216-3 Multi-chronometer assessment of episodic copper mineralization in sedimentary basins: examples from the Paradox Basin, USA

Session: Geochronology of Critical Mineral Deposits with Special Reference to U-Th-Pb Dating of Common-Pb-Rich Minerals

Presenting Author:

Authors:

Abstract:

Episodic mineralization is a common feature in many ore-forming settings, the timescales of which generally range from thousands to tens of millions of years. New U-Pb dating of syn-ore carbonates provides temporal constraints for a previously unrecognized period of fluid flow and sediment-hosted copper (Cu) mineralization between 18 and 3 Ma across an expansive portion of the evaporite-dominated Paradox Basin. Carbonate veins intergrown with Cu- and Fe-sulfides from 9 locations with a mix of geologic settings and metal traps were analyzed by LA-ICP-MS. We employed an image-based dating technique involving laser rastering to map the distribution and concentration of U, Th, and Pb isotopes for subsequent data reduction and age calculation with Iolite software. Out of the 37 samples examined, 13 from 9 mineral deposits had U-Pb contents suitable for producing radiometric ages. Middle Miocene and Late Cretaceous Re-Os ages of Cu-sulfides from some of the same deposits provide additional direct evidence for episodicity in the Paradox Basin. Results from this study add to previously reported mid-Cretaceous to Oligocene ages for Cu mineralization from coinciding areas, illustrating the large span of ages in these mineral systems. Cu mineralization requires appreciable fluid flux driven by several possible mechanisms. However, most of the new carbonate U-Pb ages predate flow related to rapid regional exhumation (<6 Ma) and postdate inferred periods of significant fluid flux in the Mesozoic and early Cenozoic. This implies a change in hydrologic regime which could have been triggered by some combination of partial removal of Paleogene and Late Cretaceous strata (supported by new detrital zircon data), and previously undocumented salt movement. These complexities identified in the Paradox Basin illustrate the challenges in evaluating many sediment-hosted Cu deposits where mineralization is difficult to date and can occur episodically from diagenesis to late-stage basin inversion. However, in prominent examples including the Paradox Basin, mineralizing processes usually happen over tens of millions of years.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-7848

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