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埃达克岩的概念是十多年前提出来的,指由俯冲的年轻洋壳熔融形成的火成岩。自从最初在现代岛弧近十个地方报道埃达克岩以来,新近又在几个地方发现有埃达克岩(如日本西南部,外墨西哥火山岩带,等等)。但是,过去十多年的研究也表明,埃达克岩可以由俯冲期间的其它过程产生(例如,沿俯冲板片的撕裂边,留在上地幔中的板片残余等)。另外,埃达克岩似乎与一些岩石是共生组合,这些岩石包括高镁安山岩、富Nb的弧玄武岩(NEAB),还可能有玻安岩(几个研究者已在玻安岩中发现有埃达克岩的组分)。高镁安山岩不是来自埃达克与地幔的相互作用(Adak-type),就是来自此相互作用期间地幔的熔融(Piip-tyPe);富Nb的弧玄武岩,据认为是来自一种被埃达克岩广泛交代的地幔的部分熔融。作为一个新的岩套,埃达克岩交代火山岩系列已被建议用来解释各种岩石组合。此外,大量的富Nb弧玄武岩也已被发现包含有超镁铁质的地幔包体,而这些包体有高亏损地幔与埃达克岩反应的明显证据。 关于主要与下地壳熔融而不是与俯冲板片有关的埃达克岩的起源已提出几种假说。一个模型认为,下地壳熔融出现在玄武质岩浆底侵下地壳时。但是,有许多理由似乎可以排除这种模式。另一种模型认为,在大陆地壳很厚的区域,下地壳可能变成榴辉岩,从而拆离并下沉到地幔中(?
The adakite concept was proposed more than a decade ago and refers to igneous rocks formed by the melting of the subducted young oceanic crust. Since the addendum rock was first reported in nearly ten modern arcs of the island, adakites (such as the southwestern Japan, the outer Mexico volcanic belt, etc.) have recently been discovered in several places. However, research over the past decade or so has also shown that adakite can be produced by other processes during subduction (eg, tearing along subducting slabs, plate remnants remaining in the upper mantle, etc.). In addition, adakites appear to be symbiotic with rocks that include high-Mg andesite, Nb-rich arc basalt (NEAB), and possibly boehmite (several investigators have identified Angstroms Dak rock component). The high-Mg andesite does not come from the Adak-type interaction between the Adak-type and the mantle derived from this interaction (Piip-tyPe); Nb-rich arc basalts are believed to originate from an adak- Part of the mantle partially melted by rocks. As a new mantle, adakite metasomatic volcanic series have been suggested to explain various rock assemblages. In addition, a large number of Nb rich-arc basalts have also been found to contain ultramafic mantle inclusions with clear evidence of high depletion mantle reactions with adakites. Several hypotheses have been proposed regarding the origin of adakites, which are mainly associated with the melting of the lower crust rather than with subducting slabs. One model suggests that the melting of the lower crust occurs when the basaltic magma invades the crust. However, there are many reasons why this pattern can be ruled out. In another model, the lower crust may become an eclogite in the thick crust of the mainland, detaching and sinking into the mantle (?