Magnetic mineralogy of the Hongqiling Cu-Ni sulphide deposit: Implications for ore genesis

Pyrrhotite is one of the common ore minerals in Cu-Ni sulphide deposits, but only monoclinic pyrrhotite is ferromagnetic at room temperature. X-ray and EPA analyses reveal that most pyrrhotite forming sideronitic texture in the Hongqiling Cu-Ni sulphide deposit is monoclinic, but that in the massive ore is a mixture of monoclinic and hexagonal pyrrhotites. Differential thermal and magnetic- thermogravimetric analyses of massive ore indicate a magnetic transition and heat absorption at 323℃, suggesting that this temperature is the thermomagnetic and phase transition point of pyrrhotite. For massive pyrrhotite ores heated at 400oC for 30 h and then quenched by cool water, the monoclinic pyrrhotite (mpo) transforms completely into the hexagonal pyrrhotite (hpo). However, all the pyrrhotites resulting from slow cooling of the sample in air are mpo. These results indicate that transformation between hpo and mpo depends upon the cooling rate. Therefore, massive ores in this deposit might have been formed via rapid cooling of ore melts. On the other hand, it is significant to study the effect of the ratio of the magnetite in total ores on the genesis of magmatic Cu-Ni suphide deposits.     

Advances in research of sulphide ore textures and their implications for ore genesis

Important advances in research of sulphide ore textures in recent years have deepened our understanding of ore genesis of related mineral deposits. Pressure solution of sulphide minerals has been suggested as a mechanism for remobilization of ore materials, whereas pressure solution of the gangues is believed to raise the grade of the primary ores. We have known that precipitation of base metal sulphides from fluids prefers crystal and crack surfaces of pyrite to form overgrowth. Therefore, pyrite-bearing embryo beds in a sedimentary sequence can be acted as effective crystal seed beds and are favorable for fluid overprinting to form huge statabound deposits. Texture studies of various sulphides can be used to interpret the entire history of sedimentation, diagenesis, deformation and metamorphism of the ores. The study of chalcopyrite disease in sphalerite has brought about the idea of zone refining, and given a new explanation to metal zonation in massive sulphide deposits. Ductile shearing of sulphide ores may form ore mylonites, which will become oreshoots enriched in Cu, Au and Ag during late-stage fluid overprinting. Despite that various modern analytical techniques are being rapidly developed, ore microscopy remains to be an unreplaceable tool for ore geologists. Combined with these modern techniques, this tool will help accelerate the development of theories on ore genesis.     

新疆富蕴县希勒库都克铜钼矿床地质特征

希勒库都克铜钼矿体严格受斑岩体(石英斑岩和花岗闪长斑岩)控制。矿石具细脉状、浸染状构造,金属矿物主要为辉钼矿、黄铜矿和黄铁矿以及少量的磁铁矿、白铁矿。蚀变主要为硅化、钾化、绿帘石化、黄铁矿化、高岭土化、绿泥石化、绢云母化、碳酸盐化等。其成矿地质背景与世界巨型斑岩铜矿十分相似,展示了良好的找矿前景。     

龙门山铜多金属矿床成矿地质条件和控矿因素及其成因分析

通过对成矿地质条件进行分析,对地层、构造、岩浆岩与成矿的关系进行探讨,对矿床形成的控矿因素及矿床成因进行分析和总结。研究结果表明:矿区内与成矿有关的地层主要为三叠系中统月山组(T2y)含膏盐白云质灰岩和下统南陵湖组(T1n)灰岩;控矿构造主要为月山岩体与围岩的接触带构造体系;成矿母岩主要为来自于上地幔的中酸性钙碱性燕山早期月山岩体;岩浆带来了大量的成矿流体、成矿物质和巨大的热能,是成矿的先决条件;构造为岩浆的侵位和就位以及成矿流体的运移和沉淀提供了良好的通道和场所;地层主要以其有利的岩性参与了成矿活动;矿体形态主要为透镜状、似层状,矿石组构主要为交代结构和块状、稠密浸染状构造,成矿作用主要为接触交代作用,围岩蚀变主要为石榴子石、透辉石等矽卡岩化及大理岩化,认为矿床的形成与燕山早期岩浆活动有密切关系,矿床成因属于以接触交代作用为主形成的矽卡岩型铜多金属矿床。     

新疆西准噶尔扎合金矿地质特征及成因

扎合金矿位于准噶尔板块萨吾尔晚古生代岛弧区的中南段,矿体赋存于海西晚期—印支早期侵入的中性闪长岩岩体及围岩接触部位.矿区内发育北西向和北东向两组断裂.北西向断裂既是成矿热液运移的通道,也是金元素富集成矿的场所,岩体为金矿提供了成矿物质和部分热液.根据矿体产出地质特征,扎合金矿属构造蚀变岩型金矿床;据成矿作用分析,该金矿属中低温热液金矿床.     

