Geochronology and Geochemistry of the Bolong Porphyry Cu-Au Deposit, Tibet and Its Mineralizing Significance
详细信息
- 责任者：Chen Huaan (Chengdu Institute of Geology and Mineral Resources ; Chengdu 610081 ; China) ; Zhu Xiangping
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(10)
- 关键词：斑岩铜矿床 ; porphyry copper deposit ; 金矿 ; gold ores ; 西藏 ; Tibet
- 页码：p.1593-1611
- 图表：10 illus., 3 tables, 48 refs.
- 分类号：1001
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
Bolong porphyry copper deposit is the largest newly discovered deposit in the middle of Tibet plateau.Three stages of granodiorite porphyries were emplaced in the Bolong porphyry deposit,and the former two stages of granodiorite porphyries are mineralized porphyries.Zircon U-Pb dating,bulk rock geochemical compositions and Sr-Nd-Hf isotopic compositions of these porphyries were analyzed.Zircon U-Pb dating results shows that all these porphyries were intruded at 119~120Ma.The former two stages of granodiorite porphyries are enriched in light rare earth elements and large ion lithophile elements,and depleted in heavy earth elements and high field-strength elements,with weak Eu anomalies,indicating that these granodiorite porphyries resemble arc magmas in composition.(87Sr/86Sr)i values of the first and the second stage of granodiorite porphyry are 0.70562~0.70711and 0.70567~0.70850respectively,withεNd(t)ranges within-4.0~-3.1and-8.0~-2.4,εHf(t)varies within 2.5~6.9and 3.3~6.9respectively,suggesting that two stages of granodiorite porphyries were derived from juvenile lower crust.The third stage of granodiorite porphyry also shows arc magma affinities in composition,its higherεNd(t)(-0.7~-0.2)andεHf(t)(1.3~12.2)might suggest that the third stage of granodiorite porphyry was also generate from lower crust with more mantle-derived materials.Bolong porphyry deposit were formed at the late stage of the northward subduction of the Bangong Lake Neo-Tethyan Ocean,and the magmatic activity in the Bolong deposit should have close relationship with oceanic subduction,melt generated from subducted oceanic crust and subarc mantle wedge was upwelled,which might triggered partial melting of juvenile lower crust and formed the Bolong porphyry copper deposit.imply that the southern Qiangtang terrane should be thickened at 120Ma.