投稿时间：2018-02-22
修订日期：2018-03-07
网络发布日期：2018-04-25
中文摘要:内蒙古卓资县大苏计斑岩钼矿化与区内花岗质杂岩（石英斑岩、正长花岗斑岩和花岗斑岩）有密切的成因联系。LA-ICP-MS锆石U-Pb定年获得石英斑岩、正长花岗斑岩和花岗斑岩的结晶年龄分别为（234±3） Ma、（225±4） Ma和（220±4） Ma。杂岩体富硅（w（SiO2）=70.37%~78.84%）、富碱（w（Na2O+K2O）=4.52%~8.77%），均属高钾钙碱性系列，普遍具有低的w（Na2O）（0.15%~2.69%）和高的铝指数（ASI介于1.13~3.35）。稀土元素总量介于48.2×10-6~527.0×10-6，石英斑岩稀土元素含量（48.2×10-6~83.1×10-6）最低，正长花岗斑岩稀土元素含量（272.1×10-6~527.0×10-6）最高，花岗斑岩稀土元素含量为162.5×10-6~236.8×10-6；杂岩体δEu介于0.15~0.93之间，（La/Yb）N介于3.0~65.5，自正长花岗斑岩、花岗斑岩到石英斑岩，其Eu负异常逐渐増大，而（La/Yb）N逐渐减小。岩体普遍富集Rb、Th、U、K、Nd、Zr、Hf等，强烈亏损Sr、P、Ti等。正长花岗斑岩具有中等Ba、Ta、Nb亏损。石英斑岩和花岗斑岩均属于高分异花岗岩，而正长花岗斑岩属于I型花岗岩。主量、稀土和微量元素特征表明，杂岩体具有后碰撞或后造山花岗岩特征，形成于后碰撞或后造山环境。杂岩体锆石的Hf同位素显示，3种岩石的εHf（t）值介于-21.1~-8.1，二阶段模式年龄tDM2介于1775~2587 Ma。石英斑岩来自于古元古代地壳物质的部分熔融；正长花岗斑岩来自于古元古代晚期地壳物质的部分熔融；花岗斑岩也主要来自于古元古代地壳物质的部分熔融，但有少量新太古代地壳物质参与。
Abstract:The Dasuji porphyry molybdenum mineralization is closely related to the Dasuji granitic complex (quartz porphyry, syenogranite porphyry, and granite porphyry) in the Dasuji ore district of Zhuozi County, Inner Mongolia. LA-ICP-MS zircon U-Pb dating for the quartz porphyry, syenogranite porphyry and granite porphyry yielded ages of (234±3) Ma, (225±4) Ma, and (220±4) Ma, respectively. The granitic rocks all have high content of SiO2 (70.37%~78.84%) and total alkali (K2O+Na2O=4.52%~8.77%), thus belonging to high-K calc-alkaline series. The granitic complex generally has a low Na2O content (0.15%~2.69%) and high aluminum index (ASI ranging from 1.13 to 3.35). The values of total rare earth elements (REEs) for the granitic rocks range from 48.2×10-6 to 527.0×10-6; of them, the REE content of quartz porphyry is the lowest (48.2×10-6~83.1×10-6); syenogranite porphyry has the highest REE content (272.1×10-6~527.0×10-6), and the REE content of the granite porphyry ranges from 162.5×10-6 to 236.8×10-6. The δEu value of the complex ranges from 0.15 to 0.93, and (La/Yb)N value ranges from 3.0 to 65.5. From the syenogranite porphyry through granite porphyry to quartz porphyry, the δEu value gradually increases, while (La/Yb)N value decreases gradually. The three rocks are all enriched in Rb, Th, U, K, Nd, Zr and Hf, but strongly depleted in Sr, P and Ti; moreover, the syenogranite porphyry reveals medium depletion of Ba, Ta, and Nb. Both quartz porphyry and granite porphyry are highly fractionated granite, while syenogranite porphyry is a typical I-type granite. The characteristics of the major, REE, and trace elements indicate that the Dasuji complex has affinity to post-collision or post-orogenic granites, suggesting that the complex formed in a post-collision or post-orogenic environment. The εHf (t) values of zircons from the three types of rocks range from -21.1 to -8.1, and their Hf two-stage model ages (tDM2(Hf)) range from 1775 to 2587 Ma. The Hf isotope compositions suggest that the quartz porphyry was most likely formed by partial melting of a Paleoproterozoic crust, the syenogranite porphyry was most likely formed by partial melting of a late Paleoproterozoic crust, and the granite porphyry was mainly formed by partial melting of a Paleoproterozoic crust with the addition of a small amount of the Neoarchaean crust.
keywords:geochemistry LA-ICP-MS zircon U-Pb dating Hf isotope Dasuji complex Inner Mongolia the northern margin of the North China craton
文章编号：
中图分类号：
文献标志码：
基金项目:国家自然科学基金项目（编号：41572061）、内蒙古自治区地质勘查基金项目（编号：2012-03-YS01）和中国地质调查局中国矿产地质与成矿规律综合集成和服务（矿产地质志）项目（编号：DD20160346）的资助
引用文本：
吴昊,武广,陶宏,张明玉,王国瑞,陈军其,杨宁宁.2018.内蒙古大苏计斑岩钼矿床花岗质杂岩年代学、地球化学、Hf同位素组成及其地质意义[J].矿床地质,37(2):311~338WU Hao,WU Guang,TAO Hong,ZHANG MingYu,WANG GuoRui,CHEN JunQi,YANG NingNing.2018.Geochronology, geochemistry and Hf isotope of granitic complex in Dasuji porphyry Mo deposit of Inner Mongolia and their geological implications[J].Mineral Deposits37(2):311~338
图/表
