Delong Au-Cu deposit, Dulan County, Haixi Mongol and Tibetan Autonomous Prefecture, Qinghai, Chinai

Regional Level Types
Delong Au-Cu deposit	Deposit
Dulan County	County
Haixi Mongol and Tibetan Autonomous Prefecture	Prefecture
Qinghai	Province
China	Country

The basement rocks, in the north-eastern district, are composed of Proterozoic schist and gneiss. Early Triassic volcanic (including dacite porphyry and volcaniclastic rocks; 249 ± 1 Ma) and sedimentary rocks (including limestone and clastic rocks) can be found in the middle and south of the ore district, with some of them having undergone metamorphism. Intrusive rocks are widespread in the ore district, including Cambrian gabbro in the east central, Middle Triassic granite and potassic granite (240 ± 1 Ma), and Late Triassic quartz diorite.
Several copper and gold orebodies/mineralization zones have been discovered in the Delong deposit. In the outcrops, these orebodies crosscut the Proterozoic basement rocks, the Early Triassic volcanic rocks (dacite porphyry and volcaniclastic rocks), and the Middle Triassic potassic granite (Figure 1C). These crosscutting relationships can be also observed in deep drill core samples, implying the later formation of orebodies than the Early-Middle Triassic magmatic rocks. Potassic alteration are intensive in the study area, especially some granites. Chloritization and epidotization can be observed in the granites, quartz diorites, and enclosed mafic enclaves. Quartz-sulfide-bearing veinlets and stockworks can be observed in the (potassic) granites and volcanic rocks. These veinlets and stockworks are mainly composed of quartz, pyrite, arsenopyrite, chalcopyrite, sphalerite, and bornite. The alteration and mineralization characteristics of this deposit together suggest a possible porphyry mineralization in the deep, which is likely related to the quartz diorite according to the crosscutting relationships.

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