| Title | Significance of the chemistry and morphology of diagenetic siderite in clastic rocks of the Mesozoic Scotian Basin |
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| Author | Pe-Piper, G; Piper, D J W |
| Source | Sedimentology 2019 p. 1-28, https://doi.org/10.1111/sed.12661 |
| Image |  |
| Year | 2019 |
| Alt Series | Natural Resources Canada, Contribution Series 20190255 |
| Publisher | Wiley |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf (Adobe® Reader®); html |
| Province | Nova Scotia; Eastern offshore region |
| NTS | 10; 11B; 11C; 11F; 11G |
| Area | Atlantic Ocean |
| Lat/Long WENS | -61.0000 -57.0000 46.0000 43.0000 |
| Subjects | marine geology; sedimentology; geochemistry; mineralogy; siderite; diagenesis; cementation; crystallization; recrystallization; continental margins; bedrock geology; lithology; sedimentary rocks;
clastics; sandstones; shales; mudstones; carbonates; conglomerates; mineralogical analyses; textural analyses; electron microscope analyses; electron probe analyses; statistical analyses; cluster analyses; geochemical analyses; cadmium geochemistry;
magnesium geochemistry; manganese geochemistry; iron geochemistry; crystallography; morphology, crystal; formation water; formation fluids; veins; lithofacies; sedimentary environments; stable isotope studies; carbon isotopes; oxygen isotopes;
paragenesis; burial history; offshore wells; core samples; geological history; Scotian Basin; Phanerozoic; Mesozoic; Paleozoic; Carboniferous; Mississippian |
| Illustrations | location maps; photographs; photomicrographs; tables; ternary diagrams; plots; schematic representations; cartoons |
| Program | Offshore Geoscience |
| Released | 2019 08 24 |
| Abstract | Siderite (FeCO3) is a widespread minor diagenetic mineral in clastic sedimentary basins. Although eodiagenetic authigenesis of siderite is well-known, siderite formed during burial diagenesis shows
habits and chemical compositions that are poorly understood. This study tests the hypothesis that diagenetic siderite cements in sandstones in the Scotian Basin, offshore eastern Canada, show systematic variability in chemistry and habit that is a
response to recrystallization and changing composition of basinal fluids. Mineral textures were determined from backscattered electron images, and chemistry mostly from electron microprobe analyses. Five chemical types of siderite are identified
using k-means cluster analysis, based on the amount of substitution of Ca, Mg and Mn for Fe. Eodiagenetic microcrystalline coated grains, concretions and intraclasts in sandstones are principally Fe-rich siderite and locally have recrystallised to
blocky equant crystals. Mesodiagenetic Mg-rich siderite partly replaced these equant crystals and also framework mica and K-feldspar grains, showing textural evidence for coupled dissolution-reprecipitation. Slender Mg-rich siderite rhombs (lozenges,
bladed or wheat-seed siderite) have precipitated before and after the formation of quartz overgrowths in geochemical microenvironments. Magnesium substitution reflects Mg-rich formation waters resulting from smectite to illite conversion. Equivalent
Ca-rich siderite occurs where sandstones overlie a Jurassic carbonate bank. Late Mn-rich siderite has complex textures resembling those of Mississippi-Valley type ores, with spheroidal rims, a honeycomb-like mesh and concentric infill around
secondary pores. It also occurs in veins or replacing intraclasts, post-dating late ferroancalcite cements in sandstones that show strong dissolution by hot basinal brines. The Ca, Mg and Mn content of diagenetic siderite, coupled with textural
evidence for recrystallization, can thus be used to track changes in ambient formation fluids. Siderite habits and chemistry described from the Scotian Basin are found in many clastic basins, suggesting that the observed recrystallization textures
and variation in chemical type are of broad application. |
| Summary | (Plain Language Summary, not published)
This study summarises and interprets the distribution of the mineral siderite in the Scotian Basin where it is an important indicator of the evolution of
fluids (including hydrocarbons) in the basin. |
| GEOSCAN ID | 314866 |
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