The volcanic stratigraphy and metallogeny of Notre Dame Bay, Newfoundland

The geology of Notre Dame Bay can be considered to be essentially an Ordovician-Silurian volcanic island arc complex built upon Cambro- Ordovician oceanic crust and intruded by a variety of igneous rocks ranging in age from Ordovician to Jurassic. The stratigraphic evolution of this island arc complex may be divided into two distinct phases: (1) an Early to Middle Ordovician (pre-Caradocian) phase of extensive submarine volcanism recognizable throughout all of Notre Dame Bay, and (2) a Late Ordovician-Early Silurian (post-Caradocian) phase characterized by contrasting volcanic styles in three different belts. The two phases are separated in the southeastern portion of Notre Dame Bay by an extensive Caradocian argillite and overlying flysch sediments. In the northwestern portion, the post-Caradocian volcanic sequences rest uncomformably either on the Cambro-Ordovician oceanic crust or on the pre-Caradocian volcanic sequences. Intrusive igneous activity accompanied the separate phases of oceanic crust and island arc evolution but was most intense in the Late Devonian during the latest stages of the Acadian Orogeny. The greatest percentage of insular Newfoundland's mineral wealth has come from the base metal sulphide deposits of Central Newfoundland, particularly from the copper deposits of Notre Dame Bay. Most of these base metal sulphide deposits are volcanogenic and stratabound and as such are integral elements of the stratigraphic sequence in which they occur. The Cambro-Ordovician ophiolitic rocks contain Cu-Zn massive sulphide deposits in mafic tholeiitic volcanic rocks. Mineral deposits of the pre-Caradocian island arc volcanic sequences are typically Cu-Zn (+ Au) massive sulphide deposits associated with felsic volcanism. Volcanogenic massive sulphide deposits in the Post-Caradocian volcanic rocks occur only in one belt, the .Roberts Arm Belt of dominantly subaqueous volcanics. These are generally more polymetallic (Pb-Zn-Cu-Ag-Au-Ba).and are associated with areas of felsic volcanics in the upper part of the volcanic sequence. Several small vein-type deposits are associated with high level phases of igneous intrusions