The Targeted Geoscience Initiative 4 contributions to the understanding of volcanogenic massive sulphide deposit genesis and exploration methods development: introduction and preface

Abstract

Research on topical aspects of the genesis of, and exploration for, volcanogenic massive sulphide (VMS) deposits was formulated and carried out under the auspices of the Volcanogenic Massive Sulphide Ore System of the Targeted Geoscience Initiative 4 Program. Research activities were focussed on addressing two main themes: 1) development of innovative, new, and unconventional detection and vectoring methodologies for VMS exploration; these studies were conducted at the Izok Lake deposit, Nunavut, and regionally throughout the Bathurst Mining Camp, northern New Brunswick, as well as at numerous VMS deposits and prospects regionally throughout the Slave Province, Nunavut and Northwest Territories; and 2) understand the controls on precious metal (gold, silver) endowment or enrichment in VMS deposits. These studies were conducted at several deposits: Lalor Mine, Manitoba; Lemarchant deposit, Newfoundland; Ming Mine, Newfoundland; and the Lemoine deposit, Quebec. Detection and development of vectoring methods focussed on the application of optical reflectance spectrometry (airborne, ground, laboratory), oxygen isotope geochemistry, laser ablation inductively coupled plasma mass spectrometric analysis of volatile elements, multiple sulphur isotope geochemistry, till geochemistry and indicator minerals, and integration of rock properties and geophysics. Each of these research activities produced results that influence exploration strategies for VMS deposits in Canada and elsewhere. Studies focussed on determining the controls on precious metal endowment or enrichment in VMS deposits employed geology, volcanology/volcanic architectural analysis, lithogeochemistry, chemostratigraphy, geodynamic setting analysis, geochronology, hydrothermal alteration systematics, petrography, mineralogy and mineral chemistry (mineralization, alteration, host rock), oxygen isotope geochemistry, sulphur isotope geochemistry, lead isotope geochemistry, and metallogenic considerations. Collectively these studies demonstrate that in all cases, gold enrichment was primary (not late/secondary; i.e., seafloor and aerial weathering, overprinted unrelated mineralizing systems) and was the result of one or more of the following processes: 1) magmatic input, as evidenced by the presence of complex mineral assemblages that include sulphosalts and native elements, anomalous trace element signatures (e.g. epithermal suite: Au-As-Sb-Ag- Hg; felsic magma-associated: Bi-W-Te-In-Sn); and 2) boiling in a shallow-water setting. Only minimal remobilization of gold occurred in deposits in response to greenschist- and amphibolite-facies metamorphism.