陆壳垂向增生的两种方式:以大兴安岭为例

Two kinds of vertical accretion of the continental crust: an example of the Da Hinggan Mts

本文讨论了大兴安岭由于中生代底侵作用形成的两种类型的陆壳增生方式： １） 来自地壳底部壳幔混源岩浆房的花岗岩和火山岩对上部陆壳的增生， 岩浆的侵位和喷发集中在１４５～１１５ Ｍａ， 它们具明显的幔源岩石同位素特征， 如正的εＮｄ （ｔ）值（０～４），低的８７Ｓｒ／８６ Ｓｒ 初始比值（０．７０４～０．７０８）等； ２）早中生代形成的镁铁－超镁铁质堆晶岩（２４１～２１４ Ｍａ）对下部陆壳的增生。

The paper expounds two kinds of vertical accretion of continental crust in Da Hinggan Mts caused by Mesozoic mantle magmatic underplating: 1) representative of the mantle substance dominated hybrid granites and volcanic rocks which are originated from the crust mantle mixing magma ponding at the base of the crust Their intrusion or/and eruption during 145～115 Ma gives rise to growth of the upper middle crust in the Late Mesozoic, and geochemically, they are characterized by distinct mantle isotopic features with positive ε Nd ( t ) (0～4) and low initial 87 Sr/ 86 Sr (0 704～0 708); 2) representative of the Early Mesozoic mafic ultramafic cumulates (241～214 Ma) They are products of direct addition of the mantle substance to the lowermost continental crust by mafic magmatic underplating, which results in the vertical accretion of the lower continental crust in Da Hinggan Mts in the Early Mesozoic