Protracted Magmatism within the North Caribou Terrane, Superior Province: Petrology, Geochronology, and Geochemistry of Meso- to Neoarchean TTG Suites

Abstract

The North Caribou Terrane forms the core of Superior Province and records a protracted history of crustal growth and modification. At the centre of the North Caribou Terrane, lies the North Caribou greenstone belt, which is surrounded by granitoids of diverse compositions and ages. This study reports whole-rock geochemistry, zircon and titanite geochronology, and hornblende geobarometry on these plutonic rocks. Although zircons as old as 3132 ± 7 Ma were found, the main magmatic pulse occurred between 2880 and 2830 Ma, and geobarometry indicates tectonic thickening during this period. This was followed by widespread hydrothermal alteration and limited magmatism from 2760 to 2680 Ma, and shallow, brittle-ductile intrusions at circa 2630 Ma. From 2730 to 2630 Ma, intrusions were emplaced at increasingly shallow crustal levels. All of the rocks, except for the youngest pegmatitic intrusions, show similar patterns in major and trace elements, with a general trend toward more evolved compositions through time. These patterns indicate that the granitoids record mostly reworking of early intrusions, which is also consistent with patterns observed in the geochronology.