Abstract

The paper presents data on amphibolites dredged during Cruise 249 of the German R/V Sonne at three sites: one at the northwestern termination of the Stalemate Ridge (ocean-side slope of the Aleutian Trench) and two at the western slope of the north Shirshov Rise (in the western sector of the Bering Sea). Data on the petrography and geochemistry of the amphibolites and their estimated P–T metamorphic parameters provide an insight into the probable geodynamic environments in which their protoliths were formed and into the geodynamic regime of their metamorphism. The magmatic protolith of amphibolites in the Shirshov Rise was produced by the melting of a strongly depleted mantle source and, perhaps, was a product of suprasubductional magmatism. The isotope composition and distribution of HFSE in amphibolites from the Stalemate Ridge suggest that the protolith of these rocks was a derivative of tholeiitic melt parental for N-MORB. The typical mineral assemblage and P–T metamorphic parameters of glaucophane-bearing amphibolites from the Shirshov Rise indicate that the protolith of these rocks was metamorphosed within a subduction zone related to the Cretaceous–Paleogene Olyutorsky Arc. Interpretations of the age and geodynamic nature of metamorphism of amphibolites in the Stalemate Ridge based on currently available data cannot be regarded as absolutely realistic, and the most likely scenario for the origin of the amphibolites is that they were produced within a subduction zone that was no younger than 55–50 Ma and preceded the modern Aleutian Arc. The extinction of this ancient subduction zone should have been associated with the development of the Aleutian Arc north of it. According to this geodynamic scenario, an ophiolite sequence was produced where the ancient subduction zone had occurred. The ophiolite consisted of rocks of an mafic–ultramafic association and amphibolites. This scenario may, however, be a matter of further discussion.

中文翻译：

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西北太平洋僵持岭和Shirshov上升的两栖动物：聚变板块边界变质作用的地球动力学机制的指示

摘要

本文介绍了德国R / V索内河249巡游期间在三个地点挖出的角闪石的数据：一个在Stalemate Ridge的西北端（阿留申海沟的洋侧斜坡），两个在北舍尔肖夫的西斜坡。上升（在白令海的西部）。数据的斜长角闪岩相学的和地球化学及其估计的P -牛逼变质参数提供了对形成原岩的可能地球动力学环境以及其变质作用的地球动力学范围的洞察力。Shirshov Rise中岩闪石的岩浆原生岩是由强烈耗尽的地幔源融化产生的，也许是超俯冲岩浆作用的产物。Stalemate Ridge闪石中的HFSE的同位素组成和分布表明，这些岩石的原岩是N-MORB母体的熔融熔体的衍生物。典型的矿物组合和P - ŤShirshov Rise中含葡花环的角闪石的变质参数表明，这些岩石的原石在与白垩纪-古近纪Olyutorsky弧有关的俯冲带内变质了。基于当前可获得的数据，无法解释在相持岭中闪石的变质的年龄和地球动力学性质，这绝对不能说是现实的，而闪石的起源最有可能的情况是，它们是在不存在俯冲带的俯冲带中产生的。年龄小于55-50 Ma，并且先于现代阿留申弧线。这个古老的俯冲带的灭绝应该与它以北的阿留申弧线的发展有关。根据这种地球动力学情景，在古代俯冲带发生的地方形成了蛇绿岩层序。蛇绿岩由镁铁质-超镁铁质的岩石和闪石组成。但是，这种情况可能需要进一步讨论。