Iron deposits in the Appalachian and Grenville regions were among the first mineral occurrences worked in Canada. Nearly every known type of iron occurrence is included in the 200 deposits described in this volume. The Clinton type ironformations, composed of
hematite, siderite, and chamosite, at Wabana, Newfoundland, are the principal source of iron ore in the Appalachian region, and have been mined for over 70 years. Other Clinton type iron-formations in Nova Scotia and Algoma type iron-formations and iron-manganese beds in New Brunswick are potential
sources of iron ore. Magnetite deposits of replacement origin and syngenetic ilmenite and titaniferous magnetite deposits are predominant in the Grenville region. The occurrence of a few small magnetite-hematite-quartz iron-formations in metasediments in the south part of the Grenville Province has
been confirmed. A study of the regional distribution of all types of magnetite and ilmenite deposits in the Grenville Province, associated host rocks, mineralogy, and iron-titanium ratios in deposits shows that ilmenite deposits occur as injected and disseminated masses in anorthosite rocks,
titaniferous-magnetite deposits occur as syngenetic bodies in gabbro and gabbroic anorthosites, and magnetite deposits containing less than one per cent Ti02 occur as replacement masses in metasediments, particularly in limestone and amphibole-rich host rocks. A close genetic relationship between
anorthosite intrusions and related gabbro, diorite, and granitic intrusions on the one hand, and the ilmenite, titaniferous magnetite, and replacement magnetite deposits on the other is indicated by their spatial relationship and by the variations in iron and titanium ratios in the iron deposits
with different host rocks. Iron-titanium ratios in ilmenite and magnetite deposits are lowest in the east and northeast part of the Grenville Province where very large anorthosite masses are exposed, and are highest in the southwest where only small gabbro and anorthositic gabbro intrusions are
known and where replacement magnetite deposits are numerous.
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