Early Paleozoic S-type granites as the basement of Southern Qiantang Terrane, Tibet.

Identifying basement rocks is critical to understanding the continent formation and evolution during orogenesis. Despite two decades of research, the age and composition of the basement rocks of the Southern Qiangtang Terrane/Microcontinent (SQT), Central Tibet are still unclear. In this study, zircon U–Pb ages and Hf–O isotopes, as well as whole-rock Nd isotopes are presented for the oldest known igneous rocks in the SQT. Precise SIMS zircon U–Pb dating of these rocks reveals that these early Paleozoic granites were crystallized at ca. 480‐465 Ma. They exhibit a wide range of isotopic values, with unradiogenic whole rock ε Nd (t) and zircon ε Hf (t) values ranging between −8.3~−7.7 and −8.2~−2.3, respectively, and by high δ18O zircon values of +8.1~+11.4‰. These results reveal that the early Paleozoic granites were crystallized from magmas that were almost entirely sediment-derived. When viewed in concert with regional data and constraints on the tectonic evolution of northern Gondwana, the sources for the early Paleozoic granites are herein proposed to have been deposited in an extensional basin, implying that these early Paleozoic granites were generated in an extensional setting within an accretionary orogen. Thus, the early Paleozoic granites are considered to represent the basement of the SQT. After a long period of attachment to northern Gondwana, the SQT became a small microcontinent when it was rifted and detached from northern Gondwana during Early Permian. After this time, it drifted northwards to Asia, and collided with the Northern Qiangtang Terrane to form a unified Qiangtang terrane in the Late Triassic. Thus, the SQT records a complete Wilson cycle from construction, rifting and departure, drifting to collision. • Pure sedimentary-derived early Paleozoic granites reported in Southern Qiangtang. • The basement of the SQT formed during early Paleozoic. • The SQT recorded a whole Wilson cycle from construction, rifting to collision. [ABSTRACT FROM AUTHOR]