Mineral composition and zircon U-Pb dating of the Hushan intrusion in Tongling area, Anhui Province

Abstract: Mesozoic intermediate-acid intrusive rocks in Hushan intrusion of Tongling area belong to the high potassium (K) calc-alkaline series, with main rock types being quartz monzodiorite and granodiorite porphyry. LA-ICP-MS zircon U-Pb dating of Hushan intrusion shows that the emplacement age of quartz monzodiorite and granodiorite porphyry are (143.2±1.2)Ma and (145.3±1.2)Ma respectively, belonging to Late Jurassic-Early Cretaceous. These data are consistent with eastern China’s J-K magmatic event. In addition, Hushan body has experienced two times of magma intrusion activities. The age of early granodiorite porphyry (145.3±1.2)Ma is consistent with the age of Yaoshan granodiorite porphyry (146.0±0.9) Ma in the Tongling ore district, and the age of late quartz monzodiorite (143.2±1.2)Ma is consistent with that of Tongguanshan and Tianebaodanshan (142±1)Ma,(141.7±1)Ma). From the study of geochemistry and plagioclase-hornblende thermobarometry, the authors conclude that the magma crystallization temperature and the corresponding pressure varied in the range of 768~838°C and 3.44×108 ~5.42×108 Pa, respectively. Hushan intrusion was derived from the mixture of the mantle magma and crustal magma, with their corresponding depths being 11~18 km.