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哀牢山造山带金矿成矿时序及其动力学背景探讨
引用本文:杨立强,邓军,赵凯,刘江涛.哀牢山造山带金矿成矿时序及其动力学背景探讨[J].岩石学报,2011,27(9):2519-2532.
作者姓名:杨立强  邓军  赵凯  刘江涛
作者单位:中国地质大学地质过程与矿产资源国家重点实验室,北京,100083
基金项目:本文受国家重点基础研究发展规划(2009CB421008)、教育部新世纪优秀人才支持计划(NCET-09-0710)、高等学校学科创新引智计划(B07011)、教育部长江学者和创新团队发展计划(IRT0755)和地质过程与矿产资源国家重点实验室项目联合资助.
摘    要:哀牢山金矿带是我国最重要的喜马拉雅期造山型金矿带,形成于三江特提斯复合造山过程中。论文基于对哀牢山造山带金矿成矿作用的同位素定年结果,探讨了成矿年代学与构造-热事件的关系,厘定了其相关的地球动力学背景。已获得的最老成矿年龄集中于海西期,但过剩氩的存在导致视年龄值偏离真实成矿年龄,而最小视年龄(345.2±16Ma)与区域蛇绿岩的形成同时;含镍金黄铁矿硅质岩的含金量可能与热水沉积有关,其地球动力学环境对应于海底扩张和初始洋盆的形成。印支期是区域主碰撞造山高峰期,也是大规模岩浆活动与Cu-Ni-Pt-Pd硫化物矿床、VMS型Cu-Pb-Zn矿床及斑岩型Cu-Au矿床成矿集中期,其中老王寨金矿含金黄铁矿的Re-Os等时线年龄为229±38Ma。燕山期成矿年龄数据分散于180Ma、135Ma、110Ma和90Ma左右等多个时段,其中最晚时段年龄谱的最小视年龄值(91±1Ma)可能代表了一次较为重要的构造动力体制转换,该期(约90~70Ma)的区域成岩成矿(斑岩及斑岩型Cu-Mo-W-Au矿床)规模较大,表明增生造山→碰撞造山构造体制转换在研究区存在重要的成岩成矿响应。喜马拉雅期可能经历了早(63.09~61.55Ma)、主(36.10~33.76Ma)和晚(30.80~26.40Ma)三期金矿成矿-热事件,分别受控于印度-亚洲大陆碰撞早期的强烈汇聚挤压、早-晚期转换构造动力学体制,并可能受青藏高原物质东向逃逸和软流圈脉动隆起的联合制约,金矿大规模成矿作用与构造动力体制转换过程中的壳幔物质强烈交换与构造变形密切相关。

关 键 词:构造热事件  成矿年代学  造山型金矿  矿床探针  哀牢山造山带  中国西南
收稿时间:2011/3/10 0:00:00
修稿时间:2011/6/25 0:00:00

Tectono-thermochronology and gold mineralization events of orogenic gold deposits in Ailaoshan orogenic belt, Southwest China: Geochronological constraints
YANG LiQiang,DENG Jun,ZHAO Kai and LIU JiangTao.Tectono-thermochronology and gold mineralization events of orogenic gold deposits in Ailaoshan orogenic belt, Southwest China: Geochronological constraints[J].Acta Petrologica Sinica,2011,27(9):2519-2532.
Authors:YANG LiQiang  DENG Jun  ZHAO Kai and LIU JiangTao
Institution:State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China
Abstract:Ailaoshan gold belt, one of the most important Himalayan orogenic-type gold belt in China, formed during the processes of superimposed orogenesis in Sanjiang Tethys. The relationship between mineralization events and tectono-thermochronology as well as the related geodynamic regimes has been discussed in terms of the isotope dating result of gold mineralization in Ailaoshan orogenic belt. Hercynian period is considered to be the oldest mineralization concentrated time through the ages obtained, however, the real metallogenic ages deviated from the apparent ages due to the excess argon, the regional ophiolites formed synchronously to the youngest apparent age (345.2±16Ma); the relationship between gold contents in auriferous pyrite silicolite and hydrothermal deposition suggest the geodynamic regime of seafloor spreading and initial ocean basin forming. Indosinian period is exactly the time at which the main collision of the regional orogen happened, when large-scale magmatism, Cu-Ni-Pt-Pd sulfide deposits, VMS type Cu-Pb-Zn deposits and porphyry Cu-Au deposits happened intensively, besides Re-Os isochron age of auriferous pyrite from Laowangzhai gold ore deposit is 229±38Ma. Metallogenic ages during Yanshan are split up into several scattered periods (180Ma, 135Ma, 110Ma and 90Ma), the apparent age of the latest age spectra (91±1Ma) is likely the response to significant transition of geodynamic regime, besides the lage-scale regional diagenesis (porphyry) and metallogenesis (porphyry Cu-Mo-W-Au deposits) during the period (ca. 90~70Ma) corresponds the transition of tectonic regimes from accretion orogeny to collision orogeny. Himalayan period are divided into three tectonic-thermal events related to mineralization, namely the early, occurred from 63.09~61.55Ma, the main, occurred from 36.10~33.76Ma, and the late, occurred from 30.80~26.40Ma, which were controlled by the strongly early convergence geodynamic regime of India-Euraisa, the early to late stage transition of geodynamic regime, and eastward escapation of the Tibetan Plateau, and pulsating uplift of asthenosphere, respectively. The metallogenic characteristics, combined with published geological and isotopic information, indicate that the large-scale gold metallogeny is closely related to the intense crust-mantle material exchange and the tectonic deformation in the transition of geodynamic regimes.
Keywords:Tectono-thermochronology  Mineralization event  Orogenic gold deposit  Ore-system as geodynamic probe  Ailaoshan orogenic belt  Southwest China
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