康定二里沟金矿床地质特征及成因探讨

发布时间：2018-07-27 16:02

【摘要】：二里沟金矿床位于大渡河金成矿带上,在大地构造位置上,处于扬子古大陆板块的西部,扬子陆块的北西缘,南北向康滇断块北部的康定杂岩北侧,北西紧邻松潘—甘孜构造带之金汤弧形构造带,南接康滇断块中部的石棉岩块和冕宁岩块。矿体赋存层位为泥盆系下统危关群第一岩组(Dwg1),岩性为黑色至深灰色炭质板岩、硅质板岩。二里沟矿床成矿类型以硫化物石英脉型为主,蚀变岩型次之。含金硫化物石英脉主要产于黑色至深灰色炭质板岩及绢云母千枚岩中,呈近南北向产出,倾向为263°~310°,倾角52°~73°。矿区内控矿条件简单,控矿地质因素主要为节理裂隙,主要构造为F1压性破碎带及“X”共轭节理。石英脉型金矿石矿物成份:脉石矿物占95%以上,其中石英80%,云母5~10%,方解石、绿泥石、帘石、榍石等微-少量。矿石中金属矿物含量约占1~5%,原生矿物以黄铁矿为主,次为方铅矿、闪锌矿、黄铜矿、磁铁矿、菱铁矿等,自然金、银金矿,碲化物少量;次生矿物有褐铁矿、针铁矿,纤铁矿等。黄铁矿粒径0.03~10mm,以自形立方体、五角十二面体黄铁矿居多,呈粒状、浸染状、细脉状分布于矿石中。矿石中的金矿物主要为自然金。金的赋存状态主要为显微金、次为明金及超显微金。自然金以形态不规则的粒状为主,与黄铁矿关系密切,常镶嵌于其裂缝之中。矿石以它形、自形晶粒状、压碎、交代残余结构为主,假晶、充填、镶嵌、交代溶蚀、嵌晶包含结构次之。矿石以块状构造为主,网状、角砾状、浸染状构造为辅,局部具星点状、斑点状、团块状、充填状、晶洞构造等。围岩蚀变主要为黄铁矿化、硅化,次为绢云母化、绿泥石化、碳酸盐化。对二里沟矿区的黄铁矿单矿物进行S同位素分析结果表明:整个二里沟矿区硫同位素组成均一,变化范围小,δ34S值为-5‰—4.6‰,平均值为2.36‰,分布较集中。除个别产于炭质板岩中的黄铁矿出现负值外,其余均为正值,且变化范围很小,在3.3-4.6‰之间,极差为1.3‰,表明该矿床的硫具有很均一的来源,具幔源硫特征。赋存于黑色碳质板岩中的黄铁矿,相对亏损重硫同位素34S。其余样品均为与石英伴生的黄铁矿,与陨硫铁标准相比,相对富重硫同位素34S。该矿床主要含硫矿物为黄铁矿,因此硫化物的硫同位素组成变化范围及平均值基本上能够代表成矿流体的硫同位素组成。二里沟矿区与金矿体密切相伴的脉岩岩石化学分析结果表明,矿区内出露的岩浆岩有两类,一类为超基性岩,一类为基性岩。其中超基性岩脉测试样品根据结合镜下特征定名为辉石橄榄岩,根据Rittmann A该样品δ=0.38,属典型的钙性岩系。基性岩化学分析成果表明,ω(SiO2)=48.27%~48.41%,平均48.34%属基性岩,低于我国辉绿岩对照值49.88%,二里沟辉绿岩的K2O+Na2O均值为2.68%,全碱含量不高,在TAS图中基性辉绿岩投影点落在玄武岩里。全碱(K2O+Na2O)介于1.587%~3.78%,CaO含量8.69%~9.41%,平均值9.05%,将SiO2和碱含量(K2O+Na2O)计算Rittmann指数σ=0.47~2.65,平均值为1.56,属于典型的钙碱性岩性。南北向构造是矿区的基本构造格架,后期又叠加了走向北西的弧形构造。南北向构造按其力学性质,除了走向南北的主构造之外,还有与其配套的横断裂及北东、北西向的扭裂面。矿区脉体的分布以南北向为主,次为北西及北东向。就矿体而言,以北西向分布为主,次为北东向,南北向只有个别矿体而且矿化偏贫。北西向矿体矿化最好,次为北东向矿体。这表明构造对矿床的形成具有首要的控制作用,南北向的主构造面为导矿构造,次级的北西、北东向构造为储矿构造,特别是北西向构造又受后期弧形构造的叠加,因此是最有利的成矿构造空间。岩浆活动、区域变质及构造运动为金矿的形成提供了热源及成矿物质来源。特别是岩浆活动,为金矿的形成起了重要的作用。矿区的基性岩脉十分发育,在区域上基性岩与金矿化有密切的关系,就矿区而言金矿体有的就直接产出在基性岩脉边部及其脉体的裂隙中,这表明金与基性脉岩在空间上具有密切的空间关系。根据锆石测年结果,矿区内的基性岩脉有两期,一期辉长岩形成年代为425.2±2.6Ma,另外一期测年结果为221±16Ma,而由ESR石英测年结果可知金成矿期约为13.2Ma,金成矿期明显晚于基性脉岩。矿区内如此强烈的基性岩浆活动指示了矿区内存在深达深部地壳或地幔的基性岩浆上升侵位通道,这些通道不仅有利于深部岩浆侵位,同时也为岩浆活动之后的含金热液流体活动提供了运移通道。
[Abstract]:Located in the Dadu River gold metallogenic belt, the second Li gully gold deposit is located in the west of the Yangtze paleo continental plate and the northern margin of the Yangtze block, North and south of the Kangding complex in the northern part of the Kang Dian fault block, and the North West of the Jin Tang arc tectonic belt near the Songpan Ganzi tectonic belt, and the asbestos rock block and Mian Ningyan in the middle of the central Kang Dian fault block. The deposit of the ore body is the first rock group (Dwg1) of the Lower Devonian group, the lithology is black to deep gray carbonaceous slate and siliceous slate. The ore-forming type is mainly sulfide quartz vein and altered rock type. The gold sulfide quartz vein is mainly produced in black to dark gray carbonaceous and sericite phyllite, and is near South. The northward output, with a tendency of 263 ~310 degrees, and a dip angle of 52 ~73 degrees. The ore controlling conditions are simple and the ore controlling geological factors are mainly joint fractures. The main structure is the F1 compressional fracture zone and the "X" conjugate joints. The mineral composition of quartz vein type gold ore is more than 95%, including stone 80%, mica 5~10%, calcite, chlorite, epidote, spite, etc. The mineral content of the ore is about 1~5%, the primary mineral is pyrite, the second is galena, sphalerite, chalcopyrite, magnetite, siderite, natural gold, silver gold and telluride, and the secondary minerals are limonite, goethite, and fibrite. The size of pyrite is 0.03~10mm, with the self shaped cube and five horns twelve hedral pyrite. The gold minerals in the ore are mainly natural gold. The gold deposits in the ore are mainly natural gold. The main state of gold is Microgold, the second is the Ming gold and the ultramicro gold. The natural gold is mainly in the irregular form, closely related to the pyrite, and is inlaid in the crack. The ore is shaped, self shaped grain, crushed and metasomatism. The residual structure is mainly pseudocrystalline, filling, inlay, metasomatism and dissolution, and the inlay contains structure. The ore is mainly lump structure, reticulate, breccia, and disseminated structure as auxiliary, local with star point, spot, lump, filling, cavity structure and so on. The alteration of surrounding rock mainly is sericite, silicification, second sericite, green mud petrifaction, carbonation. Two The S isotopic analysis of the pyrite minerals in the Li Gou mining area shows