The BLAC (Black Lake Alteration Corridor) occurrence is located at an elevation of approximately 1700 metres on a southwest-facing slope, north of the Sturdee River and approximately 5.5 kilometres north-northeast of the river's junction with Jellicoe Creek (Toodoggone Camp).
Regionally, the area is situated within a Mesozoic volcanic arc assemblage that lies along the eastern margin of the Intermontane Belt, a northwest-trending belt of Paleozoic to Neogene sediments, volcanics and intrusions bounded to the east by the Omineca Belt and to the west and southwest by the Sustut and Bowser basins.
Permian Asitka Group crystalline limestones are the oldest rocks exposed in the region. They are commonly in thrust contact with Upper Triassic Takla Group andesite flows and pyroclastic rocks. Takla volcanics have been intruded by Early Jurassic granodiorite to quartz monzonite of the Black Lake Suite and are in turn unconformably overlain by or faulted against Lower Jurassic calc-alkaline volcanics of the Toodoggone Formation (Hazelton Group).
The dominant structures in the area are steeply dipping faults that define a prominent regional northwest structural fabric trending 140 to 170 degrees. In turn, high-angle, northeast-striking faults (approximately 060 degrees) appear to truncate and displace northwest-striking faults. Collectively these faults form a boundary for variably rotated and tilted blocks underlain by monoclinal strata.
The occurrence area is underlain by a discontinuous sequence of Permian to Middle Jurassic volcano-sedimentary rocks upwarped against and in fault contact with the Early Jurassic quartz monzonite to syenite Black Lake stock. The dominant lithologies are augite feldspar phyric andesitic flows of the Takla Group and feldspar porphyry of the Toodoggone Formation. Other lithologies cropping out in the vicinity include limestone and marble of the Asitka Group and porphyritic andesitic crystal and lithic tuffs and breccias. Structurally the units in the area are intensively disrupted by steep-dipping, northeast-striking faults.
Locally, at the BLAC zone, a zone of strong silica-pyrite alteration following the contact between intermediate volcanics and the Black Lake Intrusion hosts gold and silver values. A series of subparallel quartz veins crosscut all lithologies and structures.
In 2019, a rock sample assayed 1.36 grams per tonne gold and 31.2 grams per tonne silver (P&E Mining Consultants Inc. [2021-06-28]: Technical Report and Updated Mineral Resource Estimate of the Lawyers Gold-Silver Property, Omineca Mining Division, British Columbia, Canada).
Rock sampling highlights of Benchmark's 2021-2022 program included 1.26 grams per tonne gold and 137 grams per tonnne silver, where mineralization appears to be associated with major northwest and north-northwest structures, occurring in mapped areas of basalts and limestones along the of the Black Lake pluton. Structures are intensely silicified and have high sulphide concentrations, predominantly pyrite.
Another zone of mineralization, referred to as the Silicon Valley North zone, is reported to the east of the BLAC zone and comprises metre-scale massive quartz veins hosted in intermediate volcanics near their contact with the Black Lake Intrusion. Rafts of limestone, assumed to be part of the Asitka Group, are also reported in this area. In 2021, 32 rock samples collected in this zone showed weak gold and silver results, but significant lead grades (1.19 per cent Pb). Disseminated galena was observed in vuggy quartz veins and the groundmass.
Work History
In 2019 and 2020, Benchmark Metals Inc. completed programs of geochemical (rock and soil) and biogeochemical sampling, ground and airborne geophysical surveys, 242 diamond drill holes, totaling 69 080 metres, and 191 reverse circulation drill holes, totaling 28 395 metres, on the area as part of the Lawyers property. The majority of the drilling targeted the Cliff Creek, Dukes Ridge, Phoenix and AGB zones of the Lawyers (MINFILE 094E 066) deposit.
Prospecting and rock sampling in 2021 and 2022 by Benchmark Metals Inc. extended the BLAC showing along northwest and north-northwest structural trends, where basalts and limestones are mapped along the contact of the Black Lake pluton.
On September 30, 2022, JDS Energy & Mining Consultants Inc. produced an updated Preliminary Economic Assessment Lawyers Gold-Silver Project, Stikine Terrane, B.C. for Benchmark Metals Inc. In August 2023, Benchmark Metals Inc. merged with Thesis Gold Inc., joining the Lawyer Project operations with Thesis Gold's Ranch Project located in similar Toodoggone Formation rocks to the northwest.
