The effects of temperature and f<sub>O2</sub>on the Al-in-hornblende barometer

Anderson, J. Lawford; Smith, Diane R.

doi:10.2138/am-1995-5-614

Cited by 1,083 publications

(804 citation statements)

References 32 publications

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“…Because the influence of temperature (and oxygen fugacity) on pressure calculations has to be considered, we have chosen the calibration of Anderson & Smith (1995) to calculate crystallization pressures. Equilibration temperatures for hornblendeplagioclase assemblages were calculated on the basis of iterations started from pressures calculated using Anderson & Smith (1995) and using various thermometers. Preferred values according to Anderson (1996) have been accepted (see also Anderson et al 2008;Holland & Blundy, 1994).…”

Section: Geology and Petrography Of The Mt Cer Plutonmentioning

confidence: 99%

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

et al. 2010

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-The Mt Cer Pluton, Serbia, is a complex laccolith-like intrusion (∼ 60 km 2 ), situated along the junction between the southern Pannonian Basin and northern Dinarides. It intrudes Palaeozoic metamorphic rocks causing weak to strong thermal effects. Based on modal and chemical compositions, four rock-types can be distinguished: (1) metaluminous I-type quartz monzonite/quartz monzodiorite (QMZD); (2) peraluminous S-type two-mica granite (TMG), which intrudes QMZD; (3) Stražanica granodiorite/quartz monzonite (GDS); and (4) isolated mafic enclaves (ME), found only in QMZD. 40 K-39 Ar dating and geological constraints indicate that the main quartz monzonite/quartz monzodiorite body of Mt Cer was emplaced not later than 21 Ma, whereas the emplacement ages of the Stražanica granodiorite/quartz monzonite and two-mica granites are estimated at around 18 and 16 Ma, respectively. The Mt Cer pluton is similar to the Mt Bukulja pluton, some 80 km southwestwards. Genesis of QMZD cannot be interpreted by fractional crystallization coupled with mixing or assimilation. It is best explained by a convection-diffusion process between mantle-derived minette/leucominette magmas and GDS-like magmas followed by two end-member magma mixing. The composition of GDS rocks suggests that GDS-like magmas could have formed by melting of lower crustal lithologies similar to amphibolite/metabasalts. The geochemistry of TMG is reproduced by an Assimilation/Fractional Crystallization model with a ratio of rate of assimilation to rate of fractional crystallization of 0.4, using the compositions of the least evolved TMG of the Bukulja pluton and adjacent metamorphic rocks as proxies for the parental magma and contaminant, respectively. The origin and evolution of the Mt Cer and adjacent Mt Bukulja plutons provide new constraints on the Tertiary geodynamics of the northern Dinarides-southern Pannonian region. The quartz monzonite/quartz monzodiorite is interpreted as a result of the Oligocene post-collisional Dinaride orogen-collapse, which included a limited lithosphere delamination, small-scale mantle upwelling, and melting of the lower crust. By contrast, the two-mica granite magmas formed through melting in shallower crustal levels during the extensional collapse in the Pannonian area.

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Section: Geology and Petrography Of The Mt Cer Plutonmentioning

confidence: 99%

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

et al. 2010

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“…In turn, estimated plagioclase composition for the porphyries was always higher than the measured one (estimated An30-60 vs a Calculated according to Ridolfi and Renzulli (2012) b Calculated according to Giesting and Filiberto (2014) measured An10-30, respectively). However, using the measured plagioclase and amphibole compositions with the thermobarometric formulation of Holland and Blundy (1994) in conjunction with the Al-in-hornblende barometer of Anderson and Smith (1995) resulted in a restricted near-solidus temperature range around 700 °C and a large pressure range of 400-100 MPa (Chelle-Michou et al 2015). This is inconsistent with the well-developed edenite exchange vector and the lack of tschermak exchange in amphibole from Coroccohuayco (Fig.…”

