Depositional response to the Emeishan mantle plume: evidence from the eastern Sichuan Basin, South China

Abstract

ABSTRACT The Emeishan large igneous province (ELIP) is among the prominent large igneous provinces in the world and has been associated with mantle plume activity. In this study we investigated the impact of the Emeishan mantle plume on generating the sedimentary rock suites of the eastern Sichuan Basin. We present petrology, detrital zircon U – Pb ages, trace elements, and Hf isotopic compositions of the Middle-Late Permian sedimentary sequences in the Huayingshan region to constrain the provenance and characterize the depositional response to the Emeishan mantle plume activity. The detrital zircon U – Pb ages of the Middle Permian Maokou Formation indicate that terrigenous detritus was mainly sourced from the Kangdian paleoland in the southwestern margin of South China. Detrital zircon grains from the bottom of the Late Permian Longtan Formation yield a lower intercept age of 257 ± 28 Ma, interpreted as the contemporaneous metamorphism related to the ELIP magma. The detrital zircon U – Pb ages of the middle part of the Longtan Formation are characterized by unimodal age spectra with a peak at 259 Ma. Provenance analysis indicates that the Longtan Formation was mainly sourced from the Emeishan volcanic rocks in the Huayingshan region. We propose that the Kangdian paleohigh may have been regionally uplifted as the result of the pre-eruption rise of the Emeishan mantle plume in the late Middle Permian. Moreover, this paleohigh was translated into a denuded zone and provided voluminous detritus into the eastern Sichuan Basin. In the early Late Permian, the ELIP magmas upwelled and outpoured from the Huayingshan fault, and flowed past the peripheral rocks to the low terrain in the Huayingshan region. The ELIP volcanic rocks in the Huayingshan region underwent intense post-eruption erosion, resulting in the deposition of voluminous volcanic detritus in the eastern Sichuan Basin.