大别—苏鲁超高压地体折返过程中岩石组合演化的地球化学约束  

Geochemistry Constrains on Rock Association of UHP Terrane during Exhumation

作　　者：杨启军[1] 钟增球[1] 周汉文[1] 

机构地区：[1]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学（中国地质大学学报）》2003年第3期241-249,共9页Earth Science-Journal of China University of Geosciences

基　　金：国家重点基础研究发展规划项目 (G19990 75 5 0 6 ) .

摘　　要：大别—苏鲁超高压地体现今的岩石组合是超高压变质岩石经历快速折返过程中各种地质作用叠加改造的最终产物 ,其中拆沉、底侵、构造体制转换是改造的动力 ;退变质作用、构造置换、深熔作用是改造的主要方式 .超高压地体的主要岩石组合有榴辉岩、大理岩、硬玉石英岩、斜长角闪岩、片麻岩和面理化花岗岩 .地质、常量、微量、同位素地球化学研究表明 ,斜长角闪岩是榴辉岩退变的产物 ,片麻岩、面理化花岗岩是榴辉岩退变的斜长角闪岩递进深熔的产物 ,即退变榴辉岩折返到中下地壳 ,初次熔融产生相当于片麻岩成分的半原地英云闪长质-花岗闪长质 -花岗质岩浆 ,片麻岩再次熔融产生成分相当于面理化花岗岩的A型花岗岩岩浆 .The present rock association of the UHP terrane in Dabie-Sulu region, China results from the result of source UHP rocks rebuilt by retrogressive metamorphism, tectonics, anatexis during the exhumation. The dynamics of reformation is the conversion of tectonics, basal erosion and delimitation by means of metamorphism, structure-replacement and anatexis. The UHP terrane is composed of ecologite, marble, jadeite-quartzite, amphibolites, gneisses and foliated granites. In terms of geology and geochemistry, the amphibolite is found to have evolved from ecologite by retrogressive metamorphism and gneisses, foliated granite to have evolved from the amphibolite by anatexis. The anatexis started at 230 Ma when the UHP terrane exhumed to the low crust and turned intense in the middle-low crust. The melting composition from the anatexis of amphibolite is equal to tantalite or granodiorite (in agreement with gneisses). Moreover, the melt from the partial-melting of gneisses with A-type granite composition (which is the same with the foliated granite). The gneisses and foliated granites have both evolved from ecologite by retrogressive metamorphism and delivery anatexis.

关 键 词：大别-苏鲁超高压地体 折返过程 岩石组合 榴辉岩 大理岩 硬玉石英岩 片麻岩 斜长角闪岩 地质作用 退变质作用 地球化学 

分 类 号：P588.3[天文地球—岩石学] P59[天文地球—地质学]