内蒙古维拉斯托锡多金属矿床含矿斑岩体钾长石斑晶的有序度及成因探讨

钾长石有序度及结构温度可以为探讨成矿物化条件等提供依据.为阐明本区钾长石的成因,通过对维拉斯托斑岩体中钾长石斑晶的红外光谱分析,其有序度为0.85~0.95,三斜度为0.7~0.9,测定的结构温度为547.17~578.36℃,表明钾长石斑晶为微斜长石.并探讨了钾长石的成因,认为它是热液蚀变的产物.     

云南都龙超大型锡锌多金属矿床中闪锌矿微量及稀土元素地球化学特征

云南马关都龙锡锌多金属矿床位于滇东南老君山锡锌钨多金属成矿区南部,是我国三大锡石硫化物矿床之一,目前对其矿床成因认识存在较大分歧。本文采用ICP-MS对都龙矿床中闪锌矿微量元素及稀土元素组成进行分析,以探讨该矿床成矿作用,为甄别已有成因观点提供证据。结果表明,矿床中闪锌矿以富集Fe、Mn、In、Co、Sn和贫Cd、Ga、Ge、Ni等元素为特征,成矿温度属于中—高温,其微量元素组成与白牛厂矿床(与燕山晚期花岗岩有关的矽卡岩型矿床)中的闪锌矿非常相似,和远源矽卡岩型铅锌矿床(核桃坪和芦子园)中闪锌矿存在一定差异,明显有别于喷流沉积型铅锌矿床(云南澜沧老厂和广东大宝山)中闪锌矿。此外,该矿床闪锌矿稀土配分模式多为轻稀土元素富集中等的向右倾斜曲线,以LREE/HREE值高、Eu负异常明显和Ce异常不明显为特征,与矿区燕山晚期隐伏花岗岩稀土元素特征基本一致,成矿物质来源以矿区燕山晚期隐伏花岗岩为主。结合近期矿山开采和地质勘探所揭露的矿化和矽卡岩蚀变的垂向分带等矿床地质特征,认为云南马关都龙锡锌多金属矿床属于与燕山晚期花岗岩有关的矽卡岩型多金属矿床,其中层状矽卡岩的形成应为成矿流体顺层交代的结果,矿化类型和围岩蚀变的分带与隐伏岩体的距离有关。     

川南沐川地区宣威组底部铌-稀土多金属富集层富集规律、沉积环境与成矿模式

云南、贵州地区对晚二叠世宣威组底部Nb-REE多金属富集层的研究取得了重要进展,但其成因还有较大争议.为厘清沐川地区宣威组底部Nb-REE多金属富集层成因机制及富集规律,本研究开展了野外实地调查、矿物学、岩相古地理与岩石地球化学等系统性研究,探讨其物源、富集规律,建立了成矿模式.结果 表明,川南沐川地区宣威组底部Nb-...     

湖南省七宝山钙矽卡岩-镁矽卡岩共生型多金属矿床地质地球化学特征

七宝山多金属矿床是一种罕见的钙矽卡岩和镁矽卡岩共生型矿床。矿床赋存于印支期-早燕山期斑状花岗岩与中-上石炭统碳酸盐岩地层的接触带及附近。矿床的形成经历2个成矿期：早期以形成钙-镁矽卡岩和磁铁矿为主的金属矿物为特征,后期以发生多次金属硫化物的矿化为特征。矿床的物质组成十分复杂,可利用的组分除Cu、Pb、Zn之外,Ga、Ge、In、Cd、Au、Ag、Te、Fe等亦可综合利用。斑状花岗岩是幔源岩浆与上地壳物质同熔混染的产物,同位素组成特征显示成矿流体为岩浆水,成矿物质主要来自岩浆。地质地球化学证据一致支持斑状花岗岩为成矿母岩;围岩的化学性质变化决定了矽卡岩化的类型。七宝山多金属矿床既属特殊的成因类型,又极具工业价值,值得进一步深入研究。     

集安南部大青沟铜及多金属矿区成矿潜力及找矿方向

大青沟铜及多金属矿区地表矿化线索较多,矿化类型复杂。在充分研究已有资料的基础上,认为该区的成矿在初始矿源层(块状硫化物的矿化阶段)的背景上,叠加了与燕山期火山岩、次火山岩有关的多种矿化类型,成矿潜力较大。     

Geochemical types of pacific polymetallic nodules: An application of multivariate analysis

A total of 843 samples of Pacific Ocean polymetallic nodules (PNs) from five survey areas have been studied (metals analyzed: Mn, Fe, Ni, Cu, Co, Zn, Pb). The statistical analysis included the following techniques: factor R analysis, quick cluster Q analysis into 50 preclasses, various hierarchical cluster Q analyses (HCAs) using the preclasses (application of different HCAs to an identical set of data and of an identical HCA to two different subsets of the data), comparison of the HCA. The PNs of the survey areas can be grouped into five geochemical types (I‐V). The genesis of the PNs was interpreted as early diagenetic, hydrogenetic, and mixed (early diagenetic/hydrogenetic and hydrogenetic/hydrothermal. In addition, some further conclusions regarding the applicability of various HCA techniques depending on the structure of the data set have been drawn.     

