新疆卡拉塔格矿集区含矿地层地质和地球化学特征研究

发布时间：2018-01-25 16:48

本文关键词： 东天山卡拉塔格含矿地层地球化学 SIMS锆石U-Pb年龄　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：卡拉塔格位于东天山吐哈盆地南缘,属于大南湖-头苏泉古生代增生岛弧带。区内主要发育了VMS、斑岩-矽卡岩、次火山热液型以及铜镍硫化物等四类成矿系统。其中,VMS和次火山热液型矿床主要赋存于古生代地层中,至下而上可分为三个岩性段。本文利用实测地质剖面,系统采集火山岩样品,开展岩石主微量、Sr-Nd同位素以及SIMS锆石U-Pb同位素实验。对其地层特征有以下几点创新性认识:卡拉塔格核部早古生代晚期的含矿地层属于大柳沟组。大柳沟组火山岩第一岩性段为海相中基性火山岩,其形成时代上限为晚奥陶世(450Ma),具中钾钙碱性-低钾钙碱性特征,富集LREE和Rb、Ba、U、K等大离子亲石元素,以及Pb、Th、Zr、Hf元素,而亏损Nb、Ta以及元素P、Ti和Sr。大柳沟组火山岩第二岩性段为海相中性火山岩-火山碎屑岩,其形成时代上限为早志留世(440Ma),受海底热液作用明显,发生了强烈的黄铁绢云母化、绿泥石化和硅化,有较强的蚀变分带性。富集LREE和Rb、Ba、U、K等大离子亲石元素,而亏损Nb、Ta以及元素P、Ti。大柳沟组火山岩第三岩性段为浅海相-陆相中酸性火山岩-火山碎屑岩,其形成时代上限为晚志留世-早泥盆世(420Ma),低钾、富钠、中基性较酸性富钙,从中性火山岩到酸性火山岩,稀土总量随着岩浆分异演化顺序逐渐提高、Eu元素从无异常到明显负异常,富集Rb、Ba、K等大离子亲石元素,而亏损Nb、Ta、P、Ti、Sr等元素。大柳沟组整体上表现出典型的岛弧岩浆的地球化学特征,第三岩性段明显富钠,而第一、第二岩性段的火山岩蚀变强烈,其Na2O含量降低。Sr-Nd同位素显示火山岩(87Sr/86Sr)i介于0.704701~0.707351,εNd(t)介于2.12~7.44,侵入这套火山岩地层的中酸性岩浆岩(87Sr/86Sr)i介于0.703770~0.705203,εNd(t)介于5.66~6.84,表明其来源于亏损地幔,受到较弱的地壳物质的混染,而受海水影响明显。随着卡拉麦里洋向南俯冲,卡拉塔格形成了一系列海相岛弧火山岩,红海VMS铜锌矿床在第二岩性段岩浆喷发晚期形成于火山洼处,并随着第三岩性段中酸性岩浆持续快速喷发使得红海VMS铜锌矿床得以迅速掩埋、保存。
[Abstract]:Karatagh is located in the southern margin of the Turpan-Hami basin in the East Tianshan Mountains and belongs to the Paleozoic accretionary island arc zone of Dananghu-Tousuquan. VMS porphyry skarn is mainly developed in the area. There are four types of ore-forming systems, such as subvolcanic hydrothermal type and copper-nickel sulfide, in which the VMS and subvolcanic hydrothermal deposits mainly occur in the Paleozoic strata. It can be divided into three lithologic sections from the bottom to the top. In this paper, the volcanic rock samples are collected systematically and the main trace amount of the rocks is carried out by using the measured geological profile. Sr-Nd isotopes and SIMS zircon U-Pb isotopic experiments. The ore-bearing strata in the late early Paleozoic in Karatagh nuclear area belong to the Daliugou formation. The first lithologic member of the volcanic rock of the Daliugou formation is marine meso-basic volcanic rock. The upper limit of its formation age is the late Ordovician calc-low calc-calc-alkaline, which is characterized by the enrichment of large ion lithophile elements, such as LREE and RbPU UK, as well as PBO Th. The second lithologic member of the volcanic rocks of the Daliugou formation is marine neutral volcanic rocks and pyroclastic rocks. The upper limit of its formation time is the early Silurian Silurian (440Ma), which is obviously affected by the hydrothermal action on the bottom of the sea, resulting in a strong yellowish sericite, green mud fossilization and silicification. It is rich in large ion lithophile elements, such as LREE and RbBX, but depleted in NB, Ta and P. Ti. the third lithologic member of the volcanic rocks of the Daliugou formation is shallow-marine intermediate-acid volcanic rocks and pyroclastic rocks, the upper limit of which is the late Silurian to the early Devonian Jiao 420 Mai, low potassium and sodium rich. From neutral volcanic rocks to acidic volcanic rocks, the total amount of rare earth elements increases gradually with the order of magmatic differentiation and evolution from no anomaly to obvious negative anomaly. K and other large ion lithophile elements, but depleted elements such as NbTa-Ta-Pu, Ti-Li and Sr. The Daliugou formation as a whole shows typical geochemical characteristics of island arc magma, the third lithologic member is obviously rich in sodium, and the first is the first. The alteration of volcanic rocks in the second lithologic member is very strong, and its Na2O content decreases. Sr-Nd isotope shows that the 87 Sr / 86 Sr ~ (-) I of volcanic rock is between 0.704701 ~ 0.707351 and 0.707351. 蔚 Ndndt) is between 2.12 and 7.44, and the intermediate acid magmatic rock intruding into this set of volcanic strata is between 0.70377070 and 0.705203, and the intermediate acid magmatic rock with 87s r-86SrtI is between 0.703770 and 0.705203. 蔚 Ndct) is between 5.66 and 6.84, indicating that it originated from the depleted mantle and was contaminated by weak crustal materials, but obviously influenced by sea water, and subducted southward with the Kalamaili Ocean. A series of marine island arc volcanic rocks were formed in Karatagh, and the VMS copper-zinc deposit in the Red Sea formed in the volcanic depression in the late stage of magmatic eruption in the second lithologic section. Along with the rapid eruption of intermediate acid magma in the third lithologic section, the VMS copper and zinc deposit in the Red Sea can be buried and preserved rapidly.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P59;P536

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