Crustal scale strike-slip faulting facilitated the rise of magmas, resulting in high heat flow driving an active hydrothermal system.
Regional extension of the Magdalen Basin caused asthenospheric upwelling and melting of the previously metasomatized sub-continental lithospheric mantle. The abundant magmatic Na, halogens and CO2 in veins and some magmatic bodies, characteristic of IOCG systems, were derived from the deeply subducted Rheic Ocean slab with little terrigenous sediment. 327 (-305?) Ma siderite-magnetite and sulfide mineralization, resembles Precambrian iron-oxide-copper-gold (IOCG) systems in the literature. 355 Ma riebeckite and albite veins to ca. Vein emplacement occurred preferentially during fault movement recognised from basin-margin inversion, as a result of fractures opening in the damage zone of master faults. Vein mineralization was closely linked to magmatic events. Chronology was determined from literature reports and new U-Pb LA-ICPMS dating of monazite and allanite in veins. The general paragenesis is: albite ± quartz ± chlorite ± monazite → biotite → calcite, allanite, pyrite → Fe-carbonates, Fe-oxides, minor sulfides, calcite and synchysite. The 50 Ma history of hydrothermal mineralization following pluton emplacement is difficult to resolve from field relationships of veins, but SEM study of thin sections provides clear detail on the sequence of mineralization. In late Carboniferous to Permian, Alleghanian collision of Africa with Laurentia formed the E-W trending Minas Fault Zone, reactivating parts of the Cobequid Shear Zone. The Cobequid Shear Zone formed part of a NE-SW-trending, orogen-parallel shear system in the late Devonian-early Carboniferous, where syn-tectonic granite-gabbro plutons and volcanic rocks 4 km thick were progressively deformed.
Intra-continental shear zones developed during continental collision may experience prolonged magmatism and mineralization. Sangster, Chris Zhang, Yuanyuan Boucher, Brandon
Petrology, chronology and sequence of vein systems: Systematic magmatic and hydrothermal history of a major intracontinental shear zone, Canadian Appalachians
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