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青海玉树东莫扎抓和莫海拉亨铅锌矿床与逆冲推覆构造关系的确定 ——来自粗晶方解石Rb-Sr和Sm-Nd等时线年龄证据
Confirmation of connection between Dongmozhazhua and Mohailaheng Pb-Zn ore deposits and thrust nappe system in Yushu area, southern Qinghai: evidence from Rb-Sr and Sm-Nd isochron ages of macrocrystalline calcite
投稿时间:2011-03-02  修订日期:2011-04-14
中文关键词:Rb-Sr等时线  Sm-Nd等时线  粗晶方解石  逆冲推覆构造  构造控矿模式  青海玉树东莫扎抓和莫海拉亨铅锌矿床
英文关键词:Rb-Sr isochron  Sm-Nd isochron  calcite  thrust nappe system  tectonic model  Dongmozhazhua and Mohailaheng Pb-Zn deposits in Yushu area, Qinghai Province
基金项目:"十一五"国家科技支撑计划重大资助项目(2006BAB01A08); 国土资源大调查资助项目(1212010818096); 国家973资助项目(2011CB403104,2009CB421007和2009CB421008);国家自然科学联合基金资助项目(U09336051)
作者单位
田世洪 中国地质科学院 矿产资源研究所, 北京 100037
国土资源部成矿作用与资源评价重点实验室, 北京 100037 
杨竹森 中国地质科学院 矿产资源研究所, 北京 100037 
侯增谦 中国地质科学院 地质研究所, 北京 100037 
杨天南 中国地质科学院 地质研究所, 北京 100037 
张洪瑞 中国地质科学院 地质研究所, 北京 100037 
刘燕学 中国地质科学院 地质研究所, 北京 100037 
宋玉财 中国地质科学院 地质研究所, 北京 100037 
刘英超 中国地质科学院 地质研究所, 北京 100037 
王银喜 南京大学 现代分析中心, 江苏 南京 210093 
于玉帅 中国地质科学院 矿产资源研究所, 北京 100037 
王富春 青海省地质 调查院, 青海 西宁 810012 
薛万文 青海省地质 调查院, 青海 西宁 810012 
鲁海峰 青海省地质 调查院, 青海 西宁 810012 
张玉宝 青海省地质 调查院, 青海 西宁 810012 
朱田 青海省地质 调查院, 青海 西宁 810012 
俞长捷 青海省地质 调查院, 青海 西宁 810012 
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中文摘要:
      青海玉树地区的东莫扎抓和莫海拉亨铅锌矿床位于青藏高原金沙江缝合带和班公湖-怒江缝合带夹持的羌塘地体东北缘,是"三江"北段铜铅锌多金属成矿带铅锌矿床的典型代表,处于玉树逆冲推覆构造带的前锋带位置,但矿床与逆冲推覆构造之间的关系并不明确。野外研究表明,方解石为乳白色,结晶粗,呈不规则状、囊状,被后期矿化所穿切,形成于挤压(逆冲推覆阶段)到拉伸(成矿阶段)的过渡阶段,是联系逆冲推覆构造与铅锌矿床之间的"纽带"。本文对该阶段方解石开展了Rb-Sr和Sm-Nd等时线方法定年,测定东莫扎抓铅锌矿床过渡阶段的年龄为35.2~35.5 Ma,平均为35.4 Ma,与其成矿时代35 Ma非常接近;测定莫海拉亨铅锌矿床过渡阶段的年龄为34.0~34.6 Ma,平均为34.3 Ma,与其成矿时代33 Ma也非常接近。结合区域成矿地质背景,建立了玉树地区铅锌矿床从逆冲推覆阶段到成矿阶段的构造控矿模式:伴随着印度-亚洲大陆持续碰撞,青藏高原北缘中生代构造岩片向盆地中央推覆叠置,形成逆冲推覆构造(37~40 Ma),之后处于由挤压到拉伸的松弛状态,早期造山带流体、盆地流体混合形成巨晶方解石脉(34~35 Ma),最后,流体从造山带沿拆离滑脱带长距离向前陆盆地方向运移,运移过程中淋滤围岩的金属物质,并与先期造山带流体混合,形成富铅、锌的成矿流体,通过主逆冲断裂垂向沟通,进入浅部的反冲断层形成铅锌矿床(33~35 Ma)。
英文摘要:
      Located in the northeast margin of Qiangtang terrane between Jinshajiang suture zone and Bangonghu-Nujiang suture zone, the Dongmozhazhua and Mohailaheng Pb-Zn deposits in Yushu area of Qinghai Province are typical Pb-Zn deposits in the Cu-Pb-Zn polymetallic mineralization belt within the northern part of the Nujiang-Lancangjiang-Jinshajiang area. Although these Pb-Zn deposits are in the front belt of Yushu thrust nappe system, the connection between Pb-Zn ore deposits and thrust nappe system remain unclear. Field investigations show that calcite is milk white in color, macrocrystalline, irregular and sack-like in form and is intersected by late mineralization. It was formed during the transitional stage from the compression stage (thrust nappe stage) to the extension stage (mineralization stage) and can be regarded as the link between Pb-Zn ore deposits and the thrust nappe system. Formation ages of the transitional stage in the Dongmozhazhua and Mohailaheng ore districts, determined by both Rb-Sr and Sm-Nd isochron methods for calcite, are 35.2~35.5 Ma with an average of 35.4 Ma and 34.0~34.6 Ma with an average of 34.3 Ma, respectively. Formation ages of such a transitional stage are synchronous with Pb-Zn mineralization epoch (35 Ma and 33 Ma, respectively). In combination with regional mineralization geological setting, the authors established a tentative tectonic model for metallogeny of the Pb-Zn deposits from the thrust nappe stage to the mineralization stage in Yushu area, i.e., India-Asian collision led to the lifting of the orogenic belt relative to the Tertiary foreland basins in the northern margins of the Qinghai-Tibetan plateau, and strong compression resulted in the thrusting of these basins (37~40 Ma). During the transitional stage from the compression stage to the extension stage (34~35 Ma), the mixing of early orogenic fluid and basin fluid resulted in the formation of macrocrystalline calcite. At last, fluids generated from the orogen migrated laterally along gently-dipping detachment faults of the thrust systems toward the basins and evolved into Pb-Zn ore-forming fluids through the interaction with country rocks and the mixture of early orogenic fluid. The ore-forming fluids migrated vertically along major thrust faults and finally accumulated in the back thrust induced by thrust-nappe structures at shallow levels to form Pb-Zn ore deposits.
田世洪,杨竹森,侯增谦,杨天南,张洪瑞,刘燕学,宋玉财,刘英超,王银喜,于玉帅,王富春,薛万文,鲁海峰,张玉宝,朱田,俞长捷,2011,青海玉树东莫扎抓和莫海拉亨铅锌矿床与逆冲推覆构造关系的确定 ——来自粗晶方解石Rb-Sr和Sm-Nd等时线年龄证据[J].岩石矿物学杂志,30(3):475~489.
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