- 责任者：Liu Yingchao (Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 100037 ; China) ; Yang Zhusen
- 刊名：Acta Petrologica Sinica
- 出版年：2013
- 卷期：29(11)
- 关键词：铜矿 ; copper ores ; 青藏高原 ; Qinghai-Tibetan Plateau
- 页码：p.3852-3870
- 图表：13 illus., 5 tables, 90 refs.
- 分类号：1001
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
Jilong Cu deposit, located in the Yushu area, Qinghai, which is in the central part of the ＇ Sanjiang＇ orogenic belt of the northeastern Tibetan Plateau, has similar mineralization characteristics with the sediment-hosted vein type Cu deposits in the Lanping basin in the southern part of the same belt. A study of this deposit is helpful to the understanding of ore-forming regularity of the regional sediment-hosted vein type Cu mineralization in the belt and also useful for the regional prospecting. Based on detailed field work and systematic thin section observation of ores, the authors indicate that the Cu mineralization in Jilong Cu deposit is produced as quartz-carbonate-sulfide veins and formed along a facies transition between clastic rocks and limestones in the Upper Zaduo Group, Carboniferous. Chalcopyrite, bornite, tennantite and chalcocite are the main ore minerals and quartz and calcite are the main gangue minerals. The Sm-Nd isochrone age of calcite from ore-forming stage is about 34Ma, indicating that the Cu mineralization formed at a regional geological background with active strike slipping faults and potassic magmatic activates. Only LV fluid inclusion rich in liquid occur in main ore-forming stage and it suggests a kind of hydrothermal fluid with middle temperature （230 - 250% ） and low salinity （3% - 6% NaCleqv）. The value of 8Dv.sMow （ -154‰- -80‰） is with big fractional distillation and the δ^18OV.SMOw （7. 72‰ - 10. 30‰） is with small fractional distillation, together of which indicate the ore fluids derived from magmatic hydrothermal fluid which has undergone degasification in open system. The δ34 S values of hydrothermal fluids in ore-forming stages are in unanimity （ 3.4‰ - 11.6‰）, which are with bigger fractional distillation than sulfur from magma. These δ34S values indicate reducing sulfur for ores came from thermal sulfate reduction, in which the sulfate belonged to the sulfate trapped in limestone in Carboniferous. The ranges of 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb of chalcopyrite and calcite in main ore-forming stage are 18. 668 - 18. 707, 15. 657 - 15. 792 and 38. 645 - 38. 873, respectively. They are in unanimity with the Pb isotope composition of Cenozoic potassic igneous rocks in the region, indicating the metal for ores origin from regional potassic magmatic hydrothermal fluids. The moralization model of Jilong sediment-hosted vein type Cu deposit can be explained as followings： The strike slipping faults led to regional potassic magmatic activates. The magmatic hydrothermal fluid underwent degasification in open system and formed ore-forming fluid rich in metal. The ore-forming fluid moved along the regional thrust faults and strike-slip faults and finally met sediment strata rich in sulfate. The sulfate in the strata was thermal reduced by organic and produced reduced sulfur. The reduced sulfur mixed with metal in the ore-forming fluid and the sulfide finally precipitated. By comparing Jilong Cu deposit with sediment-hosted vein type Cu deposits in the Lanping basin in the southern part of ＇ Sanjiang＇ belt, the authors found that they are similar in geological background, mineralization geology, characteristics and origin of ore-forming fluid, and origins of sulfur and metals, and finally point out that there may be a 1000km-long sediment-hosted vein type Cu deposit belt in the ＇ Sanjiang＇ belt.