Geochemical constraints on the origin of Early Cretaceous alkaline intrusions and its tectonic implication,Sulu Orogenic Belt,Eastern North China Craton  

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

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

出　　处：《Acta Geochimica》2020年第5期616-641,共26页地球化学学报（英文）

基　　金：supported by the National Natural Science Foundation of China(41373028 and 41573022)。

摘　　要：Post-orogenic alkaline intrusions from the Sulu Orogenic Belt of eastern North China Craton consist of A-type granites.In this study,we report U-Pb zircon ages,geochemical data,Sr-Nd-Pb,and zircon Hf isotopic data for these rocks.The LA-ICP-MS U-Pb zircon analyses yield consistent ages ranging from 127.1±2.4 to 119.5±4.8 Ma for four samples.The alkaline rocks are characterized by high total alkalis(K2 O+Na2 O=8.32-10.11 wt%),light rare-earth element enrichment,and heavy rare-earth element depletion,with a wide range(La/Yb)N values(20-48),moderate negative Eu anomalies(Eu/Eu*=0.50-0.74),enrichment in large-ion lithophile elements(LILEs,i.e.,Rb,Th,U and Pb),and depletion in Ba,Sr and high field strength elements(HFSEs,i.e.,Nb,Ta,and Ti),high(87Sr/86Sr)i ranging from 0.708 to 0.7089,low sNd(t)values from-19.4 to-16.8,(206Pb/204Pb)i=16.751-16.935,(207Pb/204Pb)i=15.381-15.535,(208-Pb/204Pb)i=37.472-37.838,negativeεHf(t)values between-21.3 and-25.7 for the magmatic zircons,and larger TDM2 model ages from 2.5 to 2.8 Ga.These results suggest that the rocks were derived from a common enriched lithospheric mantle source that was metasomatized by foundered lower crustal eclogitic materials before magma generation.Furthermore,the geochemical and isotopic feature implies that the primary magma of these rocks originated through partial melting of ancient lithospheric mantle that was variably hybridized by melts derived from lower crust eclogite.These rocks in this study may have been generated by subsequent fractionation of potassium feldspar,plagioclase,ilmenite,and/or rutile.However,negligible crustal contamination occurred during the diagenesis process.

关 键 词：Post-orogenic magmatism Alkaline rocks Contamination Sulu Orogenic Belt North China Craton 

分 类 号：P534.53[天文地球—古生物学与地层学] P588.12[天文地球—地质学] P597.3