Yandong porphyry Cu deposit, Xinjiang, China鈥擥eology, geochemistry and SIMS U-Pb zircon geochronology of host porphyries and associated alteration and mineralization

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• 作者：Ping Shen ; Hongdi Pan ; Lianhui Dong
• 关键词：Volcanic complex ; Porphyry ; Alteration ; Zircon U&ndash ; Pb age ; Yandong ; Xinjiang
• 刊名：Journal of Asian Earth Sciences
• 出版年：5 February, 2014
• 年：2014
• 卷：80
• 期：Complete
• 页码：197-217
• 全文大小：11088 K

文摘

The Yandong porphyry copper deposit, located in the Eastern Tianshan Mountains, Xinjiang, China, is part of the Central Asian Orogenic Belt. The Yandong deposit is hosted by a volcanic complex in the Early Carboniferous Qi鈥檈shan Group and a felsic intrusion. The complex consists of andesite, basalt, diorite porphyry, and porphyritic quartz diorite. The felsic intrusion is a plagiogranite porphyry emplaced within the complex. The diorite porphyry and plagiogranite porphyry yield SIMS zircon U-Pb ages of 340.0 卤 3 and 332.2 卤 2.3 Ma, respectively. Element geochemistry shows that both the complex and plagiogranite porphyry formed in the Dananhu-Tousuquan island arc, a Carboniferous magmatic arc.

The diorite porphyry and plagiogranite porphyry are host porphyries, but the plagiogranite porphyry is a productive porphyry. It caused the porphyry-style Cu mineralization and associated alteration. The alteration assemblages include early potassic and propylitic assemblages. These were overprinted by a chlorite-sericite assemblage, which in turn was overprinted by a late phyllic assemblage. The phyllic alteration is associated with the highest Cu grades. The mineralization is recognized to include three stages, from early to late: stage 1, a potassic alteration associated with a chalcopyrite + pyrite assemblage; stage 2, represented by chlorite-sericite alteration with a chalcopyrite + pyrite assemblage; and stage 3, the main-ore stage that is marked by phyllic alteration with chalcopyrite + pyrite 卤 molybdenite and producing more than 70% of the total copper production at Yandong. Yandong may represent a common scenario for Paleozoic porphyry Cu systems in the Central Asian Orogenic Belt.