Petrological and geochemical constraints on tectonic settings of the Late Carboniferous-Early Permian, Central Junggar, China

摘要

It is assumed that the central part of Junggar underwent continuous deposition from the Mesozoic to Cenozoic, but few data are available from deep well to support this hypothesis. The tectonic settings of the late Paleozoic central region have been used to focus on the folded mountain belts around the Junggar Basin. In this study, petro-geochemical and lithological characters of drilling samples in Upper Carboniferous-Lower Permian of the Central Junggar Basin were discussed, through core and thin section identification, major and trace element analyses. The results reveal the following: (1) Brown tuff is present in various layers of these well, suggesting a eruption environment around sea/lake; (2) the volcanic rocks in the study area are mainly included alkali-basalts, andesites and small amounts of dacite. Most samples characterized by high alkali that likely erupted from thickened crust, (3) suggesting a continental tectonic setting, and the Central Junggar Basin was part of a continental tectonic setting during the late Paleozoic. These results suggest that there may be a more ancient continental basement below the Carboniferous volcanic rocks.