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Dexing - Tongchang, Fujiawu, Zhushalong
Jiangxi, China
Main commodities: Cu Mo


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The Dexing copper district is located in Jiangxi Province in south-eastern China, ~365 km SSW of Nanjing. It contains three large porphyry copper deposits, Tongchang, Fujiawu and Zhushahong aligned within an 8 km northwest-southeast trending corridor. The Guanmaoshan gold deposit on the same line, lies between Fujiawu and Tongchang (#Location: Tongchang - 29° 0' 53"N, 117° 43' 45"E).

This deposit cluster lies within the South China Block, which is composed of the Yangtze Craton to the northwest and the Cathaysia Block in the southeast, separated by the early Neoproterozoic NE-SW trending Qinzhou-Hangzhou suture zone marking the amalgamation of the two blocks between ~1.1 Ga to 0.9 Ga. This same structural zone coincides with a zone of Mesozoic rifting. The principal structure in the eastern part of this suture zone is know as the Jiangshan–Shaoxing shear zone. The Dexing ore cluster is located on the southern margin of the Yangtze Craton, 50 km north of the Neoproterozoic Jiangshan-Shaoxing shear zone. The basement Yangtze Craton in this area is composed of Archaean to Proterozoic rocks. Phanerozoic cover over the Yangtze Craton comprises Cambrian to Early Triassic carbonates intercalated with clastic rocks, and Jurassic to Cretaceous clastic rocks, intercalated with volcanic rocks. The Cathaysia Block to the SE of Dexing has a Proterozoic basement composed of Sinian (Neoproterozoic) to Ordovician metasandstone and slate, overlain by Devonian to Permian carbonate rocks. Intercalated Jurassic clastic and volcanic rocks, as well as Cretaceous red-bed sandstones, occur in a series of NE-trending rift basins.

See also the more detailed regional setting section of the Yinshan porphyry-epithermal Cu-Au-Pb-Zn-Ag deposit record which is 25 km to the southwest and also part of the greater Dexing copper-gold polymetallic district.

The country rock sequence at Dexing comprises Mesoproterozoic low grade metamorphic rocks composed of alternating phyllite, slate, dacitic meta-tuff and meta-sandstone, overlain by thin Carboniferous to Permian marine sedimentary rocks.   These sequences were cut and overlain by 5 stages of Jurassic to Cretaceous Yanshanian magmatic activity, commencing with 193 to 190 Ma mafic to ultramafic intrusives, the ore related 196 to 172 Ma granodiorite, diorite, quartz-diorite and granite porphyries, 145 to 125 Ma dacitic volcanism and sub-volcanic intrusives, 127 to 103 Ma intermediate to acid volcanics and 100 to 96 Ma post mineralisation granite, granite porphyry, quartz porphyry and quartz-diorite.

Three pipe-like, NW plunging cupolas of granodiorite porphyry, ranging in size up to the largest at Tongchang which is some 1300 x 300 to 800 m at surface, host the three porphyry deposits. These have dimensions of ~0.7 km2 and 0.2 km2 at Tongchang and Fujiawu respectively and at surface outcrop as a swarm of dykes at Zhushahong. Each is surrounded by a 100 to 400 m wide hornfels zone and has a core rich in K feldspar, chlorite and hydro-muscovite.   The alteration is centred on the contact zone, grading inwards and outwards from strong quartz-sericite, to chlorite-sericite-(epidote)-carbonate-anhydrite to chlorite-epidote-illite-albite-anhydrite.   Ore is principally associated with strong quartz-sericite alteration, occurring as stockwork sulphide and quartz veins and disseminations of chalcopyrite and molybdenite with minor tennantite, tetrahedrite, bornite, chalcocite and electrum.   At Tongchang the orebody forms a 2500 m diameter cylinder with a barren core and extends down plunge for 1000 m.

Re-Os molybdenite ages from Tongchang of 170.4±1.8 Ma (Lu et al., 2005) is consistent with the granodiorite age of 171±3 Ma (Wang et al., 2004), indicating that the mineralization event occurred in the Middle Jurassic.

Reserves at Tongchang in 2003 amounted to 1.17 Gt @ 0.47% Cu, 0.01% Mo, 0.19 g/t Au at a 0.3% Cu cut-off for 5.2 Mt of copper and 215 tonnes of gold (Rui et al., 2005).

Measured reserves in 2000 are quoted by Mao et al. (2011), after Qian et al. (1996) as:
Tongchang - 1160 Mt @ 0.45% Cu, 0.01% Mo, 0.19 g/t Au, 0.9 g/t Ag, containing 5.2 Mt Cu, 0.128 Mt Mo, 215 t Au and 1279 t Ag;
Fujiawu - 520 Mt @ 0.5% Cu, 0.03% Mo, containing 2.57 Mt Cu, 0.168 Mt Mo;
Zhushahong - 145 Mt @ 0.42% Cu containing 0.6 Mt Cu.

For more detail consult the references below.

The most recent source geological information used to prepare this decription was dated: 1986.    
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.


