Field relationships, petrology, and petrogenesis of neoarchean granitoids in the northern migmatite sub-domain, Committee Bay Belt, Nunavut.

摘要

Granitoid rocks comprise over 90% of the exposed geology and extend for up 500 km along strike from west of Wager Bay through to the southern portion of the Melville Peninsula.; These granitoids are divided into 3 major series including 8 different lithologies. The divisions are: a plagioclase-rich series, a potassium-feldspar-rich series, and a peraluminous series. The plagioclase-rich series is comprised of two types of tonalite and a quartz dioritic unit. These units have &egr;Nd(t) values ranging from +0.79 to +3.51 and crystallized ca. 2.72--2.61 Ga. The potassium-feldspar-rich series is comprised of two types of granodiorite and one granitic unit. These rocks crystallized ca. 2.61--2.58 Ga and have &egr;Nd(t) values ranging from -2.00 to +0.16. Two granitic units comprise the peraluminous series and contain &egr;Nd(t) values ranging from -1.40 to +0.89.; The formation of tonalitic magmas was the result of dehydration melting of amphibolitic source rocks. As a result of tonalite emplacement, crustal thickening occurred and the temperature gradient increased in the mid- to low-crustal levels causing melting/migmatization of sediments. This led to the formation of granodioritic and granitic plutons that are both metaluminous and peraluminous in character.