Date of Award


Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Geology (MS)

Administrative Home Department

Department of Geological and Mining Engineering and Sciences

Advisor 1

Chad Deering

Committee Member 1

Greg Waite

Committee Member 2

Adam Kent


Caldera forming eruptions represent some of the largest simultaneous releases of mass and energy on the planet and pose a looming risk on a global scale. The study of the underlying magmatic systems is integral in understanding what leads to these large eruptions. This approach pairs a suite of major and trace element profiles from plagioclase with a grain texture classification and statistical analysis using Polytopic Vector Analysis (PVA) as proxies to explore potential changes in the thermomechanical state of the magmatic system at Okataina Volcanic Complex (OVC), New Zealand through its most recent caldera cycle. Results indicate systematic changes in plagioclase chemistry and textures that are highlighted by: 1) pre-caldera crystals that are compositionally evolved yet primarily fed by a mafic chemical end-member, 2) syn-caldera crystals that are compositionally heterogenous yet texturally restricted, and 3) post-caldera crystals that are initially texturally broad and least evolved but migrate towards pre/post compositions and textures by the end of the analyzed samples. Paired with the contributions of the four distinct geochemical end-members generated using PVA, it is suggested that OVC was primarily in a “cold storage” state during the pre- and post-caldera timeframe, while a “warm” storage scenario best describes the state of the system during the building of the syn-caldera eruptions.

Bonessi_MS_ThesisAppendices.xlsx (477 kB)
Appendices for Bonessi MS Thesis