Exsolved volatiles in magma reservoirs

Abstract

Introduction 2. Achieving volatile saturation in magmas 2.1. Volatiles in natural magmatic systems 2.2. Sulfur partitioning into the exsolved volatile phase 3. Consequences of exsolved volatiles in magma reservoirs for rheology and dynamics 3.1. Magma compressibility 3.2. Pressure increase during second boiling 3.3. Effect of compressibility on the mass of magma erupted 4. The role of the exsolved volatile phase in magma mixing and mingling 4.1. Magma mixing and overturn, driven by vesiculation of the lower magma layer 4.2. Vesiculation of underplating magmas and formation of mafic enclaves 5. Exsolved volatile phase generation and transport through crystal-rich magma bodies 5.1. Transport of an exsolved volatile phase in crystal-rich magma 5.2. Implications of our new understanding of the transport of the exsolved volatile phase

Multi-Sensor SAR Geodetic Imaging and Modelling of Santorini Volcano Post-Unrest Response

“…This increase has been interpreted as an increase in the permeability of the volcanic pile along the Kameni fault resulting from the seismic activity during the unrest. According to these data, and taking into account the results of recent models of degassing from magma chambers [64], we propose that dynamics of our sill-like deflating source is related to the passive degassing (second boiling) of the magma intruded at 4-5 km depth during the unrest. This interpretation is consistent with the shallower depth (about 2 km) and geometry (sill-like) of the top of the magma reservoir, in which a volatile saturated zone is formed at the top by accumulation of gases associated to initial states of fractional crystallization and cooling [64][65][66].…”

“…According to these data, and taking into account the results of recent models of degassing from magma chambers [64], we propose that dynamics of our sill-like deflating source is related to the passive degassing (second boiling) of the magma intruded at 4-5 km depth during the unrest. This interpretation is consistent with the shallower depth (about 2 km) and geometry (sill-like) of the top of the magma reservoir, in which a volatile saturated zone is formed at the top by accumulation of gases associated to initial states of fractional crystallization and cooling [64][65][66]. This interpretation is also supported by the available geochemical data, which show a significant increase of CO 2 concentration values from the unrest, uplift period (May 2010-February 2012, CO 2 = 400 mmol/mol) to the post-unrest (deflation) period (March-July 2012; CO 2 = 800 mmol/mol) [62].…”

“…According to the conceptual model proposed above, such volatiles migrated in the uppermost portion of the reservoir and were passively released to the surface along the Kameni line. A component of deformation related to magma cooling can also be invoked for the observed subsidence, however, according to Reference [64], it plays a minor role.…”

Supereruption quartz crystals and the hollow reentrants

“…Gassy magma has different physical properties than volatile-undersaturated melt. Of particular importance is the compressibility of magma because it affects the evolution of magma pressure and the volume of magma that will erupt (Edmonds and Woods, 2018).…”

“…Many observations now exist to geochemically establish pre-eruptive volatile saturation, or lack thereof (Edmonds and Woods, 2018). Excess sulfur has been documented via remote sensing at other volcanoes, including El Chichón (Mexico), Mount St. Helens (Washington State, USA), and Mount Redoubt (Alaska, USA) (Gerlach and McGee, 1994;Gerlach et al, , 1996.…”