Sedimentary Environment and Mineralization of the Black Shale Polymetallic Layer in the Early Cambrian, SW China: Constraints from in situ LA-ICP-MS Analysis of Pyrite

A polymetallic layer is usually developed at the bottom of the early Cambrian black shale in Guizhou Province. The mineral that makes up the polymetallic layer is related to the sedimentary facies. To analyze the differentiation mechanism between polymetallic deposits (Ni-Mo and V), the Zhijin Gezhongwu profile located in the outer shelf and the Sansui Haishan V deposit located in the lower slope are selected to study the in situ sulfur isotopes and trace elements of pyrite. The results show that δ34S values of pyrite vary widely from ?7.8 ‰ to 28 ‰ in the Gezhongwu profile, while the δ34S values are relatively uniform (from 27.8 ‰ to 38.4 ‰) in the Haishan profile. The isotopic S composition is consistent with the transition that occurs in the sedimentary phase from the shelf to the deep sea on the transgressive Yangtze platform; this indicates that the δ34SO42? values in seawater must be differently distributed in depositional environments. The sulfur in the Ni-Mo layer is produced after the mixing of seawater and hydrothermal fluid, while the V layer mainly originates from seawater. Overall, the Ni-Mo and V deposits have been differentiated primarily on the basis of the combined effect of continental weathering and hydrothermal fluid.     

赣西北大雾塘钨矿区地质特征及Re-Os同位素年代学研究

通过对大湖塘钨矿田的大雾塘钨矿区辉钼矿Re-Os同位素年代学的研究,测得辉钼矿的w(Re)为0.3368×10~(-6)~8.256×10~(-6),获得的5个模式年龄比较一致,介于(136.6±2.2)Ma~(138.4±2.4)Ma,加权平均年龄为(137.7±2.7)Ma(MSWD=0.07)。将5个模式年龄进行等时线年龄计算,获得一条相关性较好的~(187)Re-~(187)Os等时线,计算得到辉钼矿Re-Os等时线年龄为(137.9±2.0)Ma(MSWD=0.20),与加权平均年龄一致,可代表辉钼矿的形成年龄。结合石门寺和狮尾洞矿区典型矿床地质、地球化学特征和成岩作用时空关系,认为大雾塘矿床的形成是大湖塘钨矿田的第二期次(140 Ma)大规模成矿作用的产物,2期成矿作用可能是大湖塘钨矿田巨量成矿元素堆积的重要原因之一。     

广东锡坪钼铜多金属矿床辉钼矿Re-Os同位素定年及其地质意义

广东锡坪钼铜多金属矿床位于钦杭成矿带的西南端,为一大型的斑岩型矿床。本文利用辉钼矿Re-Os同位素定年方法对锡坪钼铜多金属矿床4件辉钼矿样品进行了成矿年代学测定,获得的模式年龄为85.15~88.34Ma,加权平均值为86.1±2.3Ma,对应的等时线年龄为89.9±3.4Ma,模式年龄和等时线年龄结果在误差范围内基本一致,指示锡坪钼铜多金属矿床的成矿时限为晚白垩世。锡坪钼铜多金属矿辉钼矿样品的Re含量较低,表明其成矿物质可能主要来自于壳源。钦杭成矿带成岩成矿作用以中生代燕山期为主,存在180~150Ma、110~80Ma两个爆发期,两期成岩成矿作用可能均与太平洋板块的俯冲有一定的关系。锡坪钼铜多金属矿床是在岩石圈伸展减薄环境下发生的大规模成矿作用的产物。     

Chronology and Geochemistry of the Berezitovoe Polymetallic Gold Deposit in Eastern Siberia, Russia and its Geological Significance

The Berezitovoe deposit is a large-sized Au-Ag-Zn-Pb deposit in the east of the SelengaStanovoi superterrane, Russia. Au-Ag orebodies are hosted by tourmaline-garnet-quartz-muscovite metasomatic rocks; Zn-Pb orebodies are hosted by granodiorites, porphyritic granites and tourmalinegarnet-quartz-muscovite metasomatic rocks. These orebodies are surrounded by wall rocks dominated by the Tukuringra Complex granodiorites, porphyritic granites, and gneissic granodiorites. The alteration includes silicification and garnet, sericitization chloritization, carbonatization and kaollinization. LA-ICP-MS U-Pb zircon dating indicates that the gold mineralization can be divided into two stages in the Berezitovoe polymetallic gold deposit(at 363.5 ± 1.5 Ma, and133.4± 0.5).Hornblende-plagioclase gneisses of the Mogocha Group in the study area underwent Paleoproterozoic metamorphism(at 1870 ± 7.8 and 2400 ± 13 Ma), gneissic granodiorite of the Tukuringra Complex yields a late Paleozoic magmatic age(at 379.2 ± 1.1 Ma),and subalkaline porphyritic granitoid of the Amudzhikan Complex yield late Mesozoic magmatic ages(133-139 and 150-163 Ma). Granodiorites of the Tukuringra Complex in the study area have high concentrations of SiO_2(average of 60.9 wt%), are aluminum-oversaturated(average A/CNK of 1.49), are enriched in the large ion lithophile elements(e.g.,K, Rb, and Ba), U, Th, and Pb, are depleted in high field strength elements(e.g., Ta, Nb, and Ti), and have slightly negative Eu and no Ce anomalies in chondrite-normalized rare earth element diagrams.Fluid inclusions from quartz veins include three types: aqueous two-phase, CO_2-bearing three-phase,and pure CO_2. Aqueous two-phase inclusions homogenize at 167℃-249℃ and have salinities of 4.32%-9.47% NaCl equivalent, densities of 0.86-0.95 g/cm~3, and formed at depths of 0.52-0.94 km. In comparison, the C0_2-bearing three-phase inclusions have homogenization temperatures of 265℃-346℃,salinities of 7.14%-11.57% NaCl equivalent, and total densities of 0.62-0.67 g/cm~3. The geochemical and zircon U-Pb data and the regional tectonic evolution of the study area, show that the Berezitovoe polymetallic gold deposit formed in an island arc or active continental margin setting, most probably related to late Paleozoic subduction of Okhotsk Ocean crust beneath the Siberian Plate.