that the sulfur isotope composition of the mine is uniform, the range of variation is small, the value of delta 34S is -5% to 4.6 per thousand, the average value is 2.36 per thousand, and the distribution is more concentrated. The difference between.6 per thousand and 1.3 per thousand indicates that the sulphur of the deposit has a very homogeneous source, with the characteristics of the mantle derived sulfur. The pyrite in the black carbonaceous slate, the relative loss of the sulfur isotope 34S., is the pyrite associated with the quartz. Compared with the standard of the meteorite iron, the main sulfur bearing mineral of the rich sulfur isotope 34S. is yellow. Therefore, the sulfur isotope composition of the sulphide can basically represent the sulfur isotope composition of the ore-forming fluid. The chemical analysis of the vein rocks closely associated with the gold ore body in the two Li gully mining area shows that there are two types of magmatic rocks exposed in the mining area, one is ultrabasic rock and the other is basic rock. The pulse test samples are named pyroxene peridotite based on the characteristics under the combined mirror. According to the Rittmann A, the sample is a typical calcite rock. The results of chemical analysis of the basic rock indicate that omega (SiO2) =48.27%~48.41%, with an average of 48.34% genera rock, is lower than the control value of the diabase in our country, 49.88%, and the K2O+Na2O mean of the Dili diabase is 2.68%, and the total alkali content is 2.68%. Not high, the basic diabase projection point in the TAS map falls in the basalt. All alkali (K2O+Na2O) is between 1.587%~3.78%, CaO content is 8.69%~9.41%, the average value is 9.05%. The Rittmann index Sigma =0.47~2.65 is calculated by SiO2 and alkali content (K2O+Na2O), the average value is 1.56, which belongs to the typical calcic lithology. The north and South structure is the basic tectonic framework of the mining area, and later later The North-South structure is superimposed on the north-west structure. In addition to its mechanical properties, in addition to the main tectonics of the north and south, there are also the cross split and north-east and north-west torsional surface. The distribution of the vein in the mining area is mainly North and south, and the second is north-west and northward. In the case of the ore body, the distribution is mainly North West, and the second is north to North and North and south. There are only individual orebodies and poor mineralization. The mineralization of North West to ore body is the best, which indicates that the structure has the primary control effect on the formation of the deposit, the main tectonic surface of the north and the north is the ore guide structure, the secondary North West and the NE trending structure is the reservoir structure, especially the North West structure is superimposed by the late arc structure. This is the most favorable metallogenic space. Magmatic activity, regional metamorphism and tectonic movement provide the source of heat source and metallogenic material for the formation of gold deposits. Especially magmatic activity, it has played an important role in the formation of gold deposits. The basic rock veins of the mining area are very well developed, and the basic rock is closely related to gold mineralization in the area, and gold is concerned with gold mine. Some of the ore bodies are directly produced in the cracks in the edge of the basic rock veins and their veins, which indicates that the gold and the basic vein rocks have a close spatial relationship in space. According to the results of zircon dating, there are two phases of the basic rock veins in the mining area, the formation age of the first phase of the gabbro is 425.2 + 2.6Ma, the other phase is 221 + 16Ma, and the ESR quartz is measured by quartz. The result shows that the gold mineralization period is about 13.2Ma, and the gold mineralization period is obviously later than the basic vein rock. The strong basic magmatic activity in the mining area indicates the basic magma emplacement channel in the deep crust or mantle, which is not only beneficial to the deep magma emplacement, but also the gold bearing fluid after the magmatic activity. Body activity provides a transport channel.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P618.51

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