The late Paleozoic tectonic framework of the southeastern Central Asian Orogenic Belt is key to restricting the accretion orogeny between the Siberia Craton and the North China Craton.To clarify the framework,petrogenesis of early Permian intrusive rocks from southeastern Inner Mongolia was studied.Zircon U-Pb dating for bojite and syenogranite from Ar-Horqin indicate that they were emplaced at 288-285 Ma.Geochemical data reveal that the bojite is highly magnesian and low-K to middle-K calc-alkaline,with E-MORB-type REE and IAB-like trace element patterns.The syenogranite is a middle-K calc-alkaline fractionated A-type granite and shows oceanic-arc-like trace element patterns,with depleted Sr-Nd-Hf isotopes,(87Sr/86Sr)I=0.7032-0.7042,εNd(t)=+4.0 to+6.6 and zircon εHf(t)=+11.14 to+14.99.This suggests that the bojite was derived from lithospheric mantle metasomatized by subducted slab melt,while the syenogranite originated from very juvenile arc-related lower crust.Usng data from coeval magmatic rocks from Linxi-Ar-Horqin,the Ar-Horqin intra-oceanic arc was reconstructed,i.e.,initial transition in 290-280 Ma and mature after 278 Ma.Combined with regional geological and geophysical materials in southeastern Inner Mongolia,an early Permian tectonic framework as'one narrow ocean basin of the PAO','two continental marginal arcs on its northern and southern'and'one intra-oceanic arc in its southern'is proposed.

QIAN Cheng;LU Lu;SHI Lu;DU Jiyu;WANG Yan;YANG Xiaoping;ZHANG Yujin

Shenyang Center,China Geological Survey,Shenyang 110034,China;College of Paleontology,Shenyang Normal University,Shenyang 110034,China;Key Laboratory of Evolution of Past Life in Northeast Asia,Ministry of Land and Resources,Shenyang 110034,China

地质学报（英文版）

[1]QIAN Cheng;LU Lu;SHI Lu;DU Jiyu;WANG Yan;YANG Xiaoping;ZHANG Yujin-.Petrogenesis of Early Permian Intrusive Rocks from Southeastern Inner Mongolia,China:Constraints on the Tectonic Framework of the Southeastern Central Asian Orogenic Belt)[J].地质学报（英文版）,2022(05):1566-1586

Intrusive,bojite,magnesian,to+6,to+14,Usng

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