江西铜山—船坑中酸性侵入岩成岩机制与成矿潜力探讨

发布时间：2018-03-29 02:25

本文选题：江西铜山-船坑　切入点：中酸性侵入岩　出处：《成都理工大学》2017年硕士论文

【摘要】：铜山-船坑中酸性侵入岩产出于钦杭结合带东段,华夏板块北西缘,位于萍乡-广丰-江山-绍兴超壳深大断裂带北西侧。研究区围岩地层单一,主要发育北东向断裂,三叠系地层经印支期运动发生褶皱,形成一系列倒转背、向斜复式褶皱。铜山-船坑中酸性侵入岩岩石类型主要有石英闪长玢岩和花岗闪长斑岩。石英闪长玢岩:斑晶主要为斜长石、角闪石和碱性长石,以及极少量黑云母或石英斑晶;基质成分主要由微晶长英质矿物和隐晶质物质组成。花岗闪长斑岩:斑晶主要由斜长石、碱性长石、石英组成,角闪石和黑云母含量较少;基质为全晶质,主要由石英和长石微细晶组成。石英闪长玢岩在岩浆分离结晶作用中先于花岗闪长斑岩侵位成岩:石英闪长玢岩和花岗闪长斑岩有明显的岩相分异界线;与花岗闪长斑岩接触带的石英闪长玢岩一侧发育烘烤硅化边;可见花岗闪长斑岩脉穿插进石英闪长玢岩脉中;两者接触带的构造作用仅使石英闪长玢岩组成矿物发生变质变形现象。铜山-船坑中酸性侵入岩具有类弧型地球化学特征,属于广义的钙碱性性偏铝质-过铝质花岗岩系列,高CaO、K_2O和低Na_2O,A/CNK值小于1.1,里特曼指数(σ)小于1.8;富集Rb、Ba、Th和U等大离子亲石元素(LILF),强烈亏损Ta、Nb和Ti等高场强元素(HFSE);轻重稀土分异明显,富集轻稀土、亏损重稀土,无明显Eu负异常,稀土元素配分为向右陡倾型。铜山-船坑中酸性侵入岩为埃达克质I型花岗岩类。原生岩浆为增厚下地壳物质角闪榴辉岩重熔形成,“继承”了新元古代形成的弧型岩石的地球化学特征,岩浆源区位于地壳50km以下,残留相主要为角闪石,其次为石榴石,并且有稳定的金红石残留相。MgO#值总体偏低(平均为0.41),且MgO、Ni和Cr含量总体较低,FeO/MgO值较高,表明原生岩浆受地幔橄榄岩混染极少;同时略高于大陆地壳的Nb/Ta值(平均为13.8),表明重熔岩浆有地幔物质的加入。在古太平洋板块斜向俯冲挤压构造体系的挤压松弛阶段,增厚下地壳部分重熔形成的埃达克质岩浆在穿越上地幔的过程中加入了极少量地幔物质后,“壳幔混源”岩浆沿萍乡—广丰—江山—绍兴超壳深大断裂向地表运移,在地表浅部沿北东-南西向断裂和褶皱构造系统以及岩层脆弱面分流侵位,最终形成了铜山-船坑中酸性侵入岩带。铜山-船坑中酸性侵入岩成岩年龄为171±1.6 Ma(n=15,MSWD=0.16)与德兴铜矿成矿岩体成岩年龄171±3 Ma基本一致,两者有相似的原生岩浆来源,均为埃达克质I型花岗类,都具有类弧型岩石地球化学特征。而且中酸性侵入岩Cu、Mo、Zn等元素含量远高于背景值,主要来源于成岩原生岩浆,这也与德兴铜矿成矿物质来源相似。说明研究区中酸性侵入岩有良好的含矿性。铜山-船坑地区基本具备了斑岩型铜矿的成矿物质来源、岩浆运移通道、导矿和容矿空间以及围岩条件等因素,成矿条件优越,成矿潜力巨大。
[Abstract]:Tongshan-Chuankeng intermediate-acid intrusive rocks occurred in the eastern section of Qinghang binding belt, the western northern margin of the Huaxia plate, located in the north west of Pingxiang-Guangfeng-Jiangshan-Shaoxing super crust deep fault zone. The surrounding rock strata in the study area are single and mainly developed NE trending faults. The Triassic strata fold over the Indosinian movement, forming a series of inversion backs. The main rock types of Tongshan-Chuankeng intermediate-acid intrusive rocks are quartz diorite porphyrite and granodiorite porphyry. Quartz diorite porphyrite: porphyry is mainly plagioclase, hornblende and alkaline feldspar. The matrix is mainly composed of microcrystalline feldspar minerals and cryptonite. Granodiorite: porphyry is mainly composed of plagioclase, alkaline feldspar, quartz, hornblende and biotite. Quartz diorite porphyrite was prior to granodiorite emplacement diagenesis during magmatic separation and crystallization: quartz diorite porphyrite and granodiorite porphyry had distinct lithofacies differentiation lines. On the side of quartz diorite porphyrite in contact zone with granodiorite porphyry, bake siliconized edge is developed, and the granodiorite porphyry vein is inserted into quartz diorite porphyrite vein. The tectonics of the two contact zones only resulted in metamorphic deformation of the minerals of quartz diorite porphyrite. Tongshan-Chuankeng intermediate-acid intrusive rocks have arc-like geochemical characteristics and belong to the generalized calc-alkaline metamorphic and peraluminous granite series. The CNK values of high CaOK2O and