MASSIVE SULFIDE CLASTS WITHIN DEBRIS FLOWS IN THE MEDUCTIC GROUP, SOUTHWESTERN NEW BRUNSWICK: VOLCANOLOGIC AND CHEMOSTRATIGRAPHIC ANALYSIS

The Eel River area in the southwestern Miramichi Terrane of New Brunswick contains a complete calc-alkaline suite of volcanic rocks that are interlayered with intervals of sedimentary and polylithic fragmental rocks, and are overlain by a thick sedimentary sequence. This package, collectively referred to as the Meductic Group, was deposited in a submerged volcanic arc setting interpreted to be part of the Popelogan arc. Rifting of this arc led to the development of the Tetagouche-Exploits basin and generation of VMS deposits in bimodal volcanic rocks of the Bathurst Mining Camp in the northeastern Miramichi Terrane. Unlike the Bathurst Mining Camp, volcanic rocks in the southeastern Miramichi Highlands form a continuous calc-alkaline suite characterized by increasing Zr/TiO2 (0.006 to 0.29) with increasing SiO2 (46.0 to 82.6 wt%), in part resulting from progressive coupled assimilation and fractional crystallization of nested magma systems. Slumping of semi-consolidated volcanic and sedimentary rocks in topographically unstable areas resulted in numerous debris flows and slumps that are preserved throughout the Eel River area.

A large sulfide clast uncovered in a road cut along the Benton road has sparked interest in the VMS potential of the Eel River area. Subsequent drilling intersected smaller fragments, one clast of which grades 16.7% Zn, 5.6% Pb, 90 ppm Ag, and 220 ppb Au. The intersection of thin lenses of stratiform sulfides in another drill hole indicates favorable conditions for the preservation of massive sulfides. Their subsequent disruption by synvolcanic debris flows resulted in the transport and deposition of sulfide clasts from hydrothermal vents to more distal locations. Unlike the Buchans deposits of Newfoundland, these debris flows contain only rare clasts of sulfides. However, tracing the debris flows back to their source would be beneficial from an exploration perspective.