Geochemical and Nd-Sr Isotopic Compositions of Hypabyssal Adakites in the Torud-Ahmad Abad Magmatic Belt,Northern Central Iran Zone:Analysis of Petrogenesis and Geodynamic Implications  

作　　者：Fazilat Yousefi Ryan D.Mills Mahmoud Sadeghian David R.Lentz Christina Wanhainen Habibollah Ghasemi Laicheng Miao 

机构地区：[1]Department of Earth Sciences,University of New Brunswick,Fredericton,Canada [2]Department of Geological Sciences,University of North Carolina at Chapel Hill,Chapel Hill,USA [3]Faculty of Earth Sciences,Shahrood University of Technology,Shahrood,Iran [4]Department of Civil,Environmental and Natural Resources Engineering,Lulea University of Technology,Lulea,Sweden [5]Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing,100029,China

出　　处：《Journal of Earth Science》2021年第6期1428-1444,共17页地球科学学刊（英文版）

基　　金：supported by the NSERC Discovery to David R.Lentz。

摘　　要：Eocene intermediate to felsic subvolcanic rocks of the Torud-Ahmad Abad magmatic belt(TAMB),in the northern part of the Central Iran zone,are exposed between the Torud and Ahmad Abad regions in South-Southeast Shahrood.These igneous rocks include hypabyssal dacite,trachyte,andesite,trachy-andesite,and basaltic andesite;they are mainly composed of phenocrysts and microcrystalline groundmass of pyroxene,amphibole,and plagioclase,with minor biotite and titanomagnetite;they form domal structures(plugs and stocks),dikes,and sills that intruded into Neoproterozoic to cogenetic Eocene volcano-sedimentary sequences.Based on isotopic analysis of these intermediate to acidic rocks,initial ratios of^(143)Nd/^(144)Nd range from 0.512775 to 0.512893 and initial ratios of^(87)Sr/^(86)Sr range from 0.703746 to 0.705314,with quite positiveε_(Nd(i))values of+3.69 to+6.00.They are enriched in light rare earth elements and large ion lithophile elements and depleted in heavy rare earth elements and high-field strength elements,the SiO_(2) content is(52-62)wt.%,and Na_(2)O content>3 wt.%,Al_(2)O_(3) content>16 wt.%,Yb<1.8 ppm,and Y<18 ppm.These geological,geochemical,and Sr and Nd isotopic data are consistent with adakitic signatures originating by partial melting of the subducted Neo-Tethys oceanic slab(Sabzevar branch)and lithospheric suprasubduction zone mantle.The mantle signatures typifying the rapidly emplaced adakitic rocks(slab(high-silica adakite)and suprasubduction zone(low-silica adakite)melts)together with their locally voluminous extent are evidences that support a locally extensional geodynamic setting;and the evidence is consistent with an evolution to local transpression in the Late Eocene in this convergent margin are environment to rifting(basalts to adakites)towards submarine conditions in the Neogene.

关 键 词：isotope geochemistry adakite rocks Central Iran zone Shahrood Iran 

分 类 号：P588.1[天文地球—岩石学] P597.3[天文地球—地质学]