关键词: 全新世, 火山碎屑堆积, 天池火山

Abstract: The Changbaishan Tianchi volcano on the border between China and North Korea (42? N,128? E) is the most dangerous one with high destructive eruption potential in China. In the research of recent eruption history of the Tianchi volcano, a set of recent ejecta were recognized through field investigation, grain size analysis and petrochemistry analysis. The new ejecta were found on the northeast side of the Tianchi Lake. It is a set of multi-layered pyroclastic deposits of 9.2m thick overlying the 1668 AD airfall deposit. Grain size analysis shows that the ejecta are composed mainly of fall deposit with an interbed of surge deposit, and the type of eruption is phreatomagmatic. Fractal dimension value of the surge deposit is 2.7113, while that of the fall deposits ranges from 2.3028 to 2.4627, having an average value of 2.36. In the microscope, skeleton vitric fragments are observed but clay mineral is not found in the deposits, indicating that they are primary deposit produced by explosive eruption. Petrochemistry analysis of pumice component indicates that the magma can be assigned to trachytic magma. Based on historical records, stratigraphic correlation and features of the deposits, it is estimated that the ejecta are the product of 1903 AD eruption.

Key words: Holocene, pyroclastic deposit, Tianchi volcano