Previous research has shown that more than three-quarters of the world’s Cu and half of the world’s Mo are supplied by porphyry deposits. Moreover, copper is one kind of important strategic resource for a country, and closely involved into many aspects of people's livelihood. Therefore, from both industrial andacademic points of view,porphyry Cu deposits have always attracted much more attentions than any other kinds of Cu deposits.

Porphyry deposits are generally considered to occur in continental margin or island arc settings, and intimately associated with subduction-related magmas. However, the discovery of Gangdese porphyry Cu belts (GPCB) in Tibet in 1999 indicates that they can also present in post-collisional settings. Researchers have revealed that porphyry Cu-(Mo-Au) deposits in this belt are genetically related to the Miocene adakitic porphyries. On the other hand, both the genesis of the Cu-bearing adakitic magma and its genetic link with porphyry Cu deposits in the GPCB still remain highly controversial.

Since 2008, Dr. LENG Chengbiao, Prof. ZHANG Xingchun and their coworkers mainly from the State Key Laboratory of Ore Deposit Geochemistry (SKLODG) at Institute of Geochemistry, Chinese Academy of Sciences (IGCAS) have conducted a research on a newly discovered porphyry Cu-Mo deposit (Gangjiang) in Tibet.

In their research, the ages of ore-bearing porphyries and associated Cu–Mo mineralization in the Gangjiang Cu–Mo deposit have been studied carefully by using drill core logging, field mapping, molybdenite Re-Os dating and zircon U-Pb dating. The results indicated that the porphyry magmatism and Cu–Mo ore deposition in the Gangjiang deposit could have lasted about 2.7 and 0.3 Ma, respectively.　

In addition, the in-situ Lu-Hf isotope analyses revealed that the intro-mineralization porphyry had much higher positive εHf(t) and lower Hf model ages (TDM2) than pre-mineralization porphyry, which suggested that mantle contributions to magmatism and mineralization increased with time.

Based on this study and the previous works, the researchers proposed that the Gangjiang deposit could have resulted from the convective thinning of the lithospheric root, and the input of upper mantle components into the magma could have played a key role in the formation of the porphyry deposits in the Miocene Gangdese porphyry copper belt in the Tibetan Orogen.

The above research progress has been published in Mineralium Deposita, an Official Bulletin of the Society for Geology Applied to Mineral Deposits.

(By LENG Chengbiao and ZHANG Xingchun)