International Workshop on ＂Central Asian Orogenesis and Metallogeny＂

An ＂International Workshop on Central Asian Orogenesis and Metallogeny＂, sup- ported by Department of Science and Tech- nology of Xinjiang Uygur Autonomous Region, the Geosciences Department of the Natural Science Foundation of China, the Bureau of Science and Technology for Resources and Environment, the Chinese Academy of Science, Xinjiang Petroleum Company, and China National Petroleum Corporation, was held in Urumqi, Xinjiang, from 18-24 September, 2007 （hosted by the National 305 Project Office）.     

Tectono-Magmatic Events and Gold Metallogeny in the Qinling Orogen

Please refer to the attachment(s) for more details.     

内蒙乌拉山金矿控矿条件及成矿作用

乌拉山金矿是华北地台北缘中西部地区近年来探明的有一定远景的金矿床。该矿床受大桦背岩体、韧性剪切带、脆性断裂构造和乌拉山群变质岩系等多种条件所控制，矿体呈脉状产出，成矿具有多期多阶段性，成矿时代较华北地台东缘金矿床早，为晚华力西期，其类型为中深成脉状金矿床     

International Eclogite Field Symposium and Workshop of the Task Force IV, International Lithosphere Program

The 2007 International Eclogite Field Sym- posium held in Portree, Isle of Skye, Scotland from June 29th to July 6th was a joint meeting of the International Eclogite Confer- ence, International Lithosphere Program Task Force IV ＂Ultra-deep Continental Crust Subduction＂, and the Metamorphic Studies Group. The Symposium consisted of two days of conference sessions and inter-, pre- and post-conference field excursions. The thematic conference included two sessions,     

中国金矿资源特征及成矿规律概要

我国金矿资源较为丰富,金矿是中国重要的战略矿种之一.本文在全国潜力评价项目开展过程中,在典型矿床研究的基础上,通过对我国资源特征、勘查进展、金矿类型、时空分布、成矿谱系的分析与归纳,初步总结了中国金矿成矿规律.文章总结了我国金矿的资源特征及存在的问题;从预测的角度,将我国金矿分为花岗绿岩型金矿、火山岩型金矿、与岩浆岩有关金矿、沉积建造中的金矿、与表生作用有关金矿等五大预测类型;在统计的基础上,将我国金矿分为新太古代—古元古代、中—新元古代、古生代、中生代和新生代5个成矿期,并初步总结了各成矿期金矿的空间分布特征等;提出了成金带的概念,并划分了53个成金带,概括了其主要特征;厘定出71个与金矿有关的成矿系列,建立了中国金矿成矿谱系.认为应该继续加强我国金矿成矿体系和成矿规律研究,通过理论指导找矿勘查部署并综合评价,以期取得更大的找矿进展.     

Highly pure placer gold formation in the Nilambur Valley,Wynad Gold Field,southern India

Placer gold grains in the Nilambur Valley of Wynad Gold Field in southern India are characterized by very high purity levels (985–1000). Their Ag-depleted core compositions, enhanced grain size and microscale growth patterns correlate with gold grains associated with laterite profiles in the weathering fronts. From the morphological and chemical evolution of gold grains associated with primary, supergene and secondary deposits in this region, we identified a two-stage process for the evolution of the highly pure placers, which shows that gold in the primary veins was mobilized, chemically purified, and reconcentrated in the laterite profiles, effecting enhanced purity and grain growth before transfer to the fluvial system. Further refinement was achieved during fluvial transport, generating natural concentrations of pure gold in the placers.     

青海双朋西—斜长支沟地区金矿成矿地质条件及成矿规律

双朋西—斜长支沟地区是青海东部较为重要的贵金属和有色金属成矿区.在已探明的金矿床中,有矽卡岩型、破碎蚀变岩型、石英脉型三类.金的成矿作用受构造-岩浆控制,在不同的岩性组合中分布着不同类型的金矿.矽卡岩型和石英脉型金矿赋存于二叠系中,破碎蚀变岩型金矿赋存于三叠系中.     

Metallogeny of the Lannigou Sedimentary Rock-hosted Disseminated Gold Deposit in Southwestern Guizhou Province, China

The Lannigou deposit is a large-sized sedimentary rock-hosted disseminated gold （SRHDG） deposit located in the Youjiang Basin. It is hosted by the Middle Triassic turbidite. Wall rock alterations, including silicification, pyritization, arsenopyritization, carbonatization and argillization, commonly occur along fractures. PGE study demonstrates that either Permian basalts or Triassic ultrabasic intrnsives are unlikely to be the main source of gold mineralization. Coupled with the lack of other nmgmatic activity in the vicinity of the mining area, an amagmatic origin is proposed. Organic matter compositions and GC-MS analysis of the ores and host rocks show that the organics in the ores and the host rocks have a common source; the organic matter in the ores was mainly indigenous. The positive correlation between S2 and Au contents, along with the common occurrence of organic inclusions, suggest involvement of organic matter in the ore-forming process in terms of promoting Au leaching from the source rocks, making colloidal Au migration possible, as well as hydrocarbon reduction of sulphate. Geological and geochemical characteristics of the Lannigou deposit suggest that it was formed through circulation of meteoric water and probably less importantly organic bearing formation water driven by high geothermal gradient caused by late Yanshanian extension, which leached Au from the source bed, and then migrated as Au-bisnlfides and colloidal Au, culminating in deposition by reduction-adsorption and surface complexation of gold onto the growth surface of arsenlan pyrite.     

Geochemistry and Tungsten Metallogeny of the Balda Granite,Rajasthan, India

Balda granite occurs along the western margin of the middle Proterozoic South Delhi Fold Belt. It is a medium grained leucogranite associated with tungsten mineralisation. Wolframite mineralisation is confined to pneumatolytic quartz veins and greisenised pegmatites located mainly along shear zones within Balda granite and neighbouring metasediments. Geochemistry of Balda granite suggests that it is highly evolved, peraluminous and volatile -rich granite formed from the melt derived by partial melting of metasediments. Borates and fluorides in various complexes favoured the concentration of W in the melt, whereas sodium cations, chlorides and phosphates were the carrier of tungsten in fluid. The shear zones developed within Balda granite and neighbouring metasediments provided the channelways for fluid movement and deposition of wolframite.     

The XIV International Workshop on Marine Geology

Lithology and Mineral Resources -