Fluid migration, rock deformation, and mineral alteration in the Earth's crust. Insights from giant quartz veins and their host rocks in the Pyrenees
[eng] The interplay between fluid migration, rock deformation, and mineral alteration processes is key to determining dynamic variations in the Earth’s crust strength, understanding changes in the physicochemical properties of rocks, and constraining the conditions responsible for the formation of o...
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| Format: | doctoral thesis |
| Status: | Published version |
| Publication Date: | 2025 |
| Country: | España |
| Institution: | Universidad de Barcelona |
| Repository: | Dipòsit Digital de la UB |
| OAI Identifier: | oai:diposit.ub.edu:2445/222698 |
| Online Access: | https://hdl.handle.net/2445/222698 http://hdl.handle.net/10803/695044 |
| Access Level: | Open access |
| Keyword: | Petrologia Geologia estructural Deformació de les roques Pirineus Petrology Structural geology Rock deformation Pyrenees |
| Summary: | [eng] The interplay between fluid migration, rock deformation, and mineral alteration processes is key to determining dynamic variations in the Earth’s crust strength, understanding changes in the physicochemical properties of rocks, and constraining the conditions responsible for the formation of ore deposits. Investigating these processes may also provide insights into the sedimentary, magmatic, and metamorphic evolution of different geological systems, helping to reconstruct regional tectono-thermal histories and tectonic plate evolution. However, bridging the gap between these phenomena is challenging due to the very different length scales (i.e., from the scale of atomic chemical changes, ca. 10^-9 m, to that of orogenic deformation, ca. 10^5 m) and timescales (i.e., from crystal dislocation glide, at ca. 10^-9 s, to ductile flow of rocks in shear zones, at ca. 10^14 s) at which their underlying processes operate. This PhD thesis aims to explore the interplay between fluid migration, rock deformation, and mineral alteration during the formation of Giant Quartz Veins (GQVs) in the Pyrenean fold-and-thrust belt, at the Iberia-Eurasia plate boundary. The fluid evolution history, GQV formation mechanisms and conditions, their geometry and distribution, as well as their relationships with host rock alteration processes, GQV ages and deformation are holistically investigated from the orogen- to the grain- scale in four representative sectors: the Canigó, Cap de Creus, Roc de Frausa, and La Cerdanya areas. This is achieved by a multidisciplinary approach that includes remote sensing analysis, fieldwork and geological mapping, structural and microstructural studies, whole-rock and mineral chemistry, mass-balance modelling, fluid inclusion microthermometry and element concentration determinations, geochronology, and crystal orientation analysis in GQVs and their host rocks, present both in basement and cover orogenic settings. Alterations of granitic rocks associated with GQVs have also inspired a literature review about our current understanding of granitic rocks, and on how granites have been defined and interpreted in the context of the major theories that have successively governed the Earth Science history. The interpretations presented in this thesis provide new insights into metasomatic and rock deformation processes, and how these are related to the formation of GQVs and the development of mylonite belts. It is suggested that GQVs are mostly formed by mineral replacement processes and that, accordingly, they form by deformation-controlled metasomatic reactions in coupled, coeval and long-lasting processes of pulses of fluid supply and shear zone activity. The results of this PhD thesis allow for a better understanding of the deformation of crustal rocks, the formation mechanisms of GQVs, and the tectono-thermal history of the Pyrenees. The thesis further challenges practices commonly used for paleotemperature and fluid provenance determinations, classical interpretations of the formation mechanisms, origin, and significance of GQVs worldwide, and assumptions that Pyrenean mylonite belts and GQVs developed during the retrograde stages of the Variscan orogeny. |
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