Chronology and geochemical characteristics of granite in Weilianhe of Inner Mongolia and its geological significance

The Weilianhe W deposit in eastern Ujumchin of Inner Mongolia is a quartz-vein type deposit in the mid-eastern part of the Central Asian Orogen. Based on spatial relationships, the authors revealed that granite is closely associated with mineralization. The authors conducted precise laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) U-Pb zircon dating and geochemical analysis of the granite. The U-Pb dating shows that the granite is (145 ±1)Ma, and the weighted average age is (143±1)Ma. Major and trace element geochemistry shows that the granite is characterized by high SiO₂ and K₂O content, a "rightinclined" shape of the chondrite normalized REE patterns, enrichment of large ion lithophile elements (LILEs), and depletion of high field strength elements (HFSEs) such as Nb, P, Ba. The granite is high-K calc-alkaline, has a strong negative Eu anomaly (Eu/Eu^*=0.22-0.42), low P₂O₅ content, A/CNK near the value of 1, enriched in large-ion lithophile elements (LILEs such as Th, U, Nd, and Hf), and notably depleted in Ba, Sr, P, Ti, and Nb. These characteristics define the Weilianhe granite as a highly fractionated peraluminous granite. According to the granite age and the characteristics of granite, the authors hold that the Weilianhe deposit is related to a major Early Cretaceous mineralizing event in China known as the Yanshanian movement. The tectonic setting for the ore deposit was the post-tectonic stretching setting after the oblique subduction of the Pacific plate.