Abstract

The paper presents the first data on the Sr and Nd isotope composition of rocks from a unique collection of magmatic rocks of all petrographic types (basalts, gabbro, and peridotites) belonging to the lithosphere at the convergent plate boundary in the Aleutian Arc area. The rock samples were collected over large areas in the Northwest Pacific and Bering Sea. The results of this study provide reliable information on the geodynamic nature of the central segment of the Shirshov Rise, which is made up of magmatic rocks whose isotopic–geochemical features indicate that they were produced by magmatic melts that evolved within the crust and were derived by the partial melting of MORB parental source, which may have belonged to a mantle wedge. The isotopic–geochemical characteristics of the rocks at the Shirshov Rise suggest that the mafic–ultramafic rocks association may have been produced at a backarc spreading center. Petrological and isotopic–geochemical traits of rocks dredged at the northwestern flank of the Stalemate Ridge indicate that the sources of the parental melts were heterogeneous. Data on the rocks suggest that magmatism in this part of the Northwest Pacific may have involved a source responsible for the origin of the oldest seamounts in the Hawaiian–Emperor Volcanic Chain. Ultramafic rocks in the northwestern segment of the Stalemate Ridge show similarities with plutonic rocks found as xenoliths in volcanics of the Aleutian Island Arc. With regard for the scarcity of information on the structure of the lithosphere in this part of the Pacific, it can be cautiously suggested that the oceanic slope of the Aleutian Trench and adjacent segment of the Stalemate Ridge involve fragments of the basement of the Aleutian Island Arc.

中文翻译：

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西北太平洋岩浆源的地球动力学性质：对在相持山脊，本构低陷和Shirshov上升挖出的岩石的Sr和Nd同位素组成的数据的解释

摘要

本文提供了有关岩石中Sr和Nd同位素组成的第一批数据，这些数据来自阿留申弧区会聚板块边界处岩石圈的所有岩石学类型（玄武岩，辉长岩和橄榄岩）的唯一岩浆类型的集合。岩石样品采集于西北太平洋和白令海的大片区域。这项研究的结果提供了有关Shirshov隆起中心段的地球动力学性质的可靠信息，该岩石段由岩浆岩组成，其同位素-地球化学特征表明它们是由地壳内演化的岩浆熔体产生的，并由MORB父母源的部分融化，可能属于地幔楔。Shirshov Rise岩石的同位素-地球化学特征表明，镁铁质-超镁铁质岩石的结合可能是在后弧传播中心产生的。在僵局山脊西北侧疏rocks的岩石的岩石学和同位素地球化学特征表明，母体熔体的来源是异质的。岩石上的数据表明，西北太平洋这一地区的岩浆作用可能与夏威夷-皇帝火山链最古老海山的起源有关。僵持山脊西北段的超镁铁质岩与阿留申岛弧火山岩中的异种岩发现的深成岩相似。关于太平洋这一部分岩石圈结构的资料稀少，