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Phase Equilibria of Pantelleria Trachytes (Italy):
Constraints on Pre-eruptive Conditions and on the
Metaluminous to Peralkaline Transition in Silicic
Magmas
Pierangelo Romano, Joan Andújar, Bruno Scaillet, Nunzia Romengo, Ida Di
Carlo, Silvio Rotolo
To cite this version:
Phase Equilibria of Pantelleria Trachytes (Italy):
Constraints on Pre-eruptive Conditions and on
the Metaluminous to Peralkaline Transition in
Silicic Magmas
Pierangelo Romano
1*, Joan Andu´jar
2,3,4, Bruno Scaillet
2,3,4,
Nunzia Romengo
1, Ida di Carlo
2,3,4and Silvio G. Rotolo
1,51
Dipartimento di Scienze della Terra e del Mare (DiSTeM), Via Archirafi, Universita` degli Studi di Palermo, Palermo 36-90123, Italy;2Universite´ d’Orle´ans, ISTO, UMR 7327, 45071 Orle´ans, France;3CNRS/INSU, ISTO, UMR 7327, 45071 Orle´ans, France;4BRGM, ISTO, UMR 7327, BP 36009, 45060 Orle´ans, France;5Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, Via Ugo La Malfa 153, Palermo 90146, Italy
*Corresponding author. E-mail: pierangelo.romano@unipa.it Received October 1, 2016; Accepted March 22, 2018
ABSTRACT
The relationships between trachytes and peralkaline rhyolites (i.e. pantellerites and comendites), which occur in many continental rift systems, oceanic islands and continental intraplate settings, is unclear. To fill this gap, we have performed phase equilibrium experiments on two representative metaluminous trachytes from Pantelleria to determine both their pre-eruptive equilibration condi-tions (pressure, temperature, H2O content and redox state) and liquid lines of descent. Experiments
were performed in the temperature range 750–950C, pressure 05–15 kbar and fluid saturation conditions with XH2O [¼ H2O/(H2Oþ CO2)] ranging between zero and unity. Redox conditions were
fixed below the nickel–nickel oxide buffer (NNO). The results show that at 950C and melt water
contents (H2Omelt) close to saturation, trachytes are at liquidus conditions at all pressures.
Clinopyroxene is the liquidus phase, being followed by iron-rich olivine and alkali feldspar. Comparison of experimental and natural phases (abundances and compositions) yields the follow-ing pre-eruptive conditions: P¼ 1 6 05 kbar, T ¼ 925625C, H
2Omelt¼ 2 6 1 wt %, and fO2between
NNO – 05 and NNO – 2. A decrease in temperature from 950C to 750C, as well as of H
2Omelt,
promotes a massive crystallization of alkali feldspar to over 80 wt %. Iron-bearing minerals show gradual iron enrichment when T and fO2 decrease, trending towards the compositions of the
phenocrysts of natural pantellerites. Despite the metaluminous character of the bulk-rock tions, residual glasses obtained after 80 wt % crystallization evolve toward comenditic composi-tions, owing to profuse alkali feldspar crystallization, which decreases the Al2O3of the melt, leading
to a consequent increase in the peralkalinity index [PI¼ molar (Na2Oþ K2O)/Al2O3]. This is the first
experimental demonstration that peralkaline felsic derivatives can be produced by low-pressure fractional crystallization of metaluminous mafic magmas. Our results show that the pantelleritic magmas of basalt–trachyte–rhyolite igneous suites require at least 95 wt % of parental basalt crys-tallization, consistent with trace element evidence. Redox conditions, through their effect on Fe–Ti oxide stabilities, control the final iron content of the evolving melt.
Key words: peralkaline silicic magmatism; experimental petrology; trachyte; pantellerite; liquid line of descent; Pantelleria; metaluminous–peralkaline transition
VCThe Author(s) 2018. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com 559
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doi: 10.1093/petrology/egy037 Advance Access Publication Date: 10 April 2018 Original Article
INTRODUCTION
Pantelleria is the type locality of pantellerite, an iron-and alkali-rich rhyolite (peralkalinity index, PI >12). Peralkaline rhyolites (i.e. pantellerite and comendite)
and trachytes usually represent the felsic
end-members in the following settings: (1) continental rift systems (e.g. Pantelleria, Tibesti, Ethiopia, Afar, Kenya, Basin and Range province, South Greenland;
Barberi et al., 1975;Civetta et al., 1998; Peccerillo et al., 2003); (2) oceanic island settings (e.g. Socorro, Easter Is., Iceland and the Azores; Macdonald et al., 1990;
Mungall & Martin, 1995; Bohrson & Reid, 1997); (3) continental intraplate suites (Liu et al., 1998; Brenna et al., 2015). The origin of peralkaline rhyolites in these different tectonic settings is still a matter of debate and three hypotheses have been suggested: (1) crystal fractionation of alkali basalt magma in a shallow reser-voir to produce a trachyte whose subsequent crystal-lization gives rise to a pantellerite (e.g.Barberi et al., 1975;Mungall & Martin, 1995;Civetta et al., 1998); (2) partial melting of cumulate gabbros to form a trachyte, which then produces pantellerite (e.g. Lowenstern & Mahood, 1991;Bohrson & Reid, 1997); (3) partial melt-ing of different lithospheric sources fluxed by volatiles, which add excess alkalis to the melt (Bailey & Macdonald, 1975,1987). Recent petrological work has helped to define the temperature range and redox con-ditions of comenditic to pantelleritic magmas (Scaillet & Macdonald, 2001, 2003, 2006; White et al., 2005,
2009;Di Carlo et al., 2010) as well as their pre-eruptive volatile contents (e.g.Gioncada & Landi, 2010;Neave et al., 2012; Lanzo et al., 2013). In contrast, little is known about the conditions of magma storage and evolution of the associated trachytes. At Pantelleria, trachytes and pantellerites constitute most of the out-cropping rocks (e.g.Mahood & Hildreth, 1986), the for-mer being erupted dominantly as lava flows whereas the pantellerites are erupted either explosively or effusively.
We have experimentally investigated the phase relationships of two representative trachytes from Pantelleria to shed light on their pre-eruptive magma storage conditions (pressure, temperature, H2Omelt,
oxygen fugacity) and define their liquid lines of des-cent. We have established the phase relationships at P¼ 05–15 kbar, T ¼ 750–950C, fO
2 NNO – 1 (where
NNO is the nickel–nickel oxide buffer) and XH2Ofluid
[H2O/(H2Oþ CO2), in moles] between unity and zero.
By comparing the experimental phase assemblages, abundances and compositions with the natural prod-ucts we set constraints on the storage conditions of trachytic magmas at Pantelleria and on the putative parent–daughter relationship between trachytic and pantelleritic magmas. Our results form the basis for understanding the long-debated petrological issue regarding the link between silica-oversaturated per-alkaline and metaluminous magmas.
GEOLOGICAL SETTING
Eruptive history
The island of Pantelleria is the emerged portion of a large Quaternary volcanic edifice rising from the Sicily Channel rift zone (Fig. 1; Rotolo et al., 2006;Catalano et al., 2009). The eruptive products of Pantelleria form a bimodal suite that consists of mafic (mildly alkali basalt) and felsic (metaluminous or slightly peralkaline tra-chytes and pantellerites) end-members (Civetta et al., 1998;Avanzinelli et al., 2004;Ferla & Meli, 2006). From the volcanological point of view, the eruptive history of Pantelleria is characterized by large explosive ignim-britic eruptions, low-energy Strombolian eruptions and lava flows. The eruptive history can be divided into three major periods. During the first period (324–180 ka) pantelleritic lavas were mostly erupted, producing ei-ther welded tuffs or pumice fallout deposits (Mahood & Hildreth, 1986;Civetta et al., 1988;Rotolo et al., 2013). The second period (180–45 ka) was characterized by more than eight ignimbrite-forming eruptions, includ-ing the La Vecchia caldera-forminclud-ing eruption and the Green Tuff eruption (GT). The GT eruption, recently dated at 441 6 06 ka (Scaillet et al., 2013), is the last highly energetic eruption and the only one that blan-keted the entire island; about 7 km3dense rock
equiva-lent (DRE) of tephra were erupted. Moreover, it is thought to be the cause of the Cinque Denti Caldera, which is nested within the La Vecchia caldera collapse (Fig. 1) (Mahood & Hildreth, 1986; Speranza et al., 2012). During the third period (45–8 ka), the activity con-sisted of felsic resurgent volcanism confined almost en-tirely inside the Cinque Denti caldera. This third period started with a long phase of effusive activity that pro-duced at least 3 km3
of trachytic lavas, building the Montagna Grande–Monte Gibele system, a large vol-canic complex that is tectonically uplifted and tilted and forms the island’s highest elevation. This phase was fol-lowed by low-energy Strombolian eruptions associated with effusive events, yielding pumice fall sequences, lava flows and lava domes with pantelleritic composi-tions (Mahood & Hildreth, 1986; Civetta et al., 1998;
Rotolo et al., 2007). At the end of the third period, extra-caldera basaltic volcanism occurred in the NW side of the island (Fig. 1), simultaneously with pantelleritic magmatism. The last eruptive episode (1891) occurred offshore, at about 5 km off the NW coast, emitting lavas of broadly basaltic composition (Kelly et al., 2014).
Petrological background: the origin of
pantellerites and previous constraints on storage
conditions
Pantelleria is very well known in the petrological litera-ture for the presence of a typical compositional gap (Daly Gap) in the eruptive sequence between the mafic and felsic end-members. Intermediate products are, however, sporadically found as enclaves within the
felsic rocks and as a single small-volume lava flow with a benmoreitic bulk-rock composition. In both cases, these rocks show the characteristics of a magma that originated from basalt–rhyolite mixing (Ferla & Meli, 2006;Romengo et al., 2012).
