Oceanic Crust Formation in the Mid-Atlantic Ridge Segment between Azores and Icelandic Plumes: Results of Geological and Petrogeochemical Studies

IF 1 4区地球科学 Q3 GEOCHEMISTRY & GEOPHYSICS Geotectonics Pub Date : 2023-10-01 DOI:10.1134/s0016852123050084

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Abstract

The structure of the ocean floor and the composition of basalts and dolerites of the MAR segment between the Maxwell and Charlie Gibbs FZs (North Atlantic) were studied based on the data obtained during the 53rd cruise of the R/V Akademik Nikolaj Strakhov organized and performed by the Geological Institute of the Russian Academy of Sciences over the period of July 7–August 15, 2022. In this segment, areas of greater and lesser magmatic productivity, which correspond to higher and lower bottom relief, alternate along the spreading axis. In high-relief areas, spreading cells form in the axial zone, and rises of tectonic and volcanic genesis dominate in the crest zone. In low-relief areas, the rift valley consists of deep rift basins; low ridges are developed on the flanks, which are separated by wide depressions. Oceanic N- and T-type tholeiites and E-MORB-type basalts and dolerites are distinguished among the studied volcanics. The N-tholeiites are widespread and were derived from mainly depleted mantle (source of DM). E-MORB-type basalts and dolerites are found in high-relief areas. Their mantle substrate is formed by a mixture of DM and EM-2 material with the subordinate role of HIMU. T-MORB volcanics are mainly localized on large volcanic rises in the southern part of the studied MAR segment and were melted from a substrate formed by a mixture of DM and HIMU material with the subordinate role of EM-2. Two types of mantle inhomogeneities involved in melting are reconstructed: passive and active. The former are represented by blocks of the transformed continental lithosphere that are similar in composition to the EM-2 mantle source. Active inhomogeneities associate with the uplift near Maxwell FZ of the microplume of the enriched mantle with a composition close to HIMU and with its subaxial flow in the north direction up to the Charlie Gibbs FZ.

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亚速尔群岛和冰岛羽流之间的大西洋中脊部分的洋壳形成：地质和岩石地球化学研究结果

摘要根据俄罗斯科学院地质研究所于 2022 年 7 月 7 日至 8 月 15 日组织和实施的 Akademik Nikolaj Strakhov 号考察船第 53 次航行期间获得的数据，研究了 Maxwell 和 Charlie Gibbs FZ 之间 MAR 区段（北大西洋）的洋底结构以及玄武岩和辉绿岩的成分。在这一区段，岩浆生产力较高和较低的地区（相当于较高和较低的底部起伏）沿扩张轴交替出现。在高低起伏区，轴向区形成扩张单元，峰顶区则以构造和火山成因的隆起为主。在低起伏地区，裂谷由深裂盆地组成；侧翼形成低山脊，山脊之间有宽阔的洼地相隔。在所研究的火山岩中，有大洋型 N 型和 T 型透辉岩以及 E-MORB 型玄武岩和辉长岩。N 型透辉岩分布广泛，主要来自贫化地幔（DM 的来源）。E-MORB型玄武岩和辉长岩分布在高凸起地区。它们的地幔基质由DM和EM-2物质混合形成，HIMU起辅助作用。T-MORB火山岩主要分布在所研究的MAR段南部的大型火山隆起上，由DM和HIMU物质混合形成的地幔基质熔融而成，EM-2起辅助作用。参与熔化的地幔不均匀性有两种类型：被动型和主动型。前者由转化的大陆岩石圈块体代表，其成分与 EM-2 地幔源相似。主动非均质性与富集地幔微积层在麦克斯韦FZ附近的隆起有关，其成分接近HIMU，并与其向北的次轴向流动有关，直至查理-吉布斯FZ。

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来源期刊

Geotectonics 地学-地球化学与地球物理

CiteScore

1.90

自引率

9.10%

发文量

审稿时长

3 months

期刊介绍： Geotectonics publishes articles on general and regional tectonics, structural geology, geodynamics, and experimental tectonics and considers the relation of tectonics to the deep structure of the earth, magmatism, metamorphism, and mineral resources.