Zhulazhaga Au deposit, Alxa Left Banner (Alashan Zuoqi), Alxa League (Alashan Prefecture), Inner Mongolia, Chinai

Regional Level Types
Zhulazhaga Au deposit	Deposit
Alxa Left Banner (Alashan Zuoqi)	County
Alxa League (Alashan Prefecture)	Prefecture
Inner Mongolia	Autonomous Region
China	Country

Reduced gold skarn system, similar to the Fortitude and Phoenix gold skarn deposits in Nevada. The deposit is located along the eastern extension of the Tian Shan gold belt, which hosts important deposits in Uzbekistan and Kyrgysztan to the west.

46 ore bodies have been delineated in the Zhulazhaga gold deposit, including seven major ore bodies. The principal ore body strikes NE and dips 25–45° SE. The ore bodies predominantly exhibit a layered and lenticular morphology, but there are also minor vein-type occurrences. The dimensions of the ore bodies range from 1200 to 1700 m along strike and from 150 to 800 m down-dip. They are 5.42–10.89 m thick and occur at depths >800 m. The gold grades (0.30–193.14 g/t) correlate with the geometry and mineralization styles of the orebodies. A total of 235.82 tons of gold were outlined in the mining lease, classifying the Zhulazhaga deposit as a super-large gold deposit. Notably, the ore grades remain undisclosed. The ore bodies of the Zhulazhaga gold deposit are primarily hosted within the metamorphosed siltstone of the Agulugou Formation. The recently discovered thick and high-grade ore bodies at depth occur between the siltstone and marble or between the siltstone and andesite. Locally, the ore body penetrates the strata. Therefore, rather than strictly controlled by the lithology of the strata, the ore body of the Zhulazhaga gold deposit may be controlled by interlayer fractures or sliding fracture zones. In addition, no obvious mineralization and alteration has been observed in the metamorphic sandstone outside of the ore district.
The paragenetic sequence in the Zhulazhaga gold deposit can be divided into five stages: (1) The silicification stage consists of intense silicification in the early stage of hydrothermal alteration, with local greisenization but no observed gold mineralization. Late-stage tremolite fills the intergranular spaces between quartz grains. In this stage, the pyrite exhibits euhedral to subhedral granular texture. (2) The actinolite-tremolite stage is dominated by actinolite alteration, tremolite, and diopside, as well as minor sulfides such as chalcopyrite and subhedral pyrite. Native gold occurs near the tremolite. (3) In the early quartz-sulfide stage, many sulfides, including pyrrhotite, pyrite, chalcopyrite, and minor arsenopyrite, precipitated in the quartz veins. Native gold is found interstitially between quartz grains. Actinolite, present in earlier stages, was thermally altered to form talc. The pyrite in this stage exhibits a relict texture, indicating that it experienced metasomatism. (4) The late quartz-sulfide stage is mainly composed of anhedral chalcopyrite, pyrite, and minor amounts of sphalerite and galena, and gold can also be identified in this stage. (5) The carbonate stage is the final mineralization phase. It precipitated from low-temperature hydrothermal fluids. This stage is dominantly composed of calcite veins and euhedral pyrite, which contains invisible gold. Stages 2–4 constitute the primary phases of gold mineralization. Pyrite is a persistent mineral throughout all of the mineralization stages, and its distinct crystal morphologies in the different phases provide an ideal research object for comprehensive metallogenic studies.

Other Regions, Features and Areas containing this locality

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