Detrital zircon U–Pb geochronology and Hf isotopic compositions of Middle–Upper Ordovician sandstones from the Quruqtagh area, eastern Tarim Basin: implications for sedimentary provenance and tectonic evolution

Abstract

Figuring out whether the sedimentary provenance regions of the thick deep-water turbidite systems deposited during Middle–Upper Ordovician in South Quruqtagh are the intracontinental uplifts or the peripheral orogenic belts is of great significance for us to understand the tectono-sedimentary nature of the northeastern Tarim Basin and basin-range coupling processes in the middle Paleozoic. This paper reports the in situ LA-ICP-MS U–Pb ages and Hf isotope data on detrital zircons from two Middle–Upper Ordovician sandstone samples which were collected from the Charchag Formation and the Zatupo Formation in South Quruqtagh, respectively. The results show that the studied two samples have extremely similar U–Pb age patterns and Hf isotopic compositions, reflecting multiphase tectono-thermal events with age groups of 527–694, 713–870 Ma (peaking at 760 Ma), 904–1,090, 1,787–2,094 Ma (peaking at 1,975 Ma) and 2,419–2,517 Ma. Combining previous studies, the presence of age groups of 713–1,090 and 1,787–2,094 Ma, respectively, demonstrates that Tarim had ever been a part of Rodinia and Columbia supercontinent. Moreover, 98 % of 713–870 Ma detrital zircons are characterized by negative eHf (t) values ranging from −38.07 to −0.61, which are highly consistent with those of Neoproterozoic granites from the Quruqtagh area. No Early Paleozoic ages (~470–500 Ma) signifying subduction or collision events in Altyn Tagh were detected in the two samples, indicating that the Middle–Late Ordovician sediments in South Quruqtagh and northern Mangar depression were mainly derived from intracontinental uplifts, i.e., the North Quruqtagh uplift or the Tabei paleo-uplift, rather than the Altyn Tagh. In conjunction with regional sedimentary-tectonic background and previous studies, we proposed preliminarily that the northeastern Tarim remained as a passive continental margin in Late Ordovician and changed into an active-continental margin in Silurian due to the southward subduction of the South-Tianshan Ocean.