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Abstract: 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.

Abstract: The available petrochemical data indicate that volcanic rocks in the Sanshui basin of Guangdong Province are characteristic of the island-arc tholeiite-calc-alkaline series.Their K-Ar ages range from 43 to 64 Ma, corresponding to Early Tertiary. The Nd-Sr-Pb isotopic correlations give two binary mixing trends, indicating a mixed source of Leiqiong depleted mantle, seawater and altered sediments pertaining to subduction.Our studies have confirmed the existence of an ancient subduction zone beneath the South China continent, which is considered to have resulted from the suturing of various terrains in southern China.

Abstract: Li-F granites all over the world can be represented by three end members, i. e., the Na-rich ongonite (O), the K-rich xianghualingite (X) and the Si-rich topazite (T). Characters and criteria are presented for these end-member rocks. Vertical zoning in Li-F granites, as reflected by increasing normative Q and C (corundum) and decreasing ALK (K2O+ Na2O) with increasing content of fluorine, can be explained using the three-end-member scheme in terms of petrochemistry and norms. Considering the difference in melt structure, viscosity and density between the end members, in couple with the regularities that govern the Na-K and SiALK segregation known from field evidence and experiments, it is suggested that the three end members may have resulted from liquid segregation (immiscibility) rather than from crystal fractionation as commonly believed.