Woxi Mines (Wuxi Mines; Xiangxi Mines; Xianxi Mines), Yuanling Co., Huaihua, Hunan, Chinai

Regional Level Types
Woxi Mines (Wuxi Mines; Xiangxi Mines; Xianxi Mines)	Group ofMines
Yuanling Co.	County
Huaihua	Prefecture-level City
Hunan	Province
China	Country

The Woxi deposit was discovered in 1875 and since then has been continuously exploited. Reserves amount to 1.76 million tons of ore, grading at 12.98 g/t Au, 6.45% Sb and 0.47% WO3. Currently, about 800 tons of ore is mined and processed per day. There are several mines in the area, including Hongyanxi, Lijiaxi, Shangwoxi (Upper Woxi), Shilupenggong, Sujiaxi, and Yuershan.

Country rocks are Proterozoic low-grade metamorphic rocks, comprising the Lengjiaxi group (base) with sandy, greyish green slates and locally phyllites, and the Banxi group (top), consisting of (a) the Madiyi Formation of red slates, locally interbedded with sandy rocks and sandstones, and (b) the Wuqiangxi Formation of sandy, greyish green slates, arkoses and sandstones. The Madiyi Formation is a very important host unit for gold deposits in northwestern Hunan. The mineralization is controlled by the E-W striking Woxi thrust fault and by anticlines and synclines. At the fault, the older Madiyi Formation dips below the younger Wuqiangxi Formation. To the southwest, the Lengjiaxi Group is disconformably overlain by the Madiyi Formation. The stratabound orebodies occur in red slates of the Madiyi Formation and may be associated with a magmatic intrusion.
The Woxi deposit contains 9 auriferous quartz lodes in the shape of stratiform, tabular, and lenticular, which occurred discontinuously in interlayer fracture zones subparallel to the Woxi fault and distributed in Hongyanxi, Yu’ershan, Lijiaxi, Shiliupenggong, and Shangwoxi ore zones. The auriferous quartz lode consists of the banded lode that parallels to the bedding of the wall rocks, and discordant lode that occurs in the joints of the host rocks, showing open-space filling structures, and intersects with the banded lodes at a high angle. Wall rock alterations in the Woxi comprise bleaching, sulfidation, sericitization, silicification, carbonatization, and chloritization. Bleaching, or color fading, is the most remarkable type of alteration recorded as a direct indicator for prospecting at Woxi. It occurred mainly in the interlayer fractures of the purplish-red sericite slate and sandy slate, and formed pale grey bleached alteration halos with a width range of a few to 30 cm, accompanied by the conversion of hematite in the fresh host rocks through siderite to pyrite in the alteration halos.

The primary type of mineralization is the quartz veins of more than 50 cm, which occurs in the interlayer shear zones, accounting for 70 % of the total mineral resources. This type of mineralization has been the main high-grade veins exploited in the past, with grades reaching up to 20 g/t, such as V3-1. The network vein type, altered shale type, and fragmented breccia type in the secondary fractures on both sides of the interlayer shear zones account for about 30 % of the total mineral resources. These lower-grade veins (generally less than 3 g/t) have been increasing in proportion in recent years. The main thick interlayer veins are generally trending approximately east–west and dip gently to the north (dipping angle 20° to 30°). The dip direction tends to extend deeper than the strike extension, and their attitude changes locally with folding. The main types of ore include gold-quartz type, antimony-gold-quartz type, tungsten-gold-quartz fine vein type, and gold-antimony-tungsten altered slate type.

The ore bodies are mostly hosted by the purple-red slate of the Madiyi Formation, and most of the ore bodies are vein-type, which are parallel to the strata. There is no magmatic rock exposure in the deposit. Previous investigations categorize the mineralization into four stages: the scheelite-wolframite-quartz stage, pyrite-gold-quartz stage, stibnite-gold-quartz stage and carbonate-quartz stage.


Notes:
(1) Xiangxi (sometimes erroneously spelled Xianxi) is a misnomer. This term generally refers to Western Hunan Province. Papers on a "Xiangxi Sb-W-Au deposit" are in fact mostly dealing with the Woxi deposit, but this is not necessarily the case.
(2) Papers variously refer to the locality as a deposit or an ore field.
(3) The grid reference is centered on the area.

Other Regions, Features and Areas containing this locality

References