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.

You do not currently have access to this article.