DEHYDRATION-MELTING OF BIOTITE GNEISS AND QUARTZ AMPHIBOLITE FROM 3 TO 15 KBAR
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dc.contributor.author | Patino Douce A.E. | |
dc.contributor.author | Beard Ja.S. | |
dc.date.accessioned | 2020-11-30T01:45:53Z | |
dc.date.available | 2020-11-30T01:45:53Z | |
dc.date.issued | 1995 | |
dc.identifier | https://elibrary.ru/item.asp?id=10500650 | |
dc.identifier.citation | Journal of Petrology, 1995, , 3, 707 | |
dc.identifier.issn | 0022-3530 | |
dc.identifier.uri | https://repository.geologyscience.ru/handle/123456789/19898 | |
dc.description.abstract | We performed vapor-absent melting and crystallization experiments on two bulk compositions that model metamorphic rocks containing a single hydrous phase: a biotite gneiss [37% bio (mg-number 55), 34% qtz, 27% plg (An38), 2% ilm] and a quartz amphibolite [54% hbl (mg-number 60), 24% qtz, 20% plg (An38), 2% ilm]. Experiments were performed at 3 and 5 kbar in internally heated pressure vessels (IHPV), and at 7, 10, 12,5 and 15 kbar in piston cylinder apparatus (PC), from the vapor-absent solidi to (at least) the temperature at which the hydrous mineral disappeared. Dehydration-melting begins at similar temperatures in both bulk compositions, ranging from T~850°C at P = 3 kbar T~930°C at P = 15 kbar. The hydrous mineral disappears ~50°C above the solidus in both systems, except in IHPV experiments at f(O2) above Ni–NiO, in which biotite stability extends up to atleast 80°C above the solidus. At the T at which the hydrous minerals disappear the biotite gneiss produces 2–3 times more melt than the quartz amphibolite (50–60 wt% vs 20–30 wt%). In both systems, variations in melt productivity with P are controlled by three competing factors: (1) the positive d P/dT slopes of the solidi, (2) decreasing H2O activity with increasing P at constant H2O content, and (3) Na2O activity, which increases with P concomitantly with breakdown of plagioclase. Melt productivities at T = 920–950°C are maximized at intermediate pressures (~7 kbar). The biotite gneiss produces strongly peraluminous granitic melts (SiO2>70 wt%) and residual assemblages of quartz norite (P>12,5 kbar) or garnet pyroxenite (P>12,5 kbar). The quartz amphibolite produces strongly peraluminous granodioritic melts (SiO2>70 wt%) that coexist with clinopyroxene + orthopyroxene + plagioclase + quartz ? at P>10 kbar)garnet. The results of coupled melting and crystallization experiments on the quartz amphibolite suggest that strongly peraluminous granitoid rocks (e.g. cordierite-bearing and two-mica granites) can be derived from melting of Al-poor protoliths. | |
dc.title | DEHYDRATION-MELTING OF BIOTITE GNEISS AND QUARTZ AMPHIBOLITE FROM 3 TO 15 KBAR | |
dc.type | Статья |
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