地质学报2017，Vol.91Issue(12)：2697-2709,13.
山东西部中生代青山群火山岩的地球化学特征及其岩石成因
Geochemistry and Petrogenesis of the Mesozoic Volcanic Rocks from the Qingshan Group in Western Shandong Province
摘要
Abstract
With volcanic rocks of the Mesozoic Qingshan Group in the Xidong area in western Shangdong province as study objective,we carried out systematical analysis of element-isotope geochemical analysis on the volcanic rocks to understand source area of magmatic rocks and their petrogenesis.This study will expand the geochemical features of rock sequences in this area.SiOz content of Qingshan Group volcanic rocks ranges from 52.8％ to 59.8％,suggesting they belong to calc-alkaline series.The rock assemblage consists of basaltic trachyandesite to trachyandesite.SiO2 shows negative relation to MgO,TFe2O3,MnO and TiO2,but positive to Al2O3 and Na2O.Large ion lithophile elements such as Rb,Ba,Th,U and K are enriched while high field strength elements such as Nb,Ta and Ti are depleted.The total REE ranges from 100×10-6 to 187×10-6,with (La/Yb)N=8.2～11.1 and no significant Eu anomaly (Eu=0.9～ 1.02).The volcanic rocks have homogeneous and enriched Sr-Nd isotopic compositions with (87Sr/86Sr)t ratios of 0.7047 ～0.7050 and Nd(t) values of-16.5 ～-14.2.Nd and Sr isotopic compositions of Qingshan Group volcanic rocks in the Xidong area show no distinct negative relation to SiO2,Nb/Ta and La/Nb has no negative relation,and Nb and Th shows positive relation.All these features indicate that crust contamination had much influence on chemical compositions of magma of Qingshan Group volcanic rocks during the uprising and evolution process of magma.The fact that the volcanic rocks have higher MgO content than melt resulted from partial melting of basalt indicates that forming process of intermediate-mafic volcanic rocks of the Qingshan Group was probably related to interaction between continental crust and mantle rock series.Integrated analysis indicates that the volocanic rocks of Mesozoic Qingshan Group in the Xidong area were the emplacement of partially melting continental lower curst materials onto the Earth surface,which were firstly metasomatized with upper mantle rocks in the mantle environment due to delamination.关键词
山东西部/中生代/青山群/地球化学/岩石成因Key words
Western Shandong Province/Mesozoic/Qingshan Group/geochemistry/petrogenesis引用本文复制引用
张永清,凌文黎,张军波,段瑞春,任邦方,杨红梅..山东西部中生代青山群火山岩的地球化学特征及其岩石成因[J].地质学报,2017,91(12):2697-2709,13.基金项目
本文为国家自然科学基金委员会创新研究群体科学基金项目(编号40521001)资助的成果. （编号40521001）
