Hunan, China

Main commodities: Sb
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The Xikuangshan Sb deposit, is one of the world's largest antimony resources. It is located in the northern part of Xiangzhong Basin, near Lengshuijiang City, Hunan Province, P.R. China.

The Xiangzhong Basin hosts to the Xikuangshan Sb deposit were deposited on a passive continental margin. Pull-apart fault subsidence associated with a series of NE-trending tensional faults led to sedimentation on the shallow marine platform and intra-platform troughs with repeated transgression and regression throughout the Devonian. The immediate host to the ores was deposited during the last and largest transgression, which led to the development of an anoxic environment.

Regionally distributed, weakly metamorphosed pre-Devonian rocks within the same basin, have high Sb backgrounds and a thickness exceeding several kilometers. Numerous smaller Sb deposits and prospects are also known, mainly to the west of the Xikuangshan Sb deposit. Intrusions and stocks of Caledonian, Indosinian, and Yanshan stage sialic rocks occur in the area. The Upper Devonian (Frasnian Epoch) Shetianqiao Formation of the Xiangzhong Basin is dominated by a black shale series, consisting of black shale, marl, and limestone, with a mean organic carbon content of 0.97%. The Shetianqiao Formation, which hosts the Xikuangshan deposit and many other small Sb deposits is regionally enriched in Sb.

The Xikuangshan deposit covers an area of about 16 sq. km, following the axis of a short anticline that strikes at 30° and plunges both north and south. It is also localised at the intersection of the NNE-trending Chengbu-Xinhua fault, and the NW-trending Shuangfeng-Xikuangshan fault. The host Shetianqiao and adjacent Xikuangshan Formations occur in the core of the anticline, surrounded by the Lower Carboniferous Yanguan and Datang Formations.

The Xikuangshan Sb deposit is hosted by a dark grey chert in the black shale series of the Shetianqiao Formation and is cut by the No. 75 fault. The deposit is exploited by the south mines (Feishuiyan and Wuhua) and the north mines (Laokuangshan and Tongjiayuan), which are all located on the east limb of the anticline. A 10 km long lamprophyre dyke occurs to the southeast.

The 287 m thick host Shetianqiao Formation can be divided into three parts: i). the upper 20 m thick Laojiangchong member composed mainly of greyish black dolostone, limestone and shale; ii). the middle 217 m thick Qilijiang member, the most important ore-bearing unit; and iii). the lower 50 m thick Longkouchong member comprising mainly sandstone and intercalated black shale, locally with a stibnite chamber orebody near the footwall of the No. 75 fault.

The main ore-bearing sequence in the middle Qilijiang member of the Shetianqiao Formation consists of 27 sub units grouped into two parts, namely:
i). the 45 m thick upper part, composed mainly of interbedded greyish black bioclastic micrite, black chert, and shale with the two largest ore beds (I) and (II), and secondary ore veins (III). Ore bed I, which is located in sub-units 1-6, is stratabound, extending for several hundreds to thousands of metres and is up to 2.5 m in thickness. Ore bed II, which comprises 4-5 m ore beds and lenses, is hosted by sub-unit 7. The two ore beds occur in chert layers and constitute 80% of the total Sb reserves of the deposit.
ii). The 172 m thick lower part, consists of interbedded greyish black bioclastic and micritic limestone, black shale and chert. The mean organic carbon content of these rocks is 0.85%. Mineralisation occurs in veinlets, vugs, and radiating fascicles concentrated in different layers of chert, which coalesce to form ore bed III, along the footwall of the major fault cutting the deposit.

Ore textures range from massive to disseminated, and from drusy to coarsely crystalline. Stibnite is the only ore mineral. Trace amounts of pyrite, pyrrhotite and sphalerite are found in the ore along with the main primary gangue minerals of quartz and calcite, and secondary barite and fluorite. Ores can be divided into four types: i). quartz-stibnite ore, ii). calcite-stibnite ore, iii). barite-quartz-stibnite ore, and iv). fluorite-quartz-stibnite ore. The first two types are the most important and occupy 90% of the total Sb reserves of the deposit.

In 1980 geological reserves calculated were approximately 21 Mt @ 2.7% Sb at a 0.7% Sb cut-off. Mining reserves were 11.5 Mt @ 3.5% Sb. Production to that date had totalled 53 Mt.

For detail consult the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 2003.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Delian Fan, Tao Zhang and Jie Ye  2004 - The Xikuangshan Sb deposit hosted by the Upper Devonian black shale series, Hunan, China: in    Ore Geology Reviews   v24 pp 121-133
Fu, S., Hu, R., Yin, R., Yan, J., Mi, X., Song, Z. and Sullivan, N.,  2020 - Mercury and in situ sulfur isotopes as constraints on the metal and sulfur sources for the world’s largest Sb deposit at Xikuangshan, southern China: in    Mineralium Deposita   v.55, pp. 1353-1364.
Wu Jiada  1993 - Antimony vein deposits of China : in    Ore Geology Reviews   v8 pp 213-232

Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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