东昆仑地区哈西亚图铁多金属矿床地质特征及成因

发布时间：2018-08-27 06:43

【摘要】：哈西亚图铁多金属矿床位于东昆仑西段祁漫塔格地区,是区域典型的层控矽卡岩矿床,也是近年来首例在金水口岩群中发现的与中酸性岩体有关的矽卡岩矿床,目前铁、金、锌已达中型,进一步找矿潜力巨大。本文利用岩石学、矿物学、地质年代学、岩石地球化学等研究手段,结合前人研究成果,针对东昆仑祁漫塔格地区三叠纪地球深部动力学与矽卡岩成矿作用提出了新的认识,在此基础上对哈西亚图矿床进行了剖析,并结合同时期大地构造背景建立了成矿模式,同时通过对比地层建造与岩浆岩性质,论述了哈西亚图矿床与区内其他矽卡岩矿床的异同点,拓宽了区域找矿思路。通过研究取得以下认识:1.通过对搜集到的784个火成岩同位素年龄数据分布特征与地质演化过程对比研究,认为:受古特提斯残留洋盆(阿尼玛卿洋盆)闭合作用影响,俯冲与碰撞作用在东昆仑地区影响广泛,集中表现在印支期岩浆活动极为强烈,与之对应的矽卡岩成矿事实多,表明:印支期俯冲碰撞作用可以为该区矽卡岩成矿提供良好的地质背景条件。同时,区域同时期含暗色微粒包体花岗质岩石是幔源岩浆经历多个MASH(Melting Assimilation Storage Homo-genization,即:熔融—同化—存储—均一)过程后与壳源岩浆混合的结果,在混合岩浆中,富镁铁质端元是由辉长质岩浆进化而来的闪长质岩浆,在此过程中富镁铁质端元由于来源较深,因而混合岩浆中富集铁、金等元素,为本区矽卡岩成矿提供了充足的幔源金属矿物。2.哈西亚图矿床中矿体呈层状、似层状产出,矿体总体沿地层产状顺层产出;矿石结构构造类型多样,主要有半自形粒状结构、不规则状结构、交代结构、包含结构,构造有块状、稠密浸染状构造、浸染状构造、星散状—星点状构造、条带状构造;围岩蚀变类型主要有:矽卡岩化、硅化、绿泥石化、绿帘石化、碳酸盐化等。根据矽卡岩分布情况大致以3号勘探线为中心,向西及向东分为石榴子石矽卡岩带、透辉石矽卡岩带、绿帘石矽卡岩带、阳起石矽卡岩带、透闪石矽卡岩带等。3.通过精确LA—ICP—MS同位素测年工作,获得矿床石英闪长岩成岩时代为246.8±1.8Ma,矿区外围花岗闪长岩年龄为240.1±0.8Ma。表明哈西亚图矿床形成于早三叠世。磁铁矿的δ18O值介于2.7‰~4.1‰,表明成矿流体中除了岩浆水外,还有大气降水。黄铁矿与闪锌矿δ34S值为4.63‰~6.30‰,总硫值为3.77‰,说明矿区硫来源于壳幔混合岩浆,并有地壳物质混入。黄铁矿铅同位素变化较小(208Pb/204Pb、207Pb/204Pb、206Pb/204Pb分别为38.471~38.629、15.627~15.671和18.435~18.473),同样显示出壳幔混合成因特点,此外,地层建造也为成矿提供了丰富的铁质。4.根据矿床地质特征认为成矿要素包括:(1)矿区片麻岩类与大理岩的脆性接触带,同时大理岩具备诸多有利于矽卡岩化作用的发生的先决条件。(2)矿区NE向断裂与东昆仑区域性大断裂关系密切,可能是区域性断裂引发的小型次级断裂,但切割深度较深。(3)矿区具壳幔混合成因的石英闪长岩产出部位距矿体较远,为岩体浅成侵位后从地层中摄取铁质提供足够的空间与时间。结合同时期大地构造背景认为矿床成矿模式如下:在经历俯冲作用之后,壳幔源岩浆在深部熔融并混合,在岩浆侵位间隙大气降水或地层同生水沿昆中大断裂诱发的次级断裂带下渗,与此同时,从地层中淋滤出金属物质并与石英闪长岩再次发生混合形成成矿流体。受压力差作用影响,成矿流体沿裂隙面上升,遇到这些因机械性质不同而性质脆弱的地层界面后,引发含矿热液顺层交代碳酸盐岩,形成矽卡岩,同时形成早期的磁铁矿体,矽卡岩期后酸性淋滤阶段形成金属硫化物、自然金等。哈西亚图铁多金属矽卡岩矿床虽然具有典型矽卡岩矿床分带性、交代反应等特征,但更符合层控矽卡岩矿床定义,通过研究,本文认为哈西亚图铁多金属矿床成因属层控矽卡岩矿床成因类型。
[Abstract]:The Hasitu iron polymetallic deposit is located in the Qimantag area of the western section of East Kunlun Mountains. It is a typical stratabound skarn deposit in the region. It is also the first skarn deposit related to intermediate-acidic rock mass discovered in Jinshuikou rock group in recent years. At present, iron, gold and zinc have reached medium-sized and have great potential for further prospecting. Geochronology, petrogeochemistry and other research methods, combined with predecessors'research results, put forward a new understanding of the Triassic geodynamics and skarn mineralization in the Qimantag area of East Kunlun Mountains. On this basis, the Hashiatu deposit was analyzed, and the metallogenic model was established in combination with the geotectonic setting of the same period. By comparing the stratigraphic formation and magmatic rock properties, this paper discusses the similarities and differences between the Hashiatu deposit and other skarn deposits in the area, and broadens the regional prospecting ideas. The following understandings are obtained through the study: 1. By comparing the distribution characteristics of 784 igneous rock isotope age data collected and the geological evolution process, it is believed that the Hashiatu deposit was subjected to Paleo-Tethys. The closure of residual oceanic basin (Animaqing oceanic basin) is influenced by subduction and collision widely in East Kunlun area. The intensive magmatism in Indosinian period is the main manifestation. There are many related skarn mineralization facts, which indicate that the Indosinian subduction and collision can provide favorable geological background for skarn mineralization in this area. The dark-grained xenoliths in the same period