Abstract

The orogenic development after the continental collision between Laurussia and Gondwana, led to two contrasting associations of mantle-derived magmatic rocks on the territory of the Bohemian Massif: (i) a 340–310 Ma lamprophyre-lamproite orogenic association; and (ii) a 300–275 Ma lamprophyre association of anorogenic affinity. Major types of potassic mantle-derived magmatic rocks recognized in the orogenic and anorogenic associations include: (i) calc-alkaline to alkaline lamprophyres; (ii) alkaline ‘orthopyroxene minettes’ and geochemically related rocks grouped here under the new term lampyrite; and (iii) peralkaline lamproites. These three types significantly differ with respect to mineral, whole-rock and Sr–Nd–Pb–Li isotope composition and spatial distribution. The calc-alkaline lamprophyres occur throughout the entire Saxo-Thuringian and Moldanubian zones, whereas the different types of malte-derived potassic rocks are spatially restricted to particular zones. Rocks of the Carboniferous lamprophyre-lamproite orogenic association are characterized by variable negative εNd_(i) and variably radiogenic Sr_(i), whereas the rocks of the Permian lamprophyre association of anorogenic affinity are characterized by positive εNd_(i) and relatively young depleted-mantle Nd-model ages reflecting increasing input from upwelling asthenospheric mantle. The small variation in the Pb isotopic composition of post-collisional potassic mantle-derived magmatic rocks (of both the orogenic and anorogenic series) implies that the Pb budget of the mantle beneath the Bohemian Massif is dominated by the same crust-derived material, which itself may include material derived from several sources. The source rocks of ‘orthopyroxene minettes’ are characterized by isotopically light (‘eclogitic’) Li and strongly radiogenic (crustal) Sr and may have been metasomatized by high-pressure fluids along the edge of a subduction zone. In contrast, the strongly Al₂O₃ and CaO depleted mantle source of the lamproites is characterized by isotopically heavy Li and high SiO₂ and extreme K₂O contents. This mantle source may have been metasomatized predominantly by melts. The mantle source of the lamprophyres may have undergone metasomatism by both fluids and melts.

中文翻译：

---

波西米亚断层的长（65 Ma）区域晚晚造山后的瓦里斯坎地幔源性岩浆岩对比

摘要

月桂与冈瓦纳大陆碰撞后的造山运动导致了波希米亚地块领土上两个由地幔衍生的岩浆岩形成的对比：（i）340-310 Ma的煌斑岩-红闪石造山运动协会；（ii）厌食性亲和力在300-275 Ma的煌斑岩之间。在造山带和造山带协会中认识到的钾质幔源岩浆岩的主要类型包括：（i）钙碱性至碱性煌斑岩；（ii）在新术语“黄铁矿”下归类于此的碱性“邻苯二酚缩合物”和与地球化学相关的岩石；（iii）碱性碱性锂矿。这三种类型在矿物，全岩以及Sr–Nd–Pb–Li同位素组成和空间分布方面存在显着差异。钙碱性煌斑岩遍布整个萨克森-图林根和摩尔达努比地区，而不同类型的麦芽钾盐岩在空间上局限于特定区域。石炭纪煌斑岩-蓝闪石造山带组合的岩石具有可变的负εNd特征_（i）和放射成因的Sr _（i），而二叠纪煌斑岩的厌食性亲和性岩石的特征是正εNd _（i）相对较年轻的Nd模式枯竭地幔，反映了软流圈地幔上升的输入增加。碰撞后钾质地幔衍生的岩浆岩（造山带和非造山系列）的Pb同位素组成的微小变化意味着，波西米亚地块下方的地幔的Pb预算主要由相同的地壳衍生的材料主导。本身可能包含来自多种来源的材料。“邻二甲苯min”的烃源岩具有同位素轻（“本征”）锂和强放射源（地壳）锶的特征，并且可能已被俯冲带边缘的高压流体交代。相反，强Al ₂ O ₃铝铁矿的CaO耗尽地幔源的特征是同位素重的Li和高的SiO ₂和极高的K ₂ O含量。该地幔源可能主要是由熔岩交代的。煌斑岩的地幔源可能已经经历了流体和融化的交代作用。