Examination of mesothermal to epithermal orogenic- to intrusion-related Sb-bearing gold systems in a southern New Brunswick segment of the Northern Appalachians
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University of New Brunswick
Several Sb-Au mineralization styles are diversely scattered within the boundary of Gondwana and Laurasia in southern New Brunswick. Some research has been completed regarding the timing and genesis of the structurally-controlled, mesothermal to epithermal orogenic and intrusion-related Sb-Au mineralization types in the regionally correlative Annidale (New River and Annidale belts) and Clarence Stream areas (St. Croix and Mascarene belts). LA-ICP-MS U-Pb and 40Ar-39Ar geochronology of hydrothermal rutile and white mica in the Annidale area suggested that orogenic gold type mineralization is related to Ordovician Penobscot orogeny. However, several further orogenies overprinted some mineralization in the area. The apatite and titanite U-Pb and white mica 40Ar39Ar data confirmed the Early Devonian age for intrusion-related gold type in the Clarence Stream area. Zircon U-Pb data on several mafic to felsic intrusive rocks showed the age range of Silurian to Late Devonian; however, the relation of the Early Devonian intrusions (Magaguadavic and Lower Tower Hill granites) to the gold mineralization has been reaffirmed. The sulphur isotope data suggests a mantlederived source for sulphide phases. The lead isotope results show highly radiogenic Pb, which might be due to the addition of Pb during or after ore formation, that overprinted the initial Pb isotopic system. As no later major magmatic activities occurred, Ordovician orogenic gold was preserved in the Annidale area. It is probable that similar orogenic gold mineralization was formed at the same time in the southwestern part of the New River Belt (Clarence Stream area). A combination of several factors, including preexisting orogenic gold deposits, advanced hydrothermal activities related to the emplacement of multi-phase intrusions during Devonian, and the presence of local brittle-ductile shear zones, were crucial, explaining the greater concentration of gold in intrusion-related deposits in the Clarence Stream area than the orogenic gold deposits in the Annidale area.