In-situ LA–ICP-MS trace elemental analyses of magnetite: The late Palaeoproterozoic Sokoman Iron Formation in the Labrador Trough,Canada |
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| Institution: | 1. Department of Earth Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong, China;2. State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China;1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;2. State Key Laboratory for Mineral Deposits Research, Nanjing University, Nanjing 210093, China;3. Department of Earth Sciences, The University of Hong Kong, Hong Kong, China;1. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China;2. Department of Earth Sciences, The University of Hong Kong, Hong Kong, Hong Kong, China;3. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China;4. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an 710069, China;1. Département de géologie et de génie géologique, Université Laval, Quebec, QC G1V0A6, Canada;2. Département de Génie Chimique, Université Laval, Quebec, QC G1V0A6, Canada;3. Department of Earth and Environmental Sciences, University of Waterloo, Waterloo, ON N2L3G1, Canada;4. Geological Survey of Canada, Ottawa, ON K1A0E8, Canada;1. Key Laboratory of Mineralogy and Metallogeny, Chinese Academy of Sciences, Guangzhou 510640, China;2. Graduate University of Chinese Academy of Sciences, Beijing 100049, China;3. Guangdong Provincial Key Laboratory of Mineral Physics and Materials, 511 Kehua Street, Guangzhou 510640, China;4. No. 1 Geological Party, Xinjiang Bureau of Geology and Mineral Exploration, Changji 831100, China |
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| Abstract: | The Sokoman Iron Formation in the Labrador Trough, Canada, a typical granular iron formation (GIF), is coeval with the ~ 1.88 Ga Nimish volcanic suites in the same region. It is composed of the Lower, Middle and Upper Iron Formations. In addition to primary and altered magnetite in iron formations of the Hayot Lake, Rainy Lake and Wishart Lake areas, magnetite in volcanic breccia associated with the iron formation is identified for the first time in the stratigraphy. Trace elemental compositions of the most primary, altered and volcanic brecciated magnetite of the Sokoman Iron Formation were obtained by LA–ICP-MS. Commonly detected trace elements of magnetite include Ti, Al, Mg, Mn, V, Cr, Co and Zn. These three types of magnetite have different trace elemental compositions. Primary magnetite in the iron formation has a relatively narrow range of compositions with the depletion of Ti, Pb, Mg and Al. Magnetite from volcanic breccia is rich in Ti, Al, V, Mn, Mg, Zn, Cu and Pb, indicative of crystallization from mantle-derived magmas. Altered magnetite in the iron formation shows a relatively wide range of trace elemental compositions. Mineralizing fluids associated with magmas that generated the ~ 1.88 Ga Nimish volcanic suites circulated through the sedimentary piles to further enrich the iron formations and to form magnetite with variable compositions. The comparisons of different types of primary and altered magnetite in the iron formation in the region show distinct provenance discrimination. Our findings also support the origin of iron formations in association with multiple stages of exhalative volcanic and hydrothermal processes. |
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