New zircon U-Pb geochronological and geochemical data reveals the earliest Cretaceous tectonic shift event in the Lanqi Basin, Inner Mongolia, northern China

1.Objective The Lanqi Basin about 790 km2 in size is located in the Zhenglan Banner area,to the south of the Erlian Basin,and it is not only the tectonic transition region between the North China Craton and the Xingmeng orogenic belt,but also the area between the Great Khingan Mountains volcanic belt and the northern Hebei-western Liaoning volcanic belt.Its key tectonic location involves the Paleo-Asian Ocean,the Mongol-Okhotsk suture zone and the transition of the Paleo-Pacific tectonic domain,which should be paid more attention to.What's more,the Lanqi Basin is controlled by two groups of faults in the NE and NW directions,respectively.Among them,the NW faults are mainly small in scale,while the NE faults are basement faults those are the main controlling fault for volcanic eruption.

Provenance of the Early Permian bauxitic claystone in Huayingshan region,Sichuan Basin,South China:Constraints from U-Pb ages and trace elements of detrital zircons

The Early Permian bauxite in the Sichuan Basin is an important part of karst-type bauxite deposits in South China Block and its provenance is poorly understood.Here we present results of mineralogy,wholerock geochemistry,detrital zircon U-Pb ages and trace element compositions of the bauxitic claystone from the Lower Permian Dazhuyuan Formation and those of the siltstone from the underlying Lower Silurian Hanjiadian Formation in Huayingshan region,Sichuan Basin,South China Block to constrain the provenance of the bauxitic claystone.Detrital zircons from bauxitic claystone and siltstone have similar age spectra,and the ages of bauxitic claystone are classified into five groups of 2600-2200 Ma,1800-1600 Ma,1200-900 Ma,900-650 Ma,and 650-400 Ma respectively.Those of the siltstone are classified into four groups of 2600-2200 Ma,1200-900 Ma,900-650 Ma,and 650-400 Ma respectively.We propose that the bauxitic claystone in the study region has mixed sources:the siltstone of the Lower Silurian Hanjiadian Formation probably constitutes the dominant source,and the Late Paleoproterozoic magmatic rocks along the western margin of the Yangtze Block are probably the secondary source.Moreover,the source materials of the Hanjiadian Formation siltstone are mainly sourced from Grenville-aged magmatic rocks in the Cathaysia Block and Neoproterozoic magmatic rocks in the Jiangnan orogen,with minor contributions from the underlying clastic sediments in the Cathaysia Block and Pan-African magmatic rocks in the orogen in eastern Gondwana.