Petrology and Geochemistry of Jinlongdingzi Active Volcano—the Most Recent Basaltic Explosive Volcano at Longgang

The Jinlongdingzi active volcano erupted before 1600a, and it is the latest basaltic explosive volcano at Longgang Volcano. Its volcanic products include the Jinlongdingzi volcanic cone (elevation 999.4m), the lava flow and the widely\|spread volcanic pyroclastic sheet (Sihai Pyroclastic Sheet). Jinlongdingzi volcanic rocks are trachybasalts with very similar REE patterns and incompatible element patterns, and their \{\{\}\+\{87\}Sr\}/\{\{\}\+\{86\}Sr\} and \{\{\}\+\{143\}Nd\}/\{\{\}\+\{144\}Nd\} ratios range from \{0.704846\} to \{0.704921\} and from \{0.512619\} to \{0.512646\}, respectively. It is revealed that the trachybasalt has the character of primary magma derived directly from mantle sources with very little evolution and crust contamination during its ascending. The younger mantle xenoliths demonstrate that the mantle source of the Jinlongdingzi Volcano is hydrous, with relatively low temperature.