The use of palaeomagnetism and rock magnetism to understand volcanic processes: introduction

Abstract

This Special Publication provides a snapshot of our understanding of volcanic processes through the use of palaeomagnetic and rock magnetic techniques. Here, we provide a context for the book, placing individual chapters within the milieu of previous work, including some magnetic techniques that were not used in the particular studies described herein. Thermoremanent magnetization is a powerful tool to understand processes related to heating and cooling of rocks, including estimating the temperature of emplacement of pyroclastic deposits, which may allow us to better understand the rates of cooling during eruption and transport. Anisotropy of magnetic susceptibility and anisotropy of remanence are used primarily to investigate rock fabrics, and allow the interpretation of flow dynamics in dykes, lava flows and pyroclastic deposits, as well as the location of the eruptive vents. Rock magnetic characteristics can help in the correlation of volcanic deposits but also provide means to date volcanic deposits and to better understand the processes of cooling of the deposits, as the magnetic minerals can change with temperature. In addition, volcanic rocks may be key recorders of past magnetic fields, allowing a better understanding of changes in field intensity and, perhaps, providing clues of how the magnetic field is formed.

AMS and rock magnetism in the Caviahue-Copahue Volcanic Complex (Southern Andes): Emission center, flow dynamics, and implications to the emplacement of non-welded PDCs

“…In these cases, interpreting AMS results and extracting flow direction pose a challenge (e.g., LaBerge et al, 2009;Alva-Valdivia et al, 2017). Deviations from the parallel AMS fabrics in PDCs have been attributed to several causes, including flow dynamics (Ort et al, 1999;LaBerge et al, 2009;Agrò et al, 2014;Ort et al, 2014Ort et al, , 2015, and mineralogy (e.g., Rochette et al, 1992;Moncinhatto et al, 2020).…”

“…In PDCs, the flow dynamics play a significant role in the distribution and orientation of magnetic particles (Ort et al, 1999(Ort et al, , 2014(Ort et al, , 2015Giordano et al, 2008).…”

AMS and rock magnetism in the Caviahue-Copahue Volcanic Complex (Southern Andes): emission center, flow dynamics, and implications to the emplacement of non-welded PDCs

“…Following this reasoning, several studies have associated the orientation of AMS axes with distance from the vent and associated PDC dynamics (e.g., Fisher et al, 1993;Baer et al, 1997;Ort et al, 1999Ort et al, , 2003Ort et al, , 2015Porreca et al, 2003). In these studies, proximal sites show overlapping, dispersed, or random K 1 and K 2 axes, while more distal portions tend to result in well-defined axes, with K 1 parallel to flow direction (Ort et al, 2014).…”

“…Manuscript submitted to Journal of Volcanology and Geothermal Research have been attributed to several causes, including flow dynamics (Ort et al, 1999;LaBerge et al, 2009;Agrò et al, 2014;Ort et al, 2014Ort et al, , 2015, and mineralogy (e.g., Rochette et al, 1992;Moncinhatto et al, 2020).…”

Guía rápida para el estudio de rocas deformadas a partir del análisis de la Anisotropía de la Susceptiblidad Magnética (ASM)

“…The application of AMS to igneous rocks emerged lately when compared to sedimentary or metamorphic rocks (e.g., Khan, 1962;King, 1966;Wing-Fatt and Stacey, 1966). This technique has been traditionally used to characterize the primary magmatic flows and/or the location of preferential pathways for magma ascent of plutonic, volcanic and subvolcanic rocks (e.g., Tarling and Hrouda, 1993;Bascou et al 2005;Hrouda et al 2005;Ort et al, 2015;Nagaraju and Parashuramulu, 2019) (Fig. 5).…”