31 New Perspectives on Mineral Resources of the Northeast (Posters)

Monday, 18 March 2019
8:00 AM - 12:00 PM
Casco Bay Hall

STRUCTURALLY CONTROLLED GOLD MINERALIZATION IN CENTRAL NEWFOUNDLAND: IMPLICATIONS FOR GOLD POTENTIAL AND TIMING OF MINERALIZATION

Paper number: 31-1
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The structurally controlled gold belt of central Newfoundland is emerging as one of the next significant mining and exploration jurisdictions in Canada. The gold district occurs within a northeast-trending structural corridor defined by crustal-scale faults extending from southwestern to north-central Newfoundland. Silurian synorogenic polymict conglomerates (e.g., Rogerson Lake Conglomerate) characterizes the structural corridor. The presence of conglomerate reflects preservation of upper crustal clastic sequences (i.e., the synorogenic near-surface environment) commonly associated with orogenic gold vein systems through time.

Detailed structural study of a newly discovered gold-bearing quartz vein system along the structural corridor demonstrates that the main ~2 m-wide vein, which extends for ~230 m along strike, cuts deformed polymict conglomerate host and occurs within an oblique left-lateral reverse shear zone that involved a component of north-northeast directed thrusting. An early set of stacked, moderately dipping extensional quartz veins, consistent with left lateral reverse shear, emanate outwards into the country rock from the main vein. A later, more steeply dipping set of extensional quartz veins cross-cut the main vein and the earlier extensional vein set, and are consistent with at least transient phases of horizontal extension. Chalcopyrite and secondary malachite occur locally in the early extension vein set, but are more abundant overall within the later, steeper, extensional vein sets. A nearly conjugate set of steeply dipping extension fractures cross-cut the main vein and the two vein sets. These fractures are typically filled with an assemblage of vuggy quartz-chalcopyrite-malachite±tourmaline±pyrite±hematite±goethite. Field data indicate that the mineralized quartz vein system experienced a progressive structural history characterized by early oblique compressional left-lateral shear and subsequent transient phases of sub-horizontal extension and a final overprint of weak dextral strike-slip.

These results confirm that the quartz vein system preserves a similar structural evolution to a 4.2 Moz gold resource along strike to the southwest at Valentine Lake. Considering the structural setting, is gold mineralization Salinic, Acadian, or younger?

Geological Society of America Abstracts with Programs. Vol. 51, No. 1

doi: 10.1130/abs/2019NE-328685

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