INNOVATION Sept-Oct 2019

F E A T U R E

Baffinland Iron Mines Corporation are extracting iron ore at Mary River in the Qikiqtani Region. On the Hall Peninsula, about 120 kilometers from Iqualuit, Nunavut’s capital, De Beers Canada are developing the Chidliak diamond mining project. And elsewhere around the island, there are known occurrences of the carving rock used by the Inuit, and the marble in the south is recognized for its outstanding gem potential. Canada’s only known sapphire deposit, where the Inuit brothers found those first samples, is located in the well-explored Kimmirut area, a community in the Qikiqtaaluk Region on the shore of Hudson Strait on Baffin Island’s Meta Incognita Peninsula. SAMPLING SAPPHIRES Groat first visited the sapphire location near Kimmirut in 2004, and returned in 2006 to sample the gems and surrounding rocks. Over the next decade, several of Groat’s students studied various aspects of the materials he had collected, but none of them had tried to tie all the threads of the gem formation story together— until PhD student Philippe Belley arrived. Before starting his PhD, Belley was an enthusiastic gem and mineral collector, and during his undergraduate studies he had completed a project on spinel, a relatively common oxide mineral containing aluminium and magnesium. For his PhD project, he set out to understand the metamorphic and geochemical controls on gemstone genesis in the metacarbonates, or marble, in the Precambrian Lake Harbour Group (LHG), a sequence of volcanic and sedimentary rocks on Baffin Island. Gem occurrences are rare and are seldom as well-exposed as in the rocks of southern Baffin Island. Previous studies had documented

Seal on an iceberg in the Hudson Strait. P hoto : l ee g roAt , Ubc

gem occurrences in the LHG, including high-quality gem sapphire, low-grade lapis lazuli (a rock composed of the blue mineral haüyne), violet spinel, and the highly prized vivid cobalt-blue spinel, first discovered by True North Gems Inc. while prospecting on their Nunavut exploration properties. Belley studied Groat’s 2006 samples, and then travelled to Baffin Island with Groat in 2016 to collect rocks associated with spinel occurrences. “The idea,” said Belley, “was to understand the differences and similarities in the genesis of different types of gemstones and how they compare to barren rock nearby.” IN THE LAB To revisit the cake-baking analogy, examining these rocks in the laboratory was like taking a slice of a baked cake apart, studying the texture, and then working backwards to identify the cake’s ingredients and how it had been baked. Each rock sample that Groat and Belley collected was about the size of two fists. A portion of each sample was sent to a commercial laboratory for whole rock geochemical analysis to find out what elements were in the rock. Another portion was cut and polished into a 30-micron slice—thinner than a human hair—and mounted on a glass slide for examination under a petrographic microscope and then under a scanning electron microscope; this last step confirmed the identity and composition of the minerals viewed under the petrographic microscope. The overall goal was to identify the primary and secondary minerals in the samples, and their relationships with each other, and uncover any evidence of reactions that took place between them. At the next stage, the samples were examined under an electron microprobe to detect different elements in the minerals at a scale of parts per hundred, and then laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was used to detect trace element compositions in parts per million. c ontinUes on PAge 33...

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