U-Pb age and Sm-Nd isotopic studies in Archean Hood River and Torp Lake supracrustal belts, northern Slave Province, Northwest Territories

Abstract

U-Pb zircon isotopic data from the Hood River and Torp Lake belts indicate the presence of two temporally and lithologically distinct supracrustal sequences. A 2668 ± 4 Ma age was obtained from a dacite sill in the southeastern part of the area, coeval with 2.71-2.66 Ga volcanism documented throughout the Slave Province. This date provides a minimum age for the older of two supracrustal sequences in the Hood River and Torp Lake belts, which appears to be correlative with the Yellowknife Supergroup. Concordant detrital zircon ages from a turbidite in the western part of the Hood River area range from 2720Ma to 2679 Ma, indicating a synvolcanic source. The detrital zircon data plus juvenile eNd values are consistent with previous evidence pointing to an absence of Mesoarchean basement in the eastern Slave Province. Banded iron-formation in Hood River belt is restricted to the older, dominantly metasedimentary supracrustal sequence. For at least part of the younger volcano-sedimentary sequence in the Hood River belt, a 2605 +2/-3 Ma maximum age limit is provided by zircons from a felsic clast in a boulder bed. Preliminary maximum ages for some volcanic rocks in the younger sequence are 2600 ± 2 Ma, from felsic tuffaceous sediments and 2622 ± 3 Ma, from a quartz-feldspar porphyry. A 2600 ± 2 Ma younger limit for this volcano-sedimentary sequence is established by a cross-cutting granodiorite, late in the regional structural sequence. A syntectonic diorite from the Torp Lake belt is dated as 2604 ± 4 Ma. Deposition of the younger sequence was, therefore, contemporaneous with plutonism.