The geology of Nunavut began to form nearly three billion years ago in the Archean and the territory preserves some of the world's oldest rock units. Geologic History, Stratigraphy & Tectonics Archean Archean rocks dominate much of the territory's surface and places with overlying rock. Greenstone belts are common together with migmatite gneiss, granodiorite, and quartz monzonite, on the Melville Peninsula and northern Baffin Island, as well as the southwest mainland. Lenses and bands of amphibolite, granitoid and metasedimentary rocks are common in these areas, along with less common ultramafic rocks. Gold and other base metals are widespread as mineralization in siliclastic, felsic, mafic and ironstone rocks of the greenstone belts. The George Lake, Boston and Ulu deposits are all hosted in the Yellowknife Supergroup of the Slave Craton in the west as well as the Lupin gold mine. In the western Churchill Province of south-central Nunavut are the Noomut, Heninga Lake and Meliadine gold deposits, and the Victory Lake and Ferguson Lake base metals deposits. Ultramafic volcanic rocks, quartzite and iron formations in the northern Churchill Province hold the Woodhurn, Prince Albert and Meadowbank gold deposits. The Churchill Province experienced widespread metamorphism 2.5 billion years ago. Baffin Island represents the eastern margin of the Canadian Shield and the long-term thermal history of southern Baffin suggests temperatures remained high (above 400C) following Trans-Hudson Orogeny peak metamorphism at c. 1.85 billion years ago, slow cooling and minor reheating ensued throughout the Proterozoic, followed by episodic sedimentary burial during the Paleozoic through Mesozoic of <3-4 km. Paleozoic (539-251 million years ago) Paleozoic rocks cover one-third of the territory, northwest of Fury and Hecla Strait, forming part of the Arctic Platform and continuing north to Ellesmere Island. In the southeast, they are continuation of the Hudson Platform beneath the Foxe Basin. Subsidence and craton rifting are recorded in Cambrian strata, with clastic sequences left by a marine transgression. A stable platform developed from the Cambrian through the Silurian and thick carbonates with high oil and gas potential deposited. The Caledonian orogeny brought uplift and erosion from the Silurian through the Early Devonian, generating potential red bed related copper deposits in a thick clastic wedge. The Ellesmerian orogeny produced Mississippi-valley type zinc-lead mineralization in the Polaris district of the Canadian Arctic Archipelago. Thick clastic and carbonate sediments deposited in the Sverdrup Basin in the north during the Carboniferous. Proterozoic (2.5 billion-539 million years ago)