The Front Range of the Southern Rocky Mountains near Boulder, CO contains a rock record that spans nearly 1.7 billion years. Zircon U-Pb geochronology is an isotopically-based chronometer for measuring deep earth time. We apply this method to a series of small igneous intrusive bodies from the Front Range west of Boulder, CO. These instrusives are collectively known as the Colorado Mineral Belt (CMB) for the economic mineral deposits associated with the instrusives. Past geochronological methods have provided only rudimentary constraints on the geologic timing of emplacement of these bodies. We demonstrate the CMB magmatic activity in the Front Range occurred in two discrete pulses, one at ~67 Ma (million years ago) and one at ~47 Ma. Additional application of the same methodology to a sedimentary rock, the Neoproterozoic Tavakiav Quartzite, uses the zircon U-Pb ages as tracers to constrain the provenance and depositional age of this unique sand body.
Murray, K. E., Niemi, N. A., & Clark, M. K. (2025). Evidence for the Neoproterozoic rifting of Rodinia in the Rocky Mountain Front Range. Tectonics, 44, e2023TC008216.
