Global spatio-temporal variations and metallogenic diversity of karst bauxites and their tectonic, paleogeographic and paleoclimatic relationship with the Tethyan realm evolution

Karst bauxites over the world have significant economic value and the geodynamic controls of their formation have attracted wide attention. 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. This study reviews the spatio-temporal distribution of karst bauxites and their geodynamic and paleoclimatic settings based on paleogeographic reconstruction of the Tethyan realm. 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. 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 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. 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. In the oceanic subduction phase, the arc volcanism provided abundant volcaniclastic materials, especially for the bauxite deposits on isolated carbonate platforms. In the arc accretion phase, weathered remnants were transported from complex nappes into intracontinental carbonate depressions. 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. 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.