GU Jing1, HUANG Zhi-Long1, JIN Zhong-Guo2, DING Ping3
(1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;
2. Guizhou Nonferrous Metal and Nuclear Industry Geological Exploration Bureau, Guiyang 550005, China;
3. No.5 Geological Team, Hebei Bureau of Geology, Tangshan 563000，China)
Abstract: The Wachangping Bauxite deposit is one of the largest deposits in the Wuchuan-Zheng’an- Daozhen alumina metallogenic province, and belongs to paleo-weathering of crustal sedimentary deposits. Bauxite occurs in sandstone and shale of the lower-middle Silurian Hanjiadian group (S1-2hj), or on the limestone surface erosion of the Upper Carboniferous Huanglong formation (C2h) . Ore controlling strata are middle Permian Liangshan Formation (P2l). Diaspore, boehmite, kaolinite, smectite and hematite are the major mineral components in the bauxite ore with small amounts of gibbsite, illite, goethite, pyrite, anatase, zircon, quartz and feldspar. The textural features of the ore suggest that the bauxite has an authigenic origin but locally underwent transportation and re-deposition. We can conclude that the main source of the Wachangping bauxite deposits is the underlying sandstone and shale of the lower-middle Silurian Hanjiadian formation (S1-2hj) in view of their similar chondrite-normalized REE patterns. The weathered Hanjiadian group was partly converted to bauxite by means of progressive in situ lateritic weathering. Factors such as type of parent rock, pH variation in weathering solutions, grain sizes of the minerals, groundwater chemistry, variation of Fe concentration in the weathering profiles, the degree of mineral leaching , and the geochemistry of elements present, play a significant role in the distribution of trace and REE during weathering of lateritic bauxite. Based on the mineralogical, petrographical and geochemical analysis, a four stage ore-forming processes is proposed.
Keywords: rare-earth element (REE) geochemistry; Wuchuan-Zheng’an-Daozhen area; Wachangping bauxite deposit; ore-forming process
Email: gujing@vip.gyig.ac.cn
ACTA MINERALOGICA SINICA Vol. 35, No. 2, 2015, Page 229-238
