【作者】 李世金；

【导师】 孙丰月；

【作者基本信息】 吉林大学 ， 矿物学、岩石学、矿床学， 2011， 博士

【摘要】 祁连造山带位于秦祁昆中央造山系的中段,呈-北西向的大型山链构成青藏高原北部边缘的一部分。由于所处的独特的地质构造背景及漫长的地质演化历史,使其成为一个典型而又复杂的复合造山带,并形成了在各地质演化时期,不同地质构造环境下产生的一系列矿床组合,成为我国西部重要的成矿带之一,也是西北地区有色金属、黑色金属和贵金属的重要产地。论文以造山带理论为指导,通过对区内以往地质资料的综合分析和研究,进一步探讨和重新厘定了祁连造山带各地质历史时期的地球动力学背景及其演化过程,建立了地球动力学演化模型；并以现代测试技术为支撑,应用现代成矿理论,通过对区内不同成因类型的典型矿床的调查和研究,系统总结了祁连造山带在不同地质时期、不同动力学背景下的成矿作用特征及其形成的矿床系列,进而阐明了内生金属矿产的矿化特征和时空分布规律。研究表明,祁连造山带曾经存在三个古大洋(北祁连洋、党河南山一拉鸡山洋、柴北缘洋)以及除南北的柴达木地块和阿拉善地块外的两个陆块(中祁连陆块、南祁连陆块)。三个大洋的厘定说明过去不少研究者所称的大陆裂谷的证据存在偏差。同时,过去认为大洋的出现时间为新元古代末期,但是通过中元古代朱龙关群火山岩的研究,显示其为中元古代大洋玄武岩高原的组成部分,受当时地幔柱活动的控制,形成于成熟大洋板块内,因此,研究区在中元古代已经存在成熟的大洋,故大洋形成时间应早于中元古代,具体时间尚需进一步探讨。通过对柴北缘滩间山金矿的研究,首次提出和确定了滩间山变质核杂岩及其对金矿的控制作用,而非前人认为的逆冲推覆构造控矿。用LA-ICP-MS锆石U-Pb法确定了组成变质核杂岩的斜长花岗斑岩的年龄为394.4±6.0Ma,属华里西早期陆陆碰撞的产物；具有金矿化的中酸性脉岩的年龄为344.9±2.2Ma,为华里西晚期伸展阶段的产物,亦即为变质核杂岩最终侵位上隆和形成金矿化的时间。它们代表了同一岩浆活动在不同阶段连续演化和成矿的产物。系统总结了区内不同拉张环境下的海底热水喷流成矿作用特征及其形成的矿床类型,提出了热水喷流矿床特有的由热水喷流岩和黑色岩系组成的“双岩石组合”,它们在空间上相伴产出,可作为热水喷流矿床的重要识别标志。详细研究了区内与中酸性侵入岩浆活动有关的热液成矿作用类型及其矿化特征,认为在中酸性岩浆演化和侵位的不同阶段和不同部位形成不同的矿化类型。对部分矿床的流体包裹体和成矿年龄进行了研究。研究结果表明,大黑山钨矿床为典型的矽卡岩型矿床,其形成经历了两期4个阶段：矽卡岩期的流体温度在360-480℃,成矿深度在4.8-5.6 km;石英-硫化物期的成矿温度集中在200-3200C,成矿深度在2-2.4km,反映该区从早期到晚期发生了强烈的抬升；LA-ICP-MS锆石U-Pb年龄为422 Ma,为晚奥陶世。而双口山铅锌矿、绿梁山铜矿的形成温度在120-260℃,成矿深度在1.4-2.86km,属中低温热液脉型矿床。确定了拉鸡山地区泥旦沟金矿床为矽卡岩型矿床而非前人所称的造山型金矿,同时指出了在高钙火山岩地区寻找同类矿床的意义。此外,论文详细研究了区内造山型金矿的矿化特征及类型,建立了区内造山型金矿连续成矿模式。流体包裹体研究结果表明,区内多为浅成亚类的造山型金矿。论文根据柴北缘新发现的牛鼻子梁铜镍矿点矿化特征,通过与区内及邻区同类矿床的对比研究,认为区内具有岩浆熔离型矿床形成的良好条件,找矿潜力大。论文在研究和系统总结成矿规律的基础上,根据本次研究成果及区内找矿取得的新进展,从找矿方向、主攻矿种等方面提出了一些新的找矿思路和建议。更多还原

