The first high-temperature geochronometric data are presented for the peraluminous, multiple phase Musquodoboit Batholith, the second largest intrusion in the Meguma terrane of Nova Scotia. Previous geochronology includes 40Ar/39Ar mica (i.e., muscovite and biotite, 363 to 370 Ma) and Rb-Sr whole-rock (266 Ma) and mineral (biotite, 370 Ma) ages. These earlier ages contrast with new data for zircon and monazite which together define an age of 378 ± 1 Ma for the high-temperature crystallization (i.e., ca. >650-800°C) and, therefore, provide a more reliable time for emplacement and solidification of the batholith. Integration of the new data with previous work is reconciled in the context of a protracted cooling history for the intrusion that reflects the depth of emplacement (i.e., 10-12 km) and potentially high geothermal gradient due to the radioelement-rich nature of parts of the complex. This study suggests that absolute dating of large intrusive bodies emplaced at moderate crustal levels (i.e., ≥3-4 kbars) should employ high-temperature geochronometers rather than the commonly used 40 Ar/39Ar mica technique, which is limited due to the relatively lower blocking temperatures of ≤350°C.
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Kontak, D. J., Ham, L. J., & Dunning, G. (2004). U-Pb dating of the Musquodoboit Batholith, southern Nova Scotia: Evidence for a protracted magmatic-hydrothermal event in a Devonian intrusion. Atlantic Geology, 40(2–3), 207–216. https://doi.org/10.4138/1040