Early Permian plutons from the northern North China Block: constraints on continental arc evolution and convergent margin magmatism related to the Central Asian Orogenic Belt

Abstract

Recent zircon dating identified several late Carboniferous to early Permian hornblende gabbro-diorite-quartz diorite-granodiorite-tonalite-granite plutons in lithological assemblages at the northern margin of the North China Block (NCB) that were previously regarded as Archaean to Palaeoproterozoic. Our geochronological results indicate that emplacement of these plutons was a continuous process during the late Carboniferous to early Permian, from 324 ± 6 to 274 ± 6 Ma, and lasted for at least 50 Ma. In this paper, the early Permian components with compositions from gabbro to granite within the intrusive complex were studied. The early Permian plutons exhibit calc-alkaline or high-K calc-alkaline, metaluminous geochemical features and highly variable SiO 2 contents. They have no significant Eu anomaly in their REE patterns, and in primitive-mantle-normalized spidergrams they display depletion in Th, U, Nb, Ta, P and Ti, and enrichment in Ba, K, Pb and Sr. The granitoid bodies within these plutons display I-type and adakitic geochemical signatures. The early Permian rocks exhibit low whole-rock initial 87 Sr/ 86 Sr ratios from 0.70520 to 0.70615 and have negative whole-rock e Nd (t) values ranging from -17.4 to -9.3 and zircon e Hf(t) values of -23.2 to -10.5. The gabbros exhibit higher e Nd (t) values from -11.1 to -9.3 and e Hf (t) values from -16.5 to -10.5, and one granodiorite exhibits an even lower e Nd (t) value of -17.4 and zircon e Hf (t) values of -23.2 to -15.1. Geochemical, Sr-Nd and in situ zircon Hf isotopic compositions suggest that the hornblende gabbros were derived from a metasomatized lithospheric mantle, and the diorite and quartz diorite were generated from a gabbroic magma by fractional crystallization, coupled with differential assimilation of ancient lower crustal material. The granodiorite was likely derived from partial melting of ancient lower crust with involvement of some mantle components. Involvement of both lithospheric mantle and ancient lower crust in the generation of the early Permian plutons indicates strong crust-mantle interaction in the northern NCB. Petrological associations as well as geochemical and Sr-Nd-Hf isotopic results show that the early Permian plutons were emplaced along an Andean-type active continental margin during southward subduction of the Palaeo-Asian oceanic plate beneath the NCB. Integration of our results with previously published data for late Carboniferous and late Permian to middle Triassic intrusions suggests that the continental arc on the northern margin of the NCB existed for at least 50 Ma during the late Palaeozoic, and final amalgamation of the Mongolian arc terranes with the northern NCB likely occurred during a period from *270 to *250 Ma, i.e, in the late Permian to earliest Triassic.Electronic supplementary material The online version of this article (

Origin of PGE-Depleted Ni-Cu Sulfide Mineralization in the Triassic Hongqiling No. 7 Orthopyroxenite Intrusion, Central Asian Orogenic Belt, Northeastern China

“…after subduction has completely stopped (Davies and Blanckenburg, 1995). The Paleo-Asian Ocean was closed along the Solonker-Changchun suture at ~250 Ma, subsequently the region underwent arc-arc and arc-continent collision (Wu et al, 2007;Zhang et al, 2009). Wu et al (2004) have suggested that many Late Triassic mafic-ultramafic intrusions in the region, including the Honqiling 7 intrusion, formed by basaltic magma generated by decompression melting of asthenospheric mantle, similar to our model.…”

End-Permian to mid-Triassic termination of the accretionary processes of the southern Altaids: implications for the geodynamic evolution, Phanerozoic continental growth, and metallogeny of Central Asia

“…Xiao et al (2003b) proposed that there was southward subduction under a narrow accretionary wedge in front of the North China craton, although without evidence of a continental margin magmatic arc. However, Zhang et al (2007cZhang et al ( , 2008b reported Carboniferous to early Permian hornblende-bearing granitic plutons (324 ± 6-274 ± 6 Ma) that were emplaced in an Andean-type, active continental arc on the northern margin of the North China craton, confirming that southward subduction also contributed to the closure of the Paleo-Asian ocean. From these relations Zhang et al (2008b) concluded that final amalgamation of the Mongolian arc terranes with the North China craton occurred in the late Permian to earliest Triassic.…”

Variable sediment flux in generation of Permian subduction-related mafic intrusions from the Yanbian region, NE China

“…In NE China, especially in the central Mongolia, the Permian mafic rocks show geochemical and isotopic features of N-MORBs and E-MORBs, reflecting the existence of oceanic basin at that time (Chen et al, 2012;Li et al, 2015). Permian arc magmatism along the northern margin of the North China Craton suggested a Cordillera-type active continental margin related to subduction of the paleo-Asian Ocean (Zhang et al, 2009). In the Yanbian area, Cao et al (2011) suggested that the subduction of the Paleo-Asian Ocean could last at ca.…”