ODDS’N’SODS — Roscoe knew Canadian Shield well

The late Stuart Murray Roscoe, an inveterate explorer of the Canadian Shield and a highly respected scientist for the Geological Survey of Canada (GSC) became part of Canada’s mining heritage at an early age.

He was born in 1924 at the Murray mine near Sudbury, Ont. In 1926, his family moved to Noranda, Que., where his father, a mining engineer, became manager of the Horne mine. Stu attended St. Andrews College in Aurora, Ont., and Queen’s University in Kingston, Ont., where he obtained BSc and MSc degrees, respectively, in geology.

He earned his PhD from Stanford University in California in 1951. His doctoral thesis was on vein-type deposits in the Rambler-Slocan area in south-central British Columbia. It was sponsored by well-known mining personalities George and Viola MacMillan.

He joined the GSC in 1951, took up private consulting during the period 1968-77, and then rejoined the GSC for the remainder of his career. In his work, he blended fundamental scientific inquiries with the pragmatic aspects of mineral exploration.

His early assignments with the GSC included regional mapping in the Labrador Trough. This work was followed by a metallogenic study of the Blind River basin on the north shore of Lake Huron, which led to the most significant achievements of his career. The exploration boom in 1952 had revealed this early Proterozoic basin as a vast storehouse of uranium.

Stu’s task was to study the ore deposits and their geological setting. From his detailed mapping and examination of cores from holes drilled in the search for uranium, he was able to correlate the beds seen in outcrops with those intersected in drilling, and interpret the detailed stratigraphy and structure of the basin. His conclusion that the uranium minerals and associated heavy minerals were detrital in origin and that their occurrence was delimited within relatively narrow boundaries in space and time was of outstanding importance to science and industry.

Stu also concluded that the survival of readily oxidizable uraninite and pyrite in these paleoplacers indicated that the atmosphere at that time lacked any significant amount of free oxygen. He pointed out that the overlying strata in the sequence contained hematite-rich sediments which must have formed in surface environments capable of oxidizing iron. He coined the term “oxy-atmoversion” for this transition from the reducing to oxidizing atmosphere in the Earth’s history. Later work suggests that this transition occurred 2,400 million years ago.

These important conclusions, although scientifically sound and of enormous economic benefit to industry, clashed with the established thinking of the day and, initially, were not welcomed. At that time, the GSC’s program on uranium was top secret under government regulations, and so his first paper on these important discoveries was circulated only privately to the mining industry, on a “need-to-know” basis. It provoked a few irate letters to the GSC’s director, demanding that Stu be dismissed immediately. Stu dedicated his career to unravelling the mysteries of the Canadian Shield, to shedding light on its mineral potential and to developing a comprehensive view of its metallogeny. In this endeavor, he quickly realized the advantages of flying his own small, fixed-wing aircraft, and so he took to the air for more than three decades.

He published more than 40 papers and wrote numerous reports. He did this without preconceived scientific notions and by “allowing the rocks to speak for themselves,” as he liked to put it. Thus he was always open to new ideas and was keen to test them through meticulous field observations and careful laboratory studies, be they for exploration or for research. Stu Roscoe died in January of this year at his Ottawa home.

— Sunil Gandhi is a research scientist with the mineral resources division of the GSC.