Visiting Speaker - Dr. Christopher Beckett-Brown 

Geological Sciences and Geological Engineering Distinguished Speaker Program presents Dr. Christopher Beckett-Brown 

On Thursday, January 19, Dr. Christopher Beckett-Brown, Geological Survey of Canada, will be giving a talk for the Queen's Department of Geological Sciences and Geological Engineering.

Talk Title: "Using Indicator Mineral Texture and Chemistry as a Vector to Porphyry Cu Deposits: An Example from the Casino Deposit, Yukon Territory"

Date: Thursday, January 19, 2023

Time: 11:30 am

Location: Miller Hall, Room 201

Coffee and treats will be served.

Abstract: 

Colour, texture, and chemistry were used to determine the source of tourmaline grains in local surficial stream sediments surrounding the Casino calc-alkaline porphyry Cu-Au-Mo deposit, which occurs in the unglaciated terrain of west-central Yukon Territory, Canada. Tourmaline from mineralized porphyry bedrock samples has been well characterized and shown to be unique from that forming in other geological environments. Porphyry tourmaline from bedrock is generally dark brown to black and is texturally distinct, forming as clusters of radiating prismatic aggregates and almost never as individual isolated grains. In terms of major-elements, porphyry tourmaline plot along the oxy-dravite – povondraite solid-solution. Tourmaline in porphyry systems has been previously shown to be chemically distinct in terms of its trace-element character. Detrital tourmaline collected from stream sediments surrounding the Casino deposit occurs as two morphological types; 1) sub- to euhedral individual grains, 2) sub- to euhedral grain aggregates of radiating prismatic grains. Its trace-element content shows grains of mineralized porphyry origin as well as grains from metamorphic and pegmatitic (background) environments. Consequently, those forming as radiating prismatic grains are the same grains that exhibit porphyry derived trace-element chemistries as well. In Canadian Creek, which directly drains from the Casino deposit, samples closest to the deposits contain >70% porphyry derived tourmaline, while other streams in the region from unprospective drainage basins contain no porphyry tourmaline. At the most distal sample site in Canadian Creek, ~20 km downstream from the deposit, nearly 30% of the recovered tourmaline in the stream sediments is classified as porphyry related. Overall, a combination of physical and chemical characteristics including 1) macro-color, 2) morphology, 3) inclusion populations, 4) X-site composition, and 5) trace-element compositions are useful in discriminating between porphyry- versus non-porphyry–derived (or related) tourmaline in surficial sediments. This highly accurate method provides an additional tool to regional stream sediment and indicator mineral surveys when exploring for porphyry Cu-Au-Mo systems in both unglaciated and glaciated terrains.

Bio: 

Christopher Beckett-Brown is an applied mineralogist and postdoctoral research person in the applied geochemistry unit of the Geological Survey of Canada. Chris completed his PhD in 2022 in Mineral Deposits and Precambrian Geology at Laurentian University. His PhD research focused on assessing the indicator mineral potential of tourmaline supergroup minerals in mineralized porphyry systems. His previous research focused on sulfide mineral intergrowths as well as the crystal chemistry of Ni-rich spinel group minerals. Chris has been the recipient of significant awards including: the NSERC-Alexander Graham Bell Canada Graduate Doctoral Scholarship, the Mineralogical Association of Canada Foundation PhD Scholarship, the Society of Economic Geology Research Grant as well as SEG Graduate Student Fellowship-sponsored by Anglo American. Besides research, Chris has spent two summers with the Ontario Geological Survey bedrock mapping in the Swayze Greenstone belt and the West arm of Lake Nipissing. Outside of geology, he spends most of his time in the outdoors on white water canoe trips, backpacking adventures, and winter camping.