K—Ar Geochronology and Evolution of Cenozoic Volcanic Rocks in Eastrn China

Cenozoic volcanic rocks widespread in eastern China constitute an important part of the circum-Pacific volcanic belt.This paper presents more than 150K-Ar dates and a great deal of petrochemical analysis data from the Cenozoic volcanic rocks distributed in Tengchong,China‘s southeast coast,Shandong,Hebei,Nei Monggol and Northeast China.An integrated study shows that ubiquitous but uneven volcanic activities prevailed from the Eogene to the Holocene,characterized as being multi-eqisodic and multicycled.For example,in the Paleocene(67-58Ma),Eocene(57-37.5Ma),Miocene(22-18,16-19Ma),Pliocene(8-3Ma),and Early Pleistocene-Middle Pleistocene(1.2-0.5Ma) there were upsurges of volcanism,while in the Oligocene there was a repose period.In space,the older Eogene volcanic rocks are distributed within the region or in the central part of the NE-NNE-striking fault depression,while the younger Neogene and Quaternary volcanic rocks are distributed in the eastern and western parts.Petrologically,they belong essentially to tholeiite-series and alkali-series basalts,with alkalinity in the rocks increasing from old to youg.The above regularities are controlled by both global plate movement and regional inherent tectonic pattern.

K-Ar geochronology and evolution of Cenozoic volcanic rocks in eastern China

Cenozoic volcanic rocks widespread in eastern China constitute an important part of the circum-Pacific volcanic belt. This paper presents more than 150 K-Ar dates and a great deal of petrochemical analysis data from the Cenozoic volcanic rocks distributed in Tengchong, China’s southeast coast, Shandong, Hebei, Nei Monggol and Northeast China. An integrated study shows that ubiquitous but uneven volcanic activities prevailed from the Eogene to the Holocene, characterized as being multi-episodic and multicycled. For example, in the Paleocene (67-58Ma), Eocene (57-37.5Ma), Miocene (22-18, 16-19Ma), Pliocene (8-3Ma), and Early Pleistocene-Middle Pleistocene (1.2-0.5 Ma) there were upsurges of volcanism, while in the Oligocene there was a repose period. In space, the older Eogene volcanic rocks are distributed within the region or in the central part of the NE-NNE-striking fault depression, while the younger Neogene and Quaternary volcanic rocks are distributed in the eastern and western parts. Petrologically, they belong essentially to tholeiite-series and alkali-series basalts, with alkalinity in the rocks increasing from old to young. The above regularities are controlled by both global plate movement and regional inherent tectonic pattern.