In 2016, Eldorado Gold Corporation sold its 82% interest in the Jinfeng Gold Mine to a subsidiary of China National Gold Group Corporation (CNGC). Following this transaction, CNGC became the sole owner of the Jinfeng Gold Mine.
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Summary:
The Jinfeng deposit has many geological and geochemical characteristics in common with the renowned sediment-hosted deposits of the Carlin district in the western United States, and is best classified as a Carlin-like gold deposit.
In contrast to the Carlin deposits, zones of quartz veins spatially associated with mineralization are common at Jinfeng. In addition, the Jinfeng deposits (and other sediment-hosted deposits in the region) lack any evidence for spatially or genetically associated intrusions.
The Jinfeng Deposit is a sediment-hosted disseminated gold deposit showing strong elements of structural and stratigraphic control. Nearly all of the known gold resource occurs within or adjacent to major fault zones (F2, F3, and F6), or secondary faults either splaying from or linking with these structures. Overall, the deposit occurs as a steeply dipping tabular body, with a long axis plunging shallowly to moderately to the east-southeast. The deposit extends over 1,200 m along this axis, has a vertical extent of up to 1,100 m, and a thickness typically ranging from 10 m to 50 m.
High-grade shoots within the deposit are spatially associated with intersections between the controlling fault zones and either secondary faults or lithologically favourable sandy beds in the Bianyang and Xuman Formations. Gold is commonly localized along east-west striking segments of either the main controlling faults or secondary structures. The ore shoots typically plunge moderately to the east-southeast, parallel to the overall deposit axis, to fold axes, and to fault intersections. Within the F3 fault zone, high grade pods often show a right-stepping enechelon geometry in plan view, with well mineralized associated older fault segments linked and offset by northeast-dipping minor thrust faults.
Gold mineralization is typically associated with highly carbonaceous gouge material or cataclastic breccia, but is also concentrated within more intact sandstone layers adjacent to structurally disrupted zones. Quartz and sulphide (pyrite, arsenopyrite) veins are common, occurring as either steeply-dipping or shallowly-dipping sheeted sets preferentially within sandstone beds. Quartz-rich veins contain trace amounts of dolomite, and become more carbonate-rich distal to mineralization.
Sulphides present in mineralized zones are pyrite, arsenopyrite, cinnabar, stibnite, orpiment, and realgar. Petrographic analyses document arsenic-pyrite overgrowths common on pyrite cores in mineralized zones. Trace amounts of cinnabar, stibnite, orpiment, arsenopyrite, and galena are also associated with pyrite overgrowths.
In mineralized areas, alteration is typically weak, and includes dolomitization of calcite, sericite+clay alteration of matrix material, and minor introduction of secondary quartz.
Mineralized zones also have elevated arsenic, mercury, and antimony concentrations, with arsenic commonly forming broad halos surrounding ore zones. Gold is introduced late in the deformation sequence at Jinfeng, as evidenced by mineralization localized along minor thrust faults formed during the latest period of contractional deformation.
The major fault network (F2, F3, F6) was well established at this time, and the fault zones served as primary hydrothermal conduits during mineralization, due to their high degree of structural permeability. This permeability may also have been enhanced by syn-mineral fault reactivation. The age of the mineralization is constrained by rhenium-osmium (Re-Os) dating of arsenian pyrites to be 193+/-13 Ma (Chen et al., 2007).