Date of Award
2024-08-01
Degree Name
Master of Science
Department
Geological Sciences
Advisor(s)
Benjamin B. Brunner
Abstract
Zebra rocks displaying alternating light and dark-colored millimeter to centimeter thick bands of crystals have been found at the Gypsum Valley salt diapir, Colorado in the Paradox Basin where they are associated with gypsic diapiric caprock. Elucidating their origin may provide crucial information about intermittent fluid flow at the margin of salt diapirs and about Zebra rock formation, which often is associated with carbonate-hosted lead-zinc mineralization (Mississippi Valley Type, MVT) and hydrothermal dolomite -hosted hydrocarbon reservoirs.
The Gypsum Valley Zebra rocks consist of calcite, i.e., it is a Zebra limestone. It shows a finely crystalline light banding and coarsely crystalline dark color banding which is inverse to the often dolomitic Zebra rocks in the literature. It also exhibits a wide variety of crystal fabrics from regular banding to chaotic distribution of bands and vugs with sedimentary infill. Combining field observations, petrographic and geochemical analyses with new insights into the impacts of anhydrite-gypsum transformation, I conclude that Zebra limestone at Gypsum Valley originates from the replacement of a petroliferous microcrystalline dolostone. Conversion of anhydrite to gypsum in the cap of the salt diapir is both the driver and benefactor of a process that cyclically results in compression and extension of the lithologies overlying the anhydrite/gypsum cap.
This study documents numerous fluid flow events at the margin of the Gypsum Valley salt wall, offers a model to reconcile opposing explanations for Zebra rock formation by integrating cyclic extension and compression, and proposes a so far unrecognized geochemical transformation that induces replacement of dolomite by calcite while potentially releasing carbon dioxide to the atmosphere.
Language
en
Provenance
Received from ProQuest
Copyright Date
2024-08-01
File Size
106 p.
File Format
application/pdf
Rights Holder
Rebecca Navarrette
Recommended Citation
Navarrette, Rebecca, "Zebra Limestone From The Gypsum Valley Salt Diapir, Colorado" (2024). Open Access Theses & Dissertations. 4194.
https://scholarworks.utep.edu/open_etd/4194