【作者】 于晓飞；

【导师】 孙丰月；

【作者基本信息】 吉林大学 ， 矿物学 岩石学 矿床学， 2010， 博士

【摘要】 西昆仑造山带地处青藏高原西北缘,是板块北缘成矿带的重要组成部分,有着丰富的矿产资源。论文以区域动力学背景和区域成矿理论为基础,以成矿作用为核心,采用成矿动力学背景-区域成矿分析与典型矿床研究相结合,在阐明成矿动力学背景、成矿作用、控矿因素的基础上,建立不同矿床的成因类型和成矿模式,总结成矿规律,确定找矿远景区。区域成矿动力学背景表明,本区区域构造演化经历了长期而复杂的地壳演化,包括太古代陆核形成、俯冲、碰撞和陆内构造作用。以往研究认为库地蛇绿岩和其曼于特蛇绿岩是裂解洋和弧后洋盆的重要证据,本文研究发现它们是古大洋发育成熟的产物,并且库地蛇绿岩现在的位置并不是西昆北洋碰撞缝合的位置,而是受后期挤压作用的影响仰冲上来的。对中新元古代火山岩地球化学特征分析,认为长城系、蓟县系基性火山岩形成于洋中脊和洋岛环境;阿克塔什、萨洛依热水喷流沉积块状硫化物矿床类型的确定,进一步证明大洋环境的存在。这些证据表明西昆仑-塔里木古元古代并不存在统一大陆裂解形成的裂陷槽,而是一个古大洋。以往多认为本区中新元古代时期从塔里木板块裂解出去的,有着共同的基底,通过对比研究发现,西昆仑地块并不是从塔里木地台裂解出来的微陆块,而是完全独立的太古宙古陆块,具有独立的地质构造演化历史,被南北两侧的古大洋所分隔,本文称之为“西昆北洋”和“西昆南洋”。针对西昆仑中间岩浆岩带,分别针对各个时期的花岗岩,尤其是对加里东期和海西期花岗岩进行地球化学、年代学和构造环境研究,认为自510~480Ma(寒武纪)开始,西昆北洋东部洋壳向南、北两侧大陆俯冲,在440~430Ma(早志留世)两个陆块发生碰撞,直到410Ma(早泥盆世)西昆北洋东部南、北两侧大陆完全对接,而这时期的西部仍然为浩瀚的大洋。海西早期东部进入后造山阶段,西昆北洋西部洋壳开始向两侧俯冲,于270Ma(二叠纪)南北两侧大陆对接碰撞,大洋闭合,结束了西昆北洋的历史,是一种自东向西“剪刀式”演化过程。在此基础上,总结出西昆仑造山带地球动力学演化经历了如下4个阶段:①西昆仑古陆的形成②西昆北洋的演化与闭合-内部造山③西昆南洋的演化与闭合-边缘造山④西昆仑造山带的后期演化-隆升。研究中以构造-岩浆活动和成矿作用为主线,对西昆仑地区各时代侵入岩进行了年代学研究:采用LA-ICP-MS锆石U-Pb法高精度定年方法对大同布斯拉津铜钼黑云母石英二长岩和花岗细晶岩、塔什库尔干班迪尔闪长玢岩和斯如依迭尔碱性花岗岩进行了系统的年龄测试,它们分别是449Ma和446Ma、239.8Ma、13Ma。446Ma和449Ma年龄代表后造山花岗岩,证明加里东期造山带的存在,这个时期东部已经开始碰撞造山,是一俯冲间歇期伸展环境的产物;239.8Ma年龄代表了印支早期岩浆热事件;13Ma年龄代表了帕米尔构造结作用的结果。另外,首次对布斯拉津铜钼矿床的辉钼矿进行Re-Os法定年,获得了439 Ma辉钼矿Re-Os年龄,指示了西昆仑地区加里东期的成矿事件。对研究区内部分金矿床(点)形成的地质背景和成矿因素进行研究,首次提出黄羊岭锑(金)矿、帕西木金矿点、叶尔羌河金矿、木吉金矿等为造山型金矿床的观点,采集矿区样品进行流体包裹体测试分析,通过获得的成矿温度,计算出不同成矿深度,认为区内造山型金矿存在从低温-中温、从浅成(黄羊岭锑(金)矿、帕西木金矿点、叶尔羌河金矿)-中成(木吉金矿)等连续成矿的特点,从而建立起该区造山型金矿的地壳垂直连续成矿模式。研究了西昆仑北带的塔木铅锌矿床的地质背景、矿化蚀变特征和岩浆岩特征,并采样测试了成矿物理化学条件,获得流体盐度为3.45wt%NaCl,密度为0.90g/cm3,首次提出了塔木-卡兰古一带的铅锌矿床不是前人认为的密西西比河谷型铅锌矿,而是与基性辉绿岩脉有关的中低温热液脉状铅锌矿床。根据热水喷流沉积矿床的特点,我们按照块状硫化物矿床和贫硫化物型喷流矿床进行研究。西昆北带石炭纪海底火山喷流-喷气沉积成矿特点,明确提出阿克塔什、萨洛依铜矿床为热水喷流沉积成因块状硫化物矿床,萨洛依铜矿床为别子型、阿克塔什铜矿床为类黑矿型;契列克其、黑恰铁多金属矿床成矿流体研究表明,二者都是受后期岩浆热液的影响,导致矿化进一步富集,是热水喷流沉积-热液叠加改造型矿床。同时指出矿区含钠长质硅质岩和碳酸盐岩为热水沉积岩,从而为寻找热水喷流成因矿床提供了有力证据。通过对大同布斯拉津铜钼矿床的地质特征、成矿流体、成矿年代学的研究,明确认为该矿床为岩浆热液脉型铜钼矿床,成矿作用发生于加里东中期,略晚于成岩年龄;通过对含矿石英脉进行流体包裹体研究,测得成矿均一温度为147～172℃之间,辉钼矿形成于低温条件。在成矿动力学演化研究基础上,通过对典型矿床、同位素年代学、成矿地球化学、成矿作用的研究,建立了西昆仑造山带的成矿模式,并总结了成矿规律,在成矿模式、确定找矿标志和大型矿田产出条件的基础上,提出各类矿床的6个找矿方向,为该区下一步找矿勘探工作提供了科学依据。更多还原

【Abstract】 Western Kunlun orogenic belt is located in the northwest margin of Qinghai-Tibet plateau, and it accompanies with abundant mineral deposits and becomes an important part in the metallogenic belt of the north margin of the plate. Based on regional geodynamic settings, metallogenic theory, metallogenesis, and combing metallogenic geodynamic settings, regional metallogenic analysis with typical deposits analysis, the author studies metallogenic geodynamic settings, metallogenesis and ore-controlling factors, then builds genetic types and metallogenic models for different mineral deposits, finally synthesizes metallogenic laws and delineates prospective areas.According to regional metallogenic settings, it was shown that tectonic evolution of the study area underwent long and complex crust evolution, including Archean continental core formation, subduction, collision and intracontinental tectonization. The predecessors considered the Kudi ophiolite and Qimanyute ophiolite