A fluid inclusion and cathodoluminescence approach to reconstruct fracture growth in the Triassic-Jurassic La Boca Formation, Northeastern Mexico

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A fluid inclusion and cathodoluminescence approach to reconstruct fracture growth in the Triassic-Jurassic La Boca Formation, Northeastern Mexico

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dc.contributor.advisor Laubach, Stephen E. (Stephen Ernest), 1955-
dc.contributor.advisor Eichhubl, Peter
dc.creator Kaylor, Autumn Leigh
dc.date.accessioned 2012-02-17T16:35:25Z
dc.date.available 2012-02-17T16:35:25Z
dc.date.created 2011-12
dc.date.issued 2012-02-17
dc.date.submitted December 2011
dc.identifier.uri http://hdl.handle.net/2152/ETD-UT-2011-12-4453
dc.description.abstract Opening-mode fracture shapes are typically the result of brittle deformation and proportional growth in fracture height, length, and width. Based on the typical fracture shape, it is assumed that fracture tips are free to propagate in all directions. Some natural rock fractures have been shown to form as a result of slow non-elastic deformation processes. Such fractures may propagate to a finite length or height and accommodate further growth by aperture widening only. To determine the growth conditions of a fracture in the Triassic-Jurassic La Boca Formation of northeastern Mexico and to test fracture growth models, I combined fluid inclusion microthermometry and SEM-based cathodoluminescence cement texture analysis to determine the relative timing of fracture cement precipitation and related fracture opening for five samples collected along its trace. Fracture growth initiated at a minimum age of 70 Ma as two separate fractures with branching fracture tips that coalesced to a single continuous fracture under prograde burial conditions at a minimum age of 54 Ma. At this stage, fracture growth was accommodated by both propagation (i.e. increase in trace length) and by an increase in aperture during maximum burial and early exhumation. Samples collected at the fracture tips recorded temperatures reflecting fracture opening starting with maximum burial at a minimum age of 48 Ma at one tip and of 38 Ma at the other tip. Synkinematic fluid inclusions in crack-seal cement track continued fracture opening close to the fracture tips without a concurrent increase in trace length after 38 Ma until about 21 Ma. I attribute the observed change in fracture growth mechanism to a change in material response. The stage in aperture increase without propagation corresponds to an increase in elastic compliance or in non-elastic flow properties. Non-elastic flow can be attributed to solution-precipitation creep of the host rock. Dissolution of host quartz grains and subsequent quartz precipitation is consistent with the abundance of quartz fracture cement formed during exhumation. Cement textures from fractures in the La Boca Formation mimic those found in subsurface core, which allows application of the results to a variety of geologic environments.
dc.format.mimetype application/pdf
dc.language.iso eng
dc.subject Fracture growth
dc.subject Fluid inclusion
dc.subject Diagenesis
dc.subject Cathodoluminescence
dc.subject Triassic
dc.subject Northeastern Mexico
dc.subject Fracture cement
dc.subject La Boca Formation
dc.subject Quartz
dc.subject Jurassic
dc.title A fluid inclusion and cathodoluminescence approach to reconstruct fracture growth in the Triassic-Jurassic La Boca Formation, Northeastern Mexico
dc.date.updated 2012-02-17T16:36:10Z
dc.identifier.slug 2152/ETD-UT-2011-12-4453
dc.contributor.committeeMember Catlos, Elizabeth
dc.contributor.committeeMember Ketcham, Richard
dc.description.department Geological Sciences
dc.type.genre thesis
dc.type.material text
thesis.degree.department Geological Sciences
thesis.degree.discipline Geological Sciences
thesis.degree.grantor University of Texas at Austin
thesis.degree.level Masters
thesis.degree.name Master of Science in Geological Sciences

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