Jurassic provenances and their transition mechanism of the Delingha Sag in the eastern segment of northern margin of the Qaidam Basin, North Tibet

Abstract

The Delingha Sag that witnessed the Indosinian, Yanshanian and Himalayan orogenies since the Mesozoic, is a potential petroliferous Meso-Cenozoic sag located in the eastern segment of the northern margin of the Qaidam Basin in North Tibet. Surrounded by orogenic belts in the north and south boundaries, and by strike-slip faults sub-parallel to the Altyn Mountains in the east and west boundaries, the Jurassic provenances of the Delingha Sag are debated. Here, we use detrital zircon isotope age data, detritus composition and paleocurrents analyses to investigate the Jurassic provenances in the Delingha Sag. The provenance transition mechanism of faulted intermountain basin affected by strike-slip faults is also summarized. The results show that the provenances of the Delingha Sag include not only the distal, but also proximal sources. The distal provenances include that from the South Qilian Orogen to the north and that from the Aimunike-Dadakenwula Mountain to the south, which were mainly affected by the orogenic boundary fault tectonic activities in the north and south boundaries of the Delingha Sag. The more important proximal provenances, included the Zongwulong Orogen to the north, the North Qaidam HP/UHP Metamorphic Belt and the Maoniushan Mountain to the south, are mainly affected by the strike-slip faulting in the east and west boundaries of the sag. Provenance direction of early Middle Jurassic is SSW, while the direction of later Middle Jurassic and Upper Jurassic is NNW. Provenance transition from early Middle Jurassic to later Middle Jurassic and Upper Jurassic of the Delingha Sag was mainly affected by the intensity of sinistral strike-slip faulting. When the strike-slip faulting was stronger in the eastern boundary of the sag, the southern provenance was formed to provide sources for the sag during early Middle Jurassic. When the strike-slip faulting was stronger in the western boundary of the sag during later Middle Jurassic and Late Jurassic, the northern provenance worked to supply for the sag.