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Titolo:
DEHYDRATION MELTING OF A BASALTIC COMPOSITION AMPHIBOLITE AT 1.5 AND 2.0 GPA - IMPLICATIONS FOR THE ORIGIN OF ADAKITES
Autore:
SEN C; DUNN T;
Indirizzi:
KARADENIZ TEK UNIV,JEOL BOLUMU TRABZON 61015 TURKEY UNIV NEW BRUNSWICK,DEPT GEOL FREDERICTON E3B 5A3 NB CANADA
Titolo Testata:
Contributions to Mineralogy and Petrology
fascicolo: 4, volume: 117, anno: 1994,
pagine: 394 - 409
SICI:
0010-7999(1994)117:4<394:DMOABC>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Soggetto:
MOUNT-ST-HELENS; SUBDUCTED LITHOSPHERE; ARCHEAN TRONDHJEMITES; OXYGEN FUGACITY; VOLCANIC-ROCKS; OCEANIC-CRUST; PRESSURE; ARC; PETROGENESIS; GEOCHEMISTRY;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
36
Recensione:
Indirizzi per estratti:
Citazione:
C. Sen e T. Dunn, "DEHYDRATION MELTING OF A BASALTIC COMPOSITION AMPHIBOLITE AT 1.5 AND 2.0 GPA - IMPLICATIONS FOR THE ORIGIN OF ADAKITES", Contributions to Mineralogy and Petrology, 117(4), 1994, pp. 394-409

Abstract

This study presents the results of dehydration melting experiments ona basaltic composition amphibolite under conditions appropriate to a hot slab geotherm (1.5 and 2.0 GPa and temperatures of 850 to 1150 degrees C). Dehydration melting produces an omphacitic augite and garnet bearing residue coexisting with rhyolitic to andesitic composition melts. At 1.5 GPa, the amphibolite melts in two stages between 800 and 1025 degrees C. The 2.0 GPa data also define two melting stages. At 2.0 GPa, the first stage involves nearly modal melting of the original amphibolite minerals (qtz, pl, amp) to produce melt + cpx + grt. During the second stage, the eclogite restite melts non-modally (0.86 cpx + 0.14 grt = 1 melt). The experimental results were combined with data from the literature to generate a composite P-T phase diagram for basaltic composition amphibolites over the 800 to 1100 degrees C temperature range for pressures up to 2.0 GPa. Comparison of the major element compositions of the experimentally produced melts with compositions of presumed slab melts (adakites) shows that partial melting of amphiboliteat conditions appropriate to a hot-slab geotherm produces melts similar to andesitic and dacitic adakites except for significant MgO and CaO depletions. Trace element modelling of amphibolite dehydration melting using the 2.0 GPa melting reactions produces REE abundances similarto those of adakites at 10-15 wt% batch melting, but the models do not reproduce the high Sr/Y ratios characteristic of adakites. Taken together, the major and trace element results are not consistent with thederivation of adakites by dehydration melting of the subducted slab with little or no interaction with the mantle wedge or crust. If adakites are partial melts of the subducted slab, they must undergo significant interaction with the mantle and/or crust, during which they acquire a number of their distinctive characteristics.

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Documento generato il 13/07/20 alle ore 17:11:10