Abstract

Samples of the stratigraphically placed (< 400 Ma) Pokiok batholith of New Brunswick give a Rb/Sr total-rock age of 431 ± 9 Ma. This age is some 40 Ma older than the estimated age of crystallization and is interpreted to result from the mixing of variable amounts of crustal strontium with mantle-like Sr at or about 390 Ma. The existence of inherited or crustal isochrons in the Pokiok batholith implies that all uncorroborated total-rock Rb/Sr ages for granitic plutons in the Appalachians of eastern Canada should be carefully appraised in view of their importance in estimating the timing and duration of the Acadian Orogeny.

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