low Na2OO are less than 1.1, and the Ritman index (蟽) is less than 1.8; the enrichment of large ion lithophile elements, such as RbPBA, Th and U, and the strong depletion of high field strength elements such as TaNb and Ti; the difference of light rare earths, the enrichment of light rare earths, the loss of heavy rare earths, and no obvious negative EU anomalies. The distribution of rare earth elements is divided into right-dip steep dip type. Tongshan-Chuankeng intermediate-acid intrusive rock is adakitic type I granite. Primary magma is formed by thickening the lower crust material, hornblende eclogite remelting, which "inherits" the arc formed from Neoproterozoic. Geochemical characteristics of the type type rocks, The magmatic source region is located below 50km in the crust, and the residual phase is mainly amphibole, followed by garnet, and there is a stable rutile residual phase. The value of .MgO # is relatively low (average 0.41%), and the content of MgOO, Ni and Cr is relatively low, and the value of Feo / MgO is relatively high. The results show that primary magma is rarely mixed with mantle peridotite, and is slightly higher than the Nb/Ta value of continental crust (mean 13.8g), indicating that the remelted magma has the addition of mantle material. At the stage of compressional relaxation of the paleo-Pacific plate oblique subduction compressional tectonic system, The adakitic magma formed by partial remelting of the thickened lower crust added a very small amount of mantle material through the upper mantle, and the "crust and mantle mixed source" magma migrated to the surface along the deep faults of Pingxiang, Guangfeng, Jiangshan and Shaoxing supercrusts. In the shallow part of the surface along the NSE trending faults and fold tectonic systems and the distributary emplacement of the fragile surface of the strata, Finally, the Tongshan-Chuankeng intermediate-acid intrusive rock belt was formed. The diagenetic age of the Tongshan-Chuankeng intermediate-acid intrusive rock is 171 卤1.6 Ma / 15 MSWDN 0.16) and the diagenetic age of the Dexing copper ore-forming body is 171 卤3 Ma, which has similar primary magma source. All of them are adakitic type I granitic, all of them have arc-like petrogeochemical characteristics, and the contents of Cu, Mo, Zn and other elements in the intermediate-acid intrusive rocks are much higher than the background values, and are mainly derived from the diagenetic primary magma. This is similar to the source of ore-forming material in Dexing Copper Mine. It shows that the intermediate-acid intrusive rocks in the study area have good ore-bearing properties. The Tongshan-Chuankeng area basically has the source of ore-forming materials of porphyry copper deposits and the channel of magma migration. The ore-forming conditions are superior and the ore-forming potential is great.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.12;P611

【参考文献】