are important evidences for breakup ocean and retroarc ocean basin. But the author thought they are product of paleo-ocean that developed to mature. The location of Kudi ophiolite is not the suture line of North Western Kunlun Ocean collision, but rather the obduction place by compressing later. By analysis of geochemical characteristics of Meso-Neo Proterozoic volcanic rocks, Changcheng system and Jixian system basic volcanic rock formed in mid-ocean ridge and ocean island environment. Determination of Aketashi and Saluoyi VMS deposits shows that there formed in mid-ocean ridge environment. It was proved that it was a paleo-ocean rather than a taphrogenic trough between western Kunlun and Tarim blocks in paleoproterozoic. The predecessors thought that the study area breakup began at proterozoic from Tarim plate, with same basement. Comparative study shows western Kunlun block is not a microplate from Tarim plate, but a unique Archean paleocontinent with unique geological structural evolutional history. It was separated by bilateral paleo-ocean, which was so-called“North Western Kunlun Ocean”and“South Western Kunlun Ocean”.By researching geochemistry, geochronology and structural environment of granites of every era in the middle magmatic zone in westeren Kunlun belt, especially Caledonian and Hercynian granite, it was thought that east part of oceanic plate of North Western Kunlun Ocean subducted toward south and north continents scince 510-480Ma(Cambrian). These two continents collided during 440-430Ma(Early Silurian)and amalgamated completely until 410Ma(Early Devonian), while there is still an ocean in the west part of western Kunlun belt. The west plate of North Western Kunlun Ocean began to subduct bilaterally in early Hercynian, and bilateral continents collided until 270Ma (Permian)which means the history of North Western Kunlun Ocean is end. The evolution that there is a scissor-style .Based on above conclusion, it was considered that there are four stages for geodynamic evolution of western Kunlun orogenic belt, i.e.①Formation of western Kunlun paleocontinent;②Interior orogenesis----evolution and closure of North Western Kunlun Ocean;③Marginal orogenesis----evolution and closure of South Western Kunlun Ocean;④Uplifting----later evolution of western Kunlun orogenic belt.Making structural-magmatic activities and metallogenesis as mainline, the author studies petrology, geochemistry and geochronology for intrusive rocks of each era in western Kunlun belt. By LA-ICP-MS zircon U-Pb dating to biotite quartz monzonite and granite aplite in Busilajin Cu-Mo deposit in Datong town, diorite porphyrite in Bandier in Tashikuergan town, and alkaline granite in Siruuyidieer, and molybdenite Re-Os dating to Busilajin Cu-Mo deposit, the author gets lots of high precision ages, i.e. 449Ma, 446Ma, 239.8Ma, 13Ma. 446Ma and 449Ma represent post orogenic granites of Caledonian orogenic belt. Orogenesis began at east part in this era, which is a product extended environment during diapause of subduction. 239.8Ma represents early Indosinian magmatic thermal activity. 