Global Applicability of Ultramafic Serpentinization and Carbonation Magnetic Mapping
Abstract
Throughout the Earth’s lithosphere, from its formation at spreading centers to its termination at subduction and/or obduction environments, serpentinization and carbonation processes of mantle rock are recognized as important contributors in the global carbon cycle on Earth. Understanding the extent of the serpentinization and carbonation process in-situ is, thus a critical first step in deciphering the carbon cycle. We aim to assess the global applicability of potential field measurements to monitor in-situ serpentinization-carbonation progression in mantle peridotite, based on the premise that magnetite abundances correlate with the progress of the carbonation reaction (Tominaga et al., 2017). We collected 5 representative samples along a transect of fully exposed upper mantle covering the full range of carbonation sequences on the Vancouver Ophiolite in Atlin, Canada. Based on field observations, we identify that the alteration stages along the transect sequentially range from harzburgite to serpentinized harzburgite, serpentinite, and listvenite. We conducted rock magnetic measurements on the samples, including Frequency-Dependent Susceptibility, First-Order Reversal Curve (FORC), Zero-Field Cooling (ZFC) and Temperature Dependent Susceptibility, to determine magnetic domain states, changes in domain state with variations in grain size, mixing of magnetic sources, and the dominant magnetic mineral in the samples. Preliminary, first-order results from these magnetic experiments, in addition to Superconducting Quantum Interference Device (SQUID) microscopy, indicate that ferromagnetic minerals are dominant in the serpentinized samples, whereas paramagnetic minerals are dominant in the carbonated samples. Crustal gravity and magnetic anomaly measurements, analyzed with the rock sample measurements, manifest consistent results to previous studies of altered ultramafic rocks elsewhere, suggesting that the hypothesis of the global applicability of potential field methods as a monitoring scheme for serpentinization-carbonation reactions is viable.
Citation
Pruett, Paiden (2019). Global Applicability of Ultramafic Serpentinization and Carbonation Magnetic Mapping. Undergraduate Research Scholars Program. Available electronically from https : / /hdl .handle .net /1969 .1 /194532.