滇西九顶山铜钼矿花岗斑岩成因:LA-ICP-MS锆石U-Pb年龄、岩石地球化学和Sr-Nd-Hf同位素制约  

Petrogenesis of the granite porphyry related to the Jiudingshan Cu-Mo deposit in western Yunnan: Constraints from LA-ICP-MS zircon U-Pb chronology,Sr-Nd-Hf isotopes and petrogeochemistry

作　　者：刀艳[1] 李峰[1] 王蓉[1] 吴静[1] 

机构地区：[1]昆明理工大学国土资源工程学院,云南昆明650093

出　　处：《中国地质》2015年第1期134-148,共15页Geology in China

基　　金：全国危机矿山接替资源找矿项目(200653056);云南省自然科学基金项目(2011FZ035)联合资助

摘　　要：对滇西九顶山铜钼矿床主要的含矿花岗斑岩开展了系统的年代学、岩石地球化学以及全岩Sr-Nd-Hf同位素的分析工作。LA-ICP-MS锆石U-Pb定年结果表明,九顶山花岗斑岩成岩年龄为34.5-34.9 Ma,与已有的成矿年龄（33.9-35.3 Ma）一致或略早于成矿年龄,处在滇西新生代富碱岩浆活动高峰期内（45-30 Ma）,属于青藏高原碰撞造山带的晚碰撞转换成矿作用（40-26 Ma）的产物。详细的岩石地球化学研究表明,研究区花岗斑岩有高硅（Si O2=62.86%-71.57%）、高钾（K2O/Na2O=1.64-2.78）和富碱（K2O＋Na2O=8.98%-11.28%）的特点,属于钾玄岩系列岩石。岩体轻稀土元素富集（LREE/HREE=4.84-7.64）,具有轻微的负铕异常（δEu=0.82-0.93）,富集大离子亲石元素（Rb、Ba、Th、U）和亏损高场强元素（Nb、Ta、Zr、Hf）。Sr-Nd-Hf同位素的研究分析显示岩浆源区起源于＂EMII型＂富集地幔,＂EMII型＂富集地幔岩浆在上涌的过程中受到地壳物质的混染,形成壳幔混合源富钾含矿岩浆。In this study, the authors carded out a comprehensive research including zircon U-Pb dating, petrogeochemical investigation and Sr-Nd-Hf isotope analysis of the granite porphyry related to the Jiudingshan Cu-Mo deposit in western Yunnan. LA-ICP-MS zircon U-Pb chronology indicates that the porphyry was emplaced at 34.5-34.9 Ma, consistent with or slightly earlier than the formation of the Cu-Mo deposit （33.9-35.3 Ma） and similar in time to the peak of Cenozoic alkali-rich magmatic activity（45- 30 Ma） in westem Yunnan, indicating that they were formed by the ore- forming process in the period of late- collisional transformation （40-26 Ma）. The granite porphyry is silica-rich （SIO2=62.86%-71.57%）, potassium-rich （K2O/Na20=1.64-2.78） and alkali-rich （K2O＋Na20 = 8.98%-11.28%）, belonging to shoshonitic series peraluminous granite, with the characteristics of LREE enrichment, HREE depletion, and weak negative Eu anomaly （δEu=0.82-0.93）. The porphyry is enriched in LILEs such as Rb, Ba, Th and U, and depleted in HFSEs such as Nb, Ta, Zr and U. Sr-Nd-Hf isotopes imply that the magma originated from the EMII which was contaminated by crustal materials in the process of magmatic upwelling to form a potassium-rich ore-bearing magma with mixed sources of the crust and the mantle.

关 键 词：九顶山铜钼矿 过铝质花岗岩 锆石U-PB定年 SR-ND-HF同位素 

分 类 号：P597.3[天文地球—地球化学] P618.41[天文地球—地质学] P618.65