COMMENTS ON THE ARTICLE AUTHORED BY M.V. MINTS AND K.A. DOKUKINA – THE BELOMORIAN ECLOGITE PROVINCE (EASTERN FENNOSCANDIAN SHIELD, RUSSIA): MESO-NEOARCHEAN OR LATE PALEOPROTEROZOIC?

IF 0.8 Q4 GEOCHEMISTRY & GEOPHYSICS

Geodynamics & Tectonophysics Pub Date : 2021-09-17 DOI:10.5800/gt-2021-12-3-0544

S. Skublov, A. Berezin, L. I. Salimgaraeva

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引用次数: 0

Abstract

The comments are given on the article authored by M.V. Mints and K.A. Dokukina – The Belomorian Eclogite Province (Eastern Fennoscandian Shield, Russia): Meso-Neoarchean or Late Paleoproterozoic? (Geodynamics & Tectonophysics 2020, 11 (1), 151–200). The Belomorian (White Sea) province of the Fennoscandia Shield is a key site for studying the tectonics of the early periods because numerous Precambrian eclogites have been found there. It was not anticipated, but the problem of age determinations of the eclogite metamorphism of gabbroids in the White Sea mobile belt has turned out to be extremely relevant not only for this region, but also for the Precambrian geology in general. The reason is that a number of authors determine the age of eclogites as Archean (2.7–2.8 Ga), which makes the White Sea mobile belt the only example of the Archean eclogite metamorphism in the world and, therefore, the only dated evidence in support of the plate tectonic model of the evolution of the Earth’s crust at the earliest stage of its formation. The article consistently provides a critical analysis of the arguments put forward by the supporters of the Archean age of the eclogites of the White Sea mobile belt. Special emphasis is made on the isotope geochronological and geochemical features of the composition of zircons from eclogite samples, as well as on the phase and chemical compositions and distribution patterns of mineral inclusions. Considering the age of eclogite metamorphism that led to the formation of eclogites in the White Sea mobile belt, we propose our interpretation based on a set of independent isotope geochemical dating methods, including the local U- Pb method for heterogeneous zircons with magmatic cores and eclogite rims, the Lu-Hf and Sm-Nd methods for the minerals of eclogite paragenesis (garnet and omphacite). And this age interpretation is fundamentally different from the one described in the commented article: all the three methods independently determine the eclogite metamorphism as Paleoproterozoic and yield the same age of circa 1.9 Ga. According to our data, the eclogites of the White Sea mobile belt are among the most ancient high-pressure rocks, their reliably established age of metamorphism is circa 1.9 Ga, and the age of the magmatic protolith is the range of 2.2–2.9 Ga.

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m.v. mints和k.a. dokukina的文章评论——别洛莫里榴辉岩省(俄罗斯芬诺斯坎德盾东部):中新太古代还是晚古元古代?

M.V. Mints和K.A. Dokukina的文章《Belomorian榴辉岩省(东芬诺斯坎德地盾，俄罗斯):中-新太古代还是晚古元古代?》(地球动力学与构造物理，2020,11(1)，151-200)。芬诺斯坎迪亚地盾的白海省是研究早期构造的关键地点，因为在那里发现了大量的前寒武纪榴辉岩。白海活动带辉长石榴辉岩变质作用的年龄测定问题，不仅对该地区，而且对整个前寒武纪地质都具有重要意义。原因是许多学者将榴辉岩的年龄确定为太古宙(2.7-2.8 Ga)，使白海活动带成为世界上唯一的太古宙榴辉岩变质的例子，从而成为支持地壳形成初期演化的板块构造模式的唯一年代证据。本文对白海活动带榴辉岩太古宙时代的支持者所提出的论点进行了一致的批判性分析。重点讨论了榴辉岩样品中锆石的同位素年代学和地球化学特征，以及矿物包裹体的物相、化学组成和分布模式。考虑到白海活动带榴辉岩变质形成的年代，我们提出了一套独立的同位素地球化学测年方法，包括岩浆核和榴辉岩边缘的非均质锆石的局部U- Pb法，榴辉岩共生矿物(石榴石和辉长石)的Lu-Hf和Sm-Nd法。这种年龄解释与评论文章的解释有着根本的不同，三种方法都独立地确定榴辉岩变质作用为古元古代，并得出相同的年龄约1.9 Ga。根据资料，白海活动带榴辉岩属于最古老的高压岩，其可靠确定的变质年龄约为1.9 Ga，岩浆原岩年龄在2.2 ~ 2.9 Ga之间。

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来源期刊

Geodynamics & Tectonophysics GEOCHEMISTRY & GEOPHYSICS-

CiteScore

1.20

自引率

14.30%

发文量

审稿时长

24 weeks

期刊介绍： The purpose of the journal is facilitating awareness of the international scientific community of new data on geodynamics of continental lithosphere in a wide range of geolchronological data, as well as tectonophysics as an integral part of geodynamics, in which physico-mathematical and structural-geological concepts are applied to deal with topical problems of the evolution of structures and processes taking place simultaneously in the lithosphere. Complex geological and geophysical studies of the Earth tectonosphere have been significantly enhanced in the current decade across the world. As a result, a large number of publications are developed based on thorough analyses of paleo- and modern geodynamic processes with reference to results of properly substantiated physical experiments, field data and tectonophysical calculations. Comprehensive research of that type, followed by consolidation and generalization of research results and conclusions, conforms to the start-of-the-art of the Earth’s sciences.