含柯石英榴辉岩形成深度的构造校正测算  

ON THE DEPTH OF THE FORMATION OF COESITEBEARING ECLOGITE OF DABIE UHPM ZONE,CENTRAL CHINA

作　　者：吕古贤[1] 陈晶[2] 丁悌平[3] 李晓波[4] 刘瑞 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]北京大学电子显微镜实验室,北京100871 [3]中国地质科学院同位素地质开放实验室,北京100037 [4]中国地质矿产信息研究院,北京100037 [5]北京大学地质系,北京100871

出　　处：《地质力学学报》2000年第3期14-24,共11页Journal of Geomechanics

基　　金：国家攀登计划!( G1 9990 4 3 2 1 4 );自然科学基金!( 49572 1 4 9);国家科委基础研究特别支持项目!(科高 -1 994 -83 );国家计

摘　　要：应用透射电子显微镜 ( TEM)对大别地区英山县含柯石英榴辉岩、石英榴辉岩及石榴角闪岩中石榴子石进行研究 ,结果表明在强塑性变形的三类岩石中 ,石榴子石的超微构造特征存在明显差异。在含柯石英榴辉岩中的石榴子石位错密度比角闪岩中的低。修正石榴子石材料系数 α为 0 .2 5 ,用石榴子石位错密度估算了相对差异应力值 ,并讨论了在超高压榴辉岩形成和退变质过程中各阶段的变质条件。根据石榴子石位错密度测定的差异应力 ,结合石榴子石的变形测量 ,恢复构造三维主应力及构造附加静水压力值 PS,从柯石英相的转变压力 P中减去构造附加静水压力值 PS后 ,利用单纯由重力引起的静水压力值 PG换算上覆岩石的重力和厚度 ,获得大别超高压变质带含柯石英榴辉岩形成深度仅为≥ 32 .0 9～ 32 .1 1 km。因此提出 ,该含柯石英榴辉岩是在这一地壳深处 (或稍深一些 )受强烈构造作用形成的新认识。同位素资料分析表明 ,大别地区榴辉岩系地壳成因 ,这对于榴辉岩是壳内产物的认识提供了进一步证据。The plastic deformation of garnet in coesite\|bearing eclogite,quartz eclogite and garnet amphibolite of the ultrahigh\|pressure metamorphic (UHPM) complex in Yingshan County in the Dabie Mt. is studied by the transmission electron microscope (TEM). It is shown than the garnets have undergone ductile deformation during eclogite and amphibolite metamorphic facies. Microstructures of the garnet vary greatly from coesite\|bearing eclogite to quartz eclogite and garnet amphibolite.\;The 3\|D tectonic principal stresses and the hydrostatic pressure with a coupled tectonic stress(Ps) are reconstructed by differential stress and strain ratio (α) of garnet in minor coesite\|bearing eclogite,and whereby the gravity and thickness of overlying rocks are determined. The formation depth of ≥32 09～32\^11 km of the coesite\|bearing eclogite in Yingshan County in the Dabie UHPM zone is obtained from P G( P-P S) where P is the pressure where the transformation of coesite phase took place,and P S=(σ 1+σ 2+σ 3)/3. P is known to be 2\^8GPa by Qz\|coes geobarometer. This result (ca 32km depth) is much smaller than 100km depth of eclogite in Dabie UHPM zone as achived by others by the method of weight/special weight (W/SW). Strong tectonism is thought to have made a great contribution to the formation of eclogite in the Dabie UHPM zome.

关 键 词：成岩深度 含柯石英榴辉岩 构造校正测算 TEM 

分 类 号：P588.33[天文地球—岩石学]