大兴安岭额尔古纳地块北段霍洛台地区花岗闪长岩锆石U-Pb年龄、成因及构造背景OACHSSCD

To investigate the magma source and tectonic background of Early Cretaceous granites in the Great Xing'an Range,this study selected the Huoluotai granodiorite in the northern segment of the Erguna Block as the research object.By conducting zircon U-Pb dating and electron probe mineral chemical analyses of plagioclase and biotite,the formation age,plagioclase structural characteristics,biotite composition,and magma source of the granodiorite were analyzed and discussed.The results indicate that the weighted mean age of the Huoluotai granodiorite is 137.6±1.0 Ma,representing its crystallization age in the Early Cretaceous.The plagioclase in the Huoluotai granodiorite exhibits a"reverse zoning"structure,with An values ranging from 13.90 to 26.54,with an average of 20.28,and is predominantly oligoclase.Biotite is classified as magnesium-rich biotite,with crystallization temperatures ranging from 709 to 748 ℃,averaging 726 ℃,suggesting the granite formed in a relatively high-temperature environment.The crystallization depth ranges from 3.37 to 4.05 km,with an average of 3.82 km,indicating relatively shallow crystallization of the biotite.The oxygen fugacity values range from-16.52 to-15.30,indicating relatively high oxygen fugacity.The TFeO/(TFeO+MgO)-MgO diagram of biotite suggests that the Huoluotai granodiorite is of mantle origin with minor crustal material involvement during magma ascent.Based on this,this study suggests that the Huoluotai granodiorite likely formed in an active continental margin tectonic setting associated with the subduction of the Paleo-Pacific Plate.