西藏措勤县尼雄矿田矽卡岩型铁、铜矿床成矿岩体成因关系研究

发布时间：2018-05-31 00:26

本文选题：尼雄矿田 + 矽卡岩型铁　；参考：《中国地质科学院》2015年硕士论文

【摘要】：尼雄铁铜矿田由北西至南东方向划分为5个矿区：滚纠铁矿区、尼雄铁矿区、沙松南铁矿区、毛加崃铁矿区及日阿铜矿区。本文主要分析了西藏尼雄铁铜矿田中尼雄铁矿区的成矿花岗闪长岩以及日阿铜矿区的成矿二长花岗斑岩的主量元素、微量元素、稀土元素及Sr-Nd-Pb同位素特征,并做了锆石LA-ICPMS U-Pb年龄测定。取得主要成果如下： (1)尼雄铁矿区的成矿花岗闪长岩岩石地球化学分析结果显示为亚铝质中钾-高钾钙碱性岩系列,属Ⅰ-型花岗岩；地球化学上该岩体富集大离子亲石元素(LILE)Rb、Ba、Sr、Th、U、K, Pb,亏损高场强元素(HFSE) Nb、Ta, Ti,具有典型的岛弧岩浆作用的特征；稀土元素球粒陨石标准化图表现为轻稀土富集的右倾形式(LREE/HREE=5.67-8.37),缺少Eu异常,显示活动大陆边缘岩浆岩的稀土配分特征。日阿铜矿区成矿二长花岗斑岩岩石地球化学分析结果显示为亚铝质高钾钙碱性岩,为Ⅰ型花岗岩；微量元素原始地幔标准化蛛网图上同样富集大离子亲石元素(LILE) Rb、Ba、Sr、 Th、U、K、Pb,亏损高场强元素(HFSE)Nb、Ta、Ti,稀土元素球粒陨石标准化图表现为轻稀土富集的右倾形式(LREE/HREE=10.37-15.63), Eu负异常,同样表现为典型的岛弧岩浆作用的特征。 (2)尼雄铁矿区成矿花岗闪长岩锆石U-Pb LA-ICPMS测得岩体的206Pb/238U加权平均年龄为112.09±0.54Ma(MSWD=0.45),表明尼雄成矿岩体形成于早白垩世晚期；日阿铜矿区成矿二长花岗斑岩锆石U-Pb LA-ICPMS测得岩体的206Pb/238U加权平均年龄为90.1±15Ma (MSWD=1.2),表明日阿成矿岩体形成于晚白垩世早期；由此可见,尼雄矿田铁、铜矿化作用并非同时发生,而是存在早白垩世晚期(112.09Ma)的铁矿化和晚白垩世早期(90.1Ma)的铜矿化两个独立的矿化阶段。 (3)尼雄铁矿区成矿岩体和日阿铜矿区成矿岩体的Sr-Nd-Pb同位素特征一方面显示出富集地幔特征(EM11),另一方面又显示出地壳组分对岩浆生成的重要影响。笔者对班公湖-怒江中特提斯洋和雅鲁藏布江新特提斯洋演化历史做了综合分析,早白垩世晚期(尼雄铁矿形成时：112.09±0.54Ma)以及晚白垩世早期(日阿铜矿形成时：90.1±1.5Ma)雅鲁藏布江新特提斯洋壳正处于向北侧冈底斯地块之下俯冲的阶段,符合尼雄铁铜矿田的形成环境,由此作者得出尼雄铁铜矿田是雅鲁藏布江洋壳板块向北侧拉萨地块之下俯冲的结果。 (4)尼雄铁矿的源区富集主要是由板片派生流体对地幔楔交代改造的结果,而日阿铜矿的源区富集主要由板片熔体对地幔楔交代改造；地幔岩浆底侵引起下地壳物质部分熔融,两种岩浆混合形成尼雄铁铜矿田的成矿岩浆。尼雄铁矿区的混源岩浆又经历了钾长石+斜长石以及副矿物褐帘石+独居石的分离结晶作用；日阿铜矿区的混源岩浆经历了钾长石+斜长石(±黑云母)及副矿物磷灰石的分离结晶作用。
[Abstract]:The neixiong iron copper ore field is divided into 5 mining areas from the North West to the South East: the rolling iron mining area, the neixiong iron ore area, the Sha pine South iron mine, the mahastan iron ore area and the Japanese opiate ore area. This paper mainly analyzes the main element of the mineralization granodiorite and the two long granite porphyry in the neixiong iron copper mine, Tibet, in the minerogenetic granodiorite and the Japanese copper mine. The characteristics of elements, trace elements, REE and Sr-Nd-Pb isotopes have been determined and zircon LA-ICPMS U-Pb dating has been made.
(1) the geochemical analysis of the metallogenic granite diorite in the nxiong iron ore area shows that the series of potassium high potassium calcium alkaline rocks in the subaluminite belong to type I type granite, and the geochemical rock mass is enriched with large ion stone elements (LILE) Rb, Ba, Sr, Th, U, K, Pb, and the loss of high field and strong elements (HFSE) Nb, Ta, Ti, and typical island arc magmatism. The rare-earth chondrite standardization map shows the right leaning form of the enrichment of light rare earth (LREE/HREE=5.67-8.37), lacking the Eu anomaly, showing the REE distribution characteristics of the active continental margin magmatic rocks. The geochemical analysis of the two long granite porphyry rocks in the diuren copper mine area shows the subaluminous high potassium calc alkaline rock, which is type I granite. The microelement original mantle normalized arachnoid map also enriched the large ion stone elements (LILE) Rb, Ba, Sr, Th, U, K, Pb, the loss of high field and strong element (HFSE) Nb, Ta, Ti, and rare earth element chondrites, showing the right form of light rare earth enrichment, negative anomaly, and also a typical island arc MAGMATISM Characteristics.
