Mantle plume:the dynamic setting of the origin of Early Paleozoic mafic dykes in Ziyang,Shaanxi Province,Southern Qinling Block,China  

作　　者：Xiaoqing Chen Shen Liu Caixia Feng Ian M.Coulson Yan Fan Kairui Tai Tianjing Gao Siyuan Zhang 

机构地区：[1]College of Earth Science,Jilin University,Changchun 130061,China [2]State Key Laboratory of Continental Dynamics and Department of Geology,Northwest University,Xi'an 710069,China [3]Solid Earth Studies Laboratory,Department of Geology,University of Regina,Regina,SK S4S 0A2,Canada

出　　处：《Acta Geochimica》2020年第3期307-325,共19页地球化学学报（英文）

基　　金：This study was supported by the National Natural Science Foundation of China(Grant:41573022).

摘　　要：The mafic dykes(dolerites)during the Early Paleozoic are widely spread in Langao-Ziyang,southern Qiling Block,and the investigation on these dykes are very important.Previous studies have mainly focused on the Silurian mafic dykes;however,research on the Earlier Paleozoic mafic dykes is relatively weak at present.Therefore,the overall understanding of the mantle source and genetic dynamic setting during the Early Paleozoic in this area is lacking.To study the accurate age and origin of the Early Paleozoic mafic dykes in Ziyang,southern Shaanxi Province,the mafic dykes from dabacunand Qinmingzhai were selected and the petrology,zircon U-Pb chronology,geochemistry,and Sr-Nd-Hf isotopes were studied.Analysis indicates that the mafic dykes studied are mainly composed of dolerite,and they are the products of the Early Ordovician(475.8-480.7 Ma).Furthermore,the dolerites belong to alkaline rock series,and they are characterized by enrichment in LREE,Rb,Ba,Sr,Nb,(87Sr/86Sr)i=0.7020-0.7050,εNd(t)=3.0-4.0),εHf(t)=4.5-12.1,176Hf/177Hf=0.282681-0.282844.This suggests that the mafic dyke were derived from the partial melting of a depleted lithospheric mantle,and the genetic process is mainly controlled by the mantle plume based on the discussion of the genetic model.Furthermore,the genetic process experienced the separation and crystallization of olivine and clinopyroxene at the same time,with little crustal contamination.

关 键 词：Early Paleozoic DOLERITES GEOCHEMISTRY ORIGIN Mantle plume 

分 类 号：P534.4[天文地球—古生物学与地层学] P597[天文地球—地质学] P588.245