College of Earth Sciences，Jilin University，Changchun 130061，China

The petrogenesis and geodynamic setting of the Late Jurassic Baita porphyry quartz monzodiorite in Xingcheng--Liaoxi area provide information for understanding the Mesozoic tectonic evolution of the northeastern North China Craton． In this paper，geochronological，whole-rock geochemical，and in-situ zircon Hf isotopic analyses of Baita porphyry quartz monzodiorite were investigated to constrain the crystallization age and petrogenesis．Zircons exhibit typical oscillatory zoning in cathodoluminescence images and show relatively high Th /Uratios ( 0． 78--1． 62) ，and U-Pb analyses indicate that these rocks were crystallized during the Late Jurassic( 159 ± 1 Ma) ． Geochemically，they are characterized by high contents of SiO2 ( 65． 21wt%--65． 31wt%) ，Al2O3( 16． 29wt%--16． 31wt%) ，Sr ( 521 ×10 －6 －539 ×10 －6 ) ，and Sr /Y ratio ( 45． 1--47． 8) but low Y ( 10． 9 ×10 － 6 － 12． 0 × 10 － 6 ) ，with obvious adakitic geochemical affinities． These above-mentioned findings，combined with their negative εHf( t) values ( － 21． 7 to － 20． 2) ，corresponding two-stage model age ( TDM2) of 2 579--2 484 Ma，as well as low MgO ( 1． 38wt%--1． 39wt%) ，Cr ( 18． 5 ×10 －6 －19． 5 × 10 －6 ) and Ni ( 9． 45 × 10 －6 －9． 46 × 10 － 6 ) values，indicate that Baita porphyry quartz monzodiorite may be generated by partial melting of the Neoarchean-Paleoproterozoic thickened basaltic lower crust． Based on the results from this study and previous regional studies，it is concluded that Baita porphyry quartz monzodiorite was spatially related to the westward subduction of the Paleo-Pacific plate．