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Ashele |
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Xinjiang, China |
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Zn Cu Ag Au
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Super Porphyry Cu and Au
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The late Palaeozoic Ashele volcanogenic massive sulphide Cu-Zn deposit is located in Xinjiang, Northwestern China. It is believed to be within the same magmatic belt as the similar Palaeozoic deposits at Rudny Altai district some 300 km to the northwest in Kazakhstan.
The deposit is hosted within a suit of bimodal submarine volcanic rocks of the Lower-Middle Devonian Ashele Formation formed in an environment of paleocontinental margin rifting.
Lensoid orebodies are developed above a footwall spilitic rocks and below quartz-keratophyric tuff in the hanging wall.
Zonation of metallic elements in the deposit is said to be typical of volcanic-related stratabound Cu-Zn sulphide deposits found elsewhere in the world. Black ores enriched in Pb, Zn and Ag are found at the top of the No.1 orebody; yellow ores enriched in Cu occur in the middle part, with a chalcopyrite stringer zone is evident below the massive sulphides.
A zonation of ore-structure is also observed in the No.1 orebody, corresponding to the zoning of elements, i.e. lamellar and/or banded sulphide-sulphate ores occur at the top; massive sulphide ores in the middle, and stockwork veinlets associated with an altered breccia pipe in the footwall.
Four phases of mineralisation have been recognised, namely: i). the initial massive sulphide deposition representing the main phase of mineralisation; ii). subsequent suphides have subjected to thermal-metamorphism; iii). superimposed hydrothermal mineralisation; and iv). weathering or oxidation of the primary sulphide ores.
The domiant mineralogy comprises pyrite, chalcopyrite, sphalerite, tetrahedrite, galena, barite, quartz, chlorite, sericite and calcite, making up the various types of ores.
The quoted resource is approximately 30 Mt @ 3.5% Zn, 2.7% Cu, 101 g/t Ag, 0.3 g/t Au, although the total resource may exceed 45 Mt (Wang Denghong, 2003).
Zijin Mining, 2007, reported reserves to the Hong Kong stock exchange of 0.919 Mt Cu at a grade of 2.43% Cu and 0.408 Mt of Zn from ore with a grade of 1.08% Zn, which would equate with an ore tonnage of 37.75 Mt.
The most recent source geological information used to prepare this decription was dated: 2006.
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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Han, C., Xiao, W., Zhao, G., Mao, J., Li, S., Yan, Z. and Mao, Q., 2006 - Major types, characteristics and geodynamic mechanism of Upper Paleozoic copper deposits in northern Xinjiang, northwestern China: in Ore Geology Reviews v.28, pp. 308-328.
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Han, C., Xiao, W., Zhao, G., Su, B., Sakyi, P.A., Ao, S., Wan, B., Zhang, J., Zhang, Z. and Wang, Z., 2014 - Mid-Late Paleozoic metallogenesis and evolution of the Chinese Altai and East Junggar Orogenic Belt, NW China, Central Asia: in J of Geosciences, v.59, pp. 255-274.
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Pirajno, F., Seltmann, R. and Yang, Y., 2011 - A review of mineral systems and associated tectonic settings of northern Xinjiang, NW China: in Geoscience Frontiers v.2, pp. 157-185.
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Wang, D., 2003 - Geology, geochemistry and geodynamics of the Ashele VHMS Cu-Zn deposit, Northwestern Xinjiang: in Mao, Goldfarb, Seltmann, Wang, Xiao and Hart (Eds.), 2003 Tectonic Evolution and Metallogenesis of the Chinese Altay and Tianshan, Proceedings Volume of the International Symposium of the IGCI – 473 Project in Urumqi and Guidebook of the Field Excursion in Xinjiang, China: August 9-21, 2003 IAGOD Guidebook Series 10: CERCAMS/NHM London, pp 153-168
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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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