新疆“帕米尔式”铁矿床成因与成矿背景分析

发布时间：2018-01-21 15:21

本文关键词： “帕米尔式“磁铁矿床 LA ICP-MS 微量元素 Pb同位素　出处：《岩石学报》2016年12期 　论文类型：期刊论文

【摘要】：帕米尔式"铁矿床是新疆西昆仑地区重要的磁铁矿床类型之一,其矿床地质特征、形成时代明显有别于典型的BIFs类型磁铁矿床。本文以塔什库尔干地区翁吉勒磁铁矿床和孜勒依磁铁矿床作为研究对象,通过研究其赋矿围岩和岩体的岩石地球化学特征、矿石矿相学特征、磁铁矿微量元素地球化学特征和原位Pb-Pb同位素特征,探讨了"帕米尔式"磁铁矿床的矿床成因和成矿背景。岩石地球化学研究表明翁吉勒黑云母二长花岗岩具有高SiO_2、Al_2O_3、K_2O和Na_2O。低MgO、CaO和TiO_2,而Na_2O/K_2O值变化范围很小。铝饱和指数为(1.44~1.51),显示其具有为弱过铝质岩石的特征,稀土总量富集,具有强的负Eu异常。在微量元素蛛网图上显示其富集大离子亲石元素(LILE),如K、Rb、Sr、Ba及轻稀土元素(LREE),亏损Nb、Ta,P、Ti等高场强元素。而黑云母石英片岩稀土含量亦较富集,具有中等强度的负Eu异常。低的Rb/Sr比,明显的Th、Zr、Hf、Nb、Ta,P、Ti负异常,明显的Ba正异常,显示岩石具有古大陆边缘环境的富铝沉积岩特征。翁吉勒黑云母二长花岗岩和布伦阔勒岩群黑云母石英片岩地球化学性质非常相似,表明翁吉勒黑云母二长花岗岩的形成与布伦阔勒岩群黑云母石英片岩的重熔有关。锆石LA ICP-MS定年结果表明翁吉勒黑云母二长花岗岩形成于15.0±0.3Ma和15.4±0.2Ma。磁铁矿LA ICP-MS微量元素地球化学特征表明翁吉勒铁矿床中的磁矿床中主要Si、Mn、Zn、Sn、Hf和Pb相对较高,其中Mn和Ga变化范围较大,而孜勒依铁矿床中的磁铁矿具有相对较高的亲石元素,如Mg、Al、Ti、V、Co、Ni、Ga和Sc等,其Mn和Zn含量较低且变化范围较大,其它元素变化范围均相对较窄。二者相比,翁吉勒铁矿床中的磁铁矿中微量元素变化范围相对较大,而孜勒依铁矿床中的磁铁矿变化范围较小。两个矿床的磁铁矿的原位Pb-Pb同位素存在明显的不同,两类岩石全岩Pb同位素与两个矿床中磁铁矿Pb-Pb同位素研究表明翁吉勒铁矿床中磁铁矿可能与黑云母二长花岗岩有关,为热液成因。综上所述,在塔什库尔干地区不仅存在与沉积作用有关的铁矿床,还可能存在一部分与年轻岩浆岩有关的热液型磁铁矿床。
[Abstract]:Pamir type "iron deposit is one of the most important magnetite deposits in West Kunlun area, Xinjiang. The age of formation is obviously different from the typical BIFs type magnetite deposit. In this paper, the Wenggil magnetite deposit and the Zilei magnetite deposit in Tashkurgan area are taken as the research objects. By studying the petrogeochemical characteristics of the host rock and the rock mass, the ore metallographic characteristics, the trace element geochemical characteristics of magnetite and the in situ Pb-Pb isotopic characteristics. The genesis and metallogenic background of the Pamir-type magnetite deposit are discussed. The petrogeochemical study shows that the Umgil biotite monzogranite has a high SiO2AlSP-Al2O3 content. K _ 2O and Na _ 2O _ 2. Low MgO, Cao and TiOs _ 2, while Na_2O/K_2O values vary in a very small range. The aluminum saturation index is 1.44 / 1.51). It is characterized by weak peraluminous rocks, rich in total rare earth elements and strong negative EU anomalies. The trace element cobweb shows that it is rich in large ion lithophile elements, such as Ke RbPU Sr. The Ba and LREE elements are depleted, and the high field strength elements such as NbTa-Ta-Pu Ti are depleted. The REE contents of biotite quartz schist are also relatively rich. There are negative EU anomalies with medium strength, low Rb/Sr ratio, obvious negative anomalies of Th, Zr-HfT, NbTa-TaPU Ti, and obvious positive anomalies of Ba. It shows that the rocks have the characteristics of aluminum-rich sedimentary rocks in the paleo-continental margin environment. The biotite quartz schist of the Wenggil biotite monzonitic granite and the Brunkauleite group are very similar in geochemical properties. It is suggested that the formation of the Ongil biotite monzogranite is related to the remelting of biotite quartz schist in the Bloenguole group. Zircon LA. The ICP-MS dating results show that the Ongill biotite monzonitic granites were formed at 15.0 卤0.3 Ma and 15.4 卤0.2 Ma.The magnetite LA was formed at 15. 0 卤0. 3 Ma and 15. 4 卤0. 2 Ma. The geochemical characteristics of trace elements in ICP-MS indicate that the main element Si in the magnetic deposit of Wenggil iron deposit. The mn and Ga range of mn and Ga are relatively high, while the magnetite in Zilayi iron deposit has relatively high lithophile elements, such as MgAL-TI-TI-V. The content of mn and Zn is lower and the range of variation is larger, while the range of other elements is relatively narrow. The variation range of trace elements in magnetite is relatively large. However, the variation range of magnetite in Zilayi iron deposit is relatively small. The in-situ Pb-Pb isotopes of magnetite in the two deposits are obviously different. The Pb isotopes of two types of rocks and the Pb-Pb isotopes of magnetite in the two deposits indicate that the magnetite in the Wungjil iron deposit may be related to the biotite monzonitic granite, which is a hydrothermal origin. There are not only iron deposits related to sedimentation but also some hydrothermal magnetite deposits related to young magmatic rocks in the Tashkurgan area.
【作者单位】：有色金属成矿预测与环境监测教育部重点实验室中南大学地球科学与信息物理学院;中国地质调查局大陆构造与动力学创新研究中心中国地质科学院地质研究所;油气藏地质及开发工程国家重点实验室成都理工大学地球科学学院;
【基金】：国家自然科学基金项目(41672082,41472198,41472301) 中国地质调查局地质调查项目(2015020401003,20160102002) 国土资源部公益性行业科研专项经费(201211093) 中国地质科学院地质研究所中央级公益性基本业务费专项基金(J1402)联合资助
【分类号】：P618.31
【正文快照】： 1引言近些年,在新疆西昆仑布仑口-塔什库尔干地区相继发现了一批规模大小不一的铁矿床,自南向北如赞坎、乔普卡里莫、吉尔铁克沟、老并、走克本、叶里克、希尔布里、塔阿西、翁吉勒、孜勒依、吾依塔克等矿床。由于缺乏准确的矿床成矿时代的有效界定,对于这些矿床的成因,前人

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