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Title: Formation and growth of fibrous mineral veins in mudrocks during burial and uplift
Author: Meng, Qingfeng
ISNI:       0000 0004 6499 1384
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2017
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Fibrous mineral veins are extremely important structures in mudrocks because they represent phases of geological activity that occurred after the deposition of the host rocks. They are, therefore, crucial for unravelling the geological history, especially for analyzing postdepositional tectonism, diagenesis, and associated physical and chemical conditions. This research focuses on the investigation of fibrous mineral (gypsum and calcite) veins in mudrocks, using integrated field, petrographic, and geochemical methods. The aim is to obtain a better understanding of mineral vein systems in fine-grained rocks over spatial scales ranging from reservoir to microns, regarding the timing, formation mechanism, vein growth, fluid and stress conditions, fluid-rock interaction, and their expressions in vein texture. The results reveal that fibrous mineral veins are produced during different stages of basin evolution. Fibrous calcite veins in Lower Jurassic shales in the Wessex Basin have a diagenetic growth history during early burial of the sediments. In contrast, the formation of satin spar veins in the Triassic marls of the Bristol Channel Basin is closely associated with tectonic compression during basin uplift. However, both the gypsum veins and calcite veins owe their origin to overpressure and incremental fibre growth in closed systems, with their textures exhibiting similar antitaxial characteristics. Host rock lithology, defined by mineral components, fabrics and mechanical properties, mainly controls the development of the veins. The research highlights the kinematic implications of fibre orientations for host rock deformation and the EBSD measurement of crystallographic orientations of fibres for the analysis of paleo-stress state during fibre growth. Evidence for the force of crystallization exerted by mineral fibres, which has largely been ignored in previous studies, are revealed based on field and petrographic observations. The vein systems presented in this research provide an analogue for future studies on sub-seismic scale fracture/vein characterization and prediction in mudrocks either as caprock or source rocks for hydrocarbons.
Supervisor: Cartwright, Joe Sponsor: Shell International Exploration and Production B.V.
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available