Siderite concretions

Croal LR, Johnson CM, Beard BL, Newman DK (2004) Iron isotope fractionation by anoxygenic Fe(II)-phototrophic bacteria. Geochim Cosmochim Acta 68 1227-1242 Curtis CD, Coleman ML, Love LG (1986) Pore water evolution during sediment burial from isotopic and mineral chemistry of calcite, dolomite and siderite concretions. Geochim Cosmochim Acta 50 2321-2334... 

Parmar N, Warren LA, Roden EE, Eerris EG (2000) Solid phase capture of strontium by the iron reducing bacteria Shewanella alga strain BrY. Chem Geol 169 281-288 Pearson MJ (1974) Sideritic concretions from the Westphalian of Yorkshire a chemical investigation of the carbonate phase. Min Mag 39 696-699... 

Fig. 2. Carbonate minerals, which play important roles in the hydrogeochemistry of coal mines and coal mine wastes (a) A typical siderite concretion (from the mudstone overlying the Halifax Hard Seam at Bullhouse, West Yorkshire, UK) long axis of concretion is 11 cm (b) Patchy films of creamy-white ankerite on a cleat surface of coal (from the Main Seam, Ravensworth Grange Opencast Coal Mine, Durham, UK) maximum width of hand specimen is 10.5 cm.

Unlike calcite and dolomite, siderite rarely forms as an extensive pore-filling cement, but rather as discrete fine crystals, spherules and nodules scattered in the host sediments. Nevertheless, Baker et al. (1996) found that early diagenetic siderite concretions (0.5-2 mm) form up to 30% of Triassic sandstones and mudstones from eastern Australia. Laterally continuous siderite-cemented offshore shelf sandstone sheets (15 cm thick) occur in Upper Cretaceous sequences from Canada (McKay et ai, 1995). 

Curtis, C.D. Coleman, M.L. (1986) Controls on the precipitation of early diagenetic calcite, dolomite and siderite concretions in complex depositional sequences. In Roles of Organic Matter in Sediment Diagenesis (Ed. Gautier, D.L.), Spec. Publ. Soc. Econ. Paleont. Miner., Tulsa, 38, 23-33. 

Duan, W.M., Pye, K., Coleman, M., White, D.C., Ringelberg, D. Hedrick, D. (1995) Formation of unique sideritic concretions in modem salt marsh sediment, Norfolk, UK. EVG Abstract Volume. European... 

The two siderite samples investigated have very similar 6 0-5 C values, Sr/ Sr ratios and Sr contents. The 5 0-6 C values are close to, but not within, the range of values compiled by Mozley Bums (1992) for marine siderite concretions. The... 

Gautier, D.L. (1982) Siderite concretions indicators of early diagenesis in the Gammon Shale (Cretaceous). J. sediment. Petrol., 52, 859-871. 

Orr SR, Faure G, Botoman G (1982) Isotopic study of a siderite concretions, Tuscarawas County, Ohio. Ohio J Sci 82 52-54 Picdotto E, WUgain S (1963) Fission products in Antarctic snow, a reference level for measuring accumulation. J Geophys Res 68(21) 5965... 

Pye K, Dickson JAD, Schiavon N, Coleman ML, Cox M (1990) Formation of siderite-Mg-calcite-iron sulphide concretions in intertidal marsh and sandflat sediments, north Norfolk, England. Sedimentology 37 325-343... 

In some coal beds, relatively fiat, lenticular masses ranging up to several feel in diameter, composed of pyrile, calcile or siderite. were formed during plant growth. Such materials (concretions) may represent the eventual immediate roof of the coal bed. These concretions impede mining operations and cause a hazard because of their tendency to drop out of die roof unexpectedly during operation of the mine. 

Underclay and overburden sediments are typically clays with about 80% clay and 20% silt and muds with about 50% clay and 50% silt. The most distinct chemical variation in the overburden is the compact siderite- and dolomite-cemented concretion zone, 4.5 m above the base of the Kinneman Creek lignite. 

D 3.04 Concretion zone Siderite, dolomite, quartz Mica-illite, kaolinite, plagioclase... 

Growth of Concretions In sedimentary rocks we commonly find concretions, that is, material formed by deposition of a precipitate, such as calcite or siderite, around a nucleus of some particular mineral grain or fossil. The origin of most concretions is not known but their often-spherical shape with concentric internal structure suggests diffusion as an important factor affecting growth. The rate of growth, if diffusion controlled, is readily amenable to mathematical... 

The Lea Park Formation is the lowermost unit of hydrogeological interest in the area but it is covered by at least 300 m of Belly River sediments. The strata are notable for their low permeability and consist of marine deposited grey sUty shale, thin sandstones, and common sideritic ironstone concretions (Green, 1972). 

Siderite occurs as scattered, small (10-15 pm), yellowish euhedral crystals attached to detrital grains or enclosed by later carbonate cements (Fig. 4A). The siderite has a relatively Mg-rich composition, up to 40 mol% relative to Fe (Boles, 1987), probably reflecting the Mg-rich composition of marine water (Mozley, 1989). Extensive cement zones or concretions of siderite have not been found, indicating that sideritization is not as common in this deep marine environment as in shallow marine and non-marine environments (e.g. see Mozley, 1989). 

Mine roof shale commonly contains concretions made up of calcite (CaC03), dolomite (CaCOj MgCOj), siderite (FeCOj), and pyrite (FeSj) alone or in combination. In some cases, plant or animal fossils serve as nuclei around which the minerals accumulate. 

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