This study presents microstructural as well as bulk and mineral chemical investigations of deformation bands in uncemented, friable arkosic sands of Miocene age (Vienna Basin, Austria). Our microstructural study indicates grain size reduction by grain flaking in deformation bands with small offsets (0.5–8 cm), and dominant intragranular fracturing and cataclasis of altered feldspar grains at larger displacements (up to 60 cm). Relative to quartz, the sericitized feldspar grains are preferably fractured and abraded, which additionally leads to an enrichment of mainly phyllosilicates by mechanical expulsion from feldspar. Both cataclasis of quartz and feldspar grains and enrichment of phyllosilicates result in grain size reduction within the deformation bands. The measured reduction in porosity of up to 20% is in some cases associated with a permeability reduction, reflected in the retention of iron-oxide rich fluids along deformation bands. These deformation bands formed at very shallow burial depths in unconsolidated sediments indicate that fault sealing may occur in the absence of chemical alteration of the deformation bands and lead to a compartmentalization of a groundwater or hydrocarbon reservoir.

中文翻译：

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弱固结长石砂变形带中长石的优先碎裂粒度减小

本研究介绍了中新世（奥地利维也纳盆地）未胶结、易碎长石砂中变形带的微观结构以及体积和矿物化学研究。我们的微观结构研究表明，在具有小偏移量（0.5-8 厘米）的变形带中，晶粒剥落导致晶粒尺寸减小，并且在较大位移（高达 60 厘米）下主要的粒内压裂和蚀变长石颗粒的碎裂。相对于石英，绢云母化的长石颗粒优选地被破碎和磨损，这另外通过机械从长石中排出而导致主要为页硅酸盐的富集。石英和长石颗粒的碎裂和页硅酸盐的富集导致变形带内的颗粒尺寸减小。在某些情况下，测得的孔隙率降低高达 20% 与渗透率降低有关，这反映在沿变形带保留富含氧化铁的流体中。这些在松散沉积物中非常浅的埋藏深度形成的变形带表明，在变形带没有化学改变的情况下可能会发生断层封闭，并导致地下水或碳氢化合物储层的分隔。