Abstract

We use the Curie depth derived from spectral analysis of near-surface magnetic anomaly data to constrain the solution of a one-dimensional (1-D) steady-state heat-flow equation. The method, in addition to anchoring the geotherm at deep levels in the crust, yields the ratio of radiogenic heat pro- duction to thermal conductivity. We evaluate the utility of this constraint in two granitic regions in the United States where radiogenic heat production, thermal conductivity, and heat flow are well determined. We also examine the results of this method in the context of previous research in the central Red Sea and coastal Saudi Arabia. In a test case using data from New Hampshire, USA, the steady-state approximation applies, and we calculate heat-produc- tion values (~8 μW/m3 ) that agree with measurements on samples of Conway granite in the region. In the second example, our Wyoming geotherm is hotter by ~200 °C at the Curie depth, possibly reflecting the 15 km thicker crust (as observed from the dense EarthScope USArray stations in comparison to only two earlier refraction profiles) and the consequent greater radiogenic heat production in the lower crust. In the Colorado Front Range, our radiogenic heat-production value is somewhat higher than predicted from previous heat- flow studies and may reflect heat advected by intrusions. Our results indicate that basal crustal temperatures in northern Colorado may be close to solidus of rocks of felsic composition, a scenario that is consistent with the geologi- cal history of the region and has important implications for crustal rheology. Our estimates of depth-integrated heat production from the crustal columns (25 and 55 mW/m2 Wyoming and Colorado, respectively) also agree well with estimates from previous studies.

Document Type

Article

Publication Date

2016

Notes/Citation Information

© Geological Society of America

Digital Object Identifier (DOI)

https://doi.org/10.1130/GES01235.1

Funding Information 

We are very grateful to Dr. Ahmed Salem for our interactions during the development of the de-fractal method. We thank the editors of Geosphere, reviewers (C. Bouligand, C. Buecker, and C. Gerbi), and Ms. Caitlyn Hartig for their comments, which improved the manuscript. Ms. Leah Newman’s cross-checking of some of our spectral depth results is greatly appreciated. This research was funded by National Science Foundation grants EAR-1246921 to DR and EAR- 1246977 to ARL.

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