Publication Type:Journal Article
Source:Geochimica et Cosmochimica Acta, Elsevier, New York, NY, International, Volume 223, p.493-519 (2018)
Keywords:Baffin Island, basin analysis, basins, Canada, carbonate rocks, Cathodoluminescence, cementation, chemical composition, deep-water environment, depositional environment, diagenesis, eastern canada, EDS spectra, electron microscopy data, Fluid inclusions, ICP mass spectra, inclusions, isotope ratios, Isotopes, mass spectra, mesoproterozoic, metal ores, Metallogeny, mineral deposits, genesis, Mineral exploration, mounds, Nunavut, O-18/O-16, oxygen, paleoenvironment, Precambrian, proterozoic, sedimentary basins, sedimentary petrology, Sedimentary rocks, SEM data, spectra, Stable isotopes, textures, upper Precambrian, X-ray spectra, zinc ores
Ancient carbonate rocks commonly contain numerous post-depositional phases (carbonate minerals; quartz) recording successive diagenetic events that can be deciphered and tied to known or inferred geological events using a multi-pronged in situ analytical protocol. The framework voids of large, deep-water microbial carbonate seep-mounds in Arctic Canada (Mesoproterozoic Ikpiarjuk Formation) contain multiple generations of synsedimentary and late cement. An in situ analytical study of the post-seafloor cements used optical and cathodoluminescence petrography, SEM-EDS analysis, fluid inclusion (FI) microthermometry and evaporate mound analysis, LA-ICP-MS analysis, and SIMS delta (super 18) O to decipher the mounds' long-term diagenetic history. The six void-filling late cements include, in paragenetic order: inclusion-rich euhedral dolomite (ED), finely crystalline clear dolomite (FCD), hematite-bearing dolomite (HD), coarsely crystalline clear dolomite (CCD), quartz (Q), replacive calcite (RC) and late calcite (LC). Based on the combined analytical results, the following fluid-flow history is defined: (1) ED precipitation by autocementation during shallow burial (fluid 1; Mesoproterozoic); (2) progressive mixing of Ca-rich hydrothermal fluid with the connate fluid, resulting in precipitation of FCD followed by HD (fluid 2; also Mesoproterozoic); (3) precipitation of hydrothermal dolomite (CCD) from high-Ca and K-rich fluids (fluid 3; possibly Mesoproterozoic, but timing unclear); (4) hydrothermal Q precipitation (fluid 4; timing unclear), and (5) RC and LC precipitation from a meteoric-derived water (fluid 5) in or since the Mesozoic. Fluids associated with FCD, HD, and CCD may have been mobilized during deposition of the upper Bylot Supergroup; this time interval was the most tectonically active episode in the region's Mesoproterozoic to Recent history. The entire history of intermittent fluid migration and cement precipitation recorded in seemingly unimportant void-filling mineral phases spans over 1 billion years, and was decipherable only because of the in situ protocol used. The multiple-method in situ analytical protocol employed in this study substantially augments the knowledge of an area's geological history, parts of which cannot be discerned by means other than meticulous study of diagenetic phases, and should become routine in similar studies.
GeoRef, Copyright 2018, American Geological Institute.<br/>2018-041903<br/>Borden Basin<br/>Ikpiarjuk Formation<br/>Nanisivik mining district