内蒙古查干德尔斯钼矿成矿岩体地球化学及年代学研究

发布时间：2018-02-09 04:48

  本文关键词： 查干德尔斯 钼矿 花岗岩 岩石地球化学 锆石U-Pb测年　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：查干德尔斯钼矿床地处内蒙古乌拉特后旗北东方向,是近年来在中蒙边境地区发现的一个具有大型规模的隐伏矿床。该钼矿大地构造位置位于华北古陆西北缘,苏吉音花复式背斜南翼,宝音图隆起中段,其成矿与区内由斜长花岗岩-二长花岗岩-钾长花岗岩-细晶花岗岩组成的复合岩体密切相关,一般认为该矿床具斑岩型矿床的特点。本文主要对该复合岩体的地球化学及年代学特征进行研究。锆石U-Pb同位素测年显示,该复合岩体年龄225.9±4.4Ma~256.6±3.4Ma,属于印支期复合岩体。从斜长花岗岩、二长花岗岩、钾长花岗岩到细晶花岗岩的年龄逐渐变小,斜长花岗岩为252.1±3.4 Ma~256.6±3.4Ma;二长花岗岩247.5±4.4 Ma;钾长花岗岩236.8±4.5 Ma~244.3±4.2Ma;细晶花岗岩为225.9±4.4Ma。因此,可以看出,不同岩性分别代表了岩浆的不同演化阶段。辉钼矿铼锇等时限年龄为239.2±5.8Ma。该成矿年龄与复合岩体年龄225.9±4.4Ma~256.6±3.4Ma接近,因此属于印支期花岗岩侵入成矿,成矿年龄介于钾长花岗岩成岩阶段(236.8±4.5 Ma~244.3±4.2 Ma)。但对比邻区查干花钼矿,查干德尔斯矿区成岩成矿时间差上可能也具有相似特点,并且考虑到在细晶花岗岩(225.9±4.4Ma)中可见矿化石英细脉,其成矿也可能持续到细晶花岗岩岩脉形成之后。因此,总体来看,查干德尔斯矿区不同阶段侵入的不同岩性的花岗岩可能均与成矿有关。岩石地球化学特征显示,复合花岗体四种岩性均具有高硅、过铝、富碱,高钾钙碱性的主量元素特点;微量元素及稀土元素特征也表明该复合花岗岩体属于陆壳熔融成因花岗岩。在另一方面,复合花岗岩体岩体成分逐渐变化,岩浆演化过程中成分有所分异,但各类岩浆岩差异并不明显,分异较为微弱,这是由于每个岩浆侵入阶段间隔时间较短,岩浆来不及充分集中分异,而这种作用也许有利于化学性质活跃的成矿元素快速集中于晚期岩浆岩中。花岗岩成岩背景研究显示,复合岩体可能是由元古代宝音图群变质岩,在晚二叠世后,于后碰撞环境中部分熔融而成。
[Abstract]:The Chagandels molybdenum deposit is located in the north-eastern direction of Houqi, Wurat, Inner Mongolia, and is a large scale concealed deposit discovered in the border area between China and Mongolia in recent years. The tectonic location of the deposit is located in the northwestern margin of the North China Paleocontinent. The southern wing of Sujiyinhua complex anticline and the middle segment of Bao Yin's uplift are closely related to the complex rock body composed of plagioclase granite, bifeldspar granite, potassium feldspar granite and fine-grained granite. It is generally considered that the deposit has the characteristics of porphyry type deposit. The geochemistry and geochronology of the complex are studied in this paper. The zircon U-Pb isotopic dating shows that, The age of the complex is 225.9 卤4.4 Ma-256.6 卤3.4 Ma, which belongs to the Indosinian complex. The age from plagioclase granite, monzomorphic granite, potassium feldspar granite to fine-grained granite has gradually decreased. It was 252.1 卤3.4 Ma, 256.6 卤3.4 Ma, 247.5 卤4.4 Ma, 236.8 卤4.5 Ma~244.3 卤4.2 Ma, 225.9 卤4.4 Ma. for plagioclase granite, 247.5 卤4.4 Ma, 225.9 卤4.4 Ma for fine-grained granite, respectively. Different lithology represents different stages of magma evolution. The isochron age of molybdenum ore rhenium and osmium is 239.2 卤5.8 Ma.The ore-forming age is close to that of complex rock mass (225.9 卤4.4 Ma-256.6 卤3.4 Ma), so it belongs to Indosinian granitic intrusive mineralization. The ore-forming age is between 236.8 卤4.5 Ma~244.3 卤4.2Ma.However, for Chagan molybdenum deposit in the adjacent area, the time difference of diagenesis and mineralization in Chagandels ore area may also have similar characteristics, and considering that mineralized quartz veins can be seen in fine-grained granite (225.9 卤4.4 Maa), The mineralization may also continue after the formation of the fine-grained granite veins. Therefore, in general, the different lithologic granites intruded at different stages of the Chagandels ore area may be related to mineralization. The four kinds of lithology of the composite granitic body all have the main element characteristics of high silicon, peraluminum-rich alkali, high potassium calc-alkaline, trace elements and rare earth elements, which also indicate that the composite granitic body belongs to the continental crust melting origin granite, on the other hand, The composition of composite granite body changes gradually, and the composition of magmatic evolution is different, but the difference of magmatic rock is not obvious, but the differentiation is weak, which is due to the short time interval between each magmatic intrusive stage. There is no time for magma to concentrate and differentiate fully, and this process may be conducive to the rapid concentration of chemically active ore-forming elements in late magmatic rocks. Studies on the diagenetic background of granitic rocks indicate that the composite rocks may be metamorphic rocks from the Proterozoic Bao Yin group. After the late Permian, it was partially melted in the post-collision environment.
【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】：2015
【分类号】：P618.65
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本文编号：1497113