内蒙古卓资县大苏计斑岩钼矿床成矿流体研究

发布时间：2018-10-08 20:18

【摘要】：内蒙古卓资县大苏计钼矿床位于华北克拉通北缘西段的凉城断隆内,是近年来在华北克拉通北缘发现的一个大型斑岩钼矿床,矿体主要产于印支期石英斑岩和正长花岗斑岩中。成矿过程划分为石英-钾长石-黄铁矿±辉钼矿阶段(早阶段)、石英-绢云母-辉钼矿-黄铁矿阶段(中阶段)和石英-方解石-黄铁矿±菱铁矿±闪锌矿±方铅矿阶段(晚阶段)。通过锆石LA-ICP-MS U-Pb定年,获得石英斑岩、正长花岗斑岩和花岗斑岩的侵位年龄分别为234±3Ma、230±5Ma和224±4Ma。矿石中5件辉钼矿的Re-Os等时线年龄为223.5±5.5Ma(MSWD=0.026),与花岗斑岩的侵位年龄最为接近,表明大苏计钼矿床形成于印支期,且成矿岩体为花岗斑岩。石英斑岩、正长花岗斑岩及花岗斑岩富硅和钾、贫钠,均属高钾钙碱性系列。三种岩石稀土总量介于48.2×10-6~527×10-6,δEu介于0.15~0.93,微量元素Rb、Th、U、K、Nd、Zr、Hf等明显富集,而Ba、Sr、P、Ti等元素亏损。石英斑岩和花岗斑岩均属于高分异的高分异的A2型花岗岩,正长花岗斑岩属于I型花岗岩。Hf同位素显示,三种岩石的εHf(t)值介于-21.0~-7.9,二阶段模式年龄tDM2介于2585~1763Ma,石英斑岩来自于古元古代地壳物质的熔融;正长花岗斑岩来自于古元古代下地壳物质的熔融,并混入少量中元古代地壳物质;花岗斑岩也主要来自于古元古代地壳物质的熔融,但是混入了部分新太古代地壳物质。大苏计钼矿床发育富液包裹体、富气包裹体、H2O-CO2包裹体、含子矿物包裹体和纯气体包裹体。成矿早阶段均一温度介于340°C~430°C之间,流体盐度介于3.4 wt%~15.9wt%Na Cl eqv之间;中阶段均一温度为280°C~380°C之间,流体盐度介于0.9wt%~38.3 wt%Na Cl eqv之间;晚阶段均一温度介于202°C~280°C之间,流体盐度介于1.2 wt%~11.7wt%Na Cl eqv之间。早、中阶段流体均为不混溶流体,流体沸腾是成矿物质沉淀的主要机制。H-O同位素指示成矿流体主要来自于岩浆水;S同位素指示成矿物质主要来自于深源岩浆;Pb同位素指示成矿物质主要来自下地壳。
[Abstract]:The Dasuge molybdenum deposit in Zhuozi County, Inner Mongolia, is located in the Liangcheng fault uplift in the western section of the North China Craton. It is a large porphyry molybdenum deposit discovered in the northern margin of the North China Craton in recent years. The orebody mainly occurs in the Indosinian quartz porphyry and syenomorphic granitic porphyry. The metallogenic process is divided into quartz-potassium feldspar pyrite 卤molybdenum stage (early stage), quartz-sericite-molybdenum-pyrite stage (middle stage) and quartz-calcite-pyrite 卤sphalerite 卤square. Lead ore stage (late stage) The emplacement ages of quartz porphyry, syenite granitic porphyry and granitic porphyry are 234 卤3 Ma, 230 卤5Ma and 224 卤4 Ma, respectively. The Re-Os isochron age of five molybdenum ores is 223.5 卤5.5Ma (MSWD=0.026), which is most close to the emplacement age of granitic porphyry, indicating that the Dasuge molybdenum deposit was formed in the Indosinian period and the ore-forming body is granitic porphyry. Quartz porphyry, syenite granitic porphyry and granitic porphyry are rich in silicon and potassium, poor in sodium and belong to high potassium calc-alkaline series. The total amount of rare earth elements in the three rocks is between 48.2 脳 10 ~ (-6) and 527 脳 10 ~ (-6), 未 Eu is 0.15 ~ 0.93, trace elements such as Rb,Th,U,K,Nd,Zr,Hf are obviously enriched, while elements such as Ba,Sr,P,Ti are depleted. Quartz porphyry and granitic porphyry belong to highly differentiated A2 type granite, while syenite granitic porphyry belongs to I type granite. The 蔚 Hf (t) value of the three rocks ranged from -21.0 to 7.9, the two-stage model age tDM2 was between 2585 and 1763 Ma, the quartz porphyry came from the melting of Gu Yuan's ancient crustal material, the syenomorphic granitic porphyry came from the melting of Gu Yuan's lower crust material, and a small amount of Mesoproterozoic crustal material was mixed in. The granitic porphyry is also mainly derived from the melting of Gu Yuan's ancient crustal materials, but mixed with some Neo-Archean crustal materials. Fluid rich inclusions, gas inclusions, H 2O-CO 2 inclusions, submineral inclusions and pure gas inclusions are developed in the Dasuge molybdenum deposit. The homogenization temperature at the early stage of mineralization is between 340 掳C and 430 掳C, the salinity of the fluid is between 3.4 wt%~15.9wt%Na Cl eqv, the homogeneous temperature at the middle stage is between 280 掳C and 380 掳C, the salinity of the fluid is between the range of 0.9wt%~38.3 wt%Na Cl eqv, and the homogenization temperature of the late stage is between 202 掳C and 280 掳C. The salinity of the fluid is between 1. 2 wt%~11.7wt%Na Cl eqv. In the early and middle stages, the fluids are immiscible. Fluid boiling is the main mechanism of ore-forming precipitation .H-O isotope indicates that the ore-forming fluid is mainly derived from magmatic water S isotope indicating ore-forming material mainly from deep magma and Pb isotope indicating ore-forming material mainly from lower crust.
【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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