黔东南金矿构造控矿与成矿模拟实验

黔东南金矿是赋存于前震旦系下江群浊积岩(浅变质板岩、砂岩、凝灰岩)中的石英脉金矿,矿体均产于北东向背斜轴部,并向两翼延伸形成平行于地层和斜交地层的含金石英脉,明显受构造控制.据此,运用矿床地球化学国家重点实验室的构造地球化学实验装置进行了构造控矿与成矿模拟实验.模拟构造作用的高温高压条件下,岩石、矿石产生变形和破裂及成矿物质活化、迁移和聚集.其所产生变形、破裂,成矿物质以碎粒流和塑性流动方式活化迁移和聚集,充填于裂隙中形成顺层和穿层矿脉的过程;模拟实验结果与该区石英脉金矿成矿特征非常类似.它将为深入研究该区金矿成矿规律及进一步找矿提供科学实验资料和有益信息.     

清水塘矿田断裂构造与矿液致裂成矿浅析

湘中清水塘矿四定位于断裂带中。从矿脉形态、矿化类型和形式、矿液组分、矿化多阶段性等方面,论述了断裂控矿作用与矿液致裂成矿特点。地洼期构造岩浆活动,伴随矿液的充填压裂,形成矿田内主要矿脉、矿脉中心部位出现条带致密块状矿石,矿脉两端为网脉、细脉、分枝脉、脉的旁侧发育着羽列脉,在矿脉中常见有中石构造,可拼接角砾状矿石和断裂桥构造。显示出控矿断裂经历了从韧性到脆性递进变形作用过程。     

Porphyry-Type Mineralization at Selogiri Area, Wonogiri Regency, Central Java, Indonesia

The Selogiri area, situated in Wonogiri regency, Central Java, is one of several gold prospecting areas in the Southern areas Mountain Range in Java, Indonesia. Three types of dioritic–andesitic intrusive rocks occur in the Selogiri area, namely, hornblende andesite porphyry, hornblende diorite porphyry and hornblende diorite, exposed in a half‐circular depression where volcanic breccia and tuff are widely distributed. The occurrence of stockwork quartz veinlets and associated with magnetite and malachite coating along the cracks in the diorite porphyry suggests porphyry type mineralization. This is also supported by the occurrence of polyphase hypersaline fluid inclusions in the stockwork veinlet quartz. Small‐scale miners are mining NS‐trending quartz veins for gold associated with base metal sulfides. These veins are probably epithermal‐type mineralization that overprinted porphyry‐type mineralization. The Neogene intermediate to silicic hydrous magmatism in Java could have formed the porphyry‐type mineralization in Selogiri, as in the rest of the Sunda–Banda arc.     

Geochemistry and Fluid Inclusions Analysis of Vein Quartz in the Multiple Hydrothermal Systems of Mankayan Mineral District,Philippines

Several high‐sulfidation epithermal gold orebodies in the Mankayan Mineral District were formed in an environment that has been already affected by earlier porphyry‐type mineralization. This study reports the geologic and geochemical characteristics of the Carmen and Florence epithermal orebodies, which are located in the south of the Lepanto main enargite–gold orebody. The gold‐bearing epithermal quartz veins in the Carmen and Florence areas are of two types: (i) the enargite‐rich veins and (ii) the quartz–pyrite–gold (QPG) veins. The two types of veins are mainly hosted by the Cretaceous Lepanto Metavolcanics basement rocks, with minor veins cutting the Pleistocene Imbanguila Dacite Pyroclastics. The mineral assemblages and homogenization temperatures of fluid inclusions indicate that the Carmen and Florence orebodies were deposited by fluids varying from high to very high sulfidation state. The enargite and QPG epithermal veins of Carmen and Florence cut porphyry‐type quartz veinlet stockworks and veins that host polyphase hypersaline fluid inclusions that did not homogenize at or below 400°C. These high‐temperature quartz exhibits distinctly different mineral chemistry from the quartz of the QPG and enargite‐rich epithermal veins. In particular, the Ti content of quartz of the porphyry‐type veinlet stockwork is elevated (>100 ppm), whereas the Ti concentration of the epithermal vein quartz crystals are below detection limits. The Fe concentration of quartz is high in epithermal vein quartz (>300 ppm), whereas nearly undetected in the porphyry‐type stockwork veinlet quartz. Multiple generations of quartz with different mineral chemistry, fluid inclusions morphology, temperature, salinity and bulk gas compositions, and stable isotopic ratios indicate the variable hydrothermal conditions throughout the mineralization history of the Mankayan District. The temperature, pH, sulfidation state, oxidation state, and fluid composition vary among the orebodies in Carmen and Florence areas. Furthermore, the characteristics of earlier alteration affected the apparent characteristics of subsequent mineralization.     

辽宁清原线金厂金矿床地质特征及成因探讨

线金厂金矿床赋存于太古宙紫苏花岗岩、英云闪长岩中,矿床与中生代转湘湖石英闪长岩空间关系密切。矿区各类脉岩发育。脉岩和转湘湖岩体的金丰度均远高于克拉克值,二者为同源岩浆不同演化阶段的产物。金矿床由数条含金石英脉组成,矿脉与脉岩有密切的空间关系和时间联系。矿床硫同位素组成呈有规律变化,即随矿脉与转湘湖岩体之间距离增加,δ³⁴S逐渐降低。矿床各矿脉铅同位素组成变化小,表明成矿物质为单一来源。在δD-δ¹⁸O图解上,成矿流体投影点落于岩浆热液区附近,表明成矿流体主要为岩浆热液。根据以上特征,可以认为线金厂金矿床是与转湘湖岩体有成因联系的岩浆热液型金矿床。     

阿吾拉勒山琼布拉克铜矿床流体包裹体及碳氧同位素研究

琼布拉克铜矿床位于新疆伊宁县境内,前人对该矿床的成因一直存在争议.文章通过对琼布拉克铜矿床方解石中的流体包裹体进行系统的岩相学、显微测温学和碳氧稳定同位素分析研究,探讨了成矿流体的来源及演化.研究表明:琼布拉克铜矿床的流体包裹体主要为气-液两相包裹体,另有少量的气相包裹体,未见富CO2和含子矿物的流体包裹体,显示出张性...     

