粤西信宜地区坑坪细碧-角斑岩系的发现及其地质意义  

Discovery of the Kengping spilite-keratophyre series in Xinyi, western Guangdong, China and its geological significance.

作　　者：郭良田[1] 洪裕荣[1] 黄继春 陈宇湖 黄宇辉 许汉森 

机构地区：[1]中国科学院广州地球化学研究所 [2]广东省地质调查院,广东佛山528000

出　　处：《地质通报》2005年第7期648-654,共7页Geological Bulletin of China

基　　金：中国地质调查局1:25万阳春县幅;阳江市幅区域地质调查项目(编号:200113000038;200113000039)成果。

摘　　要：在两广交界的云开地区信宜坑坪新发现超镁铁质角闪黑云辉橄岩、角闪黑云辉岩、石棉矿、辉长辉绿岩、粒玄岩、细碧岩和石英角斑岩,并伴生有色深层薄和色浅层厚2种硅质岩。细碧岩的SiO2为48.44%～52.32%,K2O+Na2O=3.473%～4.77%,较正常玄武岩偏高,Na2O和CaO互为消长关系。石英角斑岩SiO2为70%左右,CaO和Na2O不稳定。这些岩石的稀土元素配分曲线总体比较平滑,略右倾,微Eu负异常,δEu=0.8～1.03;(La/Yb)n介于1.31～3.16之间;等时线年龄Sm-Nd为667Ma±43Ma,Rb-Sr为663Ma±17Ma。The major rock units in the Kengping spilite-keratophyre series at Xinyi in the Yunkai area on the border region of western Guangdong and Guangxi include ultramafic hornblende-biotite harzburgite, hornblende-biotite pyroxenite, asbestos, spilite, quartz keratophyre, dolerite and gabbro-diabase,as well as their associated melanocratic thin-bedded chert and light thick-bedded chert. Spilite contains 48.44-52.32% SiO2 and 3.473-4.77% K2O+Na2O, which are slightly higher than those of normal basalt. Na2O and CaO show an antipathetic relation. Quartz keratophyre contains ～70% SiO2 and the Na2O and CaO contents are unstable. The REE distribution patterns for these rocks are generally flat and slightly right-inclined. The Eu anomalies are weak and negative, with δEu=0.8-1.03, and the (La/Yb)n ranges between 1.31 and 3.16. These rocks have a Sm-Nd isochron age of 667±43Ma and a Rb-Sr age of 663±17Ma.

关 键 词：粤西 信宜 坑坪 早震旦世 细碧-角斑岩系 RODINIA超大陆裂解 

分 类 号：P588.14[天文地球—岩石学]