华夏地块前加里东期变质基底的特征以及深部地壳性质  

Discussions on the Characteristics of the Deep Crust andPre-Caledonian Metamorphic Basement in theCathaysia Block, Southeastern ChinaZhao Fengqing

作　　者：赵风清[1] 金文山[1] 甘晓春[1] 孙大中[1] 王祖伟[1] 

机构地区：[1]天津地质矿产研究所,中国科学院广州地球化学研究所

出　　处：《地球学报（中国地质科学院院报）》1995年第3期235-245,共11页Acta Geoscientia Sinica

基　　金：地质矿产部深部地质"华南北区深部地壳结构及演化"课题

摘　　要：通过对华夏地块前加里东期变质基底的地质、地球化学以及变质作用的研究，结合岩浆岩的同位素年代学和地球化学“示踪”研究，认为华夏地块深部存在时代为２５００—２７５０Ｍａ的太古代地壳，而时限为１８５０—１９５０Ｍａ的中条（浙闽）运动是该区一次重要的造壳运动，形成了该区分布广泛的早元古代的结晶基底。华夏地块深部地壳的物质组成是比较复杂的，但主体由长英质岩石组成，因此华夏地块老地壳活化再造作用表现较为强烈。其下地壳由于受深熔作用影响形成大量花岗质岩浆向中、上地壳运移侵位，其物质成分也由富花岗质向贫花岗质中（—基）性变化。The Pre-Caledonian metamorphic rocks in Cathaysia block can be divided into three parts in ascend-ing ordor : ( 1 ) rocks of The Zhongtiao(or Zhemin) cycle of Early Proterozoic (>1850Ma) , con-sisting chiefly biotite (two-Mica) plagioclase leptites, mica schistes and quartz mica schistes with alittle amount of amphibolites and marbles, which have been metamorphoseed to the amphibolite fa-cies ; (2) rocks of the Jinning cycle of Middle Proterozoic (<1400-1100Ma) , made up mainly ofmetamorphic bimodal spilite-keratophyre suite, staurolite gurnet nica sehistes, mica (quartz )schistes, marbles and quartzites, have been subjected to the high-grade rgeenschist to low-grade am-phibolite facies metamorphism; and (3 ) rocks of the Caledonian cycle of Late Proterozoic to EarlyPaleozoic , mainly composed of metamorphic siltstones , feldspar-quartz sandstones, graywacke , sil-icalites, phyllites, slates , plagioclase-mica-quartz schistes , and quartz feldspar leptites , which havebeen metamorphosed to the low-grade greenschis facies. According to the metamorphic character,the rocks of the Zhongtiao cycle(and/or Jinning cycle) probably represent the intermidiate crust ofthe Cathaysia block and the rocks of the Caledonian cycle represent the folded basement of the uppercrust.A large number of detrital zircon ages and depleted mantle ages of Nd(T_DM) have a range from2750Ma to 2500Ma, which indicates that an Archean crust may exist in the deep crust of theGathaysia block. Nearly all of the granitoid reeks in the Cathaysia block have negative ε_Nd(t) val-ue, suggesting that the deep crust consists chiefly of felsic rocks or metamorphic sedimentary pro-toliths. The derease in the negafive ε_Nd(t) values of granites from the Zhongtiao’an to the Calidonianand down to the Yanshanian is reflective of the evolution of the deep erust from being granite-richto granite-poor in composition ,a process resulting mainly from the differentiation of the crust.

关 键 词：华夏地块 变质基底 深部地壳 地壳 分异作用 

分 类 号：P544.1[天文地球—构造地质学] P313.3[天文地球—地质学]