Abstract The Palaeoproterozoic Bled M’Dena ring complex (BRC) dated at 2.01 Ga (Rb–Sr isochron) situated in the eastern part of the Yetti–Eglab junction-zone, belongs to the Aftout orogenic province, intruding the Aftout granite (2.07 Ga). It exhibits a centripetal evolution from gabbro to granodiorite. The western part of the Bled M’Dena ring complex is dominated by volcanic rocks varying in composition from basalt, trachyandesite, andesite, dacite to rhyolite. Andesite constitutes the major volcanic type in the Bled M’Dena ring complex. Chemistry of these rocks suggest two distinct magmatic trends: A transitional-tholeiitic suite localised at the outer part of the ring complex, and a high-K calc-alkaline suite situated within the inner ring structure. Basic volcanics exhibit flat primitive REE patterns with insignificant Eu anomalies, suggesting that they probably represent a parental basaltic melt from which the Bled M’Dena complex evolved, (Eu/Eu ∗ = 2.06–4.07). The europium anomaly did not vary significantly, as it evolved progressively through the volcanic series by differentiation and feldspar accumulation. It is proposed that a primitive basic magma from the mantle was contaminated by Eburnian crust (2.2–2.0 Ga). Thus the transitional-tholeiitic volcanic rocks, dominant in the region have developed a high-K calc-alkaline suite. Their source is melted shortly after its generation when the lithosphere was still hot, which restricts high-K calc-alkaline magmatism mainly to post-collisional settings. This has been linked to large movement along mega-shear zones (Yetti–Eglab junction) due to subduction of oceanic basins in a post collisional setting.

中文翻译：

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Reguibat Rise（阿尔及利亚 Eglab 地盾西部）碰撞后 Bled M'Dena 火山环复合体的岩石成因

摘要 位于 Yetti-Eglab 交界带东部的古元古代 Bled M'Dena 环杂岩（BRC），年代为 2.01 Ga（Rb-Sr 等时线），属于 Aftout 造山省，侵入 Aftout 花岗岩（2.07 Ga ）。它表现出从辉长岩到花岗闪长岩的向心演化。Bled M'Dena 环复合体的西部主要是火山岩，其成分从玄武岩、粗安山岩、安山岩、英安岩到流纹岩不等。安山岩构成 Bled M'Dena 环复合体的主要火山类型。这些岩石的化学性质表明了两种不同的岩浆趋势：位于环复合体外部的过渡拉斑岩套件，以及位于内环结构内的高 K 钙碱性套件。基本火山岩表现出平坦的原始 REE 模式，Eu 异常微不足道，表明它们可能代表了 Bled M'Dena 复合体演化而来的母玄武岩熔体（Eu/Eu ∗ = 2.06-4.07）。铕异常没有显着变化，因为它通过分异和长石堆积在火山系列中逐步演化。推测来自地幔的原始基性岩浆被埃本纪地壳（2.2-2.0 Ga）污染。因此，在该地区占主导地位的过渡拉斑火山岩发育了高钾钙碱性岩套。当岩石圈仍然很热时，它们的来源在其产生后不久就熔化了，这将高 K 钙碱性岩浆活动主要限制在碰撞后的环境中。这与由于碰撞后大洋盆地的俯冲而导致的大剪切带（Yetti-Eglab 交界处）的大运动有关。