Geochemistry and U-Pb-Hf zircon systematics of Cryogenian syn-rift magmatic rocks from the subsurface of the Tarim Craton: Implications for subduction-related continental rifting

Abstract

Neoproterozoic rifting within the supercontinent Rodinia is generally linked to superplume activity, although the mechanisms are not well constrained at the supercontinent’s outer margins. The Tarim Craton, on the northern margin of Rodinia, is a key area for evaluating the process. We present zircon U-Pb-Hf isotopic data and whole-rock geochemistry from Neoproterozoic granitoids from drill cores in the Tarim Craton. Zircon SHRIMP geochronology yielded U-Pb ages of 744 ± 4 Ma, 750 ± 4 Ma, 755 ± 9 Ma and 734 ± 8 Ma for granitoid emplacement. The granitoids are enriched in light rare earth elements (LREE), depleted in high field strength elements (HSFE) including Nb, Ta, Sr, P and Ti, and most samples show weak negative Eu anomalies (Eu* = 0.56–1.02). Elemental data and negative zircon εHf(t) values (-18.72 to -10.23) indicate derivation from reworked continental crust. Compiled data suggest that ca. 760–730 Ma magmatism was widespread and marks the onset of extensive rifting throughout the Tarim Craton. The early Cryogenian granitoids are mainly slab failure-related and formed in a subduction-induced rift setting. Our findings consequently suggest that active continental rifting on the Tarim outer margin of Rodinia was triggered by subduction processes.