![]() ![]() Ultra-high Ce anomalies in nodules are associated with Mn oxides, suggesting an enrichment in Mn oxide during the process of nodule formation. Bauxite samples mostly show positive Ce anomalies, indicating an oxidizing condition during deposition. Chondrite-normalized REE patterns of the nodules reflect enrichment in LREE compared to HREE and negative Eu anomalies. The nodules have a lower content of Rb and Cs that were easily depleted during the weathering process, and a higher content of Ga, Sc, V, Cr, Ni, Co, Pb and Th that enriches due to the occurrence of Fe-Mn minerals and zircon grains than the clayey soil. The nodules have higher ratios of Al/Si and stronger ferrallitization compared to the enclosing soil. Bauxite ores consist of gibbsite, kaolinite, hematite and goethite and few zircon and quartz. Iron-rich gibbsitic bauxite, located in the Yongjiang basin, southwestern part of South China Block, characterized by nodules mixed with loose clayey soil. These processes occurring within the similar favorable paleoclimatic background define a unified metallogenic system concomitant with Wilson cycle that explains the spatio-temporal distribution of karst bauxites in the Tethyan realm. The karst bauxite deposits originally formed in a specific tectonic stage were superimposed by later tectonic reworking, and were metamorphosed, or exposed, disrupted, eroded, redeposited and altered during later continental collision stage, whereas incipient bauxite accumulation restarted during post-collisional extension phase. In the arc accretion phase, weathered remnants were transported from complex nappes into intracontinental carbonate depressions. In the oceanic subduction phase, the arc volcanism provided abundant volcaniclastic materials, especially for the bauxite deposits on isolated carbonate platforms. In the continental extension phase, basement rocks were exposed to provide dominant materials for the formation of bauxite deposits on eroded carbonate platforms along continental margins. We identify common scenarios of diverse metallogenic models in specific geodynamic phases through a combined analysis of chronological data on detrital zircons and local sedimentological sequences. The spatial shift of bauxitization with time was controlled by the paleogeographic evolution of Tethys and the resulting changes of oceanic current circulation and paleoclimate. We show that karst bauxites were mainly formed in three orogenic domains: (1) the Ural-Central Asia belt, which formed at low paleolatitudes during the Cambrian through Devonian controlled by the Proto-Tethys and the Paleo-Asian Ocean, and later during Carboniferous and Cretaceous-Paleogene at mid-high paleolatitudes influenced by the heat transport from Paleo-Tethys and Neo-Tethys via seaways, (2) the Carboniferous to Permian Eastern Asia belt and westerly younger late Permian to Jurassic Turkey-Iran-Afghanistan-Pakistan belt formed in low paleolatitudes within the region of Paleo-Tethys, and (3) the Late Cretaceous-Paleogene Mediterranean belt and Neogene Caribbean belt controlled by the evolution of Neo-Tethys. This study reviews the spatio-temporal distribution of karst bauxites and their geodynamic and paleoclimatic settings based on paleogeographic reconstruction of the Tethyan realm. These deposits are distributed over a vast region in the Tethyan realm, formed in diverse geological times and tectonic settings under a relatively monotonous warm and humid paleoclimate. Karst bauxites over the world have significant economic value and the geodynamic controls of their formation have attracted wide attention. ![]()
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