科研之友
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摘要
The bauxite ore deposits are mainly found around the Az Zabirah area in the central northern part of Saudi Arabia. The age of the Az Zabirah bauxites was suggested as Cretaceous. The bauxite profile extends similar to 125 km along strike of the overlying rock units with some erosional discontinuities and is about 6 m thick in average. Discontinuous character of the Az Zabirah bauxite deposits led to identification of three zones: north, central and south. These three zones show some differences in lithology and petrology. The bauxite ore may be hard or soft, porous or dense, stratified or mottled in texture, and gray, brown, yellow, red, violet or pink in colour. Most of the Az Zabirah bauxite ore deposits occur near the Earth's surface. The south zone bauxite deposits were pisolitic-oolitic with some other colloformic textures related to bauxitization processes. Bauxitic, secondary kaolinitic and calcitic cements were recorded. Iron oxides and/or iron oxy-hydroxides were detected as coating materials for the floating pisoliths and ooliths. Mineralogically, the major minerals were gibbsite, boehmite, diaspore, kaolinite, hematite, quartz and calcite, while anatase, zircon and rutile were found as minor minerals in these bauxite deposits. Genesis and environmental condition of the Az Zabirah bauxite formation occurred during Cretaceous times by the processes of bauxitization (lateritization). Throughout the Cretaceous, the Az Zabirah was very close to the paleo-equator where tropical climate was prevailing. The main factors controlling the formation of the Az Zabirah bauxite were likely to be tectonic, lithostratigraphic and climatic.
- 出版日期2015-4
