Field relations, geochemistry, and age of Paleoproterozoic igneous rocks in the northeastern Kaipokok Bay area, Makkovik Province, Labrador.

The northeastern part of Kaipokok Bay is located in the Makkovik Province of Labrador, in the boundary zone between the Kaipokok and Aillik domains. The Kaipokok domain is characterized by reworked Archean gneiss, ca. 2100 Ma mafic metavolcanic and supracrustal metasedimentary rocks, and ca. 1895-1870 Ma plutonic rocks. The Aillik domain to the southeast is characterized by metavolcanic and metasedimentary rocks of the ca. 1860 Ma Aillik Group and younger 1800 Ma (syn-Makkovikian), 1720 Ma (post-Makkovikian), and 1670-1640 Ma (Labradorian) plutonic rocks. In the study area, the Aillik Group is dominated by metasandstone with less abundant metaconglomerate and meta-rhyolite, and rare calc-silicate and mafic volcanic rocks. The largest plutons in the area are the ca. 1802 Ma Long Island Quartz Monzonite and Kennedy Mountain granite, part of the Kennedy Mountain Intrusive Suite of the Aillik domain. A U-Pb (zircon) age of 1800.6 ± 2.3 Ma for the Kennedy Mountain granite confirms that it is the same age as the Long Island Quartz Monzonite, as inferred by earlier workers in the area. Plutons of similar age (Drunken Harbour and Hares Islands granites) have been documented farther northwest in the Kaipokok domain. The presence of compositionally similar 1800 Ma plutons in both the Aillik and Kaipokok domains is consistent with tectonic models which show that the domains were juxtaposed by that time. These plutons have within-plate, A-type characteristics, and were likely emplaced during regional transpression that was focussed on the Kaipokok Bay shear zone between the Kaipokok and Aillik domains. Labradorian-age (1670-1640 Ma) plutonic rocks occur in both the Kaipokok and Aillik domains and range in composition from ultramafic to gabbro and granite. These plutons have diverse petrological characteristics and their ages are not well constrained. Their tectonic setting during emplacement is uncertain, as they are located far from the focus of Labradorian orogenic activity in the Grenville Province. [ABSTRACT FROM AUTHOR]