Structural Diagenesis—Linked Chemical and Mechanical Processes in Sedimentary Basins
Laubach, S. E.1, J. E. Olson1, R. Lander2, K. Milliken1 (1) Jackson School of Geosciences, The University of Texas at Austin, Austin, TX (2) Geocosm, Austin, TX
An examination of the links between mechanical and chemical processes in sedimentary basins can transform our knowledge of a part of the Earth’s interior that is of great intrinsic and practical interest. Owing, perhaps, to decades of petroleum industry focus on shallow parts of sedimentary basins, where original depositional fabrics may dominate petrophysical properties, artificial boundaries have arisen between the disciplines of rock mechanics, stratigraphy, sedimentary geochemistry, sedimentary and structural petrology, structural geology, and geophysics. Current efforts at drilling into deeper and less conventional exploration targets requires breaking these disciplinary boundaries in order to exploit new analytical techniques and instruments, laboratory tests, and mechanical and diagenetic models that can advance our understanding of porosity evolution in diagenetically-altered, fractured, and faulted rocks. New data and concepts that arise from such a holistic approach can be crystallized into predictive models for geological attributes where samples are sparse or nonexistent. A benefit of cross-disciplinary programs focused on fundamental processes by which rock properties evolve is a better conceptual framework for accessing future energy supplies and for devising the means to extract these resources.
Despite temperatures that are elevated relative to those at the surface, reactions in deep basin settings are still dominated by kinetics, and rocks therefore preserve a complex history of their modifications. In such systems, prediction of reaction paths and mechanical behavior cannot be derived from an understanding of bulk composition and thermal conditions alone and a comprehensive assessment of both chemical and mechanical aspects of rock history is essential. There is an ever-growing body of evidence that, across a spectrum ranging from grain fracture in early compaction to mineral precipitation in tectonically-pro-duced veins, to mineral coatings on rock joints formed during uplift, chemical and deformational histories can be deciphered in concert to reveal links that appear to be genetic.