At Pantelleria, the petrogenesis of pantelleritic rocks has been explained through two models: (1) protracted fractional crystallization from an alkali basalt parental magma; (2) low-degree partial melting of alkali gabbroic cumulates. The first model argues for the fractional crystallization of a mineral assemblage of plagioclase, clinopyroxene, olivine 6 Fe–Ti-oxides at an oxygen
fugacity around FMQ – 1 (where FMQ is the fayalite– magnetite–quartz buffer), which produced a metalumi-nous trachytic residual liquid, which then crystallized (90%) to yield a pantelleritic magma (Civetta et al., 1998; White et al., 2009; Neave et al., 2012). Alternatively, on the basis of the low water contents observed in melt inclusions of pantelleritic composition,
Lowenstern & Mahood (1991) proposed the partial melting of gabbroic cumulates as the source of the trachytic magmas, which then produced pantellerites by low-pressure fractional crystallization. Regarding the pre-eruptive conditions of the mafic suite,Civetta et al.
Fig. 1. (a) Tectonic sketch of the Sicily Channel rift zone (modified fromCatalano et al., 2009) showing the location of Pantelleria and other volcanic islands (Graham Bank, Linosa) in the rift zone between Sicily and Tunisia. (b) Simplified geological map of Pantelleria; the stars mark the sampling sites of the starting materials used in the experiments.
(1998)reported Fe–Ti oxide temperatures in the range 940–1079C. These values are similar to the 1091 6 45C
obtained byNeave et al. (2012)based on mineral–liquid equilibria. For metaluminous trachytes, based on min-eral–mineral or mineral–liquid equilibria, White et al. (2005, 2009) reported a temperature range of 858– 922C, whereas for pantellerites they reported a range
of 650–750C. Estimates of redox conditions for
Pantelleria magmas yield an fO2 of around NNO – 1.
Such T–fO2conditions for pantelleritic melts have been
corroborated by phase equilibrium experiments byDi Carlo et al. (2010), which in addition demonstrate the water-rich character (up to 4 wt %) of these magmas. Water contents of mafic to felsic melt inclusions (MI) have been also investigated through Fourier transform infrared spectroscopy (FTIR) and secondary ion mass spectrometry (SIMS). Melt inclusions trapped in phe-nocrysts of alkali basalts yield water contents (H2O
melt) ranging from 08 to 16 wt % and CO2 up to
980 ppm (Gioncada & Landi, 2010). Water contents in MI within phenocrysts of pantelleritic magmas vary be-tween 2 and 45 wt % (Lowenstern & Mahood, 1991;
Gioncada & Landi, 2010;Neave et al., 2012;Lanzo et al., 2013). The corresponding pressures of volatile satur-ation are < 2 kbar, being consistent with both experi-mental (Di Carlo et al., 2010) and geophysical (Mattia et al., 2007) constraints, altogether suggesting the exist-ence of a shallow magma reservoir at a depth of4 km (1 kbar for an average crustal density of 26 g cm–3).
ROCKS STUDIED AND CHOICE OF THE
EXPERIMENTAL CONDITIONS
Despite being less abundant than pantellerite, trachytic magmas were erupted during the entire volcanological history of Pantelleria as lava flows (Civetta et al., 1998;
White et al., 2009; Romengo, 2011), ignimbrite units (Mahood et al., 1986;Rotolo et al., 2013) and magmatic enclaves (Prosperini et al., 2000;Landi & Rotolo, 2015). We have performed phase equilibrium experiments on two trachytic samples representative of the trachytic rocks at Pantelleria, which are spatially and temporally related to pantelleritic eruptions. On the basis of their petrographic characteristics and major and trace elem-ent compositions, these two trachytes were selected
be-cause they do not display evidence of feldspar
accumulation, unlike most Pantelleria trachytes
(Prosperini et al., 2000;White et al., 2009): hence they are likely to be on the relevant liquid line of descent of the studied system. One of the samples (GTT for Green Tuff Trachyte) comes from the trachytic (top-) member of the
Green Tuff (GT) formation (3649’1090"N,
1159’4971"E), whereas the other belongs to one of the
post-GT lava flows filling the Cinque Denti caldera (3646’4672"N, 1158’4723"E), here named PCD (for
Post Cinque Denti caldera). The Green Tuff formation, apart from an initial pumice fallout, is considered to be a single pyroclastic flow unit [for details see Williams
(2010)]. It displays continuous chemical zoning from pan-tellerite at the bottom to comenditic trachyte at the top, suggesting a zoned reservoir (Mahood & Hildreth, 1986;
Civetta et al., 1998;Williams, 2010). In contrast, the tra-chytes of M Grande/Gibele (used as starting material, PCD), which erupted immediately after the Cinque Denti caldera collapse, constitute a broadly homogeneous body, with minor differences in major and trace element composition between units, albeit forming a complex system of lava flows (White et al., 2009;Romengo, 2011). According toMahood & Hildreth (1986), the GT and PCD trachytes are genetically linked, the latter representing the deeper part of a zoned reservoir whose pantelleritic fraction had been removed during the Green Tuff erup-tion. This large volume of trachyte follows the Green Tuff eruption but also precedes the last explosive post-caldera pantelleritic eruptions (Scaillet et al., 2011).
Bulk-rock compositions of both rocks were obtained by X-ray fluorescence (XRF) and inductively coupled plasma atomic emission spectrometry (ICP-AES) ana-lysis (Table 1), the two rocks falling in the trachytic field of the total alkalis–silica (TAS) diagram (Le Bas et al., 1986). The mineralogy was determined by both petro-graphic observation and scanning electron microscopy (SEM), and the compositions of mineral phases were determined by electron microprobe analysis (EPMA) (Table 1). The two trachytes have a PI of 106 (GTT) and 097 (PCD). Crystal contents, based on point counting in thin sections, are34 vol. % for GTT and 37 vol. % for PCD. Large alkali feldspars (Af) (06 cm) make up 32 vol. % of the phenocryst content in GTT and 34 vol. % in PCD. Clinopyroxene (Cpx) and olivine (Ol) have dimensions ranging from 250 to 500 mm, representing 15 and 28 vol. %, respectively, of the crystal content. The occurrence of large glomerophenocrysts of Af and mafic minerals suggests that Ol and Cpx co-precipitated along with Af. Microphenocrysts of Ti-magnetite (Mt) and ilmenite (Ilm) occur in GTT, either in the ground-mass or in glomerophenocrysts (with Af and Cpx), but also within Cpx and Ol. In GTT, Fe–Ti oxides are either homogeneous or display oxy-exsolution textures with intergrowing lamellae of Il in Mt, whereas in PCD all oxides exhibit oxy-exsolution textures. As for oxides, apatite (Ap) crystals are often included in Ol and Cpx. The groundmass in both samples consists predomin-antly of Af microlites (<005 mm), Cpx, oxides and traces of Ol, but PCD also includes traces of quartz (Qz) and amphibole (Amph). A few pockets of residual glass (Gl) were found only in the sample GTT, which is prob-ably due to the different cooling rate between ignim-brite deposits (GTT) and lava flows (PCD). The scarcity of quenched glass in trachytes, also reported by
Gioncada & Landi (2010), explains the lack of volatile data for trachytic magmas. Af phenocrysts display com-positions ranging from An01–09Ab64–74Or16–34 (GTT) to
An03–10Ab65–69Or22–29(PCD). Cpx in both rocks is augite
(En26–28–Fs27–29–Wo42–44) with XFe [¼ Fe/(Fe þ Mg),
cal-culated using FeOtot] of 052 in GTT and 049 in PCD,
and Ol is Fo23–27. In GTT Ilm has a TiO2content of 441%
and Mt has an FeO content of 661 wt %.
The choice of experimental conditions was guided by the results of previous investigations carried out at Pantelleria. The range of pressures explored in this study reflects broadly the low pressure inferred on petrological grounds for the magma reservoir at Pantelleria (2 kbar;
Di Carlo et al., 2010; Gioncada & Landi, 2010; Neave et al., 2012), which is typical of this category of magmas (Mahood, 1984; Scaillet & Macdonald, 2001, 2006).
Temperature constraints come from the results ofWhite et al. (2009)for the metaluminous trachyte (900 6 50C)
filling the Cinque Denti Caldera, and from those esti-mated with the few analysed oxide pairs in GTT in this study. Using the formulation ofSauerzapf et al. (2008), the latter give a temperature of 932 6 68C and an fO2of
NNO – 131 6009 (i.e. 131 log units below the Ni–NiO buffer). The low-temperature experiments were per-formed to investigate the relationships between trachyte and pantellerite.
