豫西地区秦岭造山带武当群火山岩和沉积岩锆石U-Pb年龄  

Zircon U-Pb Ages of Volcanic and Sedimentary Rocks of the Wudang Group in the Qinling Orogenic Belt within Western Henan Province

作　　者：祝禧艳[1,2] 陈福坤[1] 王伟[1,2] PHAM Trung Hieu[1,2] 王芳 张福勤[1] 

机构地区：[1]中国科学院地质与地球物理研究所矿产资源研究重点实验室,北京100029 [2]中国科学院研究生院地球科学学院,北京100039

出　　处：《地球学报》2008年第6期817-829,共13页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:40525007,40721062);科技部国家重点基础研究发展计划973项目(编号:2006CB403505)资助

摘　　要：在南秦岭地体中广泛分布着武当群变质沉积—火山岩组合的基底岩石,是东秦岭造山带重要的岩石单元,但对其形成时代的认识存在分歧。笔者通过对豫西地区武当地体北部武当群上部杨坪组变质沉积岩和下部双台组变质中酸性火山岩锆石U-Pb年龄的测定,认为杨坪组变质沉积岩沉积物源主要由晚元古代(860～640Ma)和早元古代(2260～1800Ma)、少量晚太古代和中元古代地壳物质构成,与扬子陆块具有亲缘关系。沉积时代应晚于640Ma。变质中酸性火山岩形成时代为730～780Ma之间,峰值(755±6)Ma,与双台组新元古代变质基性火山岩为同期岩浆作用的产物,成因上推测与Rodinia超大陆裂解作用有关。Metamorphosed sedimentary-volcanic sequences of the Wudang Group widely distributed in the South Qinling Block are considered to be basement rocks of the Wudang Terrain and important rock units in the eastern part of the Qinling Orogenic Belt. Nevertheless, there exists controversy over the formation age of the Wudang Group. To determine the formation time of the Wudang Group, the authors reported zircon U-Pb ages obtained by the LA-ICP-MS technique in this paper. The samples were composed of a meta-sedimentary rock sample collected from the Yangping Formation in the upper part of the Group, and four meta-volcanic rock samples from the Shuangtai Formation in the lower part of the Group. Dating resuhs demonstrate that sedimentary sources of the Yangping Formation originated mainly from Neoproterozoic （ - 860 - 640 Ma） and Paleoproterozoic （ - 2260 - 1800 Ma）, and subordinately from Late Archean and Mesoproterozoic crustal materials, with an affinity to the Yangtze Block. Sedimentation should have occurred later than 640 Ma. Metamorphosed felsic volcanic rocks were formed between ～ 730 Ma and -780 Ma, with the peak at （755 ±6） Ma, being simultaneous with the metamorphosed Neoproterozoic mafic volcanic rocks of the Shuangtai Formation within the Wudang Terrain and probably related to the breakup of the supercontinent Rodinia in petrogenesis.

关 键 词：武当群 锆石U-PB年龄 秦岭造山带 豫西 新元古代 

分 类 号：P597.1[天文地球—地球化学]