| 华夏地块前加里东期变质基底的特征以及深部地壳性质 |
| |
| 关键词:Cathaysia block metamorphic basement deep crust crustal differentiation |
| 基金项目:地质矿产部深部地质“华南北区深部地壳结构及演化”课题 |
|
| 摘要点击次数: 2545 |
| 全文下载次数: 2265 |
| 摘要: |
| Discussions on the Characteristics of the Deep Crust and Pre-Caledonian Metamorphic Basement in the Cathaysia Block, Southeastern China |
| 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. |
| ZHAO Feng-qing,JIN Wen-shan,GAN Xiao-chun,SUN Da-zhong,WANG Zu-wei.1995.Discussions on the Characteristics of the Deep Crust and Pre-Caledonian Metamorphic Basement in the Cathaysia Block, Southeastern China[J].Acta Geoscientica Sinica,16(3):235-245. |
| 查看全文 查看/发表评论 下载PDF阅读器 |
|
|
|
|
|