Bayesian Markov-Chain Monte Carlo Inversion of Low-Temperature Thermochronology Around Two 8 − 10 m Wide Columbia River Flood Basalt Dikes
Affiliation
Univ Arizona, Dept GeosciIssue Date
2019-04-30Keywords
Columbia River Flood Basaltsdike mechanics
Bayesian inversion
low temperature thermochronology
large igneous provinces
thermal modeling
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FRONTIERS MEDIA SACitation
Karlstrom L, Murray KE and Reiners PW (2019) Bayesian Markov-Chain Monte Carlo Inversion of Low-Temperature Thermochronology Around Two 8 – 10 m Wide Columbia River Flood Basalt Dikes. Front. Earth Sci. 7:90. doi: 10.3389/feart.2019.00090Journal
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Copyright © 2019 Karlstrom, Murray and Reiners. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
Flood basalt volcanism involves large volumes of magma emplaced into the crust and surface environment on geologically short timescales. The mechanics of flood basalt emplacement, including dynamics of the crustal magma transport system and the tempo of individual eruptions, are not well-constrained. Here we study two exhumed dikes from the Columbia River Flood Basalt province in northeast Oregon, USA, using apatite and zircon (U-Th)/He thermochronology to constrain dike emplacement histories. Sample transects perpendicular to the dike margins document transient heating of granitic host rocks. We model heating as due to dike emplacement, considering a thermal model with distinct melt-fraction temperature relationships for basaltic magma and granitic wallrock, and a parameterization of unsteady flow within the dike. We model partial resetting of thermochronometers by considering He diffusion in spherical grains as a response to dike heating. A Bayesian Markov-Chain Monte Carlo framework is used to jointly invert for six parameters related to dike emplacement and grain-scale He diffusion. We find that the two dikes, despite similar dimensions on an outcrop scale, exhibit different spatial patterns of thermochronometer partial resetting away from the dike. These patterns predict distinct emplacement histories. We extend previousmodeling of a presumed feeder dike atMaxwell Lake in theWallowaMountains of northeastern Oregon, finding posterior probability distribution functions (PDFs) that predict steady heating from sustained magma flow over 1-6 years and elevated farfield host rock temperatures. This suggests regional-scale heating in the vicinity of Maxwell Lake, which might arise from nearby intrusions. The other dike, within the Cornucopia subswarm, is predicted to have a 1-4 year thermally active lifespan with an unsteady heating rate suggestive of lowmagma flow rate compared to Maxwell Lake, in a cool near-surface thermal environment. In both cases, misfit of near-dike partial resetting of thermochronometers by models suggests either heat transfer via fluid advection in host rocks or pulsed magma flow in the dikes. Our results highlight the diversity of dike emplacement histories within the Columbia River Flood Basalt province and the power of Bayesian inversion methods for quantifying parameter trade-offs and uncertainty in thermal models.Note
Open access journal.ISSN
2296-6463Version
Final published versionSponsors
National Science Foundation [EAR 1547594]ae974a485f413a2113503eed53cd6c53
10.3389/feart.2019.00090
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Except where otherwise noted, this item's license is described as Copyright © 2019 Karlstrom, Murray and Reiners. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY).