Neoproterozoic IAT intrusion into Mesoproterozoic MOR Miaowan Ophiolite, Yangtze Craton: Evidence for evolving tectonic settings

Based on previous studies and this contribution, a new tectonic model is proposed for the Mesoproterozoic-Neoproterozoic geodynamic evolution of the northern margin of the Yangtze Craton: (1) the N-MORB-affinity mafic-ultramafic rocks in the MOS formed in an oceanic basin at ca. 1115 Ma; (2) subduction was initiated at ca. 1100 Ma beneath the MOS on which the ca. 1100 Ma Shennongjia arc (north of the MOS) was built; the MOS formed the overriding plate in this subduction zone with the harzburgite trapped as a part of the mantle wedge and reacting with the subduction-related boninitic melts forming dunite with U-shaped REE patterns; (3) with subsequent slab roll-back and opening of a fore-arc basin, forearc-affinity mafic rocks in the LMS were generated and intruded the ophiolitic mafic-ultramafic rocks between ca. 1000 Ma and ca. 970 Ma; and (4) the northern Yangtze Craton is inferred to have collided with the Shennongjia arc and MOS + LMS at ca. 940-930 Ma.