Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8912855 | Solid Earth Sciences | 2017 | 14 Pages |
Abstract
The Beiya gold deposit is the biggest Cenozoic gold deposit in the Jinshajiang-Ailaoshan alkali-rich porphyry metallogenic belt within the Sanjiang region. Porphyry intrusions are widely distributed at the Beiya deposit. In this study, we investigate the lithological and geochemical characteristics of the Beiya alkali-rich porphyries and compare zircon Ce4+/Ce3+ ratio and magmatic oxygen fugacity (fO2) of the ore-bearing and ore-barren porphyries. The research shows that the ore-bearing intrusion is monzogranite porphyry in the area of Wandongshan, Hongnitang and their surrounding ore blocks. The intrusions have similar U-Pb zircon ages of â¼36Â Ma, and all the porphyries display patterns of enriched LREEs and depleted HREEs. The ore-bearing monzogranite porphyry is characterized with high zircon Ce4+/Ce3+ ratio (average of 80) and high fO2 value (average of â³FMQÂ =Â +3.7), whereas the ore-barren monzogranite porphyry and granite porphyry are characterized by much lower zircon Ce4+/Ce3+ ratios (average of 24 and 20, respectively) and low fO2 values (average of â³FMQÂ =Â +1.2 and â³FMQÂ =Â â0.5, respectively). This indicates that the ore-bearing porphyry intrusions had much higher fO2 of magma than the ore-barren porphyry intrusions. We suggest that oxidized magmas are more favorable to porphyry Cu-Au mineralization under the intra-continental and collisional settings, which is similar to that in arc environments. Such a conclusion may potentially be used in regional exploration for porphyry Cu-Au deposits.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Geochemistry and Petrology
Authors
Xue-Quan Gao, Wen-Yan He, Xue Gao, Xin-Shang Bao, Zhen Yang,