关键词: 新太古代晚期, 岩石地球化学, 锆石U-Pb年代学, 钾质花岗岩, 本溪地区

Abstract: The Benxi area of Liaoning Province is located in the northeastern part of the eastern North China craton, where Neoarchean plutonic intrusive rocks and metamorphic supracrustal rocks are widely developed, but no kaligranites have been reported. The formation process of kaligranites is an important symbol of the maturation and stability of the early continental crust. The discovery of kaligranites is significant for the systematic study of the formation and evolution of the early continental crust in the North China craton. In this paper, the petrology, diagenetic age, and petrogeochemistry of kaligranites in Majiagou, Benxi area are studied, and the petrogenesis and tectonic setting of formation are discussed. Majiagou pluton is a gneissic medium-fine-grained biotite monzogranite. The  zircon U-Pb dating data show that the 207 Pb/ 206 Pb weighted average age is (2 490±21) Ma, suggesting the kaligranites formed in the Late Neoarchean. The granite is weakly peraluminous and high potassium calc alkaline kaligranite. The high field strength elements La, Zr, Th and large ion lithophile elements K, Nd are enriched, while high field elements P, strength elements Nb and large ion lithophile elements Sr, Ti are depleted. The REE partition curve is rightward with negative Eu anomalies, indicating S-type granite. The magma originated from the crust and the product of partial melting of metamorphic mudstone, which formed in an extensional environment after collisional orogenesis at active continental margins. It represents the last magmatic activity before the formation of the consolidated basement of the Archean craton in North China, and marks the completion of the collage of micro-blocks in Benxi area in the Late Neoarchean, and together with other regions, forming a stable North China Archean craton.

Key words: Late Neoarchean, rock geochemistry, zircon U-Pb chronology, kaligranite, Benxi area