Composition and formation of Palaeozoic Erlangping ophiolitic slab, North Qinling: Evidence from geology and geochemistry

The analyses based on the protolith formation, metamorphic and deformation reveal that the Erlangping Group is composed of different lithological slices, without any significance in stratigraphy. It is therefore to discard the Erlangping Group into the Damiao slab, the Erlangping ophiolitic slab and the Xiaozhai slab. The Erlangping ophiolitic slab only includes the former Huoshenmiao Formation and it is mainly composed of massive basalts, pillow basalts, sheet dikes, gabbro and a few of ultramafic intrusions with patches of plagiogranite, overlain by radiolarian silicolites. A lot of microfossils were discovered in the silicolites that mark the Erlangping ophiolitic slab mainly formed in the Early to Middle Ordovician. In geochemistry, most of the basalts and diabase dikes are consistent with N-MORB except a few of samples effected by alteration. The Erlangping ophiolitic slab represents a remnant piece of ancient ocean crust which is most suitable to a back-arc basin setting. A mean 207Pb/206Pb age of 480 Ma for zircons separated from the plagiogranite intruded into the basalts seems to indicate the minimum age of the emplacement of the Erlangping ophiolitic slab.

The analyses based on the protolith formation, metamorphic and deformation reveal that the Erlangping Group is composed of different lithological slices, without any significance in stratigraphy. It is therefore to discard the Erlangping Group into the Damiao slab, the Erlangping ophiolitic slab and the Xiaozhai slab. The Erlangping ophiolitic slab only includes the former Huoshenmiao Formation and it is mainly composed of massive basalts, pillow basalts, sheet dikes, gabbro and a few of ultramafic intrusions with patches of plagiogranite, overlain by radiolarian silicolites. A lot of microfossils were discovered in the silicolites that mark the Erlangping ophiolitic slab mainly formed in the Early to Middle Ordovician. In geochemistry, most of the basalts and diabase dikes are consistent with N-MORB except a few of samples effected by alteration. The Erlangping ophiolitic slab represents a remnant piece of ancient ocean crust which is most suitable to a back-arc basin setting. A mean 207Pb/206Pb age