Volcanism at the end of continental rifting: The Cretaceous syn-rift to post-rift transition in the Songliao Basin (NE China)

The evolution of volcanism at the latest stages of continental rifting and its transition to the post-rift stage are poorly known. A Cretaceous rifting episode characterized the Songliao Basin (NE China) between 150 and 105-100 Ma. The transition to the post-rifting stage was marked by an increase in the subsidence rate due to thermal contraction. Here we present new major, trace element and Sr-Nd iso-topic data on the volcanic rocks sampled in wells located in the Songliao Basin. These rocks are represen-tative of two major eruptive cycles: K(1)yc(1) (115-106 Ma, syn-rift stage) and K(1)yc(3) (105-102 Ma, transition to the post-rift stage). The K(1)yc(1) and K(1)yc(3) rocks were erupted during the late phases of the Songliao rift-ing and have been found in the two members of the Yingcheng Formation. The K(1)yc(1) rocks consist of tra-chybasalts, basaltic trachyandesites, and rhyolites. The K(1)yc(3) rocks show a homogeneous rhyolitic composition. Both the K(1)yc(1) and K(1)yc(3) rocks display an alkaline, Within-Plate affinity. The trace element patterns and the isotopic composition of the K(1)yc(1 )mafic rocks indicate that they are the product of the fractional crystallization from a parent magma with an OIB signature. The felsic rocks from K(1)yc(1) and K(1)yc(3) have similar major and trace element patterns and originate from fractional crystallization of the K(1)yc(1) trachybasalt and assimilation of upper crust material. The bimodal K(1)yc(1) volcanism is related to fractionation processes producing low amounts of magmas with intermediate compositions. The lack of mafic eruption in K(1)yc(3) is due to the reduction of porosity of the crustal rocks and a transition from 'hot' to 'cold' crust related to the thermal subsidence from syn-rift to post-rift stage. The late stage of the Songliao rifting volcanism coincides with a shift from a roll-backing phase of the Paleo-Pacific slab to its passive sinking in the asthenosphere. (C) 2022 Published by Elsevier B.V. on behalf of International Association for Gondwana Research.