New Re-Os molybdenite and U-Pb zircon dates from deposits of the Tombstone Gold Belt provide direct timing constraints for sulphide mineralization and crystallization of spatially associated plutons. At Clear Creek Re-Os molybdenite dates (93.6 +/- 0.3 to 92.4 +/- 0.4 Ma) are in excellent agreement with the host intrusion U-Pb zircon age (92.3 +/- 0.3 Ma). Consequently we propose the nominally younger existing Ar-40/Ar-39 hydrothermal mica ages (91.7 +/- 0.4 and 90.0 +/- 0.3 Ma) for Clear Creek are a result of slow cooling. At Dublin Gulch, the Re-Os molybdenite date (93.2 +/- 0.3 Ma) for a late stage vein is nominally younger than the host intrusion U-Pb zircon age (94.0 +/- 0.3 Ma), in agreement with the deposits paragenesis. The U-Pb zircon date (92.1 +/- 0.2 Ma) for the Mactung pluton, which lies adjacent to the W-skarn, has a younger age than the Re-Os molybdenite dates (97.5 +/- 0.5 Ma). Fluid inclusion geochemical data for ore-fluid indicate a magmatic origin for the W-skarn. However, the U-Pb and Re-Os age data suggest that the exposed Mactung stock is not the source of ore-fluid for the W-skarn and that the progenitor pluton for ore-fluid is unknown. The robust age constraints obtained for mineralization and magmatism in this study are in accord with the hypothesis that these deposits are intrusion-related ore systems. The results are also in agreement with previous studies demonstrating that the Re-Os molybdenite chronometer can provide accurate and precise dates for the timing of metallic mineralization with rigorous sampling protocol.
Selby, D., Creaser, R. A., Heaman, L. M., & Hart, C. (2003). Re-Os and U-Pb geochronology of the Clear Creek, Dublin Gulch, and Mactung deposits, Tombstone Gold Belt, Yukon, Canada: absolute timing relationships between plutonism and mineralization. Canadian Journal of Earth Sciences, 40, 1839-1852. https://doi.org/10.1139/E03-077