Abstract:

Abstract:  Involved in the Cenozoic intraplate orogeny of southwestern Tianshan, the northwestern Tarim Basin had developed a series of NEtrending faults and faultrelated folds. The cause of the Cenozoic structural deformation in this region, however, remains currently in controversy. This paper aims to report the geology of the Cenozoic igneous rocks and their chronology, proposing that the structural deformation was the response of shallow crust to the mantlederived magmatism rather than the direct result of IndoAsia collision. There are many Cenozoic mafic dikes with NNW and NNE trend and nearly 90 dipping angle and four volcanic necks in the Piqiang basin. The dikes have intruded the Cenozoic lacustrine layers. Our SHRIMP UPb zircon ages determined for these igneous rocks for the first time indicate that the mafic dykes and necks were formed at about 46 Ma, while the whole rocks KAr isochron date yielded an age of (45.5±6.13) Ma. The results suggested that the magmatism appeared in the middle Eocene, almost 22 Ma earlier than the nappe structures (~24 Ma). In terms of the heat conduction model, we estimated that the distance of heat transfer from deep heat source was about 25 km. Considering that the underplating or intraplating mantlederived magmas may serve as the deep source of heat, we presume that the Cenozoic deformation of the northwest Tarim Basin may have been triggered by the Cenozoic magmatism.

Key words:

Key words: mafic dyke swarm; heat transfer; intraplate orogeny; Piqiang volcano group; Tarim Basin