Submarine eruptions of lava caused volcanic deposits which were subsequently buried and deformed and folded through extreme pressure, and brought to surface again through erosion.
Ancient examples of these types of rocks, known as volcanogenic massive sulphide (VMS) deposits, are found in the Timmins and Rouyn-Noranda areas.
To better understand these ancient, mineral-rich deposits, a Laurentian University professor recently travelled half a world away to study deposits currently being formed by volcanism under the ocean.
These seafloor massive sulphide (SMS) deposits are actively forming now and some may be about 40,000 years old — positively modern, as far as the rock world goes.
“They provide a very good modern analog to a very ancient ore system,” said Harold Gibson, the director of Laurentian's Mineral Exploration Research Centre (MERC).
Studying how the modern deposits form, and why certain minerals end up in certain areas, can help exploration companies that explore in Northern Ontario and Quebec, he said.
The more we understand the processes responsible for the formation and location of sea floor massive sulphide deposits, the better we can refine the models that exploration companies use to explore for their ancient, on-land equivalents, said Gibson, a geoscientist whose area of expertise is volcanism.
It isn't currently feasible to mine the modern, underwater deposits themselves, although some companies are looking into it, he said.
The company which has brought the venture furthest along is called Nautilus Minerals, which is hoping to mine SMS deposits on the ocean off of Papua New Guinea, he said.
Gibson spent three weeks in December studying SMS deposits on the Southern Central Indian Ocean Ridge, off the coast of Madagascar. He was part of an international team of scientists led by Germany's geological survey, known as the BGR.
A high-tech, remote-controlled underwater vehicle was used to take high-resolution images of the ocean floor, as well as to retrieve samples, which were later examined by scientists.
A type of bucket or dredge was also dragged on the ocean floor behind the ship to collect even more samples.
Gibson said he's studying the geochemistry of these samples to determine the processes responsible for their formation.
Despite 18-hour days put in by the scientists, he said he had a great time on the research trip.
The weather was “marvellous,” with temperatures of 28 to 35 C — a contrast to the sub-zero weather in Sudbury last month — and clear days, Gibson said. “It was absolutely a wonderful learning experience.”