Zircon U-Pb Age,Geochemical,and Sr-Nd-Pb-Hf Isotopic Constraints on the Time Frame and Origin of Early Cretaceous Mafic Dykes in the Wuling Mountain Gravity Lineament,South China  

作　　者：CHEN Xiaoqing LIU Shen FENG Caixia XU Jingyan ZHAO Huibo FENG Guangying Ian M.COULSON SUN Jinggui FAN Yan 

机构地区：[1]College of Earth Sciences,Jilin University,Changchun 130061,China [2]State Key Laboratory of Continental Dynamics and Department of Geology,Northwest University,Xi'an 710069,China [3]Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China [4]Solid Earth Studies Laboratory,Department of Geology,University of Regina,Regina,Saskatchewan S4S 0A2,Canada

出　　处：《Acta Geologica Sinica(English Edition)》2021年第2期419-438,共20页地质学报（英文版）

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

摘　　要：In view of the importance of mafic dyke swarms and their contribution to current scientific problems relating to South China,herein,we present the findings of studies on twenty–five representative mafic dykes cropping out in Hunan Province and Guangxi Zhuang Autonomous Region,within the southern Wuling Mountain gravity lineament,China.These results include new zircon LA-ICP-MS U-Pb age,whole rock geochemical,Sr-Nd-Pb isotopic,and zircon Hf isotopic data for these dykes.The dykes formed between 131.5±1.2 and 121.6±1.1 Ma,and have typical doleritic textures.They fall into the alkaline and shoshonitic series,are enriched in light rare earth elements(LREE),some large ion lithophile elements(LILE;e.g.,Rb,Ba,and Sr),Th,U,and Pb,and are depleted in Nb,Ta,Hf,and Ti.Moreover,the dolerites have high initial 87 Sr/86 Sr ratios(0.7055–0.7057),negativeεNd(t)and zirconεHf(t)values(-14.8 to-11.9,-30.4 to-14.9),and relatively constant initial Pb isotopic ratios(that are EM1-like,16.77–16.94,15.43–15.47,and 36.84–36.92 for 206 Pb/204 Pb,207 Pb/204 Pb,and 208 Pb/204 Pb,respectively).These results indicate that the dykes were likely derived from magma generated through low-degree partial melting(1.0%–10%)of an EM1-like garnet–lherzolite mantle source.The parental magmas fractionated olivine,clinopyroxene,plagioclase,and Ti-bearing phases with negligible crustal contamination,during ascent and dyke emplacement.Several possible models have been proposed to explain the origin of Mesozoic magmatism along the Wuling Mountain gravity lineament.Herein we propose a reasonable model for the origin of these mafic dykes,involving the collision between the paleo-Pacific Plate and South China,which led to subsequent lithospheric extension and asthenosphere upwelling,resulting in partial melting the underlying mantle lithosphere in the Early Cretaceous,to form the parental magmas to the WMGL mafic dykes,as studied.

关 键 词：mafic dykes magmatic origin Early Cretaceous Wuling Mountain gravity lineament South China 

分 类 号：P597.3[天文地球—地球化学] P534.53[天文地球—地质学] P588.124