Temporal evolution and nature of Ti–Fe–P mineralization in the anorthosite–mangerite–charnockite–granite (AMCG) suites of the south-central Grenville Province, Saguenay – Lac St. Jean area, Quebec, Canada

Abstract

In the south-central Grenville Province, Quebec, Canada, anorthosite–mangerite–charnockite–granite (AMCG) magmatism took place during four distinct episodes between 1327 and 1008 Ma. AMCG rocks crosscut several gneiss complexes composed of ~1506 Ma supracrustal rocks and massive to gneissic igneous rocks that were emplaced during two distinct episodes: ~1434 and 1393–1383 Ma. The four episodes of AMCG magmatism are (i) the 1327 ± 16 Ma labradorite-type De La Blache Mafic Plutonic Suite, (ii) the 1160–1135 Ma labradorite- and andesine-type Lac St. Jean Anorthositic Suite, (iii) a 1082–1045 Ma unnamed plutonic suite, and (iv) the 1020–1008 Ma andesine-type Valin Anorthositic Suite. The Valin Anorthositic Suite includes the 1016 ± 2 Ma andesine-type Mattawa Anorthosite, the 1010–1008 Ma andesine-type Labrieville Alkalic Anorthositic Massif, the 1020 ± 4 Ma St. Ambroise Pluton, the 1018+7–3 Ma Farmer Monzonite; the 1010 ± 2 Ma Gouin Charnockite, and the 1010 ± 3 Ma La Hache Monzonite. Study of the Ti–Te–P mineral occurrences in these four AMCG units in the south-central Grenville Province has shown that (i) apatite-bearing rocks are related only to andesine-type anorthosites, (ii) titaniferous magnetite is restricted to labradorite-type anorthosites, and (iii) hemo-ilmenite occurs only in andesine-type anorthosite and associated oxide–apatite-rich gabbronorites (OAGN) and nelsonites.