Shahewan Rock Geochemical Characteristics And Tectonic Attribution Study

The Shahewan granite pluton is located near Shangzhou, in central China. It was regarded as an important member of the Triassic "orogenic rapakivi" in the north Qinling belt based on petrographic studies^[18]. Although the formation of Rapakivi is still not well known, it is usually formed more than 100 Ma after collision, such that a rapakivi belt in the Qinling orogen was used to argue for the termination of the main orogenic process and beginning of the post-collision evolution of Qinling orogen belt^[39]. In other words, the main collision between the South and North China blocks occurred much earlier than generally accepted (Triassic)^[12]. Therefore, detailed study on the geochemcial characteristics of the Shahewan granite is important to understanding its tectonic affinity and, the evolution of Qinling orogenic belt.According to the major and trace element compositions of samples from Shahewan and nearby syn-collisional granites, Shahewan granite has the same geochemical characteristics as those of the nearby Caoping granites and other syn-collisional granites all along the South Qinling granite belt, with SiO₂ of 64.99%～69.69%, high Al₂O₃ contents (14.53%～16.2%). These samples are enriched in LREE and LILE, without obvious Eu anomaly (Eu=0.83～1.10), and thus are distinctively different from typical rapakivi. Therefore, it does not represent the end of the collision between the North and South China Blocks along the Qinling orogenic belt.