GEOCHEMICAL CHARACTERISTICS OF THE EARLY MESOZOIC GRANODIORITES AND THEIR TECTONIC IMPLICATIONS

作者：PENGTouping,XIXianwu,WANGYuejun,PENGBingxia,JIANGZhimin

摘要：The early Mesozoic granodiorites (ca. 165 Ma) in the northeastern Hunan Province (NEH) have SiO2=65.4-69.65%, K2O/Na2O=0.95-1.38 and K2O+Na2O＞6%, A/CNK=0.96-1.13 and belong to metaluminous high-K calc-alkaline series. They are characterized by LREE and LILEs enrichment, and HFSE depletion with slightly negative Eu anomalies (Eu/Eu*=0.62-0.90). The initial 87Sr/86Sr ratios are in range from 0.711458 to0.717461, and εNd values vary from -9.4 to -12.3, distinct from those of the contemporaneous granodiorites mantle-derived from the Southeastern Hunan Province (SEH) (87Sr/86Sr(i)=0.707962～0.710396, εNd(t)=-6.98～-2.30).By contrast, such signatures are roughly similar to those of the neighboring other Mesozoic granitic plutons (Eu/Eu*=0.30-0.70; 87Sr/86Sr ＞0.710; εNd = -12 to -16) in South China Block (SCB), which have been interpreted as the remelting products of Precambrian basement. The Proterozoic lower-middle crust is an important contributor to the petrogenesis of these early Mesozoic granodiorites in the NEH. An intracontinental extension setting is present in the northeastern Hunan Province at that time due to the demand of enough thermal transfer.

发文机构：GuangzhouInstituteofGeochemistry GuangzhouInstituteofGeochemistry GuangzhouInstituteofGeochemistry TubaPatroleumExolorationandDeveloomentBureau.Hami.XJ839009

关键词：花岗闪长岩碱性钙中生代湖南东北部calc-alkaline granodioriteslower-middle crustal sourceintracontinental extensionearly Mesozoicnortheastern Hunan Province

分类号： P534.5[天文地球—古生物学与地层学][天文地球—地质学]P588.15[天文地球—岩石学][天文地球—地质学]