Table 1: Major element composition of natural Green Tuff (GTT) and Post Cinque Denti Caldera (PCD) trachytes: bulk rock (XRF), mineral phases (EMP) and starting materials (glasses, EMP)
GTT Bulk-rock Starting material SD Cpx SD Ol SD Afs pheno SD Afs microlite SD Mt SD Ilm SD n: 20 10 4 20 12 3 3 SiO2(wt %) 6340 6412 039 5002 050 3172 012 6546 054 6668 054 006 000 000 001 TiO2 087 085 009 056 015 000 000 000 000 000 000 2462 076 4972 059 Al2O3 1515 1504 014 060 008 000 000 1957 036 1857 022 062 013 015 013 FeOtot 710 627 023 1696 053 5242 184 024 009 079 020 6605 258 4409 025 MnO 023 027 008 103 013 284 013 000 000 000 000 159 011 188 045 MgO 060 062 004 941 022 1075 007 000 000 000 000 080 053 102 088 CaO 129 148 005 2012 019 047 001 095 006 056 009 001 001 005 001 Na2O 675 658 022 054 004 000 000 770 013 811 015 000 000 000 000 K2O 461 460 011 000 000 000 000 413 017 486 009 000 000 000 000 P2O5 019 017 009 000 000 000 000 000 000 000 000 000 000 000 000 BaO 000 000 000 000 063 004 024 017 000 000 000 000 Sum 10019 10000 000 9924 092 9820 195 9869 096 9958 044 9375 001 9691 001 PI 106 098 Mg# Fa (mol %) 7038 050 Wo 4317 033 En 2808 057 Fs 2875 059 An 480 033 267 079 Ab 7039 095 6979 049 Or 2482 092 2754 070 PCD Bulk-rock Starting material SD Cpx SD Ol SD Afs pheno SD Afs microlite SD Mt SD Ilm SD n: 20 8 6 10 SiO2(wt %) 6378 6442 043 4879 059 3072 063 6464 202 TiO2 075 068 014 057 020 000 006 006 Al2O3 1583 1590 022 079 040 000 1923 112 FeOtot 561 540 031 1615 085 5484 283 040 020 MnO 019 020 008 098 014 279 030 005 006 MgO 052 059 003 1028 062 1047 251 001 001 CaO 187 206 008 2041 019 041 010 159 148 Na2O 663 601 032 046 020 000 749 073 K2O 422 438 011 000 002 000 403 176 P2O5 015 007 004 002 004 BaO 012 006 020 016 Sum 10000 000 9842 090 9924 068 9771 101 PI 097 092 004 Mg# Fa (mol %) 71 34 Wo 4376 1 En 3068 3 Fs 2556 3 An 796 3 Ab 6799 2 Or 2405 5
n, number of analyses; SD, standard deviation; FeOtot, total iron reported as FeO. Ol, olivine; Cpx, clinopyroxene; Afs, alkali
feld-spar, Mt, magnetite; Ilm, ilmenite. Fa (mol %)¼ 100Mg/(Mg þ FeOtot) in olivine. Wo, En and Fs were calculated as in the study by
Morimoto (1989). PI¼ peralkalinity index [molar (Na2Oþ K2O)/Al2O3]. An¼ 100[Ca/(Ca þ Na þ K)]; Ab ¼ 100[Na/(Ca þ Na þ K)];
Or¼ 100[K/(Ca þ Na þ K)]. End-members calculated as in the study byDeer et al. (1992).
EXPERIMENTAL STRATEGY
Charge preparation
The rocks chosen as starting materials were initially crushed and about 10 g of the resulting powders were fused twice in a Pt crucible at 1300C in air for 3–4 h.
Glass chips were analysed by electron microprobe and found to be homogeneous and similar to the bulk-rock analyses of the natural rocks (Table 1), the small differ-ences (Na in particular) being due to the high melting temperature needed to prepare the starting material from the natural rock. The glasses were then ground in an agate mortar under acetone to 10–40 mm mesh size and utilized as starting materials for the experiments. Au capsules (15 cm in length, inner diameter 25 mm and outer diameter 29 mm) were used to minimize iron loss. Capsules were loaded first with distilled water, then silver oxalate as a CO2 source, and finally with
30 mg of powdered glass. The amount of fluid
(H2Oþ CO2) loaded into each capsule was 3 6 05 mg
(10% of the starting material), ensuring always fluid sat-uration conditions (e.g. Scaillet et al., 1995; Andu´jar et al., 2015). Each capsule was arc-welded, with weigh-ing before and after the weldweigh-ing to check for water loss; afterwards the capsules were left in an oven at 100C to
homogenize the water distribution within the capsule before the experiment and to check further for leaks. After the experiment, capsules were re-weighed and each capsule was considered successful if the pre-run– post-run weight difference was less than 04 mg, which is the precision of the analytical balance. Each run con-sisted of several capsules loaded together in the vessel, each capsule having a different H2O/CO2ratio so as to
vary XH2O [¼ molar H2O/(H2Oþ CO2)] between 1 and
012 (Table 2) at any explored P and T. Vesicle size and proportion vary with melt water content, and the pres-ence of vesicles in all charges provides evidpres-ence for fluid saturation condition being attained at P and T.
Experimental equipment
All experiments were performed at the Institut des Sciences de la Terre d’Orle´ans using internally heated
pressure vessels (IHPV) working vertically and
equipped with either a molybdenum or a Kanthal
fur-nace. The pressuring medium was an H2–Ar mixture
(loading sequentially H2and then Ar at room
tempera-ture), the Ar/H2 ratio used to reach the desired target
fO2 being based on previous experiments (Scaillet
et al., 1992). Total pressure was recorded by a trans-ducer calibrated against a Heise–Bourdon tube gauge (uncertainty 620 bars), and temperature was
continu-ously measured by two S-type thermocouples
(accuracy 6 5C). The fO
2prevailing during the
experi-ment was determined a posteriori through redox sen-sors, which consist of two pellets of hand-pressed Co–Pd–CoO powder loaded into Au capsules with dis-tilled water, and embedded within ZrO2powder to
pre-vent alloying with the Au (Taylor et al., 1992). Run
duration varied between 60 and 180 h (Table 2)
depending on temperature. Experiments at T > 800C
were terminated using a drop-quench device (Di Carlo et al., 2006), which allows a quench rate of >100C s–1. The transient increase in total pressure during the drop-quench was taken as evidence that the sample holder had successfully fallen into the bottom cold part of the vessel. Low-temperature experiments (T 800C) were
terminated by switching off the power supply while maintaining the experimental pressure at the target value until about 300C. After the experiment, the
cap-sules were weighted to check for leaks and opened: some pieces of the run products were mounted in epoxy resin and polished for SEM–EDS (energy-disper-sive spectrometry) phase identification and EMPA.
fH
2, fO
2and water content in the experimental
charges
The fO2recorded by the redox sensors allowed us to
obtain the fH2 at T–P during the experiment. This fH2
was calculated from the water dissociation constant Kw
KW(=fH2O/fH2*fO21/2fromRobie et al. (1997), using the
fH2O (fugacity of pure water at P and T of interest;
Burnham et al., 1969) and the fO2 of the sensor. For
H2O-saturated charges (i.e. XH2O¼ 1), the fO2is that of
the sensor. The fO2of each single H2O-undersaturated
charge was calculated using the water dissociation equilibrium, the fH2 as given by the sensor, and the
fH2O of the charge, which was determined using the
re-lationship fH2O¼ fH2O XH2Oin (moles). The fO2
obtained using such a method ranges from NNO – 017 to NNO – 316, the spread reflecting essentially the fO2
decrease with decreasing XH2O (e.g.Scaillet & Evans,
1999;Di Carlo et al., 2010;Cadoux et al., 2014).
Most charges are characterized by high crystal con-tents preventing the use of techniques such as FTIR to
determine directly the dissolved water content.
Consequently, the water content in all charges was computed using the following approach. We first derived an empirical relationship between fH
2O and
H2O content (at saturation) in the melt: fH2O¼ a(H2O
wt %)b. To derive the a and b coefficients, we used the
results of a series of supra-liquidus water-saturated experiments conducted on the sample GTT. The values
determined are a¼ 72612 and b ¼ 18615. Then the
H2Omelt of each charge was computed from the
equa-tion H2Omelt (wt %)¼ (fH2O/72612)1/18615 (obtained by
inverting the previous equation between fH2O and
H2Omelt), where fH2O is given by the relationship
fH2O¼ fH2O XH2Oin. It is important to note that this
procedure is equivalent to assuming ideal behaviour in the H2O–CO2fluid phase, so that the values obtained
must be considered as maximum dissolved water con-tents. All results are listed inTable 2.
