Geology and Geochemistry of Jingxi-Yelmand Gold Deposit in
详细信息
- 责任者：An Fang (Key Laboratory of Orogenic Belts and Crustal Evolution ; Ministry of Education ; School of Earth and Space Sciences ; Peking University ; Beijing 100871 ; China) ; Zhu Yongfeng
- 刊名：Acta Petrologica Sinica
- 出版年：2010
- 卷期：26(8)
- 关键词：金矿 ; gold ores ; 新疆 ; Xinjiang
- 页码：p.2275-2286
- 图表：11 illus., 2 tables, 25 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
Jingxi-Yelmand gold deposit is located in the northwest of Tulasu Basin,North Tianshan(Xinjiang,NW China),which is hosted in tuff and tuff sandstone in Devonian to Early Carboniferous volcanic-sedimentary strata.Silicification,sericitization,pyritization,brecciation and carbonation are found in the host rocks,in which silicification is closely related to gold mineralization.Orebody in Jingxi-Yelmand gold deposit,mainly composed of hydrothermal breccias and strongly silicified host rocks,is lenticular,stratoid and stratified,parallel to the volcanic-sedimentary strata.The ore-forming process consists of four stages:Silicification and sericitization(stage I),forming abundant disseminated quartz,sericite and pyrite in host rocks;Brecciation and silicification(stage II),made the formation of hydrothermal breccia-a,composed of altered host-rock fragments,which were cemented by chalcedonic quartz,pyrite,arsenopyrite and some auriferous minerals;Brecciation and silicification(stage III),formed hydrothermal breccia-b composed of altered rock and breccia-a fragments cemented by fine-grained quartz,pyrite,arsenopyrite and auriferous minerals.The hydrothermal process is terminated by forming coarse-grained calcite-barite veins(stage IV).Geochemistry study suggests that the original ore-forming fluid enrich in V,Cr,Ni,Cu and Sb,and leach Mn,Co,Zn,Bi and LILE from wall-rocks.Ore-forming fluid is magmatic water reequilibrated with host volcanic-sedimentary rocks,and becomes more oxidized from early to late stage.Model calculation suggests that gold concentration in ore-forming fluid is about 1 × 10-6 ～ 2 × 10-6,and about 1 × 108 to 0.5 × 108 ton magmatic hydrothermal fluid is needed for forming Jingxi-Yelmand gold deposit.Brecciation and the related increase of fO2 value might be the major factors causing gold precipitation.