浙江淳安早白垩世脉岩地球化学特征及成岩动力学背景  

PETROGENESIS AND GEDYNAMIC SETTING OF EARLY CRETACEOUS DYKES IN THE CHUN′AN AREA,ZHEJIANG PROVINCE

作　　者：李福林[1,2] 谢瑜[1] 周汉文[1,3] 唐增才 李益龙[1] 汪发祥 徐于晨[5] 

机构地区：[1]中国地质大学(武汉)地球科学学院,湖北武汉430074 [2]武汉地质矿产研究所,湖北武汉430205 [3]中国地质大学地质过程与矿产资源国家重点实验室,湖北武汉430074 [4]浙江省地质调查院,浙江萧山311203 [5]中国科学院地球化学研究所,贵州贵阳烄烆烌550002

出　　处：《矿物岩石》2011年第3期55-65,共11页Mineralogy and Petrology

基　　金：浙江省国土资源厅项目(2007002); 国土资源部公益性行业科研专项经费项目(200811015); 南岭成矿带基础地质综合研究(K201024)

摘　　要：在浙西淳安地区江绍断裂带内发育规模较大的基性脉岩,野外地质特征显示其产状与区域构造应力场的方向基本一致,总体呈北东—南西向,且与围岩之间的界限截然。对含斑基性脉岩进行了锆石LA-ICPMS U-Pb定年和详细的岩石地球化学特征研究,其锆石206Pb/238 U加权平均年龄为135Ma±2Ma(n=18,MSWD=3.2),代表其结晶年龄,为燕山期岩浆活动的产物,岩石地球化学特征显示形成于板内拉张的环境。整体特征显示含斑基性脉岩是由基性岩墙的岩浆混合了部分围岩物质形成的。该区的含斑基性脉岩与基性岩墙群的形成可能与太平洋板块向亚洲大陆的俯冲有关,是早白垩世岩石圈发生伸展减薄所诱发的地幔物质部分熔融的产物。Large scale basic dykes developed in Jiangshanshaoxing fault zone in Chun＇an area, West Zhejiang Province. These basicdykes occurred mainly in NW-SE trend faults,which were consistent with the regional tectonics stress field, and the sharp contact relation between the basic dykes and the country rocks indicated that these dykes formed in a later stage. LA-ICPMS zircon U-Pb dating method and whole rock geochemistry test were applied and Zircon U-Pb dating revealedaweighted mean ^206pb/^238U ages of 135 Ma＋2 Ma（n=18,MSWD=3.2） for porphyry- bearing mafic dykes in Chun＇an area, suggesting that these dykes were the products of magmatism in the early Cretaceous. The whole rock geochemistry of the dykes showed that they were formed in intra-plate extensional background. It was showed that these porphyry-bearing basic dykes were resulted from the mixing of magma with wall-rocks. These two basic dykes （bearing-porphyry basic dykes and non-porphyry-bearing mafic dykes） in Chun＇an area may be related to the subduetion of the Pacific plate to Asian plate,and these rocks were the products of partial melting of mantle caused by lithospheric extension and decompression during the Early Cretaceous.

关 键 词：脉岩 早白垩世 U—Pb年代学 地球化学 

分 类 号：P588.13[天文地球—岩石学]