首页|Zircon SHRIMP U-Pb Ages,Geochemical,and Sr-Nd Isotopic Constraints on the Petrogenesis of the Middle Eocene Calc-Alkaline Andesitic Rocks:Implications for Continental Arc Magmatism and Slab Break-off in NE Iran

Zircon SHRIMP U-Pb Ages,Geochemical,and Sr-Nd Isotopic Constraints on the Petrogenesis of the Middle Eocene Calc-Alkaline Andesitic Rocks:Implications for Continental Arc Magmatism and Slab Break-off in NE Iran

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The Torbat-e-Heydariyeh andesitic rocks(THA)are part of the Cenozoic continental arc magmatic system of the northern branch of the Neotethys Ocean(NE Iran).Columnar jointing is the most significant feature of these rocks and they also show porphyritic,vitrophyric,and vitroglomero-porphyric textures.Plagioclase,clinopyroxene,±orthopyroxene are the major mineral phases.The SHRIMP U-Pb zircon dating yielded an age of 41.00±0.69 Ma for the rocks(Middle Eocene,Bartoni-an).Geochemically,they are of medium-to high-K calc-alkaline affinity.Primitive mantle-normalized diagrams exhibit enrichment in large ion lithophile elements(LILE),such as Cs and Rb,and also deplet-ed in high field strength elements(HFSE)and heavy rare earth elements(HREE),with prominent nega-tive anomalies of Ti,Nb,Y,and Yb,suggesting a tectonic setting of an active continental margin.The chondrite-normalized REE diagram displays enrichment of light rare earth elements(LREE;LaN/YbN=5.37-6.66)and small negative Eu anomalies(Eu/Eu*of 0.69-0.78).Thorium enrichment implies the re-action between the mantle wedge and the melt of subducting oceanic slab,and/or subducting sediment.The role of subducted sediments along with subducted oceanic lithosphere is evident in these magmatic rocks using Ba/La versus Th/Nd and Ba/Th versus LaN/SmN diagrams.The εNd(t)and(87Sr/86Sr)i,values vary between-0.1 to+0.2 and 0.704 89 to 0.705 01,respectively,and are compatible with parental melts from subduction of the lithospheric mantle.We suggest that the THA rocks were produced by the par-tial melting of the metasomatized lithospheric mantle,which corresponds to slab break-off of the north-ward subducted Neotethys oceanic slab in an extensional setting.The hot asthenospheric mantle upwell-ing triggered by the Neotethys slab break-off would severely heat the physically mixed mantle wedge pe-ridotite and therefore caused partial melting to produce the Middle Eocene volcanic rocks in NE Iran.

EoceneSabzevar zoneandesitezirconU-Pb datingcontinental arcslab break-offgeochemistry

Soheila Saki、Amir Ali Tabbakh Shabani、Mingguo Zhai、Yuruo Shi、Mahmoud Sadeghian、Xiyan Zhu、Morteza Delavari Koshan、David R.Lentz

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Faculty of Earth Sciences,Kharazmi University,Tehran,Iran

Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China

Beijing SHRIMP Center,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China

Department of Petrology and Economic Geology,Faculty of Earth Sciences,Shahrood University of Technology,Shahrood,Iran

Department of Earth Science,University of New Brunswick,Fredericton NB,Canada

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2024

10.1007/s12583-023-1839-x

地球科学学刊(英文版)
中国地质大学

地球科学学刊(英文版)

CSTPCD
影响因子：0.724
ISSN：1674-487X
年,卷(期)：2024.35(6)