13Ma stands for results of Pamir tectonic knot. 439Ma of molybdenite Re-Os dating means there are metallogenic event in Caledonian in western Kunlun area.By studying to geological settings and metallogenic factors of some gold deposits in the study area, the author first proposes Huangyangling Sb(Au), Paximu Au, Yeerqianghe Au and Muji Au deposits belong to orogenic gold deposits. It was considered that mineralization of orogenic gold deposits may consecutively happen from low-mesothermal, epizonal (Huangyangling Sb(Au), Paximu Au, and Yeerqianghe Au deposits) to mesozonal (Muji Au deposit) with analysis of metallogenic temperature and depth from fluid inclusion researches. Then a crustal continuum model of orogenic gold deposit in the study area was proposed by the author.It was thought that Tamu and Kalangu Pb Zn deposits belong to not MVT type Pb-Zn deposits but rather low-mesothermal vein-type one related to basic diabase dyke, by studying on geological settings, mineralized and alterated characteristics and magmatic natures for Tamu and Kalangu Pb-Zn deposits in the north of western Kunlun orogenic belt, and analyzing the metallogenic physico-chemical conditions where the salinity of fluid is 3.45wt%NaCl and density is 0.90g/cm3.The exhalative sedimentary deposit was divided into VMS ones and poor-sulfide type ones by their characteristics. According to the exhalative sedimentary metallogenic characteristics on the Carboniferous seafloor in the north of western Kunlun belt, the author considers Aketashi and Saluoyi Cu deposits belong to VMS exhalative sedimentary deposit. Saluoyi Cu deposit belongs to Besshi type VMS deposit, and Aketashi Cu deposit may be Koroko-like type. By studying fluid inclusions in Heiqia and Qiliekeqi siderite deposits, it was shown that both two deposits are exhalative sedimentary-hydrothermal fluid reconstructed deposits, and affected by later magmatic hydrothermal fluid which enriched mineralization. While the author considers that sodic-feldspar siliceous rock and carbonate are all exhalative sedimentary rocks, which are evidences for exhalative sedimentary deposits.By studying geological characteristics, metallogenic fluid, geochronology of Busilajin Cu-Mo deposit, it was thought that this deposit belongs to low-temperature hydrothermal vein-type Cu-Mo deposit. It formed 435Ma according to molybdenite Re-Os dating first time i.e. middle Caledonian that is posterior to diagenetic age. The molybdenite may form in low-temperature condition because the homogenization temperature is 147～172℃based on fluid inclusion studying in ore-bearing quartz.The author builds a metallogenic model of western Kunlun orogenic belt and synthesizes metallogenic laws according to researches of typical deposits, isotopic geochronology, metallogenic geochemistry and metallogenesis based on metallogenic dynamic evolution. And on the basis of metallogenic model, ore prospecting symbols and conditions of large scale ore field, the author proposes 6 prospective areas, which may be scientific evidences for further ore prospecting and exploration in this study area.更多还原