Granite batholith radiometric dating

(1964), who obtained a whole-rock Rb-Sr isochron date of 266 ± 17 Ma and a Rb-Sr biotite age of ca. Geochemical evolution of peraluminous plutons in southern Nova Scotia, Canada - a pegmatite poor suite.

Previous geochronology includes Ar 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.

Faults strongly influence the shape of the MB and, by analogy to the structure of the South Mountain Batholith (Horne 1992), these faults probably pre-dated intrusion and were active at the time of emplacement, and consequently controlled the nature of the contacts and the present day outline of the granite.

No penetrative structures occur in the MB that might suggest a late tectonic overprint.

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