ANALYTICAL TECHNIQUES
A total of 68 charges were studied by SEM–EDS (Cambridge Leo 440 at University of Palermo and
Table 2: Experimental run conditions and results Run XH2Oin (moles)* H2Omelt (wt %)† log fO2 (bar)‡
DQFM§ DNNO¶ Phase assemblage and abundances (wt %) Crystal
(wt %) R2
Green Tuff Trachyte (GTT) GT R9, 950C, 1500 bar, PH
2k¼ 65 bar (target: FMQ buffer), 96 h
1 100 495 –1209 –047 –096 Gl only 07 107 2 081 442 –1223 –061 –114 Gl only 00 078 3 052 347 –1262 –100 –153 Gl (958 ), Cpx (11 ) 42 046 4 034 276 –1299 –138 –191 Gl (97), Cpx (05 ) 30 042 5 010 144 –1404 –243 –296 Gl (968 ), Cpx (03 ) 32 030 GT R7, 900C, 1500 bar, PH 2¼ 65 bar, 115 h 1 100 495 –1255 –010 –055 Gl (971 ), Cpx (01), Mt (34), Ilm (061) 29 031 2 082 446 –1266 –021 –072 Gl (935), Cpx (37 ), Mt (683), Ilm (165) 65 045 3 053 354 –1303 –058 –110 Gl (508), Cpx (35), Ol (23) Mt (29), Afs (405) 492 013 4 028 251 –1358 –113 –165 Gl (360), Cpx (24), Ol (3), Mt (33), Afs (553) 640 027 GT R8, 850C, 1500 bar, PH 2¼ 6 bar, 125 h 1 100 495 –1373 –037 –077 Gl (943), Cpx (19), Mt (38) 57 081 2 082 447 –1380 –044 –094 Gl (334), Cpx (52), Ol (04), Mt (49), Afs (561) 666 030 3 051 346 –1421 –085 –135 Gl (242), Cpx (38), Ol (11), Mt (67), Afs (663) 758 046 4 033 275 –1459 –122 –173 Gl, Cpx, Ol, Mt, Afs n.d. n.d. 5 010 144 –1563 –227 –277 Gl, Cpx, Ol, Mt, Afs n.d. n.d. GT R10, 950C, 1000 bar, PH 2¼ 55 bar, 96 h 1 099 384 –1206 –044 –100 Gl (978), Mt (22) 22 030 2 080 342 –1228 –066 –119 Gl (983), Mt (17) 17 029 3 048 258 –1273 –112 –164 Gl (965), Cpx (06), Ol (04), Mt (457), Ilm (204) 35 007 4 030 201 –1314 –152 –204 Gl (960), Cpx (12), Ol (08), Mt (34), Ilm (13) 38 024 5 010 111 –1409 –247 –300 Gl (680), Cpx (22), Ol (26), Mt (14), Afs (258) 320 015 GT R2, 900C, 1000 bar, PH 2¼ 55 bar, 86 h 1 100 384 –1252 –007 –059 Gl (971), Cpx (04), Mt (25) 29 039 2 080 341 –1273 –028 –078 Gl (956), Cpx (09), Ol (04) Mt (31) 44 091 3 050 265 –1313 –068 –119 Gl (752), Cpx (08), Ol (23) Mt (30), Afs (187) 248 019 4 030 201 –1358 –113 –164 Gl (618), Cpx (10), Ol (30), Mt (22) Afs (320) 382 015 GT R4, 850C, 1000 bar, PH 2¼ 55 bar, 120 h 6 100 384 –1354 –018 –066 Gl (907), Cpx (36), Mt (57) 93 064 7 082 345 –1371 –035 –084 Gl (489), Cpx (52), Ol (08), Mt (34), Afs (417) 511 007 8 051 266 –1413 –076 –126 Gl (359), Cpx (23), Ol (17), Mt (37), Afs (567) 641 023 9 034 214 –1448 –112 –161 Gl (302), Cpx (09), Ol (06), Mt (19), Afs (664) 698 094 10 010 111 –1554 –217 –266 n.d. n.d. n.d. GT R14, 800C, 1000 bar, PH 2¼ 6 bar, 150 h 1 100 384 –1468 –032 –075 Gl (252), Cpx (61), Ol (09), Mt (45), Afs (633) 748 014 2 082 346 –1480 –045 –092 Gl (193), Cpx (73), Ol (05), Mt (47), Afs (692) 807 031 5 052 269 –1521 –085 –133 Gl (187 ), Cpx (12), Ol (20), Mt (40), Afs (712) 812 183 GT R3, 750C, 1000 bar, PH 2¼ 55 bar, 170 h 6 100 384 –1574 –030 –066 Gl (238), Cpx (89), Ol (14), Mt (31), Afs (628) 762 020 7 010 111 –1766 –221 –266 Gl, Cpx, Ol, Qz 1000 nd GT R11, 950C, 500 bar, PH 2¼ 55 bar, 96 h 1 100 286 –1222 –061 –112 Gl (987), Mt (13) 13 013 2 077 248 –1245 –084 –135 Gl ( 979), Ol (07), Mt (14) 21 044 3 056 208 –1273 –111 –163 Gl (976), Cpx (06), Ol (19), Mt (11) 24 030 4 037 167 –1309 –147 –199 Gl (848), Cpx (06), Ol (35), Mt (013), Afs (122) 152 054 5 010 083 –1422 –261 –312 Gl (759), Cpx (01), Ol (21), Mt (11), Afs (209 ) 241 006 GT R12, 900C, 500 bar, PH 2¼ 55 bar, 110 h 1 100 286 –1311 –066 –116 Gl (934), Cpx (16), Ol (15), Mt (35) 66 063 2 082 257 –1328 –083 –133 Gl (933), Cpx (13), Ol (20), Mt (34) 67 078 3 071 237 –1341 –096 –146 Gl (802), Cpx (22), Ol (25), Mt (14), Afs (137) 198 049 4 050 196 –1372 –127 –176 Gl (542), Cpx (17), Ol (34), Mt (16), Afs (391) 458 028 5 030 151 –1415 –169 –219 Gl (427), Cpx (05), Ol (30), Mt (2, 7), Afs (521) 573 022 6 010 083 –1511 –266 –316 Gl, Cpx, Ol, Afs, Mt nd nd
Post Cinque Denti Caldera trachyte (PCD) R1, 950C, 1500 bar, PH
2¼ 65 bar (target: FMQ buffer), 60 h
1 100 495 –1145 016 –033 leaked 2 080 441 –1141 021 –028 Gl (972) 28 129 3 060 377 –1166 –004 –054 Gl (957), Cpx (11) Mt (32) 43 135 4 045 323 –1191 –029 –079 Gl (952), Cpx (15), Mt (33) 48 17 5 010 144 –1322 –160 –209 Gl (543), Cpx (58), Ol (15), Mt (10), Afs (374) 457 012 R2, 900C, 1500 bar, 96 h, PH 2¼ 55 bar, 86 h 1 100 495 –1293 –047 –093 leaked 2 080 440 –1231 014 –038 Gl ( 943 ), Cpx (22), Mt (34) 56 094 3 057 368 –1261 –015 –067 leaked 4 046 328 –1279 –034 –086 leaked 5 010 144 –1412 –167 –219 n.d. 100% (continued)
Tescan Mira 3, XMU at ISTO-BRGM Orle´ans joint facil-ity) for preliminary phase identification and textural analysis. Experimental phases and glasses were ana-lysed by electron microprobe (CAMECA SX-Five at ISTO) using an acceleration voltage of 15 kV, sample current 6 nA and counting time of 10 s on peak and background for all elements; Na and K were analysed first and a ZAF correction was applied. Co–Pd–O solid sensors were analysed at 20 kV and 20 nA, with 10 s on each peak and 5 s on background. Mineral phases were analysed with a focused beam, whereas glasses were analysed with 10 10, 5 5 and 2 2 mm defocused beams (depending on the size of glass pools), as well as with a focused beam. Mineral and glass compositions in the natural rocks were determined using the same analytical conditions.
In our experimental glasses Na was affected by mi-gration under the microprobe beam (e.g.Spray & Rae, 1995; Hanson et al., 1996; Morgan & London, 1996,
2005). The local heating accompanied by the flux of beam energy is the most important factor in controlling Na mobility, which becomes severe in hydrous glasses and peralkaline compositions, where some fraction of the Na forms a terminal species on non-bridging O atoms associated with Si (Mysen, 1983; McMillan & Wolf, 1995; Morgan & London, 2005). As shown by
Morgan & London (2005), using a current density close to 0006 nA mm–2
the Na loss is lower than 2% in hy-drous haplogranitic glass. For our analytical conditions, a current density close to 0006 nA mm–2corresponds to a 20 20 mm defocused beam, which was inappropriate for most of the experimental charges. Hence, to obtain
reliable data on Na concentration of our experimental glasses, we calibrated the beam size effect (i.e. the cur-rent density) using diffecur-rent hydrous glass standards prepared from the starting material.
ATTAINMENT OF EQUILIBRIUM
The experimental strategy adopted in this work is well known for favouring crystal nucleation in aluminosili-cate glasses (e.g. Clemens & Wall, 1981; Pichavant, 1987), as well as the attainment of crystal–liquid equilib-rium on laboratory time-scales (Pichavant et al., 2007). Previous studies performed on haplogranitic composi-tions (equivalent to high-silica rhyolites) have shown that crystal nucleation is promoted if a fine-grained dry glass is used as the starting material, as in our case. Our compositions are less silicic than the haplogranite one and richer in alkali elements. Both factors imply a lower melt viscosity and consequently component dif-fusivities significantly higher than in high-silica rhyo-lites for which crystal–liquid equilibrium has been demonstrated (e.g. Pichavant, 1987; Scaillet et al., 1995).
As evidenced in other experimental studies on inter-mediate–felsic compositions (e.g. Martel et al., 1999), when the drop-quench failed our compositions ended up producing abundant quench minerals showing that the activation energy for crystal nucleation was not in-surmountable. More specifically, the experiments from this study are of crystallization-type and the condition of near-equilibrium crystallization reached in the experi-mental products is suggested by several observations, Table 2: Continued Run XH2Oin (moles)* H2Omelt (wt %)† log fO2 (bar)‡
DQFM§ DNNO¶ Phase assemblage and abundances (wt %) Crystal
(wt %) R2 R4, 950C, 1000 bar, PH 2¼ 55 bar, 86 h 1 100 384 –1159 086 –053 Gl (100) 0 0 2 083 347 –1179 066 –070 Gl (98), Cpx (2) 2 068 3 071 320 –1192 053 –082 leaked 4 045 250 –1232 014 –122 Gl (624), Cpx (39), Mt (30) Afs (308), 376 082 5 010 111 –1363 –117 –253 Gl (333 ), Cpx (66), Ol (32), Mt (30), Afs (604) 632 037 R3, 900C, 1000 bar, PH 2¼ 55 bar, 86 h 1 100 384 –1236 009 –043 leaked 2 082 344 –1261 –015 –066 Gl (954), Cpx (23), Mt (23) 46 113 3 058 286 –1291 –045 –096 Gl (575), Cpx (40), Ol (19), Mt (17), Afs (349) 425 083 4 047 256 –1309 –064 –114 Gl (394), Cpx (51), Ol (12), Mt (093), Afs (534) 606 052 5 010 111 –1443 –198 –249 Gl, Cpx, Ol, Mt, Afs n.d. n.d. R10, 850C, 1000 bar, PH 2¼ 6 bar, 120 h 1 100 384 –1354 –109 –066 Gl, Cpx, Mt, Afs n.d. n.d. 2 085 351 –1304 –059 –017 Gl, Cpx, Ol, Mt, Afs n.d. n.d. 3 053 272 –1345 –100 –058 Gl, Cpx, Ol, Mt, Afs n.d. n.d. 4 029 199 –1396 –151 –109 Gl, Cpx, Ol, Mt, Afs n.d. n.d.
