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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Calcic amphibole thermobarometry in metamorphic and igneous rocks: New calibrations based on plagioclase/amphibole Al-Si partitioning and amphibole/liquid Mg partitioning

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Author(s):
Molina, J. F. [1] ; Moreno, J. A. [1, 2] ; Castro, A. [3] ; Rodriguez, C. [3] ; Fershtater, G. B. [4]
Total Authors: 5
Affiliation:
[1] Univ Granada, Dept Mineral & Petrol, Granada 18002 - Spain
[2] Univ Estadual Campinas, UNICAMP, Inst Geosci, Dept Geol & Nat Resources, BR-13083970 Campinas, SP - Brazil
[3] Univ Huelva, CSIC, Fac Ciencias Expt, UA Petrol Expt, Huelva 21071 - Spain
[4] IGG Russian Acad Sci, Ekaterinburg - Russia
Total Affiliations: 4
Document type: Journal article
Source: LITHOS; v. 232, p. 286-305, SEP 1 2015.
Web of Science Citations: 38
Abstract

Dependencies of plagioclase/amphibole Al-Si partitioning, D-Al/si(plg/amp), ancramphibole/liquid Mg partitioning, D-Al/si(plg/amp), on temperature, pressure and phase compositions are investigated employing robust regression methods based on MM-estimators. A database with 92 amphibole-plagioclase pairs - temperature range: 650-1050 degrees C amphibole compositional limits: >0.02 apfu (230) Ti and >0.05 apfu Al - and 148 amphibole-glass pairs - temperature range: 800-1100 C; amphibole compositional limit: CaM4/(CaM4 + NaM4)> 0.75 - compiled from experiments in the literature was used for the calculations (amphibole normalization scheme: 13-CNK method). Statistical analysis reveals a significant dependence of D-Al/s(plg/amp) on pressure, temperature, Al fraction in amphibole T1 -site, X-Al(Tl), and albite fraction in plagioclase, X-Ab, leading to the barometric expression: P(kbar) = (8.3144 T(K) InDDAl/siplg/amp -8.7 T(K) + 23377 X-Al(Tl) + 7579X(Ab) - 11302) / - 274) (precision: +/- 1.5 to 2.3 kbar; expressed at 1 s). The D-Al/si(plg/amp) was found to have a significant dependence on temperature and the logarithm of X-ca(liq) + X-Al(liq)) ratio (glass composition expressed as anhydrous mole fraction of cation components) that led to the thermometer: T(degrees C) = 71975-11896 In{[}X-ca(liq)(X-ca(liq) + X-Al(liq))]/8.3144 InDMgamP/liq + 58 - 273 (precision: +/- 35 to +/- 45 degrees C). Amphibole-liquid compositional relationships revealed that the temperature dependence of D(Mg)(amP/liq)was mostly controlled by a positive correlation of X-Mg(liq) with temperature that led to the thermometer: T(degrees C) = 107 InXMGliq - 108 In{[}X-ca(liq)/(X-ca(liq) + X-Al(liq)] + 1184 (precision: +/- 37 to +/- 42 degrees C). The plagioclase-amphibole barometer is suitable for a large diversity of amphibole-plagioclase-bearing assemblages from metamorphic (amphibolites and mafic granulites) and igneous (metaluminous granitoids to gabbros) rocks, whereas the liquid-only and the amphibole-liquid thermometers are applicable to alkaline and suballcaline igneous rocks. The calibrated expressions yield P-T estimates consistent with those obtained with widely used barometers and thermometers. Plagioclase-amphibole barometry extends pressure determinations to quartz-free and/or garnetfree assemblages. (C) 2015 Elsevier B.V. All rights reserved. (AU)

FAPESP's process: 14/04920-0 - Geological and geochemical investigations on archaen granite-gneiss terranes of São Francisco Craton
Grantee:Juan Antonio Moreno Moreno
Support Opportunities: Scholarships in Brazil - Post-Doctoral