The Study On Mineralization Regularity And Geological Features Of Gibbsite Deposits In Cential Guangxi

The gibbsite-type bauxite deposits of Central Guangxi are located in thesouthwest of South China plate. It is the unique large gibbsite-type bauxite deposit inChina. Since its discovery in the1980s, its ore-forming conditions and metallogenicregularity have been studied in detail. Nonethless, the sequence stratigraphy, thecomposition and migration of the geochemical elements, ore-forming materialssources and ore-forming process research are insufficient. This paper studies thedeposit through field geological investigation and laboratory study. We separate theore into different grain size. And then study the feature and the contact betweenlaterate and ore, and ore in different grain size.The gibbsite, which is hosted within the Quaternary ferrallitic soil, aredistributed in the low hilly area, low hills and platform of Karst plains. The orebodiesare characterized by stratiform and stratiform-like. From bottom to top, thestratigraphic sequence of the orebodies are floor carbonate, clay, bauxite layer,surface soil in turn, and due to the late geological transformation, different sequencesare formed in the later periodlate stage. In the process of the formation andpreservation, bauxite was affected by topography.We do separate research of laterite and ore samples, with a microscope, X-raydiffraction, differential thermal and environmental method such as scanning electronmicroscopy （sem） analysises, find that main mineral composition of the clay samplesare similar to the ore samples’, that main mineral composition are gibbsite, kaolinite,hematite, and a small amount of quartz, zircon etc.Geochemical composition analysises show that: the clay and constant elementsin ore samples are characterized by Al2O3, Si_O2, Fe₂O₃and ignition loss, but there is alarge difference; In the clay, the content of Al2O3, Si_O2between30-40percent,andthe Fe₂O₃is about12percent; But in the ore samples, the content of Al2O3and Fe₂O₃are30percent and40percernt, the Si_O2is about12percent; Trace elements varyconsiderably between different samples; they Obviously enrich the REE; Malingdeposit and Shiya deposit are the most enrichment deposits; there are some differences between Ce anomaly in different mining area, also, in the ore samples thatcome from the same deposit.By analyzing material sources with stable elements ratio and zircon dating, wefind floor carbonate and rocks which are distributed in Central Guangxi andsurrounding are important sources of the ore-forming materials of gibbsite in CentralGuangxi.Comprehensive analysis of the sequence orebody, spatial variation of the oreparticle size， characteristics of the ore texture and structure, geochemicalcharacteristics and other factors， the process of mineralization is preliminarysummarized. It includes the primitive accumulation of ore, ore crushing and mixedwith clay, disspation of the ore.