【摘要】 与多数弧岩浆岩具有玄武岩、安山岩、英安岩和流纹岩的岩石组合不同,有一种弧岩浆岩以英安岩及与其成分相当的深成岩为主,由于其独特的地球化学特征被定义为埃达克岩。埃达克岩的显著特征是高Al2O3、Sr、Sr/Y、La/Yb、Zr/Sm而低Y、Yb、Sc。根据熔浆-矿物平衡热力学,岩浆被认为起源于榴辉岩相条件下俯冲板片的部分熔融。这样的熔融条件一般认为要求年轻(<25Ma)而热(≈10℃/km)的水化玄武质洋壳岩石发生俯冲作用,并在大约75～90km深处发生脱水部分熔融形成埃达克岩岩浆。在岩浆弧岩石成因体系中,这样的熔融条件最可能出现在板块俯冲的初始阶段。因此,埃达克岩概念的提出与研究可能具有重要的构造意义。更多还原

【Abstract】 Differing from most arc magmatic suites with a basalt-andesite-dacite-rhyolite association,a type of arc igneous rock,which is mainly composed of dacite and its plutonic equivalents,is defined as adakite due to its unique geochemistry.The distinct characteristics of Adakite are higher Al 2 O 3 and Sr con-tents and Sr /Y,La/Yb and Zr /Sm ratios and lower Y,Yb and Sc contents.Based on the melt-mineral equilibrium thermodynamics,it is believed that the adakitic magma originated by partial melting of a sub-ducted slab at garnet amphibolite-facies and eclogite-facies conditions.Commonly,such melting conditions require subduction of a young(<25Ma )and warm(≈10℃/km)hydrated basaltic oceanic crust in which adakitic magma is produced by dehydrated partial melting at depths of ～75-90km.In the arc petrogenesis system,such melting conditions are most likely to occur in the initial stage of slab subduction.Therefore,the presentation of the concept of adakite and its study may have important tectonic implications.更多还原