From the Cradle to the Grave: An in Situ Study of Olivine Growth and Dissolution in a Tholeiitic Magma
Abstract
From the crystallization of magmas at shallow levels to the melting of the mantle, the kinetics of crystal growth and dissolution govern the timescales of igneous processes and the distribution of elements between materials. However, rate data for crystal growth and dissolution is relatively scarce in the geo-literature. Many of today's dynamic experimental setups still grapple with challenges in controlling fundamental variables such as oxygen fugacity and the loss of volatile species at high temperatures, while hindered by the difficulty of tracking kinetic processes at fluctuating temperature and chemical composition. In this contribution, we aim to overcome these challenges by performing experiments within natural melt inclusions, using their host crystals as the experimental vessel. We studied the growth and dissolution kinetics of olivine within plagioclase-hosted melt inclusions using a heating stage equipped with a transmitted light microscope and videocamera. Olivine is a ubiquitous mineral in terrestrial and extraterrestrial rocks, and hence is relevant to a wide range of natural systems. Melt inclusions have the advantage of acting as microscopic magma reservoirs evolving in a quasi-closed system, while the heating stage provides fine temperature control. The microscope and camera facilitate in situ observations of the immediate responses of the different phases. Our experiments were run at various cooling and heating conditions (dT/dt = 0.01 - 130°C/min, +ΔT= 0 - 20°C, -ΔT = 5 - 300°C) to provide an array of quantitative and qualitive data regarding the response of olivine to variations in superheating, undercooling, and rate of temperature change. The textural evolution of olivine crystals was documented through snapshot series and their mean and instantaneous growth rates were measured. These results will be instrumental in building thermodynamic models for olivine and in understanding transient processes operating at the crystal scale.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V52A..01W
- Keywords:
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- 1036 Magma chamber processes;
- GEOCHEMISTRYDE: 1043 Fluid and melt inclusion geochemistry;
- GEOCHEMISTRYDE: 8430 Volcanic gases;
- VOLCANOLOGY