Section: Amphibolementioning

confidence: 99%

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

Chelle-Michou

Chiaradia

2017

Contrib Mineral Petrol

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Chlorine and sulfur are of paramount importance for supporting the transport and deposition of ore metals at magmatichydrothermal systems such as the Coroccohuayco Fe-Cu-Au porphyry-skarn deposit, Peru. Here, we used recent partitioning models to determine the Cl and S concentration of the melts from the Coroccohuayco magmatic suite using apatite and amphibole chemical analyses. The pre-mineralization gabbrodiorite complex hosts S-poor apatite, while the syn-and post-ore dacitic porphyries host S-rich apatite. Our apatite data on the Coroccohuayco magmatic suite are consistent with an increasing oxygen fugacity (from the gabbrodiorite complex to the porphyries) causing the dominant sulfur species to shift from S 2− to S 6+ at upper crustal pressure where the magmas were emplaced. We suggest that this change in sulfur speciation could have favored S degassing, rather than its sequestration in magmatic sulfides. Using available partitioning models for apatite from the porphyries, pre-degassing S melt concentration was 20-200 ppm. Estimates of absolute magmatic Cl concentrations using amphibole and apatite gave highly contrasting results. Cl melt concentrations obtained from apatite (0.60 wt% for the gabbrodiorite complex; 0.2-0.3 wt% for the porphyries) seems much more reasonable than those obtained from amphibole which are very low (0.37 wt% for the gabbrodiorite complex; 0.10 wt% for the porphyries). In turn, relative variations of the Cl melt concentrations obtained from amphibole during magma cooling are compatible with previous petrological constraints on the Coroccohuayco magmatic suite. This confirms that the gabbrodioritic magma was initially fluid undersaturated upon emplacement, and that magmatic fluid exsolution of the gabbrodiorite and the pluton rooting the porphyry stocks and dikes were emplaced and degassed at 100-200 MPa. Finally, mass balance constraints on S, Cu and Cl were used to estimate the minimum volume of magma required to form the Coroccohuayco deposit. These three estimates are remarkably consistent among each other (ca. 100 km 3 ) and suggest that the Cl melt concentration is at least as critical as that of Cu and S to form an economic mineralization.

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“…The change in Al tot with pressure is mainly attributed to a tschermak exchange (Mg -1 Al VI Si -1 Al IV ) and to a minor plagioclase exchange (Ca -1 Na M(4) Al -1 IV Si), whereas the edenite substitution (NaAl IV Si -1 ) is more sensitive to temperature changes (Anderson and Smith 1995;Hammarstrom and Zen 1986;Hollister et al 1987;Johnson and Rutherford 1989;Schmidt 1992).…”

Section: Determination Of Intrusion Pressuresmentioning

confidence: 99%

“…For comparison, we also determined pressures after Anderson and Smith (1995) in conjunction with the edenite-thermometer of Holland and Blundy (1994) in order to take possible differences in emplacement temperature into account (Blundy and Holland 1990). We employed the Michel-Lévy method, precise to ±2 mol%, to optically determine the anorthite content of the plagioclase.…”

Section: Determination Of Intrusion Pressuresmentioning

confidence: 99%

“…We employed the Michel-Lévy method, precise to ±2 mol%, to optically determine the anorthite content of the plagioclase. Differences in pressures calculated from the Schmidt's (1992) calibration and the Anderson and Smith (1995) fit are small (electronic appendix), indicating that almost all samples equilibrated at the wet solidus. Hence, our geological implications drawn from the pressure determinations are independent of the calibration used.…”

Section: Determination Of Intrusion Pressuresmentioning

confidence: 99%

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TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

Jagoutz¹,

Schmidt

Enggist

et al. 2013

Contrib Mineral Petrol

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We present the geochemistry and intrusion pressures of granitoids from the Kohistan batholith, which represents, together with the intruded volcanic and sedimentary units, the middle and upper arc crust of the Kohistan paleo-island arc. Based on Al-in-hornblende barometry, the batholith records intrusion pressures from *0.2 GPa in the north (where the volcano-sedimentary cover is intruded) to max. *0.9 GPa in the southeast. The Al-in-hornblende barometry demonstrates that the Kohistan batholith represents a complete cross section across an arc batholith, reaching from the top at *8-9 km depth (north) to its bottom at 25-35 km (south-central to southeast). Despite the complete outcropping and accessibility of the entire batholith, there is no observable compositional stratification across the batholith. The geochemical characteristics of the granitoids define three groups. Group

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The effects of temperature and f_O2on the Al-in-hornblende barometer

Cited by 1,083 publications

References 32 publications

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

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The effects of temperature and fO2on the Al-in-hornblende barometer

Cited by 1,083 publications

References 32 publications

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

Petrogenetic and tectonic inferences from the study of the Mt Cer pluton (West Serbia)

Amphibole and apatite insights into the evolution and mass balance of Cl and S in magmas associated with porphyry copper deposits

TTG-type plutonic rocks formed in a modern arc batholith by hydrous fractionation in the lower arc crust

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The effects of temperature and f_O2on the Al-in-hornblende barometer