关键词: 呼玛地区, 花岗岩, 锆石U-Pb测年, 地球化学, 埃达克质岩

Abstract: To elucidate the petrogenesis and tectonic settings of the Mesozoic rock formations in the Xing’an region of the Greater Khingan Range, this study employs petrology, chronology, and whole-rock geochemistry methods to investigate the Early Cretaceous intrusive rocks in the Huma area of Heilongjiang Province. The results reveal that the intrusive rocks are calc-alkaline to high-potassium calc-alkaline, quasi-aluminous to weakly peraluminous, crystallizing between (121.3±1.2) and (118.7±0.9) Ma. The rare earth element distribution patterns display a rightward trend with a weak positive Eu anomaly (0.98-1.11), enriched in large ion lithophile elements like K, Sr, Ba, and depleted in high field strength elements such as Nb, Ta, Ti, and P. The rocks show elevated ratios of Sr/Y (57.66-145.76), LaN/YbN (11.66-29.52), high Mg# (50.93-57.63), w(Cr) (77.00×10-6-92.60×10-6), and w(Ni) (23.20×10-6-32.60×10-6), indicating adakitic-like characteristics. Based on the comprehensive research, it is believed that the intrusive rocks primarily crystallized in an extensional environment following the closure of the Mongolian-Okhotsk Ocean, likely caused by lithospheric delamination thickening the lower crust and resulting in the upwelling of mantle-derived magma, forming adakitic-like rocks.

Key words: Huma area, granites, zircon U-Pb dating, geochemistry, adakitic-like rocks