Catherine Mottram on Dating Rock Deformation
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Catherine Mottram’s research focuses on dating methods that do not rely on zircon. She has successfully developed radiometric methods based on calcite, monazite, and other minerals that enable processes occurring at relatively low temperatures and pressures to be dated. Using these methods, she has helped unravel the deformation history of rocks as far afield as the far north of the Yukon in Canada and cast light on how minerals such as gold can collect along large-scale faults.
The image shows Mottram inspecting drill cores from her research area in the Yukon, Canada.
Mottram is an Associate Professor of Geology at the University of Portsmouth.
Courtesy of the University of Portsmouth and Sam Shaw
Podcast Illustrations
Images courtesy of Catherine Mottram unless otherwise noted.
Effective Closure Temperatures of Minerals Used for Geochronology
As Catherine Mottram explains in the podcast, various geological clocks record the timing of geological processes from temperatures above 800°C to temperatures as low as 100°C. Geochronometers such as uranium-lead (U-Pb) in zircon and monazite record high-temperature igneous and metamorphic processes. Mid-temperature (500-700°C) crustal metamorphic, hydrothermal, and deformation processes are recorded by methods such as U-Pb in apatite and radioactive decay of argon and rubidium in muscovite. Using U-Pb in carbonates (e.g., calcite) is a relatively novel method for dating low-temperature fluid-flow processes.
Adapted from Chew, D.M., et al. (2015) Elements 11.3: 189
Applications of Uranium-Lead Calcite Dating
Carbonate is ubiquitous in the upper crust and crystallizes during a range of geological processes, some of which are shown in this diagram together with an indication as to where each process occurs. In the podcast, Catherine Mottram discusses her work in the Yukon in Canada, in which the main processes involving calcite crystallization are fractures and fluid flow and ore mineralization. She also talks about calcite dating of a fossil turtle on the Isle of Wight, formed by a diagenetic process, and dating of faults in Turkey and the Eastern Mediterranean, which involved calcite dating of slickenfibres in the North Anatolian fault.
Geochronology of Ore Deposits
Schematic diagram of the magmatic and hydrothermal processes involved in the establishment of a porphyry deposit. In recent years, the demand for critical minerals, such as copper and molybdenite, has increased due to the crucial role in the green-energy transition. These metals precipitate with gold, silver, and other metals in porphyry deposits, where magmatic and hydrothermal fluid circulation deposits metal above granite intrusions in a volcanic setting. U-Pb zircon dating can provide timing of the short duration, high temperature of magmatic processes (dark pink granite and red dikes in the figure), but it has previously been challenging to date the lower-temperature fluid flow processes that can be critical for concentrating metal. In the podcast, Catherine Mottram explains how she applied the U-Pb carbonate geochronometer to reconstruct a more than 50-million-year record of carbonate precipitation within a strike-slip fault-controlled porphyry deposit in Yukon, Canada, revealing the previously untold longevity of fault-controlled fluid flow in ore deposits. The diagram also shows the volcanic pipe feeding the original volcano (diatreme) and faults with their associated highly fractured breccia.
The partial fossilized skeleton of the ca. 127-million-year-old Isle of Wight turtle for which Catherine Mottram and her team obtained a radiometric date from the fossil’s calcite. Top left: shell rear view; top right: front body rear view; bottom left: shell front (neck cavity) view; bottom right: front body front (neck cavity) view.
Courtesy of Megan Jacobs, Jacobs et al., 2023)
Dating the Folding in the Zanskar Valley
The Zanskar River cuts through intensely folded sediments of the former northern margin of India.
Photos: Oliver Strimpel
Calcite veins filling tension gashes created during the folding are sampled by Ian Cawood.
The large white veins are calcite that cross-cut the folding and therefore post-date the folding. Successful dating of the calcite in both types of vein would enable time constraints to be placed on the age of the folding and address the question as to whether it occurred prior to the collision of the Indian continent with Asia or following it. In this case, Catherine Mottram was unable to date the calcite as it had too little uranium and too much non-radiogenic lead.
Porphyry Deposits in the Yukon, Canada
Mining camp in the Yukon near the research area Catherine Mottram studied using drill cores such as those shown in the first picture on this page. Almost no rocks are visible on the surface as the area is largely covered by boreal forest.
Courtesy of Triumph Gold Corp.
The site of Triumph Gold's Revenue camp in the central Dawson Range near Carmacks, Canada. Though boreal forest and vegetation covers almost all of the porphyry deposit, Triumph Gold Corporation, an exploration company, has revealed the mineralization in the subsurface through extensive drilling. Catherine Mottram has conducted most of her work on longevity of hydrothermal processes in porphyry deposits here.
Mineral Exploration Site in British Columbia
Mottram spent the summer of 2023 in northern British Columbia, close to the small gold rush town of Atlin, working with Core Assets Corporation, a small mineral exploration company. Their 'Blue Property' is located high above the Juneau Icefield on the border with Alaska.
Sarah Bowie, a University of Portsmouth PhD student (back), examining plutonic rocks near Atlin, northern British Columbia, with Dawn Kellett (front), a research scientist at the Geological Survey of Canada. The igneous rocks, faults, and mineralization are wonderfully exposed in glacially polished surfaces in the high mountains.
Further Reading
Introduction to closure temperatures with reference to the U-Pb apatatie geochronometer.
Chew, David M., and Richard A. Spikings. "Geochronology and thermochronology using apatite: time and temperature, lower crust to surface." Elements 11.3 (2015): 189-194.
Introduction to isotope geochemistry.
Condon, D. J., & Schmitz, M. D. (2013). One hundred years of isotope geochronology, and counting. Elements, 9(1), 3-57. ISSN 1811-5209
Research article and local newspaper story on the Isle of Wight turtle mentioned in the podcast.
Jacobs, M. L., Pérez-García, A., Martín-Jiménez, M., Mottram, C. M., Martill, D. M., Gale, A. S., ... & Wood, C. (2023). A well preserved pan-pleurodiran (Dortokidae) turtle from the English Lower Cretaceous and the first radiometric date for the Wessex Formation (Hauterivian–Barremian) of the Isle of Wight, United Kingdom. Cretaceous Research, 150, 105590.
Fault dating and directly dating faulting and mineralisation in the Dawson Range, central Yukon.
Mottram, C. M., Kellett, D. A., Barresi, T., Zwingmann, H., Friend, M., Todd, A., & Percival, J. B. (2020). Syncing fault rock clocks: Direct comparison of U-Pb carbonate and K-Ar illite fault dating methods. Geology, 48(12), 1179-1183.
Catherine Mottram’s PhD work on monazite petrochronology in the Himalaya.
Mottram, C. M., Warren, C. J., Regis, D., Roberts, N. M., Harris, N. B., Argles, T. W., & Parrish, R. R. (2014). Developing an inverted Barrovian sequence; insights from monazite petrochronology. Earth and Planetary Science Letters, 403, 418-431.
Introduction to the concept of carbonate U-Pb geochronology.
Roberts, N. M., Drost, K., Horstwood, M. S., Condon, D. J., Chew, D., Drake, H., ... & Lee, J. K. (2020). Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb carbonate geochronology: strategies, progress, and limitations. Geochronology, 2(1), 33-61.
Review of the different geochronometers used to date geological processes.
Volante, S., Blereau, E., Guitreau, M., Tedeschi, M., van Schijndel, V., & Cutts, K. (2024). Current applications using key mineral phases in igneous and metamorphic geology: perspectives for the future. Geological Society, London, Special Publications, 537(1), SP537-2022.