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首页> 外文期刊>South African Journal of Geology: Being the Transaction of the Geological Society of South African: Syndie die Verhandelinge van die Geologiese Vereniging van Suid-Afrika >Comparative study of pseudotachylite microstructures in felsic and mafic rocks from the Vredefort impact structure, South Africa. Implications for the experimental studies.
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Comparative study of pseudotachylite microstructures in felsic and mafic rocks from the Vredefort impact structure, South Africa. Implications for the experimental studies.

机译：南非Vredefort冲击结构中肠杆菌和MAFIC岩石山岩微观结构的比较研究。 对实验研究的影响。

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While the formation of tectonic PTs is widely accepted as related to friction melting for all rock types, the mechanism of formation of impact-related pseudotachylites (PTs) is strongly debated. Moreover, the influence of the target lithology on the initial impact PT formation, development and deformation has not been considered in detail, even though impact PTs in the Vredefort structure are found in various lithologies. Here, we investigate PTs that occur in felsic (granite) and mafic (dolerite) rocks that are in contact with one another in the core of the Vredefort impact structure. In this unique outcrop, multiple granitic clasts are observed inside the PTs hosted by dolerite, which indicates material exchange between PTs in the two lithologies, pointing to simultaneous shock deformation in the adjacent rock phases. This outcrop thus provides an unusual opportunity for studying the effect of host lithology on the formation and deformation of PT. Our investigations demonstrate that microstructures and textures in PTs and their chemical composition largely depend on the host rock, suggesting particular rheological syn- and post-formation behaviour of the melt veins of different composition. In granite, melt initiates due to preferential decomposition of mafic and hydrous minerals, and subsequent ductile deformation of quartz and feldspars. In dolerite, melt initiates as a result of comminution of the bulk rock. Due to the different mineral composition of rocks, and corresponding various fracture toughness of different minerals, granitic PTs contain abundant monomineralic clasts composed of more refractory phases, most often quartz, while PT veins in dolerite contain fewer, usually lithic clasts, representing fragments of the host rock. PTs in granite are chemically zoned, which has not been observed for PTs in dolerite. In felsic rocks, PTs are often framed by an ultramylonite and are associated with post-shock ductile features, such as sigmoidal-shaped clasts and
机译：虽然构造PTS的形成被广泛接受与所有岩石类型的摩擦熔化有关，但强烈讨论了影响相关的假阴囊（PTS）的形成机制。此外，尚未详细考虑目标岩性对初始影响，发育和变形的初始影响，显影和变形的影响，即使在各种岩性中发现了vredefort结构中的影响。在这里，我们研究了在VREDFORT冲击结构的核心中彼此接触的术术（花岗岩）和MAFIC（Dolerite）岩石中发生的PTS。在这种独特的露头中，在由潮和特托管的PTS内观察到多个花岗岩含水物，其表示两个岩性中PTS之间的材料交换，指向相邻岩阶段的同时冲击变形。因此，这种露头为研究宿主岩性对Pt形成和变形的影响提供了不寻常的机会。我们的调查表明，PTS及其化学组成中的微观结构和纹理在很大程度上取决于宿主岩石，表明不同组成的熔体静脉的特定流变和形成行为。在花岗岩中，熔体引发，因为优先分解乳头和含水矿物质，随后的石英和长石的延性变形。在Dolerite中，熔体因散装岩石粉碎而发起。由于岩石的矿物成分不同，以及不同矿物质的各种断裂韧性，花岗岩PTS含有丰富的单体碎屑，由更耐火阶段组成，最常是石英，而Dolerite中的Pt静脉含有较少，通常是岩石泥浆，代表碎片主持人摇滚。花岗岩中的PTS是化学分区，其尚未观察到潮和地的PTS。在铰接岩石中，PTS通常由亚太岩框架，并且与抗冲后延展性特征相关，例如乙状物质夹斗和

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