Zircon U-Pb chronology, Nd-Hf isotope geochemistry and petrogenesis of Paleoproterozoic pyroxene syenite in Huangtuyao area, Inner Mongolia

Paleoproterozoic tectonic evolution of North China Craton has been a focal point of Precambrian geological research, particularly in the model of the last stage of collision orogeny. Research achivement of zircon U-Pb geochronology, Nd-Hf isotope geochemistry and rock geochemistry of the Paleoproterozoic pyroxene syenite, which intruded in the tonalite-trondhjemite-granodiorite (TTG) suite in Huangtuyao area, are presented in this article. Pyroxene syenite was emplaced at approximately 1824 Ma, trapping metamorphic zircons at similar to 1.92 Ga and magmatic zircons at similar to 2.4 Ga from the surrounding rocks. The pyroxene syenite are characterized by low silica content, high sodium-potassium ratio, significant light-heavy rare earth element (REE) fractionation without Eu anomaly, relative enriched large ion lithophile elements (LILE) of Rb, Ba and K, and depleted high field strength elements (HFSE) of Th, U, Nb and Ta. The epsilon(Nd)(t) values of the syenite range from -5.2 to -5.9, with Nd depleted mantle model ages (t(DM)) of 2.56 similar to 2.61 Ga. The Hf isotope single-stage model age for all zircons is similar to 2.5 Ga, with a two-stage model age of similar to 2.7 Ga, and the similar to 1824 Ma magmatic zircon exhibits relatively enriched Hf isotopic compositions (epsilon(Hf)(t)=-11.3 similar to-2.1). Petrological and chemical characteristics and isotope evidence indicates that the pyroxene syenite originated from partial melting of a middle-lower crust similar to the source of its surrounding rocks (TTG), with minimal influence from mantle materials. This study provides new evidence for constraining the timing, scale and nature of the final stage of collision-compression to uplift during Paleoproterozoic in North China Craton.