Abstract—

The paper presents newly acquired isotope-geochemical and U–Pb isotope zircon dating (SHRIMP) results on four posttectonic granitoid massifs in the southeastern part of the Karelian Granite–Greenstone Province (GGP) in the Fennoscandian Shield. The massifs are located near the Hautavaara Structure, in the southeastern part of the Mesoarchean (3.05–2.85 Ga) Vedlozero–Segozero Greenstone Belt, which is confined to the western margin of the Vodlozero crustal block with a Paleoarchean (T_NdDM > 3.2 Ga) prehistory. All four massifs (Hautavaara, Chalka, Shuya, and Nyalmozero) were shown to have similar structural–tectonic settings, were emplaced nearly simultaneously (at 2745–2740 Ma), and display variations in the rock compositions that were predetermined by differences in the composition of the magma sources and the conditions of their derivation. The Hautavaara Massif in the central part of the structure and the Chalka Massif on its western margin are made up of moderately alkaline high-Mg granitoids (sanukitoids), whose initial diorite melts were derived by melting the lithospheric mantle metasomatized in an active-margin setting at 3.00–2.90 Ga. The Shuya granodiorites and Nyalmozero leucogranites, which are confined to the eastern flank of the structure, yield highly fractionated HREE patterns (Dy_n/Yb_n = 3.5 to 5.14), negative ε_NdT = –0.9 to –2.8, and were produced by melting a Mesoarchean crustal source at various depths. This source was similar to the 3.05- to 2.90-Ga felsic volcanics in the Hautavaara Structure. The Shuya granodiorites contain elevated Cr and Ni concentrations, suggesting that the melts were generated in the crust with the involvement of mafic magma, which was likely coeval with the primitive sanukitoids. The melting of the continental lithosphere at mantle and crustal levels in the Karelian GGP in the latest Neoarchean are thought to have occurred in an extensional environment during collapse of the collisional orogen, in accordance with the model (Laurent et al., 2014).

中文翻译：

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Hautavaara结构，卡累利阿的新古代花岗岩：在增生造山带中融化的非均质岩石圈

摘要—

本文介绍了在芬诺斯堪的亚盾构的卡累利阿花岗岩-绿石省（GGP）东南部的四个后构造花岗岩地块上新获得的同位素-地球化学和U-Pb同位素锆石定年（SHRIMP）结果。地块位于Mesoarchean（3.05–2.85 Ga）东南Vedlozero–Segozero绿岩带东南部的Hautavaara结构附近，该带局限于Vodlozero地壳块的西缘，具有古古地理（T _NdDM> 3.2 Ga）史前史。四个断层（Hautavaara，Chalka，Shuya和Nyalmozero）均显示出相似的构造构造背景，几乎同时被放置（在2745-2740 Ma），并显示出岩石成分的变化，这些变化是由成分差异预先确定的岩浆源及其衍生条件。结构中部的Hautavaara地块和其西缘的Chalka地块由中等碱性的高镁质花岗岩（sanukitoids）组成，其最初的闪长岩熔体是通过融化在活动边界环境中交变的岩石圈地幔而得来的在3.00–2.90 Ga处。仅限于结构东部侧面的Shuya花岗闪长岩和Nyalmozero leucogranite产生高度分馏的HREE模式（Dy _n/镱_Ñ = 3.5〜5.14），负ε_钕T = -0.9到-2.8V，并通过熔化在不同深度的中太古代地壳源产生。该来源类似于Hautavaara结构中的3.05至2.90-Ga的长丝质火山岩。Shuya花岗闪长岩中的Cr和Ni含量较高，这表明熔岩是在镁铁质岩浆的作用下在地壳中生成的，而熔岩可能与原始的薄奇岩类同时出现。根据该模型，据认为，新近新生代的卡累利阿GGP中大陆岩石圈在地幔和地壳水平上的融化发生在碰撞造山带塌陷的伸展环境中（Laurent等，2014）。