渝东北大渡溪锰矿床地质特征及成因研究

城口地区是我国锰矿资源重要产出基地之一。以城口地区大渡溪锰矿为研究对象,详细叙述了大渡溪锰矿床地质特征(包括赋矿层位、矿体特征、矿石结构构造、矿石成分以及矿体围岩组成等)。结合沉积学和岩相古地理的综合研究,认为该矿床为原生沉积、碳酸盐还原和生物作用三者结合的产物,并在此基础上总结了成矿模式,为下一步找矿工作提出了合理的建议。     

闽西南凤山-赤坂场矽卡岩型萤石矿床地球化学特征及成因

闽西南凤山-赤坂场萤石矿主要产于晚侏罗世花岗质侵入岩与中二叠世栖霞组海相碳酸盐岩接触变质带中,通过对萤石及黑云母二长花岗岩围岩开展稀土元素地球化学及包裹体氢氧同位素研究,探讨了矿床的成因及成矿物质、流体来源。萤石稀土元素配分曲线特征和La/Ho-Y/Ho关系图表明凤山-赤坂场萤石矿体的成矿流体来自同一流体体系,成矿物源稳定且单一,为同期成矿。萤石和花岗岩围岩相近的Sm/Nd比值以及均具有δEu和δCe负异常特征,表明萤石成矿和二长花岗岩体有着十分密切的联系。结合萤石包裹体氢氧同位素结果,显示研究区萤石矿床成矿流体来源于岩浆水与大气降水的混合,成矿物质F和Ca元素来源于大气降水对围岩花岗岩和碳酸盐岩的淋滤和萃取,属于构造控制的岩浆期后气化-热液的低温热液充填萤石矿床。     

新疆白干湖钨锡矿流体包裹体特征及成因

白干湖钨锡矿床位于新疆祁漫塔格加里东褶皱带的转折部位,是东昆仑西段1个较好的钨锡(金)矿区,对白干湖矿区主成矿阶段形成的含黑钨矿石英脉中发育的包裹体进行岩相学及测温研究.研究结果表明:矿区主要发育3类包裹体:气液两相水溶液包裹体(I)、水溶液-CO2三相包裹体(Ⅱ)以及纯CO2两相包裹体(Ⅲ);Ⅰ型包裹体液相组分主要为NaCl水溶液,含少量KCl,其均一温度变化范围为160-310℃,盐度为1.82％～16.43％;Ⅱ型水溶液-CO2三相包裹体气相组分含有CO2及CH4等组分,均一温度为247～320℃,w(NaCl)为2.8％～9.4％;Ⅲ型CO2两相包裹体含量较少,均一温度为19.8～27.7℃;白干湖钨锡矿床成矿流体为中低盐度、中高温的NaCl-H2O-CO2体系.在成矿过程中,由于温度及压力降低,流体发生相分离成为较高盐度的水溶液流体和较低盐度的富CO2流体,钨锡成矿物质趋向于富集在中高盐度水溶液相中,并导致白干湖钨锡矿的成矿作用.     

宁乡式铁矿床成因的新认识

鄂西宁乡式铁矿分布广、规模大 ,普遍发育赤铁矿鲕粒。赋矿层位为加里东运动后第一个海浸沉积序列的碎屑岩向碳酸岩的过渡相 ,岩相古地理环境控制作用明显。铁矿层中赤铁矿鲕粒繁多 ,结构复杂 ,与碳酸盐鲕粒成因非常相似 ,为强烈搅动环境中的机械沉积物。经波浪和潮汐水流再次搬运富集 ,最后定位于中、弱环境或相对低凹的近滨相和远滨相上部。     

秦岭二台子金矿床地质地球化学再研究

为了指导找矿，通过近年来找矿预测获得的新突破和积累的较新测试资料，对二台子金矿床作出进一步的认识和总结，在探讨矿床成矿大地构造背景的基础上，提出矿床所在盆地的容矿岩系发育模式，在矿床成矿作用演化研究中，进一步阐述了矿床形成经历的同生与后生两次成矿作用，分别与秦岭造山带南北陆块俯冲碰撞造山导致被动大陆一侧局部出现伸展断陷式盆地和转入陆内逆冲推覆造山的构造－岩浆活动密切耦合。     

