Types Of Siderite Research Articles

Geochemical characteristics of different iron ore types from the Southern Tomašica deposit, Ljubija, NW Bosnia

Pulverized limonite ore from a Pleistocene–Quaternary lake deposit and compact limonite ore from the Olistostrome member of the Javorik flysch formation, in the Southern Tomasica iron ore deposit, were investigated and compared with different types of siderite and ankerite, limestone and carbonate shale from the same location in order to determine their possible protolith. Two limonite types display a notably distinct REE pattern, REE fractionations, Eu anomalies and other trace element and main oxide content. The REE pattern of compact limonite is characterized by relatively low light ((La/Sm) N = 2.87), heavy ((Gd/Yb) N = 0.98) and total ((La/Yb) = 3.19) REE fractionations, a strong positive Eu anomaly (Eu/Eu* = 2.11) and weakly expressed negative Ce anomaly (Ce/Ce* = 0.82). The compact limonite and siderite REE patterns almost overlap suggesting a common REE source. The same is valid for their Zr/TiