Volcanology Commons^™

Extremely High Diversity Of Sulfate Minerals In Caves Of The Irazú Volcano (Costa Rica) Related To Crater Lake And Fumarolic Activity, Andrés Ulloa, Fernando Gázquez, Aurelio Sanz-Arranz, Jesús Medina, Fernando Rull, José María Calaforra, Guillermo E. Alvarado, María Martínez, Geoffroy Avard, J. Maarten De Moor, Jo De Waele

International Journal of Speleology

The caves of the Irazú volcano (Costa Rica), became accessible after the partial collapse of the NW sector of the Irazú volcano in 1994, offering the opportunity to investigate active minerogenetic processes in volcanic cave environments. We performed a detailed mineralogical and geochemical study of speleothems in the caves Cueva los Minerales and Cueva Los Mucolitos, both located in the northwest foothills of the main crater. Mineralogical analyses included X-ray diffraction (XRD) and Raman spectroscopy, while geochemical characterization used Energy Dispersive X-ray spectroscopy (EDX) coupled to Scanning Electron Microscopy (SEM). In addition, measurements of environmental parameters in the caves, …

Giant Plagioclase In The Steens Basalt, Se Oregon: Cumulate Entrainment Revealed By Textural And In Situ Chemical Analysis, Conner H. Toth

All Master's Theses

Many of the lava flows comprising the Steens Basalt in SE Oregon, the oldest and most mafic formation of the Columbia River Basalt Group (CRBG), contain exceptionally large (up to 5 cm) and abundant (up to 40 modal %) plagioclase crystals. This thesis presents a model for giant plagioclase formation in a complex system that integrates petrographic and in situ plagioclase compositional analyses with whole-rock data and computational modeling to explain systematic textural and chemical differences between plagioclase of the lower and upper Steens Basalt sub-sections. Lower Steens plagioclase are typically more chemically homogenous than upper Steens plagioclase and exhibit …

Documenting Magma Evolution Of The Fossa Delle Felci (Salina Island, South Tyrrhenian Sea) By Integrating In Situ Plagioclase Data With Quantitative Modeling, Aaron Mayfield

All Master's Theses

Compositional diversity occurs via processes dominated by recharge, assimilation and fractional crystallization (RAFC), quantification of which can provide insights into eruption catalysts, and therefore assist in hazard mitigation. This study evaluates the relative roles of RAFC processes in Fossa delle Felci (Salina Island, Italy) magmas, which span the basalt to dacite range (52-65 wt% SiO2). Integration of petrographic, whole rock, and in situ plagioclase data with quantitative magma chamber models suggests differentiation dominated by fractional crystallization and magma recharge/mixing in reservoirs located at different crustal levels. At ~12 km depth, magma evolved through crystallization of a pyroxene dominated assemblage; plagioclase …

Documenting Magnatic Processes At Filicudi Island, Aeolian Arc, Italy: Integrating Quantitative Modeling And Plagioclase Textural And In Situ Compositional Data, Michelle Harris

All Master's Theses

Documenting the physiochemical processes that influence magma composition is critical for forecasting eruption styles and managing volcanic hazards. Compositional diversity of magmas develops through recharge, assimilation, and fractional crystallization (RAFC) within subvolcanic magma reservoirs. Integration of MELTS modeling, whole rock, plagioclase textural and in situ elemental and isotopic data from Filicudi Island, Italy allow documentation of the roles and relative chronology that RAFC played in the magmatic evolution and elucidates aspects of the magma plumbing system structure.

Results indicate a polybaric magma plumbing system with deeper (3.5-4 kilobars) and shallower (0.5-1.2 kilobars) storage regions. Within the deeper system, FC acted …

Documenting The Origin Of Compositional Diversity Of Subduction Zone Magmatism, Alicudi, Aeolian Arc (Southern Tyrrhenian Sea, Italy) Using In Situ Plagioclase Data, Rachel Hunt

All Master's Theses

Processes that generate magma compositional diversity are important to document because composition affects degree of explosivity, which impacts hazard mitigation. Magnesium to silicon rich magmas are produced by processes such as magma recharge, assimilation, and fractional crystallization (RAFC) that occur in subvolcanic magma chamber(s). This study evaluates how magma chamber processes contribute to compositional diversity at Alicudi Volcano, Italy. Analytical and petrographic data from ten samples that span the subaerial history include whole rock major and trace elements and strontium/neodymium isotopes, and plagioclase textural types, major and trace elements, and strontium isotopes; numerical modeling was also conducted. Integration of these …

Tourmaline - A Prospecting Guide For Massive Base-Metal Sulfide Deposits In The Penobscot Bay Area, Maine, John F. Slack

Maine Collection

Tourmaline - A Prospecting Guide for Massive Base-Metal Sulfide Deposits in the Penobscot Bay Area, Maine

by John F. Slack, U.S. Geological Survey

Special Economic Studies Series No.8

Maine Geological Survey, Department of Conservation, Augusta, Maine (June, 1980).

Contents: Abstract / Introduction / Geologic Setting / Massive Sulfide Deposits / Tourmaline Occurrences / Tourmaline: A Guide to Ore / Acknowledgements / References Cited