河北强震发生的地震地质条件与构造模式

地壳表层构造和深部构造互相制约是控制河北地区许多强震发生的必要地质条件。由此地质条件,在水平与垂直两个相互叠加的应力场作用下,使河北地区发生许多强震。这个构造-应力场模式,对华北地区许多强震的发生可能具有普遍意义。     

Mineralogy and ore formation conditions of the Bugdaya Au-Bearing W-Mo porphyry deposit, Eastern Transbaikal Region, Russia

The Bugdaya Au-bearing W-Mo porphyry deposit, Eastern Transbaikal Region, Russia, is located in the central part of volcanic dome and hosted in the large Variscan granitic pluton. In its characteristics, this is a Climax-type deposit, or an Mo porphyry deposit of rhyolitic subclass. The enrichment in gold is related to the relatively widespread vein and veinlet gold-base-metal mineralization. More than 70 minerals (native metals, sulfides, sulfosalts, tellurides, oxides, molybdates, wolframates, carbonates, and sulfates) have been identified in stockwork and vein ores, including dzhalindite, greenockite, Mo-bearing stolzite, Ag and Au amalgams, stromeyerite, cervelleite, and berryite identified here for the first time. Four stages of mineral formation are recognized. The earliest preore stage in form of potassic alteration and intense silicification developed after emplacement of subvolcanic rhyolite (granite) porphyry stock. The stockwork and vein W-Mo mineralization of the quartz-molybdenite stage was the next. Sericite alteration, pyritization, and the subsequent quartz-sulfide veins and veinlets with native gold, base-metal sulfides, and various Ag-Cu-Pb-Bi-Sb sulfosalts of the gold-base-metal stage were formed after the rearrangement of regional pattern of tectonic deformation. The hydrothermal process was completed by argillic (kaolinite-smectite) assemblage of the postore stage. The fluid inclusion study (microthermometry and Raman spectroscopy) allowed us to establish that the stockwork W-Mo mineralization was formed at 550–380°C from both the highly concentrated Mg-Na chloride solution (brine) and the low-density gas with significant N2 and H2S contents. The Pb-Zn vein ore of the gold-base-metal stage enriched in Au, Ag, Bi, and other rare metals was deposited at 360–140°C from a homogeneous Na-K chloride (hydrocarbonate, sulfate) hydrothermal solution of medium salinity.     

湖南湘东钨矿含矿石英脉辉钼矿Re-Os定年及地质意义

湘东钨矿是一个典型的石英脉型钨锡多金属矿床,发育百余条含矿石英脉,矿脉陡立,从北到南走向呈NE、NEE和EW向,反映了矿脉形成时处于近NW-SE向区域拉伸状态。矿区内的老山坳断层分割了重要的南、北两组矿脉。北组脉具有毒砂-黄铜矿-黑钨矿等矿物组合,富含金属硫化物,多具有平行脉壁的条带状构造;南组脉则主要体现辉钼矿-黑钨矿-黄铜矿-闪锌矿-方铅矿等矿物组合,金属硫化物含量较少,具有块状构造。本次研究通过对南组脉辉钼矿Re-Os同位素测年,获得等时线年龄为150.4±1.5 Ma(MSWD=0.52),模式年龄加权平均值为150.7±2.3 Ma(MSWD=0.10),代表成矿时间。含矿石英脉的形成略晚于区内燕山期二云母花岗岩(154.4±2.2 Ma)和煌斑岩(152.1±0.9 Ma)的侵位,指示含矿石英脉在成因上与燕山早期岩浆活动密切相关。事实上,包括湘东钨矿在内的南岭钨锡多金属成矿省均形成于165~150 Ma期间,具有统一的地球动力学背景,即由太平洋板块俯冲和俯冲板片断离所引起的弧后伸展环境。     

安徽沙溪斑岩型铜金矿床成岩序列及成岩成矿年代学研究

沙溪矿床是长江中下游成矿带中典型的斑岩型铜金矿床,位于庐枞盆地北外缘、郯庐断裂内,矿床成岩成矿时代确定对该矿床成因研究及区域成矿规律的认识具有重要意义。在详细野外地质工作的基础上,采集沙溪矿床与成矿有关的主要岩浆岩样品(粗斑闪长玢岩、黑云母石英闪长玢岩、中斑石英闪长玢岩、细斑石英闪长玢岩和闪长玢岩)和与黄铜矿密切共生的辉钼矿,分别利用Cameca、LA-ICP-MS U-Pb和Re-Os同位素定年方法,获得矿床内主要岩浆岩的成岩年龄(130.60±0.97Ma、129.30±1.00Ma、127.10±1.50Ma、129.46±0.97Ma和126.7±2.1Ma)以及成矿年龄(130.0±1.0Ma),并重新厘定了沙溪岩体从早到晚岩浆的侵位序列。通过区域对比,提出长江中下游存在两阶段斑岩型铜金矿化,沙溪矿床为长江中下游成矿带第二阶段形成的斑岩型矿床,沙溪矿床的成岩成矿作用既不同于庐枞盆地,也不同于断隆区第一阶段的斑岩矿床,而是受郯庐断裂和长江断裂动力学演化联合作用的产物。