(2) the 206Pb/238U weighted average age of the zircon U-Pb LA-ICPMS obtained from the granodiorite of the Nixiong iron ore area is 112.09 + 0.54Ma (MSWD=0.45), indicating that the neixiong metallogenic body was formed in the late Early Cretaceous, and the weighted average age of 206Pb/238U weighted 206Pb/238U of the zircon U-Pb LA-ICPMS obtained from the two long granite porphyry with the zircon U-Pb LA-ICPMS in the diuren copper mine area is 90.1 + 15Ma (MSWD=1.2) the A Cheng ore body formed in the early stage of the late Cretaceous. Thus, it can be seen that the iron and copper mineralization in the nsiong ore field did not occur simultaneously, but there were two independent mineralization stages in the late Early Cretaceous (112.09Ma) and the early Cretaceous (90.1Ma) copper mineralization.
(3) the Sr-Nd-Pb isotopic characteristics of the metallogenic rock mass of the Nixiong iron ore area and the ore-forming rock mass of the yalcu ore area show the characteristics of the enriched mantle (EM11) on the one hand, and on the other hand it shows the important influence of the crustal composition on the formation of magma. The author has made a comprehensive analysis of the evolution history of the Tethys and Yalu Zang Tethys in the and the Yalu and Yalu Zangbo River. In the late Early Cretaceous (112.09 + 0.54Ma) and the early Late Cretaceous (90.1 + 1.5Ma), the new Tethys oceanic crust in the Yarlung Zangbo River was under the subduction of the North Gangdise massif, which conforms to the formation environment of the Nixiong iron copper ore field, and the author concludes that the neixiong iron copper field is Yarlung Zangbo. The subduction of the Jiang Yang plate to the north side of the Lhasa block.
(4) the source area enrichment of Nixiong iron ore is mainly due to the transformation of mantle wedge metasomatism by plate derived fluids, and the source region enrichment of the Japanese opiate mainly consists of the metasomatism of the sheet melt to the mantle wedge; the mantle magma undertransgression causes the partial melting of the lower crust material, and the two magmas are mixed into the minerogenetic magma of the neixiong iron copper ore field. The mixed source magma also experienced the separation and crystallization of the potassium feldspar + plagioclase and the accessory mineral and the monazite, and the mixed magma of the diuren copper mine experienced the separation and crystallization of the potash feldspar + plagioclase (+ black mica) and the accessory mineral apatite.
【学位授予单位】：中国地质科学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.31;P618.41

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