黔东南锦屏金矿成矿模式的模拟实验

利用中国科学院地球化学研究所矿床地球化学国家重点实验室的实验设备对黔东南锦屏金矿进行了成矿模式的模拟实验。通过剪切实验,变形、破裂实验,成矿物质活化、迁移实验,成矿模式模拟实验和多次应力实验,获得了成矿物质以碎粒流和塑性流动的方式顺层及穿层充填并在褶曲核部富集的结果,多次应力实验使成矿物质叠加富集。实验结果初步证实了锦屏石英脉金矿的成矿模式,为该区构造控制金矿提供了重要的实验资料,也为今后研究该区金矿的成矿规律和找矿提供了有益的信息。     

分散元素成矿作用研究新进展

20世纪90年代以来,在涂光炽院士主持的国家自然科学重点基金项目"分散元素成矿机制研究"和包括多个国家基金面上项目的支持下,中国科学院地球化学研究所及其兄弟单位的科学家们对分散元素的成矿作用进行了大量研究,取得一批新的重要成果,使我国在该领域的研究走在了世界前列.     

贵州威宁地区峨眉山玄武岩型自然铜-辉铜矿矿床的成矿前景

贵州威宁一带产于峨眉山玄武岩中的自然铜．辉铜矿矿床（点）经过几十年研究，但在找矿勘探方面一直难以突破。本文从矿床地质特征、成矿物质来源出发，讨论了与成矿规律和成矿远景，认为矿化受夹层和断裂双重控制，成矿以后期热液改造作用为主。与基伟诺型矿床相比，玄武岩厚度不大及不连续分布、陆相地表喷发、埋藏深度不大、缺少成矿流体汇聚的构造条件是形成大矿的不利因素。在峨眉山玄武岩分布区内，玄武岩厚度巨大、构造应力集中的地区有可能找到中型规模以上的矿床。     

与峨眉山玄武岩有关的沉积型铜矿——“马豆子式”铜矿的成因研究

峨眉山玄武岩之上宣威组中的沉积型铜矿,矿石矿物以铜硫化物和自然铜为主,矿石构造大多具有结核状,前人根据此特征将其命名为＂马豆子式＂铜矿.本文对该矿床中的铜结核进行了矿物学和同位素方面研究.矿物学研究表明,铜结核由含铁非晶质矿物、粘土以及碳质碎屑共同胶结铜的硫化物而组成,并以交代作用和沉积作用的方式形成;结核的原始形态是凝胶状物质组合体.同位素分析显示,碳沥青的13CPDB值在-24.8‰～-23.9‰之间,表明碳沥青是原地植物沉积变质的产物;辉铜矿的34SV-CDT值为7.6‰～13.1‰,与二叠纪海水的34S（约11‰）接近,斑铜矿、黄铜矿的δ^34SV-CDT值为21.6‰～22.2‰,和海相硫酸盐的硫同位素组成（20‰）类似,显示硫的来源不同.以上特征表明铜结核的形成过程是,含铜玄武岩经风化淋滤,铜质迁移到水体中后被粘土、含铁非晶质矿物和植物碎屑吸附,并成凝胶团悬浮与搬运,在湖泊或沼泽环境下与沉积物同生沉积成核;后期再经变质交代和热液叠加,斑铜矿交代辉铜矿、黄铜矿又叠加于斑铜矿之上,最终形成了＂马豆子式＂结核铜矿.     

浊积岩型金矿

浊积岩型金矿是指产在浊积岩中的受背斜和断层控制的含金石英脉。这种浊积岩受到绿片岩相变质作用,并经历造山运动形成了许多褶皱和断层。同时有花岗岩侵入。含金石英脉是在浊积岩,造山运动和变质作用之后形成的。主要分布于背斜的轴部和两翼,且平行于地层(Bed Parallele vein;BPV)。     

中国SEDEX型矿床成矿流体硼、硅、氦-氩同位素组成研究评述

SEDEX型矿床成矿流体的研究是矿床地球化学研究的重要课题之一。正确识别系统中不同的流体来源及其混合过程,是深刻理解SEDEX型矿床形成演化的关键。系统总结了国内几个典型的SEDEX型矿床同位素研究成果,认为B和Si同位素是根据SEDEX型矿床独特的矿物组合而提出的一种示踪方法,对矿床成因和沉积环境示踪效果理想;He、Ar同位素则因为在地壳和地幔储库中有极不相同的组成,是理想的幔源流体示踪剂。鉴于SEDEX型矿床含有电气石、黄铁矿、硅质岩等特殊的矿物与岩石组合,B、Si、He-Ar同位素可能更适合SEDEX型矿床矿化流体来源研究,并指出其理论发展的薄弱之处。     