【Abstract】 Qilian orogenic belt was a NW-trending large mountain chain located in the middle of the Qin-Qi-Kun Central Orogenic System and was a part of the northern edge of the Tibetan Plateau. Because of a unique geological background with long evolution history, it became a typical and complex composite orogenic belt and an important metallogenic belt in western China, producing non-ferrous, ferrous and precious metal deposits in different geological periods and environments.Based on the theory of orogenic belt and geological data about this region in the past, the paper further discussed and re-determined the geodynamic processes of the Qilian orogenic belt, established geodynamic evolution model. Supported by modern test technology and application of modern mineralization theory, it studied different genetic types of the region’s typical deposits and summarized deposit series in the Qilian orogenic belt in different geological periods, illustrated temporal and spatial distribution regularities and mineralization characteristics of endogenous metal deposits.The results showed that there were three ancient ocean in Qilian orogenic belt (the North Qilian Ocean, Danghenanshan-Lajishan ocean, the North Qaidam ocean) and two blocks within North and South Qaidam blocks as well as inter Alashan block (Middle Qilian Block, South Qilian Block) The determination of the three oceans implied the evidences of the so-called continental rift biased over the past. Meanwhile, it considered in the past that the emergence of the ocean was in late Neoproterozoic, but our studies on volcanic rocks of Zhulongguan group in Mesoproterozoic showed it was part of the oceanic basalt plateau in Mesoproterozoic, controlled by plume activities, formed in mature oceanic plate, therefore, in Mesoproterozoic, the study area already existed mature ocean, which formed earlier than Proterozoic, that the specific time need to be further investigated.This paper identified the control of metamorphic core complex on gold mineralization for the first time, rather than the previous view that the thrust structural control in Qilian orogenic belt, by the study of Tanjianshan gold deposit in Northern Qaidam. Appling LA-ICP-MS U-Pb method, it determined the age of plagioclase granite porphyry at 394.4±6.0Ma which was the composition of metamorphic core complex, production of the continent-continent collision in Early Hercynian; the age of felsic dykes with gold mineralization were 344.9±2.2Ma, production of extension phase in late Hercynian, which was also the age of final emplacement of metamorphic core complex and gold mineralization. All of them represented continuous evolution and mineralization of the same magmatic activity.This paper proposed a systematic summary of exhalative mineralization characteristics and the deposit types in different extensional environment in the region, established the "double rock group" consist of exhalative rock and black rock series, which accompanied by the output in space. As unique in exhalative deposits, they can be used as identification of exhalative deposit.A detailed study on the felsic intrusive-related hydrothermal mineralization types and characteristics was carried out, which formed at different felsic magmatic evolution stages and different parts of their emplacement. Studies on metallogenic ages and fluid inclusions of some deposits showed that the formation of Daheishan tungsten deposit went through two periods and four stages:Fluid temperature of the skarn mineralization at phaseⅠwas 360～480℃, mineralization depth was 4.8-5.6km. temperatures of quartz-sulphide mineralization at phaseⅡconcentrated in the 200～320℃, with mineralization depth of 2～2.4km, considered as middle to high-temperature hydrothermal deposit; U-Pb age of deposit was 422 Ma, formed in the Late Ordovician. Temperature of Shuangkoushan lead-zinc deposit and Lvliangshan copper deposit concentrated in 120～260℃, the depth of mineralization in the 1.4～2.86km, both of them were low-temperature hydrothermal vein-type deposit. Also, the paper determined gold deposit in Lajishan Mountain as skarn type, and proposed ideas to find similar deposits in the high-calcium volcanic areas.Moreover, the paper gave a detailed study on orogenic gold mineralization, established a continuous orogenic gold mineralization model in the region. Fluid inclusion studies showed that the types of most deposits were orogenic gold deposit and shallow type in sub-categories.Based on the characteristics of newly discovered Niubiziliang copper-nickel mineral occurrence in Northern Qaidam and comparative studies on similar deposits in the region and adjacent areas, the paper figured out that the district had a good condition for the formation of magmatic segregation deposits and had great potential for prospecting potential.Finally, based on systematic summary of metallogenic regularity, the results of this study and the new progress made in prospecting area, this paper proposed a number of new prospecting ideas and suggestions on the prospecting orientation, chief prospecting mineral varieties and so on.更多还原