关键词: 安山岩, 早白垩世, 地球化学, Sr-Nd-Hf同位素, 大兴安岭, 索伦地区

Abstract:

Understanding the formation and source characteristics of andesite in continental arc environments holds significant implications for revealing arc magmatism. This study focuses on the Suolun area of the Great Xing’an Range, using a combined approach of chronology and geochemistry to thoroughly investigate the genesis of trachyandesite and andesite in the region and their magmatic source characteristics. Zircon U-Pb dating indicates that the trachyandesite and andesite formed during the Early Cretaceous (134-129 Ma). The studied andesite and trachyandesite have SiO2 contents of 57.13% to 58.16%, total alkali (K2O+Na2O) contents of 6.10% to 6.40%, Al2O3 contents of 17.09% to 17.59%, TFe2O3 contents of 6.71% to 6.92%, and Mg# values of 41.52 to 43.94, featuring high-potassium calc-alkaline weakly peraluminous rock characteristics. These samples exhibit enrichment in light rare earth elements and large ion lithophile elements (such as K, Rb, Ba) and relative depletion in high field strength elements (such as Nb, Ta, P, and Ti), with a slight negative Eu anomaly (δEu=0.88- 0.89), indicating that they are products of continental arc magmatism. Additionally, both types of samples have high zircon εHf(t) values (5.81 to 11.29) and whole-rock εNd(t) values (0.6 to 1.3), suggesting that the intermediate magmas in the Suolon area originated from partial melting of a subduction-fluid-modified, depleted lithospheric mantle fluids.

Key words: andesite, Early Cretaceous, geochemistry, Sr-Nd-Hf isotope , Great Xing’an Range, Suolun area