青海哈西亚图多金属矿床地质特征及成因探讨

为了加快青海省优势环境与战略矿产勘查进程,文中对哈西亚图多金属矿床成矿地质背景、矿床地质特征、控矿因素及成因进行了综合分析,研究结果表明:哈西亚图多金属矿床已发现矿体的成因类型为矽卡岩型,矿体从垂向上看,可分为4层均产于具垂直分带的矽卡岩带中,受矽卡岩类型影响矿石类型在垂向上也具有明显分带性,在华力西期花岗闪长岩与古元古界金水口岩群的碳酸盐岩的接触带附近为主要成矿部位,通过早期区域变质作用、矽卡岩化作用及晚期的热液成矿作用3个阶段,形成了以磁铁矿体为主,铜、铅、锌、金并存的多金属矿床。     

皖南黟县西坑银矿床地质特征及其成因

研究了西坑银矿床的矿体形态,矿石组成、结构、构造,成矿物理化学条件,银的赋存状态,矿区岩浆作用等矿床地质特征。研究了矿区及外围地层地球化学。通过地层地球化学和矿床地质特征的综合分析研究认为,从矿化前的热变质作用、矿化早期的透闪石和透辉石化,到晚期的硫化物矿化,是一次岩浆活动热事件引起的连续地质作用过程,成矿物质主要来源于岩浆流体,酸性的岩浆流体沿层间破碎带上升时,在化学活性相对较高的蓝田组富碳酸盐岩地层中交代充填成矿     

福建李坊重晶石矿床锶同位素组成及成因意义

通过对李坊重晶石矿床重晶石的Sr同位素分析,探讨钡的物质来源.结果显示,重晶石的Rb含量为2.70×10~(-6)～13.41×10~(-6), Sr含量为520.40×10~(-6)～2 166.00×10~(-6),~(87)Rb/~(86)Sr比值低,~(87)Sr/~(86)Sr比值介于0.710 81～0.711 80之间,平均值为0.711 26,高于同时期海水锶的~(87)Sr/~(86)Sr比值,低于壳源锶的~(87)Sr/~(86)Sr平均值,表明重晶石的锶来自海水锶与壳源锶的混合.示踪结果显示重晶石的钡主要来源于下伏地层,并暗示基底属于大陆型地壳.     

西藏甲玛铜多金属矿床主要矿石矿物特征

采用镜下鉴定及电子探针方法,研究西藏甲玛铜多金属矿床主要矿石矿物特征.显徽镜鉴定结果表明,矿石结构主要为结晶结构、交代结构及固溶体分离结构;矿石构造以细脉浸染状构造为主,中等浸染状、稠密浸染状、块状构造次之.矿石类型较为复杂,以原生硫化物矿石为主,次为氧化物矿石和混合型矿石.据赋矿岩石不同可将矿石划分为夕卡岩型、角岩型...     

Discovery of the superlarge gallium ore deposit in Jungar, Inner Mongolia, North China

Gallium, Ge, V, and U are the associated valuable elements in coal. From the 1950s to the 1970s, some researchers in the departments of coal industry and mineral resources of China investigated these elements in coal during geological explorations. The enrichment mechanism and the environmental influence of trace elements in coal have been deeply studied in recent twenty years. With respect to the ore-forming theories and practical utilizations of metals in coal, germanium was furthest studi…     

Origin of ore-forming fluids of the Dachang Sn-polymetallic ore deposit: Evidence from helium isotopes

The ore genesis model for the Dachang Sn- polymetallic ore deposit has long been in dispute, and the major debate focuses on whether the stratiform and massive orebodies formed during the Yanshanian magmatic-hydro- thermal event or they were products of Devonian syn-sedimentary exhalative-hydrothermal event. This note presents new helium isotope data from fluid inclusions of four pyrites and one fluorite. The pyrites were collected from the stratiform and massive orebodies in the deposit, and their 3He/4He ratios are significantly higher than 1, ranging from 1.7 to 2.5 Ra, which indicates a mantle component in the responsible hydrothermal fluids. It is suggested that the ore-forming fluids were a mixture of deep circulating seawater and a mantle-derived fluid, which are similar to many of those modern submarine hydrothermal fluids. In contrast, the fluorite, collected from a granite-related hydrothermal vein in the deposit, shows a low 3He/4He ratio of 0.7 Ra, which indicates no mantle component involvement in the fluids. Hence, the helium isotope data indicate that the two kinds of fluids from the Dachang deposit may have different origins. Together with other geological and geochemical evidence, it is suggested that the stratiform and massive ore formation has no genetic relation to the Yanshanian granite. Rather, they were likely formed during Devonian submarine exhalative-hydrothermal processes.