A 2.5 Ga fore-arc subduction-accretion complex in the Dengfeng Granite-Greenstone Belt, Southern North China Craton
作者： Hao Deng , Timothy Kusky , Ali Polat , Chen Wang , Lu Wang
DOI: 10.1016/J.PRECAMRES.2016.01.024
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摘要: Abstract The Dengfeng granite-greenstone belt (DGGB), located in the southern segment of Central Orogenic Belt (COB) North China Craton (NCC), consists a volcano-sedimentary assemblage, intruded by tonalite, trondhjemite, granodiorite (TTG suite), diorite, granites and late mafic dikes. assemblage DGGB mainly tectonically imbricated basaltic amphibolites, meta-gabbroic rocks with minor ultramafic rocks, metagreywacke, marble quartzite, consistent characterisitics typical Phanerozoic subduction-accretion complexes. amphibolites yield metamorphic zircon 207Pb/206Pb age 2507 ± 26 Ma, interpreted to represent peak amphibolite facies metamorphism that took place during subduction/accretion protolith. are characterized tholeiitic affinity, flat LREE patterns negative Nb Zr anomalies. Based on mixed MORB- arc-affinities, have formed fore-arc tectonic setting. One potassic granite dike cutting across fabrics yields an intrusion 2492 ± 35 constraining minimum deformation for assembly package. TTG gneisses diorites western margin center complex, respectively. sample one diorite igneous ages 2514 ± 26 Ma 2518 ± 36 respectively, their ages. display high ratios (La/Yb)cn Sr/Y, depletion HFSE Nb, Ta Ti anomalies, those Archean TTGs. therefore considered be generated from partial melting shallowly subducting oceanic slab and/or accreted arc amphibolites. concentrations MgO (2.89–6.05 wt.%), Ni (148–178 ppm) Cr (85.7–120.6 ppm), highly fractionated REE depleted HFSEs Ta, Zr, Hf We suggest high-Mg may been derived hydrated mantle wedge which was previously metasomatized subduction-derived melts fluids. Collectively, Neoarchean subduction-accretion-collision event is proposed DGGB. represents related suture zone ca. 2.5 Ga arc-continent collision between TTG-dominated terrane COB Eastern Block NCC. further propose long N-S striking occurring eastern complex south, melange Zanhuang Complex central, ophiolitic Zunhua-Dongwanzi structural north, separate
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