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《Geochimica》 2004-06
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Petrochemistry and SHRIMP U-Pb zircon age of the Chongjiang ore-bearing porphyry in the Gangdese porphyry copper belt

LIN Wu,ZHANG Yu-quan,LIANG Hua-yin g,XIE Ying-wen Laboratory of Marginal Sea Geology,Guangzhou Institute of Geochemistr y and South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou510640,China Correspondence should be addressed to LIN Wu(E-mail:linwu_2001@163.com)Received January 12,2004;revised April 19,2004;accepted August 31,2004;published November,2004  
The Gangdese porphyry copper belt is a new discovered ore belt in South Tib et,China.A lot of small ore-bearing intrusions,such as Chongjiang,Qulong,Nanmu,Tinggong,Dongga and Lakange,have been found in this ore belt.The Chongjiang porp hyritic intrusion occurs in the midd le part of the Gangdese porphyry copper belt in southern Qinghai-Xizang Plateau.The Chongjiang porphyry hosts 107m illion tons of metallic copper at an average tenor ranging from 0.48%to 0.63%and about 1.27million tons of me tallic Mo,and 21tons of metallic Au.The Chongjiang porphyry could be divided into early,main and late sta ges.The early stage rock and the main stage rock are diorite and granodioritic porphyry and quartz-monzonitic porphyry,respectively,and belon g to the high-alkaline series.The main stage granodioritic porphyry and quartz-monzonitic porphyry display massive,porphyritic texture,comprising pl agioclase,K-feldspar,minor mica a nd quartz as phenocrysts.The late stage is granitic porphyry,locating between the high-alkaline series and the sh oshonitic series.SHRIMP zircon dating of quartz-monzonitic porphyry for the Chongjiang porphyry is(12.9±0.3)Ma.It represents the formation age o f the ore-bearing porphyry.Our SHRIM P zircon age is younger than the previous zircon age犤(15.60±0.52)Ma,(14.54±0.65)Ma 犦and the related Re-Os age犤(14.85±0.69)Ma,(14.04±0.16)Ma 犦.The Chongjiang ore-bearing porphyry has two different ranges of ages:12~13.8Ma and 14~15.6Ma.It is suggested that magmatic activity of the Chongjiang ore-bearing porphyry is multiperio d.The first stage is 14~15.6Ma in age,and the second stage is 12~13.8Ma.Based on our new age data,together with the previous work,it is concluded that the diagenetic and metallogenic epoch of the ore-bearing porphyries in t he Gangdese porphyry copper belt is 18Ma to 12Ma.Duration of magmatic activity of the ore-bearing porphyries is a bout 6Ma.
【Fund】: 国家重点基础研究发展规划项目(G1999043203);; 中国科学院知识创新工程重要方向项目(KZCX2-SW-117);; 中国科学院知识创新工程领域前沿项目(GIGCX-03-04);; 国家自然科学基金(40472049)
【CateGory Index】: P597.3
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