Diffusion of Sm-Nd in Scheelite and its Significance to Isotopic Dating and Tracing

作     者：ZHANG Dongliang Ian MCOULSON PENG Jiantang LI Shijie WANG Guoqiang ZHANG Dongliang;Ian M.COULSON;PENG Jiantang;LI Shijie;WANG Guoqiang

作者机构：Key Laboratory of Metallogenic Prediction of Nonferrous MetalsMinistry of EducationSchool of Geosciences and InfophysicsCentral South UniversityChangsha 410083China Solid Earth Studies LaboratoryDepartment of GeologyUniversity of ReginaReginaSaskatchewan S4S OA2Canada Lunar and Planetary Science Research CenterInstitute of GeochemistryChinese Academy of SciencesGuiyang 550081China Xi'an Center of Geological SurveyCGSXi'an 710054China 

出 版 物：《Acta Geologica Sinica(English Edition)》 (地质学报（英文版）)

年 卷 期：2023年第97卷第2期

页      面：651-661页

核心收录：

学科分类：070902[理学-地球化学] 081803[工学-地质工程] 0709[理学-地质学] 07[理学] 08[工学] 0818[工学-地质资源与地质工程] 

基　　金：financially supported by the National Natural Science Foundation of China(Grant No.41403035) the National Basic Research Program of China(Grant No.2014CB440901) 

主　　题：Sm-Nd system diffusion scheelite closure temperature isotopic dating 

摘      要：As the principal ore mineral in various tungsten(-gold)deposits,scheelite(CaWO_(4))plays an important role in directly dating the timing of ore formation,and in tracing associated material sources through the study of its Sm-Nd geochronology and Nd isotopic *** the retention of Sm-Nd systematics within scheelite is presently unconstrained,equivocal interpretations for isotopic data resulting from this method have occurred quite often in previous studies that apply these isotopic *** order to better elucidate the closure of Sm-Nd in scheelite,the kinetics of Sm and Nd within this mineral lattice were investigated through calculation of diffusion constants presented *** following Arrhenius relations were obtained:D_(Nd)=4.00exp(-438 kJ·mol^(–1)/RT)cm^(2)/s D_(Sm)=1.85exp(-427 kJ·mol^(–1)/RT)cm^(2)/s showing diffusion rate of Nd is near identical to Sm in scheelite when at the same ***,compared to other rare earth elements(REEs),which have markedly different atomic radii to either Nd or Sm,these are shown to exhibit a great variation in *** observed trends in our data are in excellent agreement with the diffusion characteristics of REEs in other tetragonal ABO4 minerals,indicating that ionic radius is a key constraint to the diffusivity of REEs in the various crystal *** this in mind,the same substitution mechanism and a very slight discrepancy in radii will allow us to infer that significant Sm/Nd diffusional fractionation in scheelite is unlikely to occur during most geological *** upon the diffusion data determined herein,Sm and Nd closure temperatures and retention times in scheelite are discussed in terms of diffusion *** results suggest that closure temperatures for Sm-Nd within this mineral are relatively high in contrast to the temperature ranges of ore-formation responsible for scheelite-related deposits,and any later thermal *** is likely,therefore,that rel