Mailong Au deposit, Gouli goldfield, Dulan County, Haixi Mongol and Tibetan Autonomous Prefecture, Qinghai, Chinai

Regional Level Types
Mailong Au deposit	Deposit
Gouli goldfield	Gold Field
Dulan County	County
Haixi Mongol and Tibetan Autonomous Prefecture	Prefecture
Qinghai	Province
China	Country

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Proterozoic rocks are widely exposed at Mailong, mainly comprising plagioclase-amphibole schist/gneiss and marble. The Proterozoic marble was mildly skarn mineralized adjacent to intrusive rocks. Intrusive rocks in the Mailong gold deposit mainly include granodiorite, biotite granodiorite, plagiogranite and felsic/mafic dikes. The granodiorite is mainly distributed in the northern part of the area and intruded into the Proterozoic plagioclase-amphibole schist/gneiss and biotite granodiorite located in the southern part of the area, which is characterized by mafic microgranular enclave and intruded into granodiorite. The plagiogranite, which intruded into granodiorite or biotite granite normally as dikes, is primarily distributed in the middle part of the Mailong area. The orebodies commonly occur as quartz-sulfide veins or disseminated ores, structurally controlled by a series of high-angle NNE and NNE faults. To date, eighteen gold-bearing belts have been discovered in this area. The main ore bodies extend in the N-S direction, with variable lengths of 160–1040 m and thickness of 0.2 to 4.8 m. The average gold grade in the orebodies is 6.29 g/t with individual assay of up to 99.8 g/t. Four types of alteration assemblages can be identified at Mailong, including chloritization alteration, potassic alteration, sulfide alteration and supergene alteration. Gold mineralization is closely associated with sulfide alteration, which usually occurs along the contacts between granitic rocks and mafic dikes. The Mailong gold deposit can be classified as an orogenic-like (or Jiaodong-like) gold deposit.

The ore bodies in the gold field are strictly controlled by alteration zones developed in faults. A total of 15 alteration zones and 22 gold-polymetallic ore bodies have been identified in the Mailong segment in the west. Previous exploration has identified 19.81 metric tons of gold resources, with the ore body in AuVIII being the largest. The AuVIII orebody strikes at 10–20°, dips toward NNW with an angle of 50–85°, and has a thickness of 3–10 m and a maximum extension of 650 m at depth. Based on orebody continuity, the AuVIII orebody is subdivided into AuVIII-1 and AuVIII-2. The Au grade of AuVIII-1 ranges from 1.12 to 30.96 g/t, with an average of 6.43 g/t; while the Au grade of AuVIII-2 varies from 0.94 to 13.0 g/t, with an average of 5.16 g/t. The axial zoning sequence of the primary geochemical halo of the Au VIII ore body in the Mailong deposit is Cu–W–Sn–Hg–As–Ag–Sb–Au–Pb–Mo–Zn. The ratio of low- to high-temperature elements shows an increasing trend toward the rear part of the ore body.

The newly discovered Mailong gold deposit is located in the north of the Gouli area. To date, a total reserve of 13.06 t Au (average grade of 6.29 g/t) represents a promising exploration result. The exposed strata are relatively simple, dominated by medium- to high-grade metamorphic sequences of the Paleoproterozoic Jinshuikou Group. These rocks are predominantly distributed in the eastern part of the mining district and locally occur as xenoliths within intrusive bodies. The dominant lithologies comprise biotite plagiogneiss, plagioclase-amphibole schist, and marble. Deposit type is mesothermal orogenic gold system

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

10 valid minerals.

Rock Types Recorded