CONSTRAINING THE ABSOLUTE TIMING OF BRITTLE DEFORMATION IN THE ROCKY MOUNTAIN FRONT RANGE, CO, USING LA-ICP-MS U-PB DATING OF CARBONATE FILLED VEINS

The Rocky Mountain Front Range, CO, currently has an average elevation of ~2-3km resulting from a history of uplift over the past ca. 100 million years. However, little is known about the absolute timing of brittle deformation features in the area. The use of laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) U-Pb geochronology on carbonate-filled fractures has the potential to fill this gap in knowledge. Calcite-forming fluids have the potential to incorporate uranium during precipitation, making fault-hosted carbonate veins a good geochronometer for the timing of brittle deformation events. The purpose of this study is to integrate data from field observations, vein orientations, detailed petrographic analysis, cathodoluminescence (CL) imaging, and LA-ICP-MS analysis to produce a more detailed deformation and fluid flow history of the rocks in the Canon City embayment.

We have collected fault-hosted carbonate filled veins from a variety of strata and locations around the Cañon City embayment region. These were processed into polished thick sections (ca. 100 µm thick), characterized petrographically, geochemically and analyzed through LA-ICP-MS U-Pb geochronology. Preliminary results indicate that it is possible to constrain the absolute timing of brittle deformation with these methods with high precision. Initial results show a range of ages for carbonate-filled veins in this region from pre-Laramide, Cretaceous age to post Laramide, Neogene age.