Geochemistry and Formation Conditions of Mesoarchean Banded Iron Formations (BIF-1) from the Kostomuksha Greenstone Belt, Karelian Craton

IF 0.7 4区地球科学 Q4 GEOCHEMISTRY & GEOPHYSICS Geochemistry International Pub Date : 2024-03-01 DOI:10.1134/s0016702924030054

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Abstract

Three variably old groups of banded iron formation (BIF) are known in the Kostomuksha Greenstone Belt (KGB) of the Karelian Craton. This paper deals with the earliest of them, Mesoarchean (2.87–2.81 Ga) BIF-1. BIF-1 occurs among the komatiite–basalt unit of the KGB. BIF-1 consists mainly of quartz and magnetite, with varying amounts of amphibole, biotite, and garnet; the variations of SiO₂ (48.3–58.6 wt %) and \({\text{F}}{{{\text{e}}}_{{\text{2}}}}{\text{O}}_{{\text{3}}}^{{\text{T}}}\) (21.34–33.82 wt %) suggest that the rocks are BIF. BIF-1 of the KGB, as well as most Archean BIFs, contain high \({\text{F}}{{{\text{e}}}_{{\text{2}}}}{\text{O}}_{{\text{3}}}^{{\text{T}}}\) concentration, display a contrasting positive Eu anomaly, lack of Ce anomaly, and the depletion of LREE relative to HREE. However, they differ from other BIFs in the higher Al₂O₃, TiO₂, MgO, K₂O, Cr, Ni, Zr, Ba, Cu and Zn concentrations. BIF-1 was formed in a marine basin at an anoxic atmosphere due to hydrothermal fluids, the proportion of which varies from 20 to 80%, and a terrigenous component derived mainly from basalts, komatiites, and dacites of host rocks. Mesoarchean BIF-1 of the KGB was accumulated in a small rift structures within an oceanic volcanic plateau, the formation of which is associated with the influence of a mantle plume on the oceanic lithosphere.

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卡累利阿克拉通科斯托穆克沙绿岩带中生代带状铁地层（BIF-1）的地球化学和形成条件

摘要在卡累利阿克拉通的科斯托穆克沙绿岩带（KGB）中，已知有三组年代不一的带状铁岩层（BIF）。本文讨论的是其中最早的一组，即中生代（2.87-2.81 Ga）BIF-1。BIF-1 位于卡累利阿克拉通的孔雀石-玄武岩单元中。BIF-1主要由石英和磁铁矿组成，并含有不同数量的闪石、斜长石和石榴石；SiO2（48.3-58.6 wt %）和({\text{F}}{{text{e}}_{\text{2}}}}\text{O}}_{\text{3}}}^{\text{T}})（21.34-33.82 wt %）的变化表明岩石为BIF。KGB地区的BIF-1以及大多数奥陶系BIF都含有较高的\({text{F}}{{text{e}}}_{text{2}}}}\text{O}}_{text{3}}}^{\text{T}}})浓度，显示出对比强烈的正Eu异常，缺乏Ce异常，以及LREE相对于HREE的贫化。然而，它们与其他 BIF 的不同之处在于 Al2O3、TiO2、MgO、K2O、Cr、Ni、Zr、Ba、Cu 和 Zn 的浓度较高。BIF-1形成于一个大气缺氧的海盆中，由热液形成，热液所占比例从20%到80%不等，而陆相成分主要来源于基性岩、孔雀石和主岩中的大理岩。KGB的中生代BIF-1堆积在大洋火山高原内的小型裂谷结构中，其形成与地幔羽流对大洋岩石圈的影响有关。

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来源期刊

Geochemistry International 地学-地球化学与地球物理

CiteScore

1.60

自引率

12.50%

发文量

审稿时长

1 months

期刊介绍： Geochemistry International is a peer reviewed journal that publishes articles on cosmochemistry; geochemistry of magmatic, metamorphic, hydrothermal, and sedimentary processes; isotope geochemistry; organic geochemistry; applied geochemistry; and chemistry of the environment. Geochemistry International provides readers with a unique opportunity to refine their understanding of the geology of the vast territory of the Eurasian continent. The journal welcomes manuscripts from all countries in the English or Russian language.