Age and evolution of the Grenville Province in eastern Labrador from U-Pb systematics in accessory minerals

U-Pb isotope analysis of zircon, titanite, monazite and rutile extracted from 15 different Grenville Province rocks in eastern Labrador reveals: 1) major crust formation through magmatism between 1,710 and 1,630 Ma ago; no evidence of older crustal material was found. 2) Pegmatite and gabbro intrusions between 1,500 and 1,400 Ma ago, probably related to incomplete rifting of the earlier formed crust. 3) Granite and syenite plutonism, presumably anorogenic, circa 1,300 Ma ago. 4) High grade metamorphism and anatexis during the Grenvillian Orogeny, causing Pb-loss in primary zircon and new growth of zircon, titanite and monazite at circa 1,030 Ma ago in the south (Lake Melville and Mealy Mountains terranes) and circa 970 Ma ago in the north (Groswater Bay Terrane and Trans-Labrador Batholith); geochronological distinction of these large-scale crustal segments substantiates their juxtaposition along deeply rooted, intracontinental ductile thrust zones during Grenvillian Orogeny. 5) Late Grenvillian growth of rutile in gabbros circa 925 Ma ago. (orig.)