LAM-ICP-MS zircon dating of the Falcon Lake Intrusive Complex and Caddy Lake granite, southeastern Manitoba, Canada

Abstract

The Falcon Lake Intrusive Complex is a layered, compositionally zoned intrusion that intrudes the western end of the Wabigooti-Kenora Greenstone Belt of the Superior province, Canada. Cross-cutting field relations indicate that it is post-tectonic; internal contacts are complex and preserve evidence of multiple phases of magma emplacement and magmatic erosion. Xenoliths of country rock are common, as are cognate xenoliths, particularly in the central part of the intrusion. Zircon separates were collected from three of the six principal magmatic phases and dated using LAM-ICP-MS (laser ablation microprobe-inductively coupled plasma-mass spectrometry). Zircon crystals typically preserve internal textures including sector zoned cores mantled by oscillatory zoned overgrowths. These give an age of emplacement for the Falcon Lake Intrusive Complex of between 2733 ± 15 Ma and 2723 ±9 Ma. Zircon crystals from the Caddy Lake granite were also sector zoned and give an age of emplacement of 2687 ± 7 Ma.