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Millan_PhD_Dissertation_18_April.pdf (23.03 MB)

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Syntectonic Fluid Flux in a Glaciated Rift Basin: Record from vein arrays in the AND-1B and AND-2A sedimentary rock cores, Victoria Land Basin, Antarctica

Millan, Cristina
http://rave.ohiolink.edu/etdc/view?acc_num=osu1366309725

Abstract Details

2013, Doctor of Philosophy, Ohio State University, Geological Sciences.
Two Neogene sedimentary rock cores recovered by the ANDRILL project from the Victoria Land rift basin of Antarctica contain 1174 mineralized fractures that are the focus of this study. Veins are assigned into extension, shear, and extension-shear kinematic groups and into relatively `early’ and `late’ temporal generations based on initial core fracture logging, refined by microscopic, ultramicroscopic and petrologic characteristics. Vein fill is dominantly calcite, with subordinate zeolite, chlorite and pyrite. Calcite crystal shapes and growth patterns document diffusive and advective flow of fluids into, and along, veins during opening- and shear-mode displacements. In addition, the crystal textures indicate that fluid overpressures were sufficiently high in many cases to exceed the lithostatic stress and to hold fractures open during mineral precipitation. The patterns of vein distribution and frequency with depth in the core do not show any spatial correlations with horizons interpreted to mark grounded ice advance over the depositional site, and subglacial deformation appears to be an unlikely cause of vein formation. Instead, in the AND-1B core, there is a strong spatial correlation between vein abundance and volume and glass-bearing, volcaniclastic sedimentary intervals. Alteration and diagenetic reactions have clearly influenced the mechanical behavior of sediment during compaction and dewatering. Vein arrays appear to record 3D strain marked by contraction in the vertical direction, due to sedimentary and/or glacial overburden, and radial extension recorded by the trimodal orientation patterns of extension and shear-mode veins. Carbon and oxygen isotope ratios measured in vein calcite show strong variations with depth in the AND-1B veins, whereas AND-2A veins have linear depth trends. There are systematic shifts of vein calcite isotope values with respect to bulk carbonate values in host rocks. These patterns signal both the influence of fluid-host rock interactions in rapidly altering volcaniclastic intervals, and mixing of fluids from different sources via fracture pathways. Vein arrays in the Neogene strata of the Victoria Land Basin are interpreted to record interaction between diagenetic and structural processes during dewatering and compaction of the basin sediments. Veins formed during progressive compactional deformation. Early veins formed by repeated brittle fracturing of strong host rocks, then record ductile deformation after the host rock lost strength. The loss of strength is attributed to dissolution of early cement and framework collapse due to diagenetic changes. During ongoing compaction and sediment dewatering, there was continued brittle deformation and mineral precipitation. The unusual deformation path of alternating brittle and ductile sediment behavior during compaction appears to be linked with pervasive alteration of the volcanic components in the sediments. High fluid pressures and the repeated fracturing episodes produced an interconnected network of extension and shear-mode veins that formed a `fault-fracture mesh’ that provided structural permeability and served as dewatering conduits as the strata compacted and lithified. Systematic isotopic variations in vein calcite precipitated from the fluids resulted from both diagenetic alteration of sediments and mixing of fluids from different sources and was facilitated by the interconnected fracture network transecting the basin strata.
Terry Wilson (Advisor)
225 p.
Earth; Geological; Geology
rift basin; geology; mineralized veins; fractures; diagenesis; volcanic alteration; veins; isotopes; deformation

Recommended Citations

Citations

  • Millan, C. (2013). Syntectonic Fluid Flux in a Glaciated Rift Basin: Record from vein arrays in the AND-1B and AND-2A sedimentary rock cores, Victoria Land Basin, Antarctica [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366309725

    APA Style (7th edition)

  • Millan, Cristina. Syntectonic Fluid Flux in a Glaciated Rift Basin: Record from vein arrays in the AND-1B and AND-2A sedimentary rock cores, Victoria Land Basin, Antarctica. 2013. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1366309725.

    MLA Style (8th edition)

  • Millan, Cristina. "Syntectonic Fluid Flux in a Glaciated Rift Basin: Record from vein arrays in the AND-1B and AND-2A sedimentary rock cores, Victoria Land Basin, Antarctica." Doctoral dissertation, Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1366309725

    Chicago Manual of Style (17th edition)

osu1366309725
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This open access ETD is published by The Ohio State University and OhioLINK.