Pliocene coal-seam fires on southern Ellesmere Island, Canadian Arctic

摘要

Evidence for fossil coal-seam fires was found on southern Ellesmere Island, Queen Elizabeth Islands. Canadian High Arctic. Multicoloured thermally altered hilt unmelted rocks (clinker) and black, melted rocks (paralava) occur ill Lower Palaeogene clastic sediments that contain coal seams. XRD. XRF, microscopic and EMP studies detected two varieties of paralava: silicate paralava consisting of a large variety of high-temperature/low-pressure minerals (cordierite, mullite, tridymite. cristobalite, hematite, magnetite-spinel-hercynite-ulvospinel solid solutions in glass) typical of combustion metamorphism, and Uncommon, almost Pure iron-oxide paralava. The coal burned 3.3 +/- 0.5 Ma ago in the Middle Pliocene (Ar-40-Ar-39 incremental heating dating oil whole-rock silicate paralava) during a relatively warm climatic phase, when the Palaeocene to Lower Eocene strata with the coal seams were Uplifted to a Position Close to the surface. The coal fires were ignited by spontaneous combustion or by forest fires and enhanced by air circulation through pre-existing faults and fractures.