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Xiangshan District - Zhoujiashan, Shazhou |
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Jiangxi, China |
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U
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Xiangshan uranium field is located in Jiangxi province, south-eastern China. It comprises over 20 separate deposits which together account for more than 26 000 tonnes of contained U3O8.
The field is located south of the suture between the Yangtze and Cathaysia tectonic blocks. It is associated with a ~600 km wide belt of volcano-intrusive complexes which parallels to the current coastline, believed to be reflect an extensional back-arc basin related to subduction of the paleo-Pacific plate which lay to the east. Late Mesozoic magmatic activity in the belt took place in three major stages, namely 180160, 160135 and 13590 Ma. A number of Cretaceous to Tertiary red-bed basins were developed in association with the with the youngest phase of this regional magmatism as north-east trending basins filled with red clastic sedimentary rocks, accompanied by marl, gypsum and evaporites, that are locally interbedded with volcanic rocks. These basins are largely situated to the north-west of the volcano-intrusive complexes.
The Xiangshan uranium field is part of the larger Gan-Hang uranium belt which overlaps one of these red-bed basins, the Gan-Hang basin. Early Cretaceous (104 to 99 Ma) bimodal shoshonitic mafic-felsic magmatism took place within the Gan-Hang basin, as well as a series of dyke swarms of 105±1 Ma granite porphyry which intrude the Early Cretaceous red beds.
Volcanic rocks in the Xiangshan district correspond to a resurgent caldera, part of the belt of volcanic-intrusive complexes that lie along the NE-SW trending Shi-Hang tectonic zone. The caldera is elongated east-west with approximately dimensions of 26x16 km, developed on a basement of mainly of Paleo- to Mesoproterozoic amphibolite, schists, and granulites, and Sinian (~700 Ma) phyllites, slates and metasandstones. To the north-west, the caldera is overlain by Cretaceous red beds of the Gan-Hang basin. The main volcanic activity was during the Late Jurassic (149135 Ma), represented by rocks which include crystal tuff, welded tuff, rhyolite, porphyritic lava, and monzogranite and syenogranite porphyries, cut by a series of ring faults and fracture zones. A lamprophyre dyke, dated at 109±3 Ma, was intruded into the volcanic rocks in the western part of the caldera, co-eval with the shoshonitic magmatism in the Gan-Hang basin.
Uranium mineralisation within the Xiangshan caldera is largely controlled by regional NEtrending faults and local ring faults, predominantly hosted by porphyritic lava (the Zhoujiashan-type deposits) and monzogranite and syenogranite porphyries (the Shazhou-type deposits).
At the Zhoujiashan mine, where several uranium orebodies are hosted by rhyolit rocks, the uranium mineralisation occurs as hydrothermal veins within fracture zones near NE-trending faults. Seven clusters of veins are known, distributed over a lengths of 500 to 2000 m and widths of 200 to 300 m. The largest single vein is 400 m long and 5 m thick.
The Shazhou-type deposits, 12 km to the north-east of Zhoujiashan, are localised along the contact zone between syenogranite porphyry and either siltstones or Sinian metamorphic basement. The individual orebodies occur in fracture zones within the syenogranite porphyry near the contact, although some uranium bearing veins extend outward into the country rocks. Individual veins vary from several metres to tens of metres in length and are from 0.3 to several metres in thickness, the largest being is 350 m long and 20 m in thickness.
The uranium deposits of both types are accompanied by intense hydrothermal alteration, developed in four stages, as follows:
i). Pre-uranium alkali-metasomatism, represented by albite, calcite, chlorite and minor illite sandwiching the fracture zones.
ii). Pitchblende-apatite-chlorite veins accompanying the early uranium mineralisation stage, infilling fractures cutting the pre-mineralisation alteration zones.
iii). Pitchblende-fluorite-illite veins which represent both the most intense illite alteration and main stage of mineralisation. This phase has been dated at about 98 Ma, some 30 m.y. younger than the eruption of the host volcanic rocks but coincident with the regional extension, shoshonitic volcanism, and lamprophyre dyke emplacement.
iv). Post-mineralisation fluorite-illite, calcite-chlorite and minor chalcedony veins.
The most recent source geological information used to prepare this decription was dated: 2007.
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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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.
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Yao-hui Jiang, Hong-fei Ling, Shao-yong Jiang, Wei-zhou Shen, Hong-hai Fan and Pei N 2006 - Trace Element and Sr-Nd Isotope Geochemistry of Fluorite from the Xiangshan Uranium Deposit, Southeast China: in Econ. Geol. v101 pp 1613-1622
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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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