Abstract

Mafic intraplate magmatism is the main source of information about the geodynamics of processes that lead to the breakup of continental blocks. The article discusses geodynamics of the breakup of the Archean supercraton Superia in the Middle Paleoproterozoic. The discussion is based on data on 2.1 Ga magmatism in the Karelian Craton, where mafic igneous rocks of this age are represented by tholeiites of two geochemical types: depleted and enriched. Geochemically close to N-MORB, depleted tholeiites were studied in the Northern Ladoga Region where they form dike swarms at ca. 2111 ± 6 Ma (U-Pb, SIMS, zircon) in the Hatunoiya locality, and pillow lavas and sills in the Lake Maloe Jänisjärvi locality. Enriched tholeiites were studied in the Lake Tulos locality where they form a large swarm of doleritic dikes of age 2118 ± 5 Ma (U-Pb, ID-TIMS, baddeleyite). The results of these studies provide deeper insight into 2.1 Ga mafic magmatism. Depleted tholeiites with N-MORB geochemistry have a wide spatial distribution in the Karelian Craton and could be formed via decompression melting of a depleted asthenospheric mantle, raising melts along the extension zones, and minimal contamination by the Archean crust. According to modelling results, enriched tholeiitic melts probably occurred due to differentiation and crustal contamination of rising depleted tholeiitic melts through more rigid Archean crustal blocks. Data on ca. 2.1 Ga mafic magmatism in the Karelian craton are difficult to explain within the mantle plume rise model, but are consistent with the model of lithosphere extension due to a retreat of a subduction zone in the northeastern margin of the craton, in the Lapland-Kola Ocean at 2.0–2.2 Ga. The intensive thinning and rupture of the Archean continental lithosphere and opening of an oceanic basin at the western margin of the Karelian craton were probably controlled by the suture zone of the junction of Neoarchean and Paleoarchean crustal blocks, traced in the western part of the Karelian craton. An additional factor that led to the ca. 2.1 Ga lithospheric breakup could be a rise of a deep-seated mantle plume in the Hearne craton, neighboring to the Karelian craton in the Archean Superia supercraton.

中文翻译：

---

卡累利阿克拉通西部裂解的地球动力学：2.1 Ga 基性岩浆作用数据

摘要

镁铁质板内岩浆作用是有关导致大陆块破裂的过程地球动力学信息的主要来源。本文讨论了中古元古代太古代超克拉通 Superia 破裂的地球动力学。讨论基于卡累利阿克拉通 2.1 Ga 岩浆活动的数据，该时代的镁铁质火成岩以两种地球化学类型的拉斑斑玄武岩为代表：贫化型和富集型。在地球化学上接近 N-MORB 的贫拉斑斑玄武岩在北拉多加地区进行了研究，它们在大约 100 年前形成了堤坝群。Hatunoiya 地区的 2111 ± 6 Ma（U-Pb、SIMS、锆石），以及 Maloe Jänisjärvi 地区的枕状熔岩和基台。在图洛斯湖地区对富集拉斑玄武岩进行了研究，在那里它们形成了一大群年龄为 2118 ± 5 Ma 的辉绿岩岩脉（U-Pb、ID-TIMS、斜锆石）。这些研究结果为 2.1 Ga 镁铁质岩浆作用提供了更深入的了解。具有 N-MORB 地球化学特征的贫拉拉斑岩在卡累利阿克拉通具有广泛的空间分布，并且可以通过贫化软流圈地幔的减压熔融、沿延伸区升高熔体以及太古宙地壳的最小污染而形成。根据模拟结果，富集的拉斑玄武岩熔体可能是由于通过更坚硬的太古代地壳块体上升的贫化拉斑玄武岩熔体的分异和地壳污染而发生的。数据约。2.1 卡累利阿克拉通的镁铁质岩浆作用很难用地幔柱上升模型来解释，但与拉普兰-科拉洋克拉通东北缘俯冲带后退导致岩石圈伸展的模型一致2.0~2.2 Ga。太古代大陆岩石圈的强烈减薄和破裂以及卡累利阿克拉通西缘洋盆的打开可能是受新太古代和古太古代地壳块体交界处缝合带的控制。卡累利阿克拉通西部。导致大约的另一个因素。2.1 Ga岩石圈破裂可能是赫恩克拉通深层地幔柱的上升，该地幔柱与太古代超克拉通的卡累利阿克拉通相邻。