 238(5) 507(26) 001(3) 002(4) 096(4) 984 Mg66 Cpx(5) 502(10) 089(26) 484(139) 400(35) 012(12) 164(8) 236(4) 017(10) 015(20) 013(8) 005(6) 037(9) 1009 En46Wo48 Lc(2) 546(1) 003(8) 220(1) 000(4) 011(9) 010(52) 016(78) 042(18) 202(1) 000(0) 000(0) 000(1) 976 Lc97 9 Gl(5) 495(3) 094(4) 144(1) 711(18) 013(7) 661(11) 133(2) 192(10) 514(12) 004(5) 001(1) 089(7) 986 Mg69 8 Gl(7) 503(3) 096(6) 147(2) 618(29) 016(9) 666(17) 133(4) 213(5) 484(14) 002(2) 001(3) 073(9) 958 Mg72 Cpx(1) En51Wo46 6 Gl(4) 492(3) 102(4) 146(7) 724(28) 020(7) 661(21) 134(2) 176(9) 494(4) 001(2) 004(7) 090(10) 963 Mg68 Cpx(1) En47Wo47 5 Gl(6) 501(7) 104(7) 157(3) 704(60) 016(11) 563(22) 115(3) 219(9) 551(20) 008(8) 003(7) 102(8) 976 Mg65 Cpx(3) 436(4) 089(11) 709(12) 956(25) 020(4) 133(15) 229(21) 026(22) 015(92) 005(7) 000(1) 048(12) 985 En38Wo47 Lc(3) 550(4) 016(0) 213(3) 143(48) 000(0) 010(30) 026(71) 047(8) 197(5) 004(5) 001(3) 004(6) 985 Lc97 1 Glass analyses normalized to 100% anhydrous, with all Fe as FeO. Unnormalized total is reported. 2 Number of microprobe analyses. 3 One standard deviation in terms of least unit cited. 4 P 2O5 not analyzed; P2O5 concentration assumed equal to 1 wt % before normalization. 5 F concentration below detection. Mg ¼ Mg# calculated as 100 molar MgO/(MgO þ FeO). (See text for calculation of FeO.) En ¼ 100 at. Mg/(Mg þ Fe þ Ca), Wo ¼ 100 at. Ca/(Mg þ Fe þ Ca) in pyroxene, calculated with Fe ¼ FeO t. Fs (not given) ¼ 100 En Wo. Fo ¼ 100 at. Mg/(Mg þ Fe) in olivine, calculated with Fe ¼ FeO t. Phlog ¼ 100 at. Mg/ (Mg þ Fe) in phlogopite, calculated with Fe ¼ FeO t.lc¼ 100 at. K/(Na þ K) in leucite. Gl, glass; Cpx, clinopyroxene; Ol, olivine; Phl, phlogopite; Lc, leucite; n.d., not determined. 2294