Dashui Au deposit, Dashui Au ore field, Maqu Co., Gannan, Gansu, Chinai

Regional Level Types
Dashui Au deposit	Deposit
Dashui Au ore field	Ore Field
Maqu Co.	County
Gannan	Prefecture
Gansu	Province
China	Country

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Hydrothermal-metasomatic gold deposit, related to Yanshanian tectono-magmatism. The orebodies are hosted in Triassic limestones and are controlled by faults. Ore minerals mainly occur in a series of silicified rocks and silicates formed by hydrothermal activities. From the center towards the periphery hydrothermal explosive breccias, hydrothermal silicate-calcite veins, hydrothermal-metasomatic jasperoids and silicified granodiorite, and silicified limestones are observed. Hydrothermal metasomatic mineralization took place somewhat earlier than hydrothermal infilling and sedimentary mineralization, and the composition of the hydrothermal system evolved from iron-silica-rich in the earlier stages towards carbonate-rich in the late stages.

The goldfield includes the Ge’erke, Ge’ertuo, and Gongbei mining centres. Of these, the Ge’erke mining centre contains the richest and largest deposits, consisting of the Ge’erke deposit, and mineralised Ge’ertuohe pluton. The Ge’erke mining centre covers ∼ 1.2 km2 and hosts five W– to N– trending and steeply–dipping ore zones. The country rocks include sandstone, limestone, dolostone, and dolomitic limestone in the Early Triassic Maresongduo, Zalishan, and Tianba Formations.
The ore–forming stages from early to late in the Dashui goldfield are identified as an early alteration followed by sulfide deposition, and late carbonate veining and oxidation.

The early alteration followed the emplacement of alkaline magma, and is characterized by high–temperature hydrothermal fluids with high oxygen fugacity, and rich in Cl. The mineral assemblage consists of potassium feldspar–chlorite–sericite.

The middle-stage sulfide is characterized by acidic hydrothermal fluids migrating along faults where disseminated pyrite precipitated. The mineral assemblage is marked by pyrite–quartz–kaolinite.

The late-stage carbonate veining and oxidation correlated with relatively low-temperature and silica-rich hydrothermal fluids that underwent prolonged surface oxidation. This stage is characterized by calcite, hematite and magnetite.

The Dashui gold deposit exhibits well-developed veins that are closely associated with gold mineralization in both temporal and spatial contexts. These veins are predominantly distributed around the Ge'erkuohe, Zhongqu, and Zhonggezhala plutons and are controlled by NWW-, near-SN-, and NE-trending faults and their intersecting zones. The ore bodies are primarily hosted within Triassic limestone (Gerke, Zhongqu, Gonbei, and Gelto gold deposits), with additional occurrences found in the Permian (Xinqu gold deposits) and Jurassic (Gongbei and Ge’ertuo gold deposits) strata. In zones of significant hematite mineralization, ore bodies also appear at the contact points between dykes and limestone. The ores can be classified into altered rock types and filled sedimentary rock types based on different modes of mineralization. Altered rock types include hematite-silicified carbonatite, metasomatic jasperoid rock, hematite-silicified conglomerate, and hematite-silicified granodiorite. Filled sedimentary rock types consist of hydrothermal metasomatic breccia, massive siliciclastic rocks, and fine-veined or reticulated silicified granodiorite-diorite. The ore-forming stages of the Dashui gold deposit, were identified in chronological order as the uralite-chlorite stage, the quartz-kaolinite stage, and the hematite-quartz-calcite stage.

The stratigraphic sequences that crop out in the Dashui gold deposit, from oldest to youngest, are Triassic argillaceous limestone, dolomitic limestone, Jurassic gray conglomerate, and Cretaceous purple-red gray conglomerate interbedded with sandy mudstone. The ore bodies are mainly hosted in the Triassic Maresonduo Formation crystalline limestone and along the fault contact between the limestone and granodiorite porphyry dikes. They generally trend east–west, exhibiting lenticular, vein-like, or pipe-like geometries, and can be traced for tens to hundreds of meters along strike, with thicknesses varying from a few meters to several tens of meters. The wall rock alteration is intense and zoned, strictly controlled by fault structures, and characterized by a medium to low-temperature mineral assemblage, including silicification, carbonatization, hematitization, and chloritization. Gold mineralization shows a strong temporal and spatial association with silicification, carbonation, and hematitization.

Commodity List

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

Mineral List

28 valid minerals.

Rock Types Recorded