are the result of the mixing of mantle-derived magma with crustal-derived magma after several MASH (Melting-Assimilation Storage Homo-genization, i.e. melting-assimilation-storage-homogenization) processes. In the migmatitic magma, the mafic-rich end-member is dioritic magma evolved from gabbro magma. In this process, the mafic-rich end-members are rich in iron, gold and other elements in the migmatite magma, which provides abundant mantle-derived metallic minerals for skarn mineralization in this area. 2. The ore bodies in the Hashiatu deposit are stratified and occur like layers, and the ore bodies generally occur along the strata, and the ore structures are various, mainly semi-automorphic. Granular structure, irregular structure, metasomatic structure, including structure, structure block, dense disseminated structure, disseminated structure, star scattered-star structure, strip structure; wall rock alteration types are mainly skarnization, silicification, chloritization, epidote, carbonation and so on. The center is divided westward and eastward into garnet skarn belt, diopside skarn belt, epidote skarn belt, manolite skarn belt, tremolite skarn belt and so on. 3. Through accurate LA-ICP-MS isotope dating, the diagenetic age of quartz diorite in the deposit is 246.8 (?) 1.8 Ma, and the age of granodiorite in the periphery of the deposit is 240.1 (?) 0.8 Ma. It is indicated that the Hashiatu deposit was formed in the Early Triassic. The value of ~4.182 The minor element variations (208 Pb/204 Pb, 207 Pb/204 Pb, 206 Pb/204 Pb, 38.471-38.629, 15.627-15.671 and 18.435-18.473, respectively) also show the characteristics of crust-mantle mixing genesis. In addition, the strata also provide abundant iron for mineralization. 4. According to the geological characteristics of the deposit, the metallogenic elements include: (1) brittle connection between gneiss and marble in the ore area. The NE-trending faults in the mining area are closely related to the regional large faults in East Kunlun, which may be small secondary faults caused by regional faults, but the cutting depth is deeper. (3) The occurrence of crust-mantle mixed quartz diorite in the mining area is far from the orebody. Combined with the geotectonic setting of the same period, the metallogenic model of the deposit is as follows: after subduction, the crust-mantle magma melts and mixes in depth, and the secondary faults induced by atmospheric precipitation or strata associated water along the Kunzhong fault occur between the magmatic emplacement intervals. At the same time, metals leached from the strata and mixed with quartz diorite again to form ore-forming fluids. Influenced by pressure difference, ore-forming fluids rise along the fracture surface. When these strata are fragile due to different mechanical properties, the ore-bearing hydrothermal metasomatism along the carbonate rocks, forming skarns. At the same time, early magnetite bodies were formed, and metal sulfides and natural gold were formed in the post-skarn acid leaching stage. Although the Hashiatu iron polymetallic skarn deposit has the characteristics of typical skarn deposit zoning and metasomatic reaction, it is more in line with the definition of stratabound skarn deposit. Bed formation is a genetic type of stratabound skarn deposit.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.2

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