Genesis and source affinities of heterogeneous ultramafic rocks in the North Kongling Complex, Yangtze craton: Architecture of a Paleoproterozoic accretionary orogen

Ultramafic massifs are minor but meaningful components of orogens because they record the mantle properties and processes plate generation, subduction, accretion, collision, thus providing key information about crust-mantle interaction evolution orogens. Here, we present an integrated study field observations, whole-rock mineral geochemistry, zircon U-Pb ages, Sm-Nd Re-Os isotopes for serpentinized harzburgites olivine pyroxenites from Paleoproterozoic Shuiyuesi mélange belt, North Kongling Complex, to constrain tectonic Yangtze craton, South China. The characterized by enrichment light rare earth elements (LREEs) negative εNd(t) (−4.3 −3.9) values, have high Mg# (91.7−93.1) very low Re contents (<0.09 ppb) γOs(t) (−5.1 −4.0) values. Archean model ages (TRD = 2.82 Ga) that most depleted isotope composition represent estimates age initial melt extraction. Metasomatic zircons yield a weighted average ca. 2.04 Ga, which is interpreted metasomatism during subduction event. These geochemical isotopic features geochronologic results suggest protolith in Complex originated as fragments late Mesoarchean (ca. subcontinental lithospheric experienced melt/fluid subarc wedge at Ga. cumulates, MgO, Ni, Cr slightly enriched LREEs depletion strength (HFSEs). They positive (+2.0 +6.6) values Nd (2.41−2.05 Ga), suggesting were derived source. Metamorphic indicate subsequent metamorphism 2.0 response collision. together with metabasites belt dismembered oceanic lithosphere formed suprasubduction zone Paleoproterozoic. Combined rocks it appears peridotites ophiolitic simultaneously accreted orogenic We further propose channel may played important role architecture accretionary orogen, both materials would been scraped off slab subduction-accretion.