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东秦岭金堆城大型斑岩钼矿床LA ICP MS锆石U Pb定年及成矿动力学背景
投稿时间:2007-08-02  修订日期:2007-10-10  点此下载全文
引用本文:朱赖民,张国伟,郭波,李犇.2008.东秦岭金堆城大型斑岩钼矿床LA ICP MS锆石U Pb定年及成矿动力学背景[J].地质学报,82(2):204-220
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作者单位
朱赖民 西北大学地质系,大陆动力学国家重点实验室西安710069 
张国伟  
郭波  
李犇  
基金项目:本文为国家重大基础研究项目(编号2006CB4502)、中国科学院矿床地球化学国家重点实验室项目(编号20060)及陕西省教育厅基金项目(编号07JK414)资助的成果
中文摘要:对出露东秦岭金堆城大型斑岩钼矿床北部的老牛山黑云二长花岗岩和金堆城含矿斑岩利用单颗粒锆石激光探针LA-ICP-MS定年技术进行了U Pb精确定年和岩石地球化学对比研究。LA-ICPMS锆石U Pb测年得到老牛山黑云二长花岗岩和金堆城含矿斑岩锆石加权平均年龄值分别为146.35±0.55Ma和140.95±0.45 Ma,与前人多次获得的金堆城钼矿床的辉钼矿Re-Os模式年龄141±4~127±7 Ma下限值一致,显示成矿与成岩同时或略滞后于岩体,成岩成矿发生于侏罗纪-白垩纪的同一成岩成矿系统中,与发生于1
中文关键词:LA-ICP-MS定年  老牛山花岗岩  金堆城花岗斑岩  东秦岭  成矿动力学背景
 
U-Pb (LA-ICP-MS) Zircon Dating for the Large Jinduicheng Porphyry Mo Deposit in the East Qinling, China, and Its Metallogenetic Geodynamical Setting
NameInstitution
ZHU LaiminState key Laboratory of Continental Dynamics, Department of Geology,Northwest University,Xi’an, 710069
ZHANG Guowei
GUO Bo
LI Ben
Abstract:A precise U-Pb dating based on single particle zircon laser probe dating technology (LA-ICPMS), and comparative study of petrological and geochemical characteristics have been applied to the Jinduicheng ore-bearing porphyry and Laoniushan biotite-monzonitic granite north of the large Jinduicheng porphyritic molybdenum deposit in the Eastern Qinling. The weighted average ages by LA-ICPMS zircon U-Pb dating of the Laoniushan biotite-monzogranite and the Jinduicheng ore-bearing porphyry are 146.35±0.55 Ma and 140.95±0.45 Ma respectively, which are consistent with the lower limit of molybdenite Re-Os model ages by previous researchers. This indicates that the mineralization took place almost at the same with or slightly later than that of the diagenesis, with metallogenesis and diagenesis occurring in the same system in Jurassic-Cretaceous, which was coupled with the extensional geodynamical event during the later stage of tectonic system transformation occurring in East China at about 140 Ma. The formation of massif and mineralization of molybdenum occurred at the transitional period of compression-extension between the Jurassic and the Cretaceous, which corresponded to geodynamical setting of intracontinental orogeny and extension after the collision of the North China Block and the Yangtze Block. The two plutons have the similar variation on major elements and geochemical parameters, both of them belong to cal-alkaline series rock with silica super-saturation. Geochemically, the two plutons are enriched relatively in LILE, depleted in high field strength element (HFSE), with LREE especially enriched, obvious differentiation between LREE and HREE, and or no distinct negative Eu anomaly. The distribution of trace elements and rare elements are similar to that of intraplate granite and post-collision granite. Geochemical data indicate that the metallogenetic substance was deep earth in origin, and was mixing of the lower crust and upper mantle. Thus, the metallogenesis of the Jinduicheng ore deposit betided at the transformation period from continental convergency to extension as a result of thinning of lithosphere and uprising of ore-forming substance from asthenosphere, which jointly caused interaction between the crust and the mantle, sped melting of the thickened lower crustal material, and then resulted in Mo-rich grantitic magma. When the magma moved along structures developed within the upper crust, ore-bearing fluid derived from condensation fraction of the magma filled the structures and replaced country rock, thus forming the deposits
keywords:LA-ICP-MS dating  Laoniushan biotite-monzogranite  Jinduicheng granite-porphyry  East Qinling  metallogenetic geodynamical setting
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