作　　者： ; ; ; ; ;

机构地区： 中国科学院地球化学研究所

出　　处： 《高校地质学报》 2003年第2期279-292,共14页

摘　　要： 根据K Ar法和Ar Ar法定年数据 ,藏北新生代火山岩从早到晚可划分为多格错仁和走构油茶错高钾钙碱性系列 (4 0～ 30Ma)、巴毛穷宗和鱼鳞山白榴石碧玄岩 -响岩系列 (2 9～ 2 4Ma)以及黑石北湖钾玄岩系列 (1.5Ma)。从岩石化学和同位素方面对区内新生代火山岩进行了研究 ,认为藏北新生代火山岩同时具有板内碱性玄武岩和岛弧玄武岩的双重地球化学特征。在成因和源区上各系列存在着差异 ,高钾钙碱性系列为富集地幔玄武岩底侵作用导致地壳物质部分熔融的产物 ,并经历了地壳的AFC过程。而白榴石碧玄岩 -响岩系列和钾玄岩系列来自与古俯冲有关的“古老富集地幔” ,为岩浆分离结晶作用的产物。岩浆起源深度随时间变新逐渐变大。 Based on the ages determined by K Ar and Ar Ar dating methods, the Cenozoic volcanic rocks in the studied region, from early to late, can be subdivided into three series. They are high K calc alkaline series (40～30Ma), leucite basanite-phonolite series (29～24Ma) and shoshonite series (1.5Ma), respectively. The Cenozoic volcanic rocks in northern Tibet, mainly studied by petrochemical and isotope methods, have the characteristics of both WPAB (within plate alkali basalt) and IAB (Inland arc basalt). For these three series of rocks, the difference exists not only in their geneses, but also in their sources. We interprete that high K calc alkaline series was generated by partial melting of crust due to underplating of the basaltic magma from enriched mantle, and underwent the process of crust's AFC. However, the leucite basanite-phonolite series and shoshonite series were evolved from an old enriched mantle related to ancient subduction, and their geneses are attributed to the fractional crystallization in different degrees. From this study, it is clear that the depth of the sources for the Cenozoic volcanic rocks in this area gradually becomes deeper and newer from south to north.

关 键 词： 藏北 新生代 火山岩 板内 岛弧 富集地幔

领　　域： [天文地球] [天文地球]