| 大别山双河长英质片麻岩在1.0～4.5GPa下的结晶实验及其地质意义 |
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| 关键词:high-temperature high-pressure experiment felsic gneiss dehydration and hydration reactions calcalkaline magmatic arc Dabie Mountains |
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| An Experiment on the Crystallization of Felsic Gneiss from Shuanghe in the Dabie Mountains at 1.0～4.5 GPa and Its Geological Implications |
| The crystallization of felsic gneiss from Shua nghe in t he Dabie Mountains was experimentally investigated at 750～1200 ℃ and 1.0～4.5 GPa. The order of crystallization with increasing pressure at 750 ℃ are as foll ow. Amphibole appears at 1.75 GPa and disappears above 2.5 GPa.At 1.75 GPa, biot ite transform into phengite through hydration reaction. Epidote is stable up to more than 3.5 GPa and transform into lawsonite at 4.0 GPa. Garnet and omphacite occur at 1.5 GPa and plagioclase breaks down above 1.75 GPa. Quartz transforms i nto coesite at 3.0 GPa. This suggests that amphibolite facies transform into ecl ogite facies at about 1.5～1.75 GPa, and eclogite facies can further be divided into amphibolite, coesite and lowsonite eclogite subfacieses, which represents t he different stability fields of pressure. Phengite is a major mineral in felsic gneiss at high and ultrahigh pressures. The hydration reaction of biotite and p reservation of constitutional water in phengite suggest that the continental cru st did not dehydrate during subduction. This is why the calc_alkaline magmatic a rc did not form in the continental collision belts. |
| LIU Xiao-chun,YANG Nong,QU Wei.1999.An Experiment on the Crystallization of Felsic Gneiss from Shuanghe in the Dabie Mountains at 1.0～4.5 GPa and Its Geological Implications[J].Acta Geoscientica Sinica,20(2):113-120. |
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