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  

An Experiment on the Crystallization of Felsic Gneis s from Shuanghe in the Dabie Mountains at 1.0～4.5 GPa and Its Geological Impli cations

作　　者：刘晓春[1] 杨农[1] 曲玮[1] 

机构地区：[1]中国地质科学院地质力学研究所

出　　处：《地球学报（中国地质科学院院报）》1999年第2期113-120,共8页Acta Geoscientia Sinica

基　　金：国家自然科学基金

摘　　要：在７５０～１２００℃、１．０～４．５ＧＰａ条件下对取自于大别山双河的长英质片麻岩进行了重结晶实验。在７５０℃时，随压力增加矿物生成顺序为：角闪石在１．７５ＧＰａ时出现，２．５ＧＰａ时消失；黑云母在１．７５ＧＰａ时通过水化反应生成多硅白云母；绿帘石可以稳定到＞３．５ＧＰａ，在４ＧＰａ时转变成硬柱石；石榴石和绿辉石在１．５ＧＰａ时开始出现，而斜长石在１．７５ＧＰａ时消失；石英在３ＧＰａ时转变为柯石英。这表明角闪岩相与榴辉岩相的转变发生在１．５～１．７５ＧＰａ，并且，榴辉岩相可进一步划分出角闪榴辉岩相、柯石英榴辉岩相和硬柱石榴辉岩相等，它们分别指示不同的压力区间。多硅白云母是长英质岩石在高压－超高压条件下的主要共生矿物，其水化反应特性及结构水的保存致使陆壳在深俯冲过程中未发生明显的脱水作用。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.

关 键 词：高温高压实验 长英质片麻岩 结晶实验 地质意义 

分 类 号：P588.345[天文地球—岩石学]