SHRIMP dating of the Permian Guyang diorite-quartz diorite-tonalite suite in the northern margin of the North China Craton

Abstract：Using a petrogeochemical means, we recognize a diorite-quartz diorite-tonalite suit in the northern margin of the North China craton, some 100-180 km south of the Permian Solonker ophiolite-decorated suture. The granitoid rocks are all sodic, consistent in composition with a plutonic arc. SHRIMP dating of zircons from two diorites yielded weighted mean 206Pb/238U ages of 293±4 Ma and 266±4 Ma. A quartz diorite and a tonalite are dated at 272±7 Ma and 277±3 Ma respectively. These Permian granitoid rocks were thus emplaced continuously. They are nearly coeval with, or slightly younger than, the Solonker SSZ (supersubduction zone)-type ophiolite. On the basis of a specific tectonic setting and an age relationship with the Permian Solonker SSZ-type ophiolite, we interpret the sodic granitoid suit investigated, together with near-contemporaneous andesites of the area, to form a continental margin arc.