MELTING OF ALBITE AND DEHYDRATION OF BRUCITE IN H2O-NACL FLUIDS TO 9 KBARS AND 700-900 °C: IMPLICATIONS FOR PARTIAL MELTING AND WATER ACTIVITIES DURING HIGH PRESSURE METAMORPHISM
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dc.contributor.author | Shmulovich K.I. | |
dc.contributor.author | Graham C.M. | |
dc.date.accessioned | 2020-11-30T07:42:20Z | |
dc.date.available | 2020-11-30T07:42:20Z | |
dc.date.issued | 1996 | |
dc.identifier | https://elibrary.ru/item.asp?id=13238750 | |
dc.identifier.citation | Contributions to Mineralogy and Petrology, 1996, , 3, 370-382 | |
dc.identifier.issn | 0010-7999 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/19957 | |
dc.description.abstract | The melting reaction: albite(solid)+ H2O(fluid) =albite-H2O(melt) has been determined in the presence of H2O–NaCl fluids at 5 and 9.2 kbar, and results compared with those obtained in presence of H2O–CO2 fluids. To a good approximation, albite melts congruently at 9 kbar, indicating that the melting temperature at constant pressure is principally determined by water activity. At 5 kbar, the temperature (T)- mole fraction (X (H2O) ) melting relations in the two systems are almost coincident. By contrast, H2O–NaCl mixing at 9 kbar is quite non-ideal; albite melts ∼70 °C higher in H2O–NaCl brines than in H2O–CO2 fluids for X (H2O) =0.8 and ∼100 °C higher for X (H2O) =0.5. The melting temperature of albite in H2O–NaCl fluids of X (H2O)=0.8 is ∼100 °C higher than in pure water. The P–T curves for albite melting at constant H2O–NaCl show a temperature minimum at about 5 kbar. Water activities in H2O–NaCl fluids calculated from these results, from new experimental data on the dehydration of brucite in presence of H2O–NaCl fluid at 9 kbar, and from previously published experimental data, indicate a large decrease with increasing fluid pressure at pressures up to 10 kbar. Aqueous brines with dissolved chloride salt contents comparable to those of real crustal fluids provide a mechanism for reducing water activities, buffering and limiting crustal melting, and generating anhydrous mineral assemblages during deep crustal metamorphism in the granulite facies and in subduction-related metamorphism. Low water activity in high pressure-temperature metamorphic mineral assemblages is not necessarily a criterion of fluid absence or melting, but may be due to the presence of low a (H2O) brines. | |
dc.title | MELTING OF ALBITE AND DEHYDRATION OF BRUCITE IN H2O-NACL FLUIDS TO 9 KBARS AND 700-900 °C: IMPLICATIONS FOR PARTIAL MELTING AND WATER ACTIVITIES DURING HIGH PRESSURE METAMORPHISM | |
dc.type | Статья |
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