Abstract

The geology and composition of Archean terrigenous sedimentary rocks of the Karelian province (Baltic Shield) are studied in order to establish their positions in the structures of greenstone belts and their role in the provenance composition. It is shown that metaterrigenous rocks from the greenstone belts of the youngest Central Karelian domain, together with intermediate-to-felsic volcanic rocks, compose the main part of the sections, occurring at their bases, and are about 2745 Ma in age. In the belts of the West Karelian domain, metaterrigenous rocks compose the upper parts of the sections, and their age is 2745–2750 Ma. Geological data on the position of metaterrigenous rocks in the belts of the oldest Vodlozero domain also suggest their Neoarchean age. On this basis, it is concluded that metaterrigenous rocks mark the beginning of the Neoarchean stage of crust formation in the Karelian province. According to geochemical data, metagreywackes are predominant among the Archean metaterrigenous rocks of all three domains. At the bases of the sections of some structures, polymictic conglomerates are present with the predominance of tonalite, trondhjemite, and, less often, granodiorite pebbles and with a subordinate amount of igneous rocks of different compositions. Low CaO and Na₂O contents and CIA < 55 indicate an insignificant degree of weathering. The Th, Co, Sc, Hf, and La contents indicate a leading role of the TTG-association rocks in the compositions of the sources for all the studied structures. The influence of the basic source was small and affected exclusively Ti, Y, and heavy REE contents in metaterrigenous rocks. The role of komatiites as a source of detrital material was insignificant.

中文翻译：

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卡累利阿省的太古宙变质岩：地质位置，地球化学，沉积物来源

摘要

为了确定它们在绿岩带结构中的位置及其在物源组成中的作用，研究了卡累利阿省（波罗的海盾）的太古代陆相沉积岩的地质和组成。结果表明，最年轻的中卡累利阿地区绿岩带中的变质岩，与中至长石质火山岩一起，构成了这些断面的主要部分，位于它们的底部，年龄大约为2745 Ma。在西卡累利阿域的带中，变质岩构成了断层的上部，其年龄为2745-2750 Ma。关于最古老的Vodlozero矿区带中变质岩位置的地质数据也表明了它们的新时代时代。在此基础上，可以得出结论，在卡累利阿省，陆源岩标志着地壳形成的新古宙时代的开始。根据地球化学数据，在这三个领域的太古代宙级陆源岩石中，杂多灰泥岩是主要的。在某些结构的断面底部，存在多聚砾岩，主要有方钠石，长白云母，以及较少的花岗闪石卵石和少量不同组成的火成岩。低CaO和Na 花岗闪长石鹅卵石和少量不同组成的火成岩。低CaO和Na 花岗闪长石鹅卵石和少量不同组成的火成岩。低CaO和Na₂ O含量和CIA <55表示微不足道的风化程度。Th，Co，Sc，Hf和La的含量表明TTG缔合岩石在所有研究结构的烃源组成中起着主导作用。基本来源的影响很小，仅影响变质岩中的Ti，Y和重稀土元素含量。科马蒂岩作为碎屑物质来源的作用微不足道。