Geochronology of and Nd-Sr-Pb Isotopic Evidence for Mantle Source in the Ancient Subduction Zone beneath Sanshui Basin, Guangdong Province, China

<正> The available petrochemital data indicate tnat volcanic rocks in the Sanshui basin of Cuangdong Prov-ince are charactenstic of the island-arc thoieiite-calc-alkaline series. Their K-Ar ages range from 43 to 64 Ma,corresponding to Early Tertiary. The Nd-Sr-Pb isotopic comelations give two binary mixing trends,indicating a mixed source of Leiqiong depleted mantie, seawater and aitered sediments pertaining tosubduction. Dur studies have confirmed the existence of an ancient subduction zone beneath the South Chi-na continent, which is considered to have resulted from the suturing of various terrains in southem China.