投稿时间：2012-04-18
修订日期：2013-05-01
中文摘要:青藏高原南部发育有大规模的碰撞成矿作用,冈底斯北缘Pb-Zn-Ag-Cu-Fe多金属成矿带是其重要的组成部分。加拉普铁矿床是位于该成矿带东侧的矽卡岩型铁矿床,其成矿作用与区内的花岗闪长岩有密切的成因联系。LA-ICP-MS锆石U-Pb定年结果显示,该岩体成岩年龄为(63.4±0.5) Ma (n=25, MSWD=1.2),表明矿床形成于印-亚陆陆碰撞的主碰撞阶段。地球化学研究结果显示,岩石属中-高钾钙碱性准铝质花岗岩;其ΣREE较低(100.5×10-6~170.3×10-6),具弱-中等负Eu异常,富集轻稀土元素(LREE),相对亏损重稀土元素(HREE);富集大离子亲石元素(LILE)Rb、Pb、K、Th,相对亏损高场强元素(HFSE)Hf、Ta、Ti、Nb等,与早期的林子宗火山岩相类似,具有弧火山岩的地球化学特点。岩石εNd(t)值为-2.60~-2.34,(87Sr/86Sr)初始值为0.7074~0.7075,反映了重熔地壳物质与幔源物质混合的特点。锆石Lu-Hf同位素测试结果显示,岩体的锆石εHf(t)值和地壳模式年龄均分布较广,分别为-9.1~4.3和864~2368 Ma,同样表明岩石岩浆源区具有壳幔混源的特征。综合上述数据,矿区的花岗闪长岩是地幔源区岩浆与陆壳重熔岩浆混合而成的壳幔混源的I型花岗岩。已有数据显示,冈底斯北缘Pb-Zn-Ag-Cu-Fe多金属成矿带从白垩纪至中新世均有强烈的成矿作用,但其主成矿期集中在62~50 Ma,且与主碰撞阶段的岩浆活动有密切的成因联系。Pb-Zn-Ag成矿作用主要与受壳源物质控制的花岗岩密切相关,而与Fe-Cu矿化有关的岩体则更多地显示了幔源物质的贡献。
Abstract:The north Gangdise Pb-Zn-Ag-Cu-Fe belt is one of the most important metallogenic belt in the Tibetan collisional orogenic belt. The Jialapu deposit is located in the eastern part of the north Gangdise metallogenetic belt. Based on field investigation, the authors have found that the Jialapu skarn Fe-Cu deposit is genetically related to the granodio-rite in the ore district. LA-ICP-MS U-Pb dating reveals that the crystallization age of the granodio-rite is (63.4±0.5) Ma(n=25, MSWD=1.20), indicating that this deposit was formed in the period of main collisional orogenic setting in the Tibetan orogenic belt. The granodiorites are composed of medium-high-K to calc-alkaline metaluminous rocks characterized by low ΣREE content (130.48×10-6) and high δEu values (0.69), with (La/Yb)N value of 6.84. These rocks are enriched in LREE and LILEs (Rb, Pb, K and Th) and depleted in HREE and HFSEs (Hf, Ta, Ti and Nb), similar to the features of the arc-island volcanic rocks. The granodiorites have homogeneous whole-rock Nd and Sr isotopic compositions [εNd(t)=-2.81~-3.15,(87Sr/86Sr)=0.7074~0.7075],indicating that they were partially melted from a source region containing crustal and mantle components. In situ Hf isotopic analysis yielded initial εHf(t) values form -9.1 to 4.9, with Hf crustal model ages of 864~2368 Ma. The whole-rock geochemistry and the zircon Hf isotopic analyses indicate that the ore-related granodiorites were partially melted from a crust formed from a mixed magma between the asthenospheric mantle fluid and the partial melting material of the crust. It is known that the primary metallogenic epoch of the north Gangdise Pb-Zn-Ag-Cu-Fe belt is from 62 Ma to 50 Ma, which is in keeping with the time of the main collisional orogenic setting, the action of Linzizong volcanic rocks and the interrelated intrusive rocks. Combined with the previous research result and the data of regional geology, the authors hold that the Pb-Zn-Ag ore-forming process in the belt was mainly controlled by the crust material, while the Fe-Cu mineralization was mainly controlled by the mantle material.
文章编号：
中图分类号：P618.31;P597
文献标志码：
基金项目:本文得到国家重点基础研究发展计划(973计划)(2011CB403100);国家自然科学青年基金(41102033)和中国地质调查局地质调查项目(1212011121253、12120113037900)联合资助
引用文本：
付强,杨竹森,郑远川,黄克贤,李秋耘,李为,梁维,孙清钟,张松.2013.加拉普铁矿区花岗闪长岩锆石U-Pb年龄、Hf同位素及地球化学研究[J].矿床地质,32(3):564~578FU Qiang,YANG ZhuSen,ZHENG YuanChuan,HUANG KeXian,LI QiuYun,LI Wei,LIANG Wei,SUN QingZhong,ZHANG Song.2013.Zircon U-Pb ages, Hf isotope and geochemistry of granodiorite in Jialapu Fe deposit, Tibet[J].Mineral Deposits32(3):564~578
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