Temporal-spatial framework of magmatic intrusions in Luzong volcanic basin in East China and their constrain to mineralizations

Luzong Mesozoic volcanic basin is located in the Lower Yangtze River fault-depression zone, where is the north margin of the Yangtze block. The volcanic and intrusive plutons occur widely in Luzong basin, including four formations of volcanic rocks, such as, Longmenyuan Formation, Zhuanqiao Formation, Shuangmiao Formation and Fushan Formation and 34 intrusive plutons. Based on detailed field geological work and our former geochronology research on five plutons such as Bajiatan pluton, Chengshan pluton, Huashan pluton, Huangmeijian pluton and Zongyang pluton, we further carried out systematic geology and geochronology study of intrusive plutons in the Luzong Basin. LA-ICP-MS zircon U-Pb dating for 15 plutons has been carried out, which yield the ages of Huangtun pluton (134.4 2.2 Ma), Yueshan pluton (132.7 1.5 Ma), Bamaoshan pluton (132.7 1.9 Ma), Jianshan pluton (132.0 1.3 Ma), Xiewani pluton (131.6 1.1 Ma), Longqiao pluton (131.1 1.5 Ma), Jiaochong pluton (129.6 1.3 Ma), Tudishan pluton (127.4 2. 8 Ma), Fenghuangshan pluton (128.4 0.9 Ma), Luolin pluton (126.3 2.O Ma), Longwangjian pluton (126.5 1.5 Ma), Xiaolin pluton (126.2 1.8 Ma), Dagangyao pluton (125.9 1.3 Ma), Batan pluton (125.1 1.1 Ma), Maowangmiao pluton (123.9 1.9 Ma), respectively. The epoch of plutons in the Luzong basin is 134-123Ma. According to the epoch and geological characteristics, the intrusive rocks in the Luzong basin can be divided into two stages. The early stage monzonite-diorite plutons outcrop in the north part of the Luzong basin with epoch of 134-130Ma, are controlled by NNE orient structures and volcano-structure and have close relationship with Longmenyuan and Zhuanqiao cycle volcanic activity. The late stage intrusive plutons have two types. One type is syenite and outcrops in the south part of the Luzong basin, whose epoch is 129-123Ma. Those syenite plutons are mainly controlled by NNE orient structures or volcano-structure and share close relationship with Shuangmiao and Fushan cycle volcanic activity. The other type is A-type granites and outcrops in the southeast margin of the basin, whose epoch is 126-123 Ma. Those A-type granites are controlled by regional NNE deep faults and have no relationship with the basin volcano-structures. The iron, copper, gold, lead, zinc and uranium deposits in the study area related to magmatic activities can be classified into three metallogenic seiries. The monzonite-diorite plutons have close relationship with Luohe, Nihe and Longqiao iron deposits, Yueshan lead and zinc deposit and Jingbian and Bamaoshan copper deposits. The syenite plutons have close relationship with Makou and other iron deposits. The A-type granites have close relationship with No. 3440 and other gold uranium deposits. Regionally, there are three periods (145-136Ma, 135-127Ma, 126-123Ma) of magmatic and ore-forming activities in the Middle-Lower Yangtze River Valley metallogenic belt. The intrusive plutons in the Ning-Wu basin were the products of the second and third period magmatic activity and obviously later than the first period high-K calc-alkaline intrusions related to skarn-porphyry Cu-Au mineralizations in the uplift areas in the Middle-Lower Yangtze River Valley metallogenic belt. The intrusive plutons in Luzong volcanic basin were thought to be formed under regional lithospheric extension and thinning environment which has great significance for further research and exploration.