The basement property and evolution of the northern Junggar basin—evidence from zircon U–Pb chronology and trace element

Abstract

Junggar basin is an important part of the Central Asian Orogenic Belt (CAOB) which is also one of the key areas of researches about formation and evolution of the CAOB. Recently, a question of whether the Junggar basin has a Precambrian basement is one of the hottest topics. We undertook LA-ICP-MS zircon U–Pb dating from Carboniferous pyroclastic rocks and Mesozoic sedimentary rocks in northern Xinjiang Province, NW China, with the aim of constraining the evolution and features of the basement of the north Junggar basin and adjacent areas. (1) The zircon U–Pb age analysis of the Carboniferous pyroclastic rock samples clustered in the 1447∼1410 Ma and 885∼559 Ma showed that the basement of the north Junggar basin was continental crust that formed 1.4 Ga ago. The zircon U–Pb ages clustered in the 536∼420 Ma, 401∼360 Ma, and 359∼303 Ma indicated a multiple evolution of basement. (2) The zircon trace element analysis of different age groups from the Carboniferous pyroclastic rock samples showed that the basement of the north Junggar basin was continental crust composed of acid rocks and intermediate-basic intrusive rocks, which were mainly the granitoids, syenite, basalt, dolerite, and larvikite. (3) The zircon U–Pb ages and trace element analysis of the Mesozoic sedimentary rock samples clustered in the 3022∼2102 Ma, 1747∼1202 Ma, 996∼915 Ma, 885∼544 Ma, 539∼420 Ma, 419∼356 Ma, and 354∼300 Ma revealed that not only 3.0-Ga continental crust existed in the north Junggar basin and adjacent areas but also multiple crustal material evolution that occurred during the formation of the basement. (4) The evolution of sedimentary cover experienced 299∼250 Ma, 210∼176 Ma, 175∼148 Ma, and 147∼132 Ma with the corresponding peak age of ca. 290, 180, 163, and 140 Ma, respectively, indicated that the sedimentary cover of the northern Junggar basin experienced a complex tectonic evolution from Permian.