Discovery of the Mid-Late Jurassic volcanic rocks (163.4 Ma) in Nanhuangcheng Island, Shandong Province, China

1. Objectives Changshan Islands are located on the geographical boundary between the Bohai Sea and the North Yellow Sea,China. Intensively tectonic deformation developed in this area, which is an important connection point to study the tectonics of the Shandong Peninsula and Liaoning Peninsula.Previous studies have shown that the lithologies of the three northern islands（Beihuangcheng Island, Nanhuangcheng Island, and Xiaoqin Island） of the Changshan Islands include Neoproterozoic quartzite, phyllite, and slate（Fuzikuang Formation of the Penglai Group）, and a few areas are covered by Quaternary slope deposits, marine deposits and loess（Fig.1 a; Qiao EW et al., 2019）. Recently, a set of volcanic rocks was firstly discovered in Nanhuangcheng Island（Fig. 1 a）. The volcanic rocks are about 0.7 m thick, contacting with a conglomerate layer with a thickness of about 1.5 m（Fig. 1 b）.The basal Neoproterozoic quartzite（Fuzikuang Formation） is overlain by the assemblage unit of the volcanic rocks and conglomerate layer（Fig. 1 b）. This study focuses on the first evidence for the discovery of the volcanic rocks and presents a set of high-precision chronological data on the volcanic rocks in Nanhuangcheng Island.