地质学报2013，Vol.87Issue(7)：979-993,15.
郯庐断裂带莒县地区早白垩世中酸性火山岩成因及其地质意义
Petrogenesis of Early Cretaceous Intermediate-Felsic Volcanic Rocks in the Juxian Area in the Tan-Lu Fault Zone and Their Tectonic Impilcations
摘要
Abstract
Early Cretaceous volcanic rocks in the Juxian area in the Tan-Lu fault zone consist of trachyandensite,trachydacite and rhyolite,and belong to high-K calc-alkaline to shoshonite series.These rocks are characterized by enriched LREE and LILE with Rb,K and Ba,depleted HREE and HFSE with Nb,Ta and Ti.Their Sr,Nd isotope compositions (87Sr/86Sr)t=0.7082～0.7095,εNd (t)=-16.4～-19.8) are similar to mafic rock nearby.However,Pb isotope compositions exhibit EM1-like features (206pb/204pb)t =16.523～17.038,(207pb/204pb)t=15.414～15.468,(208Pb/204pb)t=37.058～37.427).There are no obvious correlation between (87 Sr/86 Sr) t,εNd (t) and SiO2,which imply no significantly crustal contamination during magma ascent combined with high Th/U,Ce/Pb ratios,low Nb/La,Nb/U ratios.Trachyandensites show high MgO,Cr,Ni contents,and Mg# value,along with ancient Nd isotopic model ages,suggesting that magmas could originate from enriched lithospheric mantle.The correlation between major oxides,trace elements and SiO2 in trachydacites and trachyandesites reflects that they were formed by fractional crystallization of co-magmatic region.Studies further indicate that these volcanic rocks in the Juxian area derived from partial melting of the NCC lithospheric mantle which had previously experienced a reconstruction of subducted Yangtze crustal melts under the lithospheric extension setting.Therefore,the Tan-Lu fault zone controlled the distribution of volcanic rocks,provided an advantage site for the generation and migration of magmas,and played an important role during the NCC destruction.关键词
郯庐断裂带/莒县/早白垩世/岩石成因Key words
Tan-Lu fault zone/ Juxian/ Early Cretaceous/ petrogenesis引用本文复制引用
吴齐,牛漫兰,朱光,向必伟,傅朋远,夏文静..郯庐断裂带莒县地区早白垩世中酸性火山岩成因及其地质意义[J].地质学报,2013,87(7):979-993,15.基金项目
本文为国家自然科学基金项目(编号41172201,40603010,41172187)和教育部留学回国人员科研启动基金(编号2011JYLH1509)资助成果. （编号41172201,40603010,41172187）
