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碱度与板块运移速度的关系近代活火山多沿板块边缘分布.板块运移速度与碱度成反相关.运移形式有扩张(洋中脊)与闭合(毕鸟夫带)两种.扩张与闭合速度均与碱度成反相关.如扩张区主要是拉斑玄武岩系列,扩张速度愈大,岩石中SiO_2含量就愈高,碱度愈低.又如闭合区主要为钙碱性系列,但当闭合速度小于2.5cm/年时则变成碱性岩. 太平洋岛弧的闭合速度可分为三类(表7),
The relationship between alkalinity and plate migration velocity Most modern active volcanoes are distributed along the edge of the plate, and the transport velocity of plates is inversely correlated with alkalinity, with two types of migration (mid-ocean ridge) and closed (viaduct). Expansion and closure speed are inversely related with alkalinity .If the expansion area is mainly tholeiite series, the greater the expansion rate, the higher the content of SiO_2 in the rock, the lower the alkalinity.For another example, the closed area is mainly calc-alkaline series , But become alkaline rocks when the closure velocity is less than 2.5 cm / year.The closure rates of the Pacific Island arcs can be divided into three categories (Table 7)