藏东主要岩金矿床类型基本特点及其找矿前景

The types and prospects of the gold deposits in eastern Xizang

关键词:  岩金矿床类型  找矿前景  藏东

Key words:  types of gold deposits  prospects  eastern Xizang

摘要:

藏东地区是西南三江复合造山带有色金属、贵金属成矿带的重要组成部分,也是三江带中北段新生代强烈陆内变形区,具有金和金银金属矿产成矿的优越条件。已发现的众多岩金矿(化)点反映出藏东有多种岩金矿床成因类型,其中以斑岩型和破碎带充填交代型两种类型最为重要。前者以新生代浸源偏碱性斑岩为成矿母岩,矿(化)体赋存于斑岩、隐爆角砾岩内部、接触带及外接触蚀变带中,主矿化元素为金、银、铅、锌,少数还有铜、钨;后者的矿(化)体一般赋存于多期活动的区域性大断裂侧次级断裂、派生断裂、层间破碎带及节理、劈理发育带内,主矿化元素亦为金及银、铅、锌、铜,个别有锑、汞等。成矿时代以新生代及白垩纪-新生代为主。文中还对藏东构造单元和新生代偏碱性岩带进行划分,对两种金矿床类型的一般矿化特征、矿源层、蚀变和化探异常与矿化关系、找矿标志及找矿方向作了简要论述。

Abstract:

The eastern Xizang area is an important part of nonferrous and precious metallogenic zone, and a highly deformed area during the Cenozoic in the central and northern parts of the Nujiang-Lancangjiang-Jinshajiang area, where the gold and silver deposits are preferentially hosted. A lot of the gold deposits in eastern Xizang have been recognized, including sedimentary (gold placer), sedimentary-diagenetic, volcanic, porphyry-type, fractured filling-metasomatic, qartz-vein and porphyry copper-associated gold deposits, of which the porphyry-type and fractured filling-metasomatic are most common. The parent rocks of the porphyry-type gold deposits consist of the Cenozoic partially alkaline porphyries. The orebodies occur generally in porphyries, cryptoexplosion breccias, contact zones and outer contact-alteration zones. The main ore-forming elements are composed of gold, silver, lead, zinc, copper and tungsten. The latter orebodies appear commonly in the secondary faults, derived faults, interformational fractured zones and joint and cleavage development zones close to the regional rifts. The main ore-forming elements consist of gold, silver, lead, zinc, copper, antimony and mercury. The mineralization ages are represented by the Cenozoic and Cretaceous-Cenozoic times. The present paper deals also with the division of the tectonic elements and Cenozoic partially alkaline rock belts in eastern Xizang, with the emphasis on the mineralization, source rocks, alteration, geochemical anomaly, indicators and prospects of the two types of gold deposits cited above.