内蒙古铁板井基性—超基性岩体地球化学特征及其含矿性评价

发布时间：2018-04-22 11:12

本文选题：铁板井 + 北大山　；参考：《中国地质大学(北京)》2017年硕士论文

【摘要】：铁板井基性-超基性岩体位于内蒙古阿拉善地块西南缘北大山隆起带西段,出露面积为0.12km2,形成于阿拉善地块板内裂陷环境,是成矿的有利部位,Cu、Ni异常发育明显。岩体岩性主要有辉橄岩、橄榄辉石岩、辉长岩,岩体分异不明显,岩体发育大量金属矿物,主要有磁铁矿、黄铁矿、磁黄铁矿、镍黄铁矿等,发育大量铜镍矿化,具有良好的成矿潜力。本文运用岩石学、矿物学、地球化学等方法对铁板井岩体的成岩时代、矿物特征、岩浆来源等问题进行研究,来探讨铁板井岩体的岩浆来源及其形成的构造环境,初步对岩体的成矿潜力进行初步评价,并为后期找矿提供指导借鉴。主要取得以下进展:1、铁板井基性-超基性岩体Mg O含量较高,可达38%,Na2O、Al2O3、K2O、Ca O含量均较低,具有明显的高镁而贫碱贫铝特征,m/f比值为8.5~19.3%,属于镁质超基性岩。岩体蚀变强烈,超基性岩体基本都已蚀变成蛇纹岩,发育大量铜镍矿化。稀土元素总量较低(ΣREE介于0.24×10-6~0.66×10-6),轻重稀土分异不明显(LaN/YbN=0.32~5.57),相对富集Rb、K、Sr等大离子亲石元素,亏损Th、Nb、La、Ce、Zr等高场强元素,Th、Nb、Ce明显负异常。铷锶比值87Sr/86Sr在0.7115~0.7138,高于幔源值0.704。2、通过LA-ICP-MS锆石U-Pb同位素地质年代学测得两套年龄数据,一套锆石年龄大于800Ma,显示继承锆石特点,为岩体形成过程中捕获结晶基底的锆石年龄;另一套年龄为473±3Ma,认为是铁板井基性-超基性岩体的形成年龄,与中奥陶世阿拉善地块的板内裂陷有关。3、铁板井基性-超基性岩体处于阿拉善地块板内裂陷带,是成矿的有利位置。铁板井岩体不同于金川岩体,而甘肃煎茶岭岩体相似。煎茶岭岩体在岩浆分异演化过程中不形成硫化物矿石,而在后期外部硫加入发生硫化作用形成铜镍硫化物矿床。铁板井岩体和煎茶岭岩体具有相似的地球化学特征,显示具有一定的成矿潜力。铁板井岩体的找矿潜力区域在岩体的深部以及岩体与地层的接触带,尤其是富硫地层的接触带。
[Abstract]:The basic-ultrabasic rock body is located in the western section of the Beidashan uplift belt in the southwest margin of the Alashan block, Inner Mongolia, with an area of 0.12 km ~ 2, which was formed in the rift environment of the plate of the Alashan block. The lithology of the rock mass is mainly pyroxenite, olivine pyroxenite, gabbro, rock mass differentiation is not obvious, there are a large number of metal minerals developed in the rock mass, mainly magnetite, pyrite, pyrrhotite, nickel pyrite, and a large number of copper-nickel mineralization. It has good metallogenic potential. In this paper, petrology, mineralogy and geochemistry are used to study the diagenetic age, mineral characteristics and magma source of the Tiebanjing rock mass, in order to discuss the magma source and the tectonic environment of its formation. A preliminary evaluation of the ore-forming potential of rock mass is carried out, and a reference for later prospecting is provided. The main progress is as follows: 1. The content of MgO in the basic-ultrabasic rock body of iron-plate well is relatively high, which can reach 38Na2O-Al _ 2O _ 3H _ 2O _ 3K _ 2O-Ca _ 2O _ O content. It has obvious high magnesium content and is characterized by a m / f ratio of 8.5m ~ (19. 3) m / f ratio of alkali and poor aluminum, which belongs to the magnesite ultrabasic rock. The ultrabasic rock bodies have almost been altered into serpentine rocks, and a large number of copper and nickel mineralization have been developed. The total amount of rare earth elements (危 REE is between 0.24 脳 10-6 and 0.66 脳 10-6), the difference between light and heavy rare earth elements is not obvious, the difference of heavy and heavy rare earth elements is not obvious, and the relative enrichment of large ion lithophile elements, such as RbBN, K, Sr, etc., and the depletion of ThNbCe and the negative anomalies of Th NbCe at the same high field strength. The ratio of rubidium and strontium 87Sr/86Sr is 0.7115 ~ 0.7138, which is higher than the mantle source value of 0.704.2. Two sets of age data are obtained by LA-ICP-MS zircon U-Pb isotopic geochronology. One set of zircon ages is more than 800 Ma, which shows the inherited zircon characteristics and is the zircon age of the crystalline basement during the formation of the rock mass. Another set of ages is 473 卤3 Ma, which is considered to be the age of formation of the basic-ultrabasic rock body in the iron plate well, which is related to the intraplate rifting of the Alashan block in the Middle Ordovician, and the basic-ultrabasic rock body of the iron plate well is located in the plate depression zone of the Alashan block. Is a favorable position for mineralization. The Tiebanjing rock body is different from the Jinchuan rock body, but the Jianchaling rock body in Gansu province is similar. In the process of magmatic differentiation and evolution, the Jianchaling rock body did not form sulfide ore, but the copper nickel sulfide deposit was formed in the late stage by the addition of external sulfur to form the Cu-Ni sulfide deposit. The Tiebanjing and Jianchaling rock bodies have similar geochemical characteristics, indicating a certain metallogenic potential. The ore-prospecting potential area of the iron-plate rock mass is in the deep part of the rock mass and the contact zone between the rock mass and the strata, especially the contact zone of the sulfur-rich strata.
【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】：P588.1;P618.41;P618.63

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