*XH2Oin, initial mole fraction of H2O of the C–H–O fluid loaded in the capsule. †H
2Omelt(wt %), dissolved melt water content determined following the method ofScaillet & Macdonald (2006)and Andujar et al.
(2016).
‡fO
2, logarithm of the oxygen fugacity (bar) calculated from the experimental fH2obtained from the solid sensors (see the text). §
DQFM,¶DNNO log fO2– logfO2of the QFM and NNO buffer calculated at P and T respectively fromPownceby & O’Neill (1994)and
Chou (1978).
kPH
2, hydrogen pressure loaded in the vessel at room temperature. Crystal content, values indicate the phase abundance in the
charge (in wt %). Gl, glass; Cpx, clinopyroxene; Ol, olivine; Mt, magnetite; Afs, alkali feldspar; Ilm, ilmenite; Qz, quartz. ‘Leaked’ indicates capsule that lost the fluid phase during the experiment.
in particular, (1) the euhedral shape of the crystals, (2) the homogeneous distribution of phases within the charges, (3) the low residuals of mass-balance calcula-tions, and (4) the fact that crystal abundances and com-positions vary regularly as a function of T and H2Omelt.
Altogether, this suggests that run durations were long enough (>60 h) to ensure close attainment of crystal– melt equilibrium, in agreement with previous work on broadly similar intermediate–felsic compositions (e.g.
Martel et al., 1999;Scaillet & Evans, 1999).
IRON LOSS TO THE CAPSULE MATERIAL
Iron loss to the capsule material is a severe problem with Pt and Au80–Pd20containers (Green & Ringwood,
1967), but less so when Au capsules are used (e.g.
Sisson & Grove, 1993). In this study we did not observe large iron losses, except in charges GT R9-3, GT R9-4 and GT R-5, which were run at 950C and in which
esti-mated FeO loss ranges between 33 and 40%. In other charges run at the same temperature and similar fO2
conditions, no iron loss was observed.
RESULTS
General observations
Our crystallization experiments show textural features similar to those observed in several crystallization experiments carried out at similar temperatures on intermediate to felsic compositions (e.g. Scaillet & Evans, 1999; Martel et al., 1999, 2013; Cadoux et al., 2014). Run products include mineral phases, glass and
vesicles. Crystals have euhedral to sub-euhedral
shapes: at T > 900C their size ranges between 10 and 15 mm, whereas at lower temperature the size exceeds 10 mm (Fig. 2). The mineral phases identified are Cpx, Ol, Af, Mt, Ilm and Qz (the last only in charge GT R3-7). Glass was present in all charges except GT R3-7. In suc-cessfully drop-quenched runs, no evidence of quench textures was found, confirming that cooling rates were fast enough to prevent quench crystallization. Overall, crystallization experiments reproduce the natural phase assemblage observed in the targeted rocks.
Mineral and glass analyses were used in mass-balance calculations (Albare`de, 1995) to obtain phase proportions for each charge (Table 2). Phase composi-tions are reported inTables 3–7. The squared residuals of mass-balance calculations are generally < 1, suggest-ing that (1) no major phases were overlooked, (2) the Na contents of the experimental glasses have been cor-rectly evaluated, and (3) iron loss to the capsule
con-tainer was negligible. The variations of phase
proportions with temperature and H2Omeltare shown in
Figs 3and4, respectively, and the phase relationships are shown in two projections of direct petrological use: T–H2Omelt sections (Fig. 5) allow constrait of
pre-erup-tive conditions and the cooling history of trachytic mag-mas, whereas isothermal P–H2Omelt sections (Fig. 6)
show the effect of decreasing P and H2Omelton
crystal-lization during magma ascent.
The experiments produced homogeneous phases and variations of the main intensive variables T, XH2O and fO2
are well displayed in the compositions of solid-solution phases. For example, small changes in fH2O (i.e. H2Omelt)
produce variations in fO2that affect all iron-bearing
miner-als (i.e. Cpx, Ol and oxides). Microprobe analyses of Af were difficult to achieve owing to the poor contrast in back-scattered electron (BSE) images with residual glasses. Moreover, Af often contains small oxide inclu-sions, which increase its iron content. Some iron-rich analyses were recalculated assuming a maximum iron content of 15 wt % and subtracting the average compos-ition of Mt. Both Mt and Ilm were always small (< 8 mm) and in some cases glass contamination during EMPA was inevitable. When glass contamination was reasonably low, the glass contribution was calculated out, otherwise Fe–Ti analyses were not considered. Similarly, the ana-lysis of residual glasses in some crystal-rich charges was not possible even with a focused beam.
Phase proportions
Phase proportions obtained from mass-balance calcula-tions show that the amount of glass in the run products Fig. 2. Selected scanning electron microscope images of run products obtained in crystallization experiments at (a) 950C,
1 kbar, H2Omelt¼ 3 wt % and (b) 800C, 1 kbar and H2Omelt
-satu-rated conditions. Ol, olivine; Cpx, clinopyroxene; Fe–Ti ox, Fe– Ti oxides; Afs, alkali feldspar; Gl, glass.
Table 3: Composition of experimental clinopyroxenes (wt %)
Run n SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 Total XFe
Green Tuff Trachyte (GTT) GT R9, 950C, 1500 bar 3 1 5211 090 118 927 116 1379 2000 057 010 001 9898 027 5 5 5236 083 101 1096 126 1375 1909 042 010 000 9969 031 SD 026 023 042 108 023 062 082 015 007 000 055 003 GT R7, 900C, 1500 bar 1 6 5238 050 069 1183 110 1279 1984 042 007 003 9966 034 SD 046 013 021 068 011 044 031 007 003 004 044 002 2 7 5177 052 129 1400 139 1105 1868 064 012 002 9948 042 SD 051 017 042 164 017 063 069 008 004 004 049 004 3 7 5154 059 159 1935 146 849 1596 075 042 006 10020 056 SD 029 019 063 178 028 064 055 021 028 004 141 001 4 2 4982 049 065 2115 152 886 1576 059 006 005 9895 057 SD 082 001 021 062 006 021 068 009 000 000 020 006 GT R8, 850C, 1500 bar 1 3 5295 024 140 1438 160 1038 1916 053 002 001 10067 044 SD 051 006 011 153 057 034 054 025 004 006 079 003 2 7 5346 068 390 1589 148 726 1567 125 020 003 9909 054 SD 115 035 063 117 017 067 097 015 020 009 124 003 3 6 5019 066 122 2197 193 645 1546 080 013 008 9881 067 SD 076 016 033 186 043 031 091 012 011 018 070 002 4 3 5063 052 248 2931 167 448 1080 093 047 028 9951 079 SD 029 016 042 062 062 021 009 015 020 000 063 005 GT R10, 950C, 1000 bar 3 11 5229 051 123 1366 121 1166 1875 051 018 008 9982 040 SD 061 011 044 099 015 034 081 012 013 009 000 002 4 15 5171 071 122 1468 122 1112 1826 049 014 003 9941 043 SD 082 012 088 114 020 076 104 028 010 005 096 002 5 7 5214 082 141 1856 160 962 1548 056 026 029 10019 052 SD 140 029 093 201 023 076 194 008 013 011 107 004 GT R2, 900C, 1000 bar 1 4 5110 049 119 1240 119 1220 2010 060 009 003 9940 036 SD 087 012 012 090 040 032 087 013 002 090 002 2 10 5202 043 171 1379 125 1159 1878 065 022 003 10047 040 SD 089 012 087 105 048 034 089 011 018 004 132 002 3 5 5082 081 151 1968 175 1027 1554 054 013 014 10119 053 SD 061 087 027 167 012 042 126 016 003 008 039 003 4 5 5067 059 115 2072 165 878 1526 065 026 010 9948 057 SD 062 012 039 195 028 041 098 017 010 017 131 001 GT R4, 850C, 1000 bar 6 10 5148 049 157 1304 142 1083 1913 096 000 000 9892 040 SD 092 033 097 111 041 072 032 020 007 005 149 003 7 2 5078 054 258 1699 156 835 1604 143 002 003 9834 053 SD 058 017 109 028 028 099 029 054 054 018 080 002 8 6 5024 052 118 2437 193 662 1341 096 002 003 132 067 SD 095 034 037 144 047 021 133 023 019 033 078 001 9 1 4958 073 150 2764 170 516 1332 130 040 006 10092 075 SD 058 041 097 028 021 032 021 016 000 000 090 GT R14, 800C, 1000 bar 1 4 5154 095 401 1656 183 761 1543 169 049 005 10032 055 SD 087 023 140 093 032 092 123 024 030 010 070 003 2 4 5252 044 273 2472 189 600 1183 160 068 012 10240 070 SD 099 005 058 054 018 024 082 043 030 010 5252 001 5 5 4986 038 141 2686 207 566 1131 104 033 011 9912 073 SD 101 001 049 066 020 040 165 041 015 014 070 002 GT R3, 750C, 1000 bar 6 3 5005 127 361 2148 154 570 1266 200 060 011 9901 068 SD 145 052 094 124 019 037 103 045 040 009 133 007 GT R11, 950C, 500 bar 3 10 5207 076 178 1445 119 1138 1767 067 019 020 9998 041 SD 120 023 069 098 014 044 090 027 006 007 090 001 4 13 5231 071 163 1573 129 1082 1694 053 035 002 9995 045 SD 126 019 132 231 023 107 178 032 027 002 067 004 5 2 5220 083 224 1679 116 981 1602 083 051 002 9988 049 SD 162 007 149 210 005 058 059 069 032 002 175 002 GT R12, 900C, 500 bar 1 10 5163 057 145 1399 131 1132 1819 074 026 008 9919 041 SD 119 034 087 147 013 034 066 034 018 013 151 002 2 11 5244 043 100 1577 150 1095 1765 047 015 008 10021 045 SD 089 011 027 127 018 027 091 011 009 011 104 002 (continued)
varies from 98 wt % to less than 20 wt %, decreasing with decreasing H2Omeltand temperature. Liquidus
con-ditions were attained at 950C and H
2Omelt 35 wt %,
whereas the highest crystal contents (80 wt %) were obtained at temperatures800C (Fig. 3a). At 750C and
nominally dry conditions no glass was detected in the charge and we consequently infer that the H2
O-satu-rated solidus for the trachytic magma is close to this temperature (a small amount of water is probably pre-sent because of the reduction of Fe2O3by the hydrogen
of the pressure medium, which produces enough water to saturate the system). In charges where Af does not crystallize, the crystal content never exceeds 12 wt %. Af, whenever present, increases linearly as the melt fraction decreases, becoming rapidly the dominant min-eral phase (Fig. 3b). At any given temperature and pres-sure, the amount of Af tends to increase with decreasing H2Omelt, but a large increase in Af content is
also observable when temperature decreases (Fig. 4a,
Table 2). Cpx never exceeds 9 wt % whereas the amount of Ol is usually below 4 wt %. The Af/Cpxþ Ol ratios of the experimental charges broadly bracket those of the natural rocks, which are around 4–6 (Fig. 4b). Fe–Ti oxide abundances range between 2 and 5 wt %. It is worth noting that the experiments performed on both starting materials show the same phase proportion variation with respect to P–T–H2Omelt. The small
com-positional difference between the two starting materials
affects the crystal contents, and, under similar P–T– H2Omeltconditions, PCD charges have a slightly higher
crystal content than those of GTT (Fig. 4a).
