Diffusion chronometry of volcanic rocks: looking backward and forward

Abstract

Diffusion of elements that result in compositional zoning in minerals in volcanic rocks may be used to determine the timescales of various volcanic processes (e.g., residence times in different reservoirs, ascent rates of magmas). Here, we introduce the tool and discuss the reasons for its gain in popularity in recent times, followed by a summary of various applications and some main inferences from those applications. Some specialized topics that include the role of diffusion anisotropy, isotopic fractionation by diffusion, image analysis as a tool for expediting applications, and the sources of uncertainties in the method are discussed. We point to the connection between timescales obtained from diffusion chronometry to those obtained from geochronology as well as various monitoring tools. A listing of directions in which we feel most progress is necessary/will be forthcoming is provided in the end.

Determining the Pressure – Temperature – Composition (P-T-X) conditions of magma storage

“…Constraining the temperatures of different magmatic processes can reveal the thermal evolution of magmatic systems and are vital inputs for many other common workflows in igneous petrology, such as calculations of timescales from elemental diffusion in erupted crystals (termed "diffusion chronometry" or "geospeedometry"). In fact, because diffusion rates are strongly sensitive to temperature (following an Arrhenius relationship), uncertainty in temperature is one of the largest sources of error when obtaining timescales using these chronometers (Chakraborty and Dohmen, 2022;Costa et al, 2020). For example, Mutch et al (2019a) show that timescales calculated from Cr diffusion in spinel change from ~4000 years at 1190°C to ~1000 yrs at 1230°C.…”

The Whakamaru Magmatic System (Taupō Volcanic Zone, New Zealand), Part 2: Evidence from ignimbrite deposits for pre-eruptive distribution of melt-dominated magma and magma mushes

“…Large, explosive volcanic eruptions demonstrate that the crust must create and accommodate large volumes of melt-dominated magma prior to eruption. Substantial advances have been made to understand the pre-eruptive conditions of the melt-dominated magma bodies that feed such eruptions (Cashman & Giordano, 2014), including crystallization timescales (Simon and Reid, 2005;Charlier et al, 2008;Druitt et al, 2012;Allan et al, 2013;Barboni and Schoene, 2014;Chamberlain et al, 2014;Cooper and Kent, 2014;Pamukçu et al, 2015a;Gualda and Sutton, 2016;Fabbro et al, 2017;Reid and Vazquez, 2017;Shamloo and Till, 2019;Chakraborty and Dohmen, 2022); storage pressures (Blundy and Cashman, 2008;Hansteen and Klügel, 2008;Putirka, 2008;Ridolfi et al, 2010;Gualda and Ghiorso, 2013a;Bégué et al, 2014a;Bachmann and Huber, 2016;Gualda et al, 2018;Pitcher et al, 2021;Pelullo et al, 2022); volatile content (Moore et al, 1998;Papale et al, 2006;Ghiorso and Gualda, 2015;Waters and Lange, 2015;Iacovino et al, 2021;Wieser et al, 2022); and oxygen fugacity (fO2) conditions (McCanta et al, 2004;Kelley and Cottrell, 2009;Ulmer et al, 2018;Pitcher et al, 2021;Ghiorso et al, 2023). These eruptions have a variety of possible pre-eruptive storage configurations as they can erupt from one magma body, as in the 'mush' model…”

A model for the evolution size and composition of olivine crystals

“…The aim of the introduced model is to improve the understanding of this process to predict under which conditions a crystal recrystallizes and under which conditions a crystal remains stable and the diffusion history can be traced back. This idea has been raised by Chakraborty and Dohmen [1].…”