2005•Dadi gouzao yu chengkuangxueRequires access
THE PORPHYRY-SKARN ORE-FORMING SYSTEM IN GANGDESE METALLOGENIC BELT, SOUTHERN XIZANG: EVIDENCE FROM MOLYBDENITE RE-OS AGE OF PORPHYRY-TYPE COPPER DEPOSITS AND SKARN-TYPE COPPER POLYMETALLIC DEPOSITS
Guangming Li
Open publisher page 5 citations
Abstract
The relationship between porphyry copper deposit and skarn-type copper polymetallic deposit is an important issue in terms of study on mineralization in Gangdese metallogenic belt. In this paper, the highly precise Re-Os ages are acquired using molybdenite from Qulong, Tingong porphyry copper deposits and Jiama, Zhibula polymetallic copper deposits in the Gangdese metallogenic belt, respectively. The Re-Os model ages vary from ( 15.75±0.42) Ma to (16.23±0.90) Ma for 4 molybdenite samples from Qulong porphyry copper deposit, from (15.5±0.3) Ma to (16.3±0.3) Ma for 7 samples from Tingong porphyry copper deposit, from (15.4±0.2) Ma to (15.5±0.2) Ma for 7 samples from Jiama copper polymetallic deposit deposit, from (16.88±0.28) Ma to (17.06±0.27) Ma for 5 samples from Zhibula copper polymetallic deposit, yielding isochron ages of (15.99± 0.32) Ma, (15.49±0.36) Ma, (15.18±0.98) Ma and (16.90±0.64) Ma, respectively for all these samples. These ages of skarn-type polymetallic copper deposits are much younger than the ages of development of Gangdese inter-arc sedimentary basin and the ages of collisional granitic intrusive rocks in Gangdese block, but are obviously consistent with the mineralization ages of the porphyry copper deposits in the nearby regions, such as Qulong, Lakange in Jiama-Qulong ore-concentration area and Chongjiang, Tinggong porphyry copper deposits in Nyemo region in Gangdese metallogenic belt. The Re-Os ages thus derived suggest that the Jiama and Zhibula copper polymetallic deposits were formed in the same porphyry-skarn ore-forming system in a post-collisional extensional tectonic setting in Miocene epoch. The porphyry copper deposits and skarn type polymetallic copper deposits in Gangdese metallogenic belt are different results of mineralization processes of the same magmatic-hydrothermal system in different wall rock environments.