Dexing

  References & Additional Information
   Selected References:
Bao, B., Webster, J.D., Zhang, D.-H., Goldoff, B.A. and Zhang, R.-Z.,  2016 - Compositions of biotite, amphibole, apatite and silicate melt inclusions from the Tongchang mine, Dexing porphyry deposit, SE China: Implications for the behavior of halogens in mineralized porphyry systems: in    Ore Geology Reviews   v.79, pp. 443-462.
He, W., Bao, Z. and Li, T.,  1999 - One-dimensional reactive transport models of alteration in the Tongchang Porphyry Copper deposit, Dexing district, Jiangxi Province, China: in    Econ. Geol.   v.94, pp. 307-323.
Hou, Z., Pan, X., Li, Q., Yang, Z. and Song, Y.,  2013 - The giant Dexing porphyry Cu-Mo-Au deposit in east China: product of melting of juvenile lower crust in an intracontinental setting: in    Mineralium Deposita   v.48, pp. 1019-1045.
Hou, Z., Zhang, H., Pan, X. and Yang, Z.,  2011 - Porphyry Cu (-Mo-Au) deposits related to melting of thickened mafic lower crust: Examples from the eastern Tethyan metallogenic domain: in    Ore Geology Reviews   v.39, pp. 21-45.
Li, L., Pei, N., Wang, G.-G., Zhu, A.-D., Pan, J.-Y., Chen, H., Huang, B., Yuan, H.-X., Wang, Z.-K. and Fang, M.-H.,  2017 - Multi-stage fluid boiling and formation of the giant Fujiawu porphyry Cu-Mo deposit in South China: in    Ore Geology Reviews   v.81, pp. 898-911.
Liu, X., Fan, H.-R., Evans, N.J., Batt, G.E., McInnes, B.I.A., Yang, K.-F., Qin, K.-Z.,  2014 - Cooling and exhumation of the mid-Jurassic porphyry copper systems in Dexing City, SE China: insights from geo- and thermochronology: in    Mineralium Deposita   v.49, pp. 809-819.
Liu, X., Fan, H.-R., Hu, F.-F., Yang, K.-F. and Wen, B.-J.,  2016 - Nature and evolution of the ore-forming fluids in the giant Dexing porphyry Cu-Mo-Au deposit, Southeastern China: in    J. of Geochemical Exploration   v.171, pp. 83-95
Liu, X., Fan, H.-R., Santosh, M., Hu, F.-F., Yang, K.-F., Li, Q.-L., Yang, Y.-H. and Liu, Y.,  2012 - Remelting of Neoproterozoic relict volcanic arcs in the Middle Jurassic: Implication for the formation of the Dexing porphyry copper deposit, Southeastern China: in    Lithos   v.150, pp. 85-100.
Mao, J., Cheng, Y., Chen, M. and Pirajno, F.,  2013 - Major types and time-space distribution of Mesozoic ore deposits in South China and their geodynamic settings: in    Mineralium Deposita   v.48, pp. 267-294.
Mao, J., Zhang, J., Pirajno, F., Ishiyama, D., Su, H., Guo, C. and Chen, Y.,  2011 - Porphyry Cu-Au-Mo-epithermal Ag-Pb-Zn-distal hydrothermal Au deposits in the Dexing area, Jiangxi province, East China - A linked ore system: in    Ore Geology Reviews   v.43, pp. 203-216.
Rui Z Y, Zhang L, Wu C, Wang L S and Sun X,  2005 - Dexing Porphyry Copper Deposits in Jiangxi, China: in Porter, T.M. (Ed), 2005 Super Porphyry Copper & Gold Deposits - A Global Perspective, PGC Publishing, Adelaide,   v.2 pp. 409-421
Wang, G.-G., Nia, P., Zhao, C., Chen, H., Yuan, H.-X., Cai, Y.-T., Li, L. and Zhu, A.-D.,  2015 - The link between subduction-modified lithosphere and the giant Dexing porphyry copper deposit, South China: Constraints from high-Mg adakitic rocks: in    Ore Geology Reviews,   v.67, pp 109-126.
Wang, Q., Xu, J.-F., Jian, P., Bao, Z.-W., Zhao, Z.-H., Li, C.-F., Xiong, X.-L. and Ma, J.-L.,  2006 - Petrogenesis of Adakitic Porphyries in an Extensional Tectonic Setting, Dexing, South China: Implications for the Genesis of Porphyry Copper Mineralization : in    J. of Petrology,   v.47, pp. 119-144.
Yu Chungwen  1981 - Mechanisms of ore formation and preliminary dispersion at the Dexing porphyry copper deposit, Jiangxi and their implications in geochemical exploration: in    J. of Geochemical Exploration   v15 pp 115-137
Zhong, J., Chen, Y.-J. and Pirajno, F.,  2017 - Geology, geochemistry and tectonic settings of the molybdenum deposits in South China: A review: in    Ore Geology Reviews   v.81, pp. 829-855
Zhou Q, Jiang Y-H, Zhao P, Liao S-Y, Jin G-D, Liu Z and Jia R-Y,  2012 - SHRIMP U-Pb Dating On Hydrothermal Zircons: Evidence For An Early Cretaceous Epithermal Event In The Middle Jurassic Dexing Porphyry Copper Deposit, Southeast China : in    Econ. Geol.   v.107 pp. 1507-1514


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