Abstract—

The comprehensive geochemical and isotopic-geochronological study of Early Proterozoic volcanic rocks in structure of the Polmak–Pechenga–Imandra–Varzuga belt and dikes and sills of the Murmansk and Kola–Norwegian terranes is conducted. Abundant swarms of mafic dikes (2.06–1.86 Ga) are established in the northwestern frame of the belt, including swarms of metadolerites (2060 ± 6 Ma), ferropicrites and gabbronorites (1983 ± 5 Ma), and poikilophitic dolerites (1860 ± 4 Ma). The comparison of volcanic rocks of the Pechenga and Imandra–Varzuga structures shows asynchronous change in volcanism style, with a significant time lapse. The geochemical features of volcanic rocks of the Tominga Formation are typical of those of continental magmatism and can hardly be correlated with those of the Pilguyarvi Formation. According to isotopic-geochronological data, depleted mantle melts in the Pechenga and Imandra–Varzuga zones intruded at 2010–1970 and 1970–1980 Ma, respectively. The analysis of the conditions of formation of volcanic series shows that Neoarchean lithospheric mantle, which produced melts with low Zr/Nb ratios, was a source for primary melts of the Kuetsjarvi Formation of the Pechenga structure and their homologs of the Imandra–Varzuga structure. In contrast, the volcanic rocks of the Kolasjoki Formation, which were weakly contaminated with crustal material, and the related Ilmozero Formation, as well as the metadolerite dikes of the Kirkenes region, were sourced mostly from asthenosphere with separation of melt above the garnet stability depth. The formation of the volcanic rocks of the Pilguyarvi Formation is related, judging from the geochemical data, to two asthenospheric sources different in depth, which produced tholeiitic and ferropicritic melts.

中文翻译：

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东北芬诺斯坎迪亚（2.06-1.86 Ga）的基性岩浆作用：火山岩地球化学及其与Dike配合物的关系

摘要—

进行了Polmak-Pechenga-Imandra-Varzuga带构造，摩尔曼斯克和科拉-挪威地体的堤坝和基岩早期元古代火山岩的地球化学和同位素-地球年代学综合研究。在该带的西北框架中形成了大量的铁镁质堤防（2.06–1.86 Ga），包括大量的变质岩（2060±6 Ma），亚铁辉石和辉长岩（1983±5 Ma），以及多闪长白云岩（1860±4 Ma）。 ）。Pechenga和Imandra–Varzuga结构的火山岩的比较显示，火山样式是异步变化的，但要经过很长时间。Tominga组火山岩的地球化学特征是大陆性岩浆作用的典型特征，与Pilguyarvi组几乎没有关联。根据同位素地质年代学数据，分别在2010–1970年和1970–1980 Ma进入的Pechenga和Imandra–Varzuga地区的地幔消融。对火山岩系列形成条件的分析表明，新生成的岩石圈地幔产生的Zr / Nb比率低，是Pechenga结构的Kuetsjarvi组及其Imandra-Varzuga结构的同系物的主要熔体的来源。相比之下，Kolasjoki组的火山岩受到地壳物质的污染较轻，相关的Ilmozero组以及Kirkenes地区的变质岩堤主要来自软流圈，且在石榴石稳定深度以上融解分离。Pilguyarvi组的火山岩的形成是相关的，