Relationships between Meso-Cenozoic denudation in the Eastern Tian Shan and uranium mineralization in the Turpan-Hami basin, NW China: Constraints from apatite fission track study

Abstract

The Eastern Tian Shan tectonic belt, located in the southern domain of the Central Asian Orogenic Belt, consists of the Bogda mountain range, Turpan-Hami (Tuha) basin and Choltagh mountain range from north to south. Understanding the Meso-Cenozoic denudation history of the Eastern Tian Shan is critical to unravel the genesis of sandstone-type uranium (U) mineralization in the Tuha basin. In this paper, thirteen granite and sandstone samples were collected along two north–south transects in the west of the Eastern Tian Shan for apatite fission track thermochronological study. The apatite fission track ages obtained in this study, in combination with the thermal history modeling results and previous thermochronological data, indicate three main episodes of denudation in the Eastern Tian Shan since the Mesozoic, i.e., Late Jurassic to Early Cretaceous (160–135 Ma), Late Cretaceous to Early Eocene (100–50 Ma) and Late Eocene to Early Miocene (35–20 Ma). The Late Cretaceous denudation events are related to the Kohistan-Dras arc accretion-collision that affects the Tian Shan mountain range extensively, whereas the Cenozoic ones are related to the India-Asia collision. Regional distribution of apatite fission track ages in the Eastern Tian Shan and comparison with U mineralization ages in the Tuha basin suggest that the Choltagh mountain range began to denudate in the Late Jurassic, exposing high U-bearing volcanic rocks on the surface and resulting in significant U mineralization in the southern part of the Tuha basin in the Cretaceous, whereas the Bogda mountain range in the north did not experience significant denudation until the Late Eocene. Due to the relatively low exhumation of the Bogda mountain range and limited exposure of U-bearing rocks, U mineralization in the Tuha basin is minor during the Cenozoic, but the newly deposited sediments helped the preservation of the U deposits that were formed in the Cretaceous.