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Huayuan District - Dong Li, Lomichang, Laozibao-Banpo-Ma Chang, Malichang, Paiwu |
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Hunan, China |
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Pb Zn
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Super Porphyry Cu and Au
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The Huayuan district near the border between the provinces of Hunan and Guizhou in southern China contains a number of small carbonate hosted lead-zinc deposits within Lower Cambrian carbonate rocks. Mineralised localities include Dong Li, Lomichang, Laozibao-Banpo-Ma Chang, Malichang and Paiwu.
The Cambrian sequence were deposited on a passive continental margin on the south-east rim of the Precambrian Yangtze plate, centred on a long lived structure, the NNE Jiangshao suture zone/regional strike-slip fault which separates the Yangtze and Huaxia plates. These carbonates were characterised by a complex system of carbonate platforms, ramps, slopes and basins. The sequence includes siliciclastic and marly shales, some of which are strongly bituminous, followed by the ore bearing carbonate sequence reflecting a ramp setting with local mounds and restricted platform environments, overlain by cyclically alternating Middle and Upper Cambrian carbonate successsions and siliciclastics. These were overlain by a thick Ordovician sedimentary pile which was uplifted in the Silurian to form an orogenic zone, later covered by Silurian terriginous sediments.
The Huayuan ore district is bounded to the west and east by major fault structures and is characterised by NE to NNE folds and by SE dipping, NE to NNE trending reverse/strike slip faults.
The mineralised carbonates are divided into four units containing cyanobacterial mounds associated with oolitic intramound deposits. The upper two units that are the ore bearing horizons are composed largely of cyanobacterial mound limestones, grainstones and packstones, with shoal facies oolitic and oncolitic grainstones to packstones on the flanks of the mounds, and calcareous mudstones with intercalated breccias on the outer slopes to the east. Lagoonal to tidal calcareous and dolomitic, mainly peloidal grainstones, often with laminated fenestrae are found to the west and over the prograding mounds.
These ore bearing carbonates form an eastward thickening (to 200 m) wedge-shaped lens that extends for 100 km along the NNE trending platform margin. The mineralised belt has an irregular width that may range up to 4 km, and contains ore as stratabound horizons which lack well developed lateral continuity.
Mineralisation occurs as open space filling of voids, breccia cement, and replacement of the host carbonates. The ore mineralogy comprises sphalerite, minor galena and traces of marcasite and pyrite. Gangue minerals include several generations of calcite and dolomite, barite and minor fluorite, while organic matter is ubiquitous as bitumen, organic compounds within fluorite and calcite and gaseous hydrocarbons in fluid inclusions. Sulphides have been deposited in two phases, 1). cockade type sphalerite (concentric bands of brown to yellow sphalerite surrounding breccia clasts) with pyrite-marcasite, fluorite with galena, barite and calcite, and 2). less important rosette sphalerite concretions with saddle dolomite and pyrobitumen.
Proven reserves in the larger deposits only amount to a "few million tonnes" of ore with a grade never exceeding 8% Pb+Zn.
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2002.
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.
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Selected References:
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Schneider J, Boni M, Lapponi F, Bechstadt T 2002 - Carbonate-hosted Zinc-Lead deposits in the lower Cambrian of Hunan, South China: a radiogenic (Pb, Sr) isotope study: in Econ. Geol. v97 pp 1815-1827
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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, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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