Baishitai Au-Ag deposit, Quyang County, Baoding, Hebei, Chinai

Regional Level Types
Baishitai Au-Ag deposit	Deposit
Quyang County	County
Baoding	Prefecture
Hebei	Province
China	Country

Cryptoexplosive breccia-type gold-silver deposit.

Hosts reported resources totaling 249 t comprising 239 t Ag at 115 g/t, 4.5 t Au at 3.2 g/t, 5.5 Mt (Zn + Pb) at 2.1 wt%. Minor amounts of Cu, Mo, and Fe have also been documented, and further exploration activities are currently underway. The Baishitai deposit hosts skarn-type Pb-Zn-Ag-Cu mineralization, overprinted by shallow breccia-type epithermal Ag-Au-Pb-Zn mineralization. Hydrothermal alteration zoning from deep to shallow level is reflected by (1) chlorite-epidote ± illite, (2) illite-carbonate-quartz-montmorillonite, and (3) montmorillonite-carbonate-illite-quartz ± chlorite. In total, 26 ore bodies have been discovered in the mining area, of which 21 orebodies were discovered in the Yindongwa section. The 11 logged drill holes and 3 cross sections for geological description are documented in this contribution. These orebodies strike N-S and dip 60° to 85° E. They are irregular in shape, occurring as vein-like or lenticular bodies that generally thicken from north to south. The major mineralization consists of Ag, Au, Pb, and Zn, with minor amounts of Cu, Mo, and Fe. The 5 orebodies from the No. 20 exploration line are in the Gaogong section. These are vein-like, striking approximately NE-SW and dipping between 50° and 80° EW. The major metal commodities are Au, with minor amounts of Ag, Pb, and Zn.
Two types of mineralization are recognized in the Baishitai deposit. The breccia-type epithermal Ag-Au-Pb-Zn orebodies are hosted in a breccia pipe. The pipe extends > 200 m from east to west and > 700 m vertically, and dips steeply eastward. The epithermal Ag-Au-Pb-Zn orebodies contain discontinuous veins with thicknesses of 0.8–9.3 m. With average grades of 109.7 g/t Ag and 2.1 g/t Au, the breccia-type orebody extends ∼760 m in length and <500 m in depth. Skarn-type Zn-Pb-Ag-Cu ores are present at the contact between the microcrystalline albite porphyry and carbonate rocks, in the southeastern part of the Baishitai deposit. These orebodies extend ∼150 m in length and >500 m in depth, with an average thickness of ∼3 m. They are defined by average grades of 4.5 wt% (Zn + Pb), 36.6 g/t Ag, and 0.2 wt% Cu. The orebodies of the two mineralization types exhibit spatial overlap. Critically, skarn occurs as clasts within the epithermal breccia. Overall, breccia-type epithermal Ag-Au-Pb-Zn mineralization is pervasive with minor skarn-type Zn-Pb-Ag-Cu mineralization at Baishitai, and recent exploration has further revealed porphyry Mo mineralization at deeper depths. Skarn-type ore can be divided into three stages: 1) prograde stage, 2) retrograde stage, and 3) sulfide stage.

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References