贵州东南部浊积岩中金矿的地质特征和成因

文章首次明确提出黔东南天柱县、锦屏县、黎平县以及相邻的湖南省靖县、会同县、洪江县存在浊积岩型金矿。研究发现,这些金矿均产在加里东皱褶带中,它们产于背斜的轴部,向两翼延伸,形成平行于地层的石英脉;另一种石英脉则充填于褶皱和剪切作用形成的剪切带或断裂带中。这些褶皱和断裂均呈北东方向。黔东南地区的浊积岩型金矿,均赋存于前震旦系下江群浊积岩中,产在板岩、凝灰岩或者在板岩和砂岩交界处。石英脉中金的富集与黄铁矿、毒砂、闪锌矿、方铅矿等密切相关。细脉比宽脉更富集金,断裂交叉处更富含金。石英脉两侧(尤其是顺层石英脉)的蚀变很弱,主要为硅化和绿泥石化。应用RB_SR方法测得石英脉的年龄为370～450Ma,成矿时代应在加里东期或期后。黔东南浊积岩金矿在品位(多数可见明金)、储量和产量方面均很有前景,研究它们具有十分重要的学术价值和经济意义。     

A simulating experiment on the geochemical variation trend at the initial period of meteoric waters converting to underground waters and ore fluids

Experimental studies were undertaken on leaching of sedimentary rocks （ dolomite and sandstone） and Hg, Sb ores by distilled water under the condition of a completely open system （room temperature and room pressure）. The aim is to find whether the halogen elements or metal elements first enter the solution at the early stage of meteoric waters converting to groundwaters and ore fluids, and, at the same time, to understand how and when they enter distilled water solutions from the rocks. The experimental resuhs have shown that F and Cl began to enter the fluids in the initial period of thirty days. With increasing leaching duration, the amounts of the elements that entered the fluids increased steadily. During the period from 120 days to 150 days the amounts increased more drastically, followed a slow increase. It is found that the capability of Cl entering the solutions is much greater than that of F. Hg and Sb were found not to have entered the solutions till 120 days later. During this period of time the pH value of the solutions began to drop. As for Hg and Sb ores, Hg and Sb began to enter the solutions on the 60th or 90th day, greatly ahead of schedule, but the two metallic elements in the rock samples began to enter the solutions 150 days later. Relatively speaking, Hg is more easily leached out than Sb from the rocks. In some rock samples, Sb could be detected in the solutions at the end of the experiment. However, Cu, Pb and Zn had not been detected in the leaching solutions from the beginning to the end of the experiment. In the whole leaching process the pH value of the solutions tend to decrease slowly from 7.1 at the beginning to 6.5 at the end. That is to say, in the interaction between pure water and rock the halogen elements in the rocks were preferentially leached out and then entered the fluids. With increasing water/rock reaction duration and amount of halogen-group elements in the solution and with decreasing pH value of the solution, some active metallic elements began to release in small amounts. This experimental result can explain the source and mechanism of volatile components and trace metals in underground waters. Meanwhile, as for those ore deposits produced by ore fluids derived from meteoric waters, the experimental result is also helpful to the understanding of the geochemical variation trend at the initial stage of conversion of meteoric waters to ore fluids.     

西昆仑库地蛇绿岩的地质特征及其形成环境

根据新藏公路沿线实际观察资料和前人的最新成果，总结了新疆西昆仑库地蛇绿岩的构造特征、层序及岩石学特征；对库地蛇绿岩形成时代、原始构造环境等有争议的关键性问题进行了分析和探讨，得出了有关库地蛇绿岩的如下新结论：①形成时代为中元古代—晚元古代，同位素年龄值为大于１６６１．９～６９８．３６Ｍａ；②形成于缓慢扩张的条件下，且没有经历过俯冲消减作用；③岩浆来源为弱亏损的、非单一的上地幔源，并受到了陆壳物质的混染；④原始构造环境为弧后盆地—岛弧—弧间盆地，属过渡性构造环境     

Potential Applications of Nano—Scale Science and Technology in Geosciences and Experimental Studies of Nanometer—Sized Gold Adsorption on Minerals and Rocks

Potential applications of Nano-scale science and technology are discussed in mineralogy,ore deposits,cosmochemistry and environmental sciences.Adsorption of nanometersized gold was experimentally studied on a variety of minerals and rocks.