Phase relationships
Phase relationships are shown in Figs 5–7. The GTT phase equilibria were established between 750 and 950C and 05 and 15 kbar, whereas for PCD narrower ranges of temperature (850–950C) and pressure (10–
15 kbar) were explored (Table 2). Isobaric phase rela-tionships as a function of temperature and H2Omeltare
shown at 15, 1, and 05 kbar for GTT and at 15 and 1 kbar for PCD, and the effect of decreasing pressure is shown at 950C (Fig. 7). In both compositions, the
stabil-ity fields of Cpx, Ol and Af are well defined, whereas oxide stability fields are constrained only in broad out-line. At 15 kbar, Mt is always present in charges below 950C, whereas Ilm occurs sporadically only in a few
charges. Below, we describe in detail the phase rela-tionships for each composition.
Green Tuff trachytic member (GTT)
At 15 kbar, Cpx is the liquidus phase appearing at 950C and H
2Omelt< 4 wt %. At 900C Cpx becomes
sta-ble at H2O-saturation at all investigated pressures and
is followed by Ol, then by Af when H2Omeltis lower than
35 wt % (Fig. 5a). Ilm and Mt appear at T < 950C
Table 3: Continued
Run n SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 Total XFe
3 8 5148 038 120 1882 174 1044 1433 050 030 013 9889 050 SD 058 010 023 068 018 026 065 013 009 007 058 001 4 7 5224 042 167 1966 168 888 1415 087 044 015 9957 055 SD 109 019 065 165 032 059 058 029 015 012 087 001 5 2 5198 039 145 2193 200 843 1322 076 030 006 10016 059 SD 011 024 041 007 010 014 146 009 000 000 078 000
Post Cinque Denti (PCD) R1, 950C, 1500 bar 3 6 5114 075 193 1536 084 1031 1964 049 016 016 10079 045 SD 059 013 026 088 014 020 030 007 020 020 028 002 4 4 4976 077 181 1678 090 960 1982 055 039 039 9999 049 SD 039 010 014 103 008 014 028 005 026 026 050 001 5 4 5078 067 199 2359 136 748 1414 077 037 005 10079 064 SD 117 030 049 140 014 023 084 015 004 004 174 002 R2, 900C, 1500 bar 2 5 5056 056 181 1311 100 1038 2098 061 016 013 9901 041 SD 089 008 049 066 017 017 044 010 032 004 104 001 R4, 950C, 1000 bar 2 4 5183 059 191 1341 078 1079 2006 056 022 010 9993 041 SD 014 023 099 026 018 105 063 009 015 010 063 003 4 6 4928 063 130 1804 120 1023 1725 051 016 005 9864 050 SD 047 019 032 117 010 052 108 010 011 008 065 003 5 2 4853 086 220 2203 152 820 1523 066 030 004 9956 060 SD 177 020 028 185 005 063 208 022 029 006 082 003 R3, 900C, 1000 bar 2 4 5113 048 141 1479 092 1024 2016 048 010 004 9974 045 SD 062 016 037 052 019 023 031 009 004 004 060 001 3 5 5036 045 094 2135 163 915 1535 046 014 011 9992 057 SD 082 010 025 102 009 027 105 008 017 011 064 001 4 3 4970 050 109 2428 168 745 1417 049 055 004 9994 065 SD 067 016 062 258 023 089 084 012 008 007 104 005
n, number of analyses; SD, standard deviation; FeOtot, total iron reported as FeO; XFe, molar Fe/(Feþ Mg) in clinopyroxene.
Table 4: Composition of experimental olivines (wt %)
Run n SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 Total Fa mol %
Green Tuff (GTT) GT R7, 900C, 1500 bar 2 4 3316 003 002 4678 298 1545 033 003 003 016 9896 6049 SD 027 004 004 029 006 028 001 003 005 022 045 027 3 6 3211 005 003 5133 317 997 049 003 000 000 9757 7114 SD 053 013 033 087 019 031 010 010 008 011 109 059 4 3 3078 013 004 5637 332 878 043 004 004 024 10019 7477 SD 006 008 005 061 016 008 008 004 003 026 075 033 GT R8, 850C, 1500 bar 2 8 3138 022 007 5173 358 844 034 007 007 017 9576 7348 SD 044 017 003 065 042 017 005 008 005 014 097 054 3 5 3104 004 012 5343 342 659 033 012 008 018 9540 7783 SD 082 090 073 095 029 078 005 034 018 016 075 144 4 4 3072 010 009 5751 270 444 032 004 010 012 9615 8436 SD 019 005 016 083 019 019 003 003 008 008 071 033 GT R10, 950C, 1000 bar 3 12 3365 000 000 4336 246 1723 036 001 000 000 9742 5737 SD 042 004 012 087 031 037 004 003 007 016 083 031 4 12 3342 002 001 4422 273 1650 040 000 000 000 9770 5845 SD 034 009 004 070 012 055 008 008 004 019 068 102 5 2 3256 000 000 4885 300 1217 000 000 000 020 9970 7071 SD 077 004 003 093 036 122 014 002 002 012 105 047 GT R2, 900C, 1000 bar 2 7 3290 001 000 4664 295 1681 031 005 002 019 10029 5905 SD 035 004 002 079 019 040 003 003 002 009 093 074 3 6 3202 018 011 4996 311 1215 038 007 006 016 9775 6663 SD 051 009 044 105 021 029 003 006 010 019 140 056 4 5 3243 014 030 5100 260 959 046 010 021 015 9652 7159 SD 052 008 017 069 064 068 009 008 015 009 063 012 GT R4, 850C, 1000 bar 7 7 3132 010 004 5273 376 940 028 004 008 027 9803 7193 SD 040 009 005 184 043 059 004 007 005 021 195 086 8 5 3086 013 001 5689 322 634 030 006 002 013 9741 7961 SD 076 007 001 085 020 040 006 004 003 016 050 078 9 2 3292 005 003 5713 295 509 035 003 000 000 9855 8510 SD 123 015 028 239 003 056 002 024 003 008 001 167 GT R14, 800C, 1000 bar 1 9 3133 005 002 5261 384 730 025 004 007 015 9539 7569 SD 030 009 003 062 024 030 010 005 004 009 042 080 2 1 3166 004 030 5611 367 672 024 019 012 013 9714 7799 SD 060 006 048 107 047 111 005 021 012 010 000 090 5 3 3114 006 001 5590 331 443 027 006 005 013 9536 8326 SD 027 006 002 094 028 040 003 003 006 012 083 073 GT R3, 750C, 1000 bar 6 5 3070 026 043 5811 306 526 025 014 012 023 9803 8232 SD 112 040 070 165 008 018 007 017 011 008 159 027 7 2 3149 012 072 5917 223 304 034 041 019 003 9773 8853 SD 201 003 093 265 030 024 017 058 023 005 121 062 GT R11, 950C, 500 bar 2 2 3340 004 007 4014 261 2036 032 004 008 015 9720 5075 SD 109 001 005 028 006 010 005 001 001 004 135 025 3 7 3373 028 004 4338 250 1805 037 004 008 019 9866 5555 SD 073 037 004 109 017 064 001 004 003 022 056 128 4 8 3235 008 005 4642 259 1469 044 006 008 022 9698 6170 SD 124 010 002 060 023 043 004 007 005 017 087 094 5 3 3230 011 001 4991 287 1303 045 003 007 016 9784 6563 SD 170 005 003 122 024 018 003 004 007 009 060 170 GT R12, 900C, 500 bar 1 2 3364 005 001 4409 311 1734 032 001 005 022 9885 5642 SD 028 008 001 067 017 044 005 002 005 015 011 103 2 7 3331 007 002 4592 327 1495 037 005 006 013 9815 6052 SD 070 007 003 118 018 077 007 003 004 009 074 163 3 5 3308 007 004 4792 335 1293 038 006 005 014 9801 6444 SD 038 007 004 063 020 045 005 005 003 008 055 070 4 6 3213 006 004 5100 335 1005 041 007 008 019 9737 7054 SD 131 006 003 078 023 035 005 010 004 009 104 057 5 7 3208 015 006 5227 338 905 046 006 005 022 9776 7278 SD 042 011 007 110 028 093 008 005 006 010 033 140 (continued)
regardless of H2Omelt. Cpx, Ol and Fe–Ti oxide are the
liquidus phases at 1 kbar, 950C and H
2Omelt close to
3 wt %, followed by Af for H2Omelt 25 wt %. The Af
sta-bility field expands with decreasing temperature,
becoming stable at H2O-saturation at T 800C
(Fig. 5b). At 05 kbar and 950C, Ol replaces Cpx as the
liquidus phase (Fig. 5c), becoming stable at H2O
satur-ation at 900C. The isothermal P–H
2Omelt projections
show that a near-isothermal ascent at either 950C or 900C (Fig. 6a and b) promotes crystallization and
con-sequently an increase in crystal content with decreasing melt water content.
Post Cinque Denti Caldera trachyte (PCD). The phase diagrams for PCD show some differences from those of GTT (Fig. 7a). At 15 kbar, 950C and H
2Omelt< 4 wt
% Cpx is the liquidus phase, being followed by Ol and Af at H2Omelt< 3 wt %. Phase relationships at 10 kbar
(Fig. 7b) show that Cpx is the liquidus phase, as observed in GTT (Fig. 5b), but is followed first by Af, then by Ol. Af displays the same behaviour as in GTT, but at H2O-saturation it becomes stable at a
slightly higher temperature, around 850C. The effect
of pressure is shown in the isothermal section at 950C (Fig. 7c); again, it is apparent that a near-iso-thermal ascent of such a trachytic melt would also promote crystallization of the three principal mineral phases.
Phase compositions
Experimental mineral phases of both compositions studied are similar, and they are reported inTables 3–7. The variation with P–T–fO2and H2Omeltof the GTT
ex-perimental phases is shown inFigs 8–13and discussed below.
Clinopyroxene
Experimental Cpx is augite with compositions in the range En26–42–Fs17–58–Wo26–42and XFe [¼ Fe/(Fe þ Mg),
calculated using FeOtot] ranging between 027 and 075
(Table 3). Compositional trends of experimental Cpx are
governed by variation in T, H2Omeltand fO2. At a given
temperature, the Wo content of Cpx decreases by 10 mol % when H2Omeltdecreases by 15–2 wt %,
where-as the Fs content shows the opposite behaviour (Fig. 8a and b). Cpx becomes progressively richer in Na2O and
FeOtotand poorer in Mg with melt evolution (and hence
with decreasing temperature and H2Omelt) (Fig. 8c and
d). At 950C, XFe ranges between 027 and 050.
where-as below 850C it reaches values up 075, displaying a good correlation with H2Omelt and fO2 (Fig. 8e). The
average Cpx liquid exchange coefficient KdFe–Mg (calcu-lated with FeO¼ FeOtot) is 015 6 006. This value is
simi-lar to that found byDi Carlo et al. (2010)andScaillet & Macdonald (2003). The covariation of XFetotwith
tem-perature, fO2,pressure and H2Omeltcan be parametrized
with the following empirical equation: XFe¼ 00024xT ðCÞ þ 00002xP ðbarÞ
02044xH2Omeltðwt %Þ þ 00718x DNNO
þ 3117 ðR2¼ 092Þ:
(1)
Equation (1)back-calculates experimental XFe to within 6002. Owing to its empirical nature, the use of such an equation, and of all similar equations that follow, is strictly recommended only for compositions similar to those of the Pantelleria trachytes.
Olivine
The composition of Ol falls in the range Fo46–Fo12
[cal-culated as Mg/(Feþ Mg þ Mn)] and can be classified as ferrohortonolite (Table 4). In the experimental P–T– H2Omelt–fO2 range explored, the highest Fo contents
were reached at 950C, whereas the lowest Fo
con-tents occur at 750C and low fO
2(Fig. 9). As for Cpx, Ol
composition varies systematically with temperature, H2Omelt and fO2, becoming Fe-rich with melt
evolu-tion. The most Fe-rich Ol occurs in low-H2Omeltor
low-temperature charges (i.e. T < 850C), where Af
domi-nates over Cpx and Ol. The composition of experimen-tal Ol is strongly affected by H2Omeltand consequently
by fO2. At constant P and T, a decrease of 15 wt % in
Table 4: Continued
Run n SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 Total Fa mol %
Post Cinque Denti Caldera (PCD) R1, 950C, 1500 bar 5 4 3159 011 017 5557 270 857 085 006 011 057 10030 7500 SD 069 005 025 110 008 050 045 006 009 055 071 068 R4, 950C, 1000 bar 5 7 3101 005 018 5562 262 1000 044 006 008 012 10019 7300 SD 062 004 018 054 015 067 009 004 002 012 097 117 R3, 900C, 1000 bar 3 5 3196 003 014 5438 293 948 047 005 009 010 9938 7300 SD 044 003 020 090 020 034 021 004 008 008 153 047 4 5 3084 010 006 5797 300 665 043 005 008 012 9905 8000 SD 055 009 006 047 017 031 007 003 004 004 063 042
n, number of analyses; SD, standard deviation; FeOtot, total iron reported as FeO; Fa (mol %)¼ 100Fe/(Fetotþ Mg þ Mn) in olivine.
H2Omelt (i.e. the average variation of water content
along a given isothermal experimental series)
produ-ces a decrease of about 15–2 log units in fO2
(Table 4), which is accompanied by a decrease in the fayalite content in Ol of 5–10 mol % (Fig. 9c and d). The average Ol–liquid exchange coefficient KdFe–Mg,
calculated considering FeO¼ FeOtot, is 037 6 012,
which is broadly similar to the Kd of previous studies (e.g. Sisson & Grove, 1993; Pichavant et al., 2002;
Barclay & Carmichael, 2004) although most of them concerned more Mg-rich Ol in equilibrium with more mafic melts.
Table 5: Composition of experimental alkali feldspars (wt %)
Run n SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 Total An–Or (%)
Green Tuff (GTT) GT R7, 900C, 1500 bar 3 3 6584 022 1810 112 002 007 097 761 475 010 9902 588–2633 SD 121 006 120 061 006 006 026 036 023 009 043 4 1 6448 038 1631 307 020 021 108 744 479 003 9787 635–2785 GT R8, 850C, 1500 bar 2 6848 030 1783 137 014 015 089 676 499 022 10112 465–3118 SD 105 001 036 076 010 007 006 074 045 012 000 3 6800 015 1779 131 012 030 122 688 506 019 10103 620–30-57 SD 021 003 034 006 000 006 039 025 029 001 016 GT R10, 950C, 1000 bar 5 2 6478 031 1902 105 002 004 104 801 433 000 9860 682–2454 SD 027 029 020 020 000 002 000 024 030 000 092 GT R2, 900C, 1000 bar 3 5 6509 044 1846 125 007 035 188 751 354 017 9896 957–2139 SD 172 017 037 135 006 012 037 082 025 022 085 4 10 6496 050 1872 100 000 005 200 750 401 013 9887 978–2123 SD 130 010 051 092 006 013 033 041 014 001 067 GT R4, 850C, 1000 bar 7 8 6644 051 1796 159 015 006 067 740 475 006 9958 341–2869 SD 164 019 079 106 008 006 021 081 035 006 175 8 2 6597 023 1798 132 009 045 153 793 464 009 9956 713–2580 SD 016 004 020 044 008 016 028 059 025 013 171 9 1 6677 017 1671 132 011 047 164 762 446 017 9783 790–2561 GT R14, 800C, 1000 bar 1 4 6734 020 1810 166 003 006 071 760 418 010 10064 334–2884 SD 049 025 067 076 005 005 022 018 000 009 128 2 4 6529 058 1747 511 016 024 103 724 414 014 9943 462–2712 SD 051 007 035 024 010 007 031 018 043 009 099 5 2 6566 076 1632 471 005 056 170 616 000 007 10026 1079–2559 035 009 024 038 015 008 028 045 038 000 070 GT R3, 750C, 1000 bar 6 7 6667 024 1858 089 005 009 023 795 535 016 9838 242–2882 SD 101 006 060 020 002 002 032 044 075 022 079 GT R11, 950C, 500 bar 4 2 6429 021 1815 074 020 011 192 755 368 008 9693 969–2148 SD 027 008 019 006 003 041 045 037 003 010 5 5 6385 011 1905 139 002 006 188 779 351 010 9775 932–2072 SD 037 008 027 094 003 003 045 041 040 002 005 GT R12, 900C, 500 bar 3 1 6433 044 1831 230 018 048 048 770 419 003 9986 929–2390 4 3 6491 050 1830 288 009 041 041 750 400 004 10032 951–2512 SD 214 014 026 063 001 010 010 036 035 002 150 5 2 6586 000 1782 141 008 036 196 734 400 015 10000 982–2380 SD 197 003 032 038 003 014 014 054 005 010 209
Post Cinque Denti (PCD) R1, 950C, 1500 bar 5 2 6553 017 1952 064 000 000 109 760 442 002 9921 54–261 SD 037 000 150 116 000 000 027 117 037 000 024 R4, 950C, 1000 bar 4 3 6580 013 1952 061 030 080 102 780 491 000 10089 49–279 SD 044 007 071 070 009 008 020 034 055 000 040 5 4 6329 026 1795 163 002 006 119 779 425 004 9648 470–247 SD 071 009 044 057 000 001 021 044 062 002 030 R3, 900C, 1000 bar 3 6 6419 010 1903 065 004 001 138 830 398 005 9772 651–2241 SD 064 007 027 018 004 001 020 042 034 006 057 4 3 6364 042 1931 210 000 001 166 769 387 004 9873 820–2286 SD 004 007 099 003 003 003 008 047 001 032 108
n, number of analyses; SD, standard deviation; FeOtot, total iron reported as FeO; An–Or (%), mol % of anorthite and orthoclase of
the alkali feldspar.
The influence of T, P, H2Omeltand fO2on Ol
compos-ition has been parameterized with the following simple empirical equation:
Faðmol%Þ ¼ 01973xT ðCÞ þ 00134xP ðbarÞ
þ 17118x DNNO 119175xH2Omeltðwt %Þ
þ 2622215 ðR2¼ 095Þ:
(2)
Equation (2) back-calculates the Fa content of experi-mental olivines to within 12 mol %.
Alkali feldspar
Microprobe analyses of Af were considered acceptable when the structural formula fulfilled the following crite-ria: 3950 < (Si þ Al þ Fe) < 4050 and 0950 < (Ca þ Naþ K) < 1050 on an 8-oxygen basis. Analyses of Af are listed in Table 5. Af in single charges usually dis-plays a small compositional variation of 1–3 mol % An, which is considered to be within the analytical uncer-tainty, given the problems mentioned above. In our Table 6: Composition of experimental magnetite and ilmenite
Run n SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 Total % Ulv
Green Tuff Magnetite (GTT) GT R7, 900C, 1500 bar 1 2 046 1958 109 6634 154 145 012 004 010 046 9058 605 SD 031 040 005 083 008 006 013 004 030 031 000 2 1 116 2015 139 6566 149 136 020 003 005 116 9140 6473 GT R8, 850C, 1500 bar 1 2 082 1574 132 6873 158 078 007 000 000 000 8904 5099 SD 006 035 000 050 013 000 003 000 000 000 107 GT R10, 950C, 1000 bar 1 7 026 1835 134 6838 138 159 005 003 011 001 9148 5759 SD 004 028 013 093 016 005 001 004 005 001 081 2 8 034 2114 135 6565 148 182 009 002 012 006 9208 6529 SD 025 046 009 031 017 002 004 004 003 006 080 3 2 106 2317 153 6425 144 169 006 013 014 002 9350 7271 SD 095 004 025 065 011 001 000 003 001 000 037 5 1 044 2633 074 6347 220 126 005 000 023 010 9482 7871 GT R2, 900C, 1000 bar 1 6 066 1798 137 7109 147 172 008 003 004 002 9436 5347 SD 068 047 037 055 021 003 004 005 007 009 133 2 2 026 1942 122 6936 133 156 013 003 004 002 9327 5783 SD 005 010 004 053 002 011 008 005 009 000 094 GT R4, 850C, 1000 bar 6 1 200 1543 220 6757 184 090 007 027 038 002 9069 593 SD 7 3 024 1958 109 6634 154 145 012 000 003 002 9041 6198 SD 010 020 003 040 030 011 002 000 001 000 009 GT R11, 950C, 500 bar 1 3 058 2013 147 6570 136 165 007 001 010 002 9097 6328 SD 026 034 009 114 028 002 002 020 010 002 000 2 2 044 2017 146 6526 177 187 010 012 012 000 9130 6702 GT R12, 900C, 500 bar 1 1 018 1824 135 6920 140 140 007 000 013 003 9200 5534 3 3 198 1747 193 7248 141 131 019 002 009 006 9694 551 02 104 034 029 009 001 005 001 002 000 042
Post Cinque Denti Magnetite (PCD) R2, 900C, 1500 bar 2 3 180 1607 294 7050 131 100 014 026 029 005 9434 5491 SD 054 035 017 029 023 006 010 008 006 004 066 R4, 950C, 1000 bar 2 2 085 2182 161 6783 159 148 010 008 012 000 9613 6686 SD 002 021 001 142 003 002 001 005 010 000 196 3 3 034 1965 119 7026 123 079 010 007 013 006 9439 5973 SD 015 007 006 082 031 002 002 003 003 003 060 R3, 900C, 1000 bar 3 4 098 2215 112 6909 138 108 010 014 011 001 9614 6708 SD 025 123 014 126 012 012 006 011 005 002 192
Green Tuff Ilmenite (GTT) GT R7, 900C, 1500 bar 1 4 014 4862 008 4114 204 221 007 005 007 000 9429 9604 SD 015 059 002 088 020 007 004 2 2 131 4811 028 4140 207 210 017 021 018 000 9583 9691 SD 173 017 029 076 029 018 001 028 004 000 222 GT R10, 950C, 1000 bar 3 3 176 4815 062 3973 198 267 012 007 025 000 9502 9851 SD 125 010 035 001 015 001 002 001 000 000 090
n, number of analyses; SD, standard deviation; FeOtot, total iron reported as FeO; % Ulv, mol % of ulvo¨spinel in the oxide; % Ilm,
mol % of ilmenite in the oxide.
Table 7: Composition of experimental glasses
Run n SiO2 TiO2 Al2O3 FeOtot MnO MgO CaO Na2O K2O P2O5 Total PI
Green Tuff (GTT) GT R9, 950C, 1500 bar 1 7 6523 095 1524 534 035 065 154 646 455 029 10000 102 SD 036 007 011 023 007 003 004 081 018 009 094 2 7 6548 078 1570 509 020 058 111 634 438 034 10000 097 SD 044 010 022 022 010 004 005 057 014 009 067 3 7 6657 085 1596 335 018 066 135 635 459 014 9697 097 SD 065 009 031 019 009 002 008 038 012 009 063 4 7 6597 087 1575 389 028 066 143 621 467 027 10000 097 SD 012 012 013 033 011 003 004 060 016 010 080 5 7 6605 094 1584 345 024 069 148 635 477 019 10000 098 SD 052 011 010 027 010 003 007 052 013 004 049 GT R7, 900C, 1500 bar 1 20 6626 063 1534 451 020 059 138 638 459 011 10000 101 SD 081 009 033 068 009 010 016 062 011 007 000 2 5 6762 047 1575 341 013 031 082 649 491 008 10000 102 SD 083 006 017 035 006 011 008 094 014 006 092 3 3 6852 038 1481 379 004 016 068 644 505 014 10000 108 SD 017 008 040 028 007 009 005 080 012 003 080 4 1 7025 049 1334 337 000 033 085 642 480 015 10000 118 GT R8, 850C, 1500 bar 1 1 6716 039 1560 376 015 015 110 622 507 040 10000 101 SD 077 007 043 050 003 000 030 050 018 002 090 2 3 6834 056 1459 385 017 012 045 674 508 009 10000 114 SD 030 004 009 072 002 004 003 020 013 002 055 3 3 6985 030 1394 310 007 014 082 674 464 038 10000 116 SD 080 002 060 022 001 003 004 000 035 008 072 GT R10, 950C, 1000 bar 1 8 6562 077 1546 479 024 060 133 633 465 021 10000 099 SD 055 008 017 025 009 003 005 073 016 007 000 2 7 6499 087 1528 493 028 064 140 673 466 022 10000 105 SD 058 028 019 055 013 004 008 055 014 014 080 3 13 6590 077 1567 399 016 054 142 670 463 022 10000 102 SD 056 006 013 048 008 002 036 058 019 028 000 4 6 6587 075 1580 430 016 044 135 672 473 019 10000 102 SD 035 010 013 035 006 002 009 056 009 007 043 5 1 6665 068 1468 480 022 035 100 636 509 016 10000 109 GT R2, 900C, 1000 bar 1 5 6572 056 1572 462 021 059 148 633 457 020 10000 097 SD 039 007 012 048 010 003 010 009 004 010 046 2 4 6638 042 1574 443 023 055 137 622 454 012 10000 096 SD 075 010 004 030 008 011 019 037 015 011 108 3 3 6761 048 1535 335 007 030 113 650 495 026 10000 105 SD 016 051 1508 039 009 029 010 007 008 009 079 4 3 6769 056 1459 427 019 027 091 629 498 025 10000 108 SD 061 011 042 070 005 003 014 073 015 022 079 GT R4, 850C, 1000 bar 6 4 6869 023 1583 230 022 014 065 724 467 003 10000 107 SD 033 007 030 008 008 001 004 152 062 007 160 7 5 6934 019 1511 307 004 013 049 680 481 001 10000 109 SD 024 002 010 016 005 001 003 020 007 001 010 8 2 7021 064 1310 413 012 019 053 648 451 009 10000 119 SD 045 010 067 044 007 009 010 030 013 004 092 9 2 7033 044 1280 394 032 038 107 622 422 027 10000 116 SD 284 014 077 057 004 019 053 092 037 016 085 GT R14, 800C, 1000 bar 1 8 7128 027 1352 287 022 011 043 655 472 003 9300 117 SD 164 008 046 035 007 015 039 086 050 012 233 2 1 7154 034 1295 294 015 017 074 652 422 045 9259 118 5 2 7275 031 1184 361 015 013 078 614 396 033 100 122 SD 121 001 058 048 012 001 014 025 004 003 113 GT R3, 750C, 1000 bar 6 8 7077 056 1210 466 004 020 073 609 429 056 10000 121 SD 020 019 080 110 013 018 043 085 052 017 412 GT R11, 950C, 500 bar 1 16 6492 087 1508 529 019 063 144 671 467 021 9482 107 SD 062 007 032 031 008 004 006 026 009 009 098 2 7 6500 087 1518 472 024 063 151 658 460 028 10000 104 SD 070 005 019 029 013 003 013 012 217 011 151 3 4 6519 086 1522 465 022 057 143 694 474 018 10000 109 (continued)
