JURASSIC U-Pb AND Re-Os AGES FOR THE NEWLY DISCOVERED XIETONGMEN Cu-Au PORPHYRY DISTRICT, TIBET, PRC: IMPLICATIONS FOR METALLOGENIC EPOCHS IN THE SOUTHERN GANGDESE BELT

The link between reduced porphyry copper deposits and oxidized magmas

“…Veinlet and disseminated mineralization occurs in the quartz diorite porphyry and its adjacent volcanic sequence. Zircon U-Pb ages of the Xiongcun porphyry range from 171.3 ± 1.0 to 173.5 ± 1.0 (2r) Ma, consistent within error with the molybdenite Re-Os age of 174.2 ± 0.2 Ma (Tafti et al, 2009). …”

“…The Xiongcun (also named as Xietongmen) porphyry Cu-Au deposit is located in the southern rim of the Gangdese orogenic belt in southern Tibet (Tafti et al, 2009;Xu et al, 2009). The Cu-Au mineralization is associated with quartz diorite porphyry, which intrudes the Early Jurassic volcanic sequence (Tafti et al, 2009).…”

“…The Cu-Au mineralization is associated with quartz diorite porphyry, which intrudes the Early Jurassic volcanic sequence (Tafti et al, 2009). It contains more than 130 t of gold with an average grade of 0.61 g/t and more than 1 million tons of Cu metal with an average grade of 0.43%.…”

Late Cretaceous (ca. 90Ma) adakitic intrusive rocks in the Kelu area, Gangdese Belt (southern Tibet): Slab melting and implications for Cu–Au mineralization

“…On the other hand, Jurassic-Early Tertiary arc magmatic rocks are widespread in the GBST, including some Early Cretaceous subducted oceanic crust-derived adakites ). The Kelu adakites are associated with the first known Cretaceous Cu-Au mineralization in the GBST arc but are geodynamically related to porphyry copper-goldhosting Jurassic ($172 Ma) arc magmatic rocks in the GBST (Tafti et al, 2009). We thus speculate that the widespread Jurassic-Early Tertiary arc magmatic rocks in the GBST may hold more potential for Cu-Au mineralization than is presently recognized.…”

“…1b) Hou et al, 2004Hou and Cook, 2009). So far, almost all reported Cu-Au-Mo deposits in this belt were formed during continental convergence after the initial India-Asia collision, and were mainly associated with Miocene (18-10 Ma) adakitic porphyries Gao et al, 2007;Guo et al, 2007b;Qu et al, 2007) and, except for one porphyry copper-gold deposit associated with a Jurassic ($172 Ma) intrusion (Tafti et al, 2009), few occurrences were found to be associated with the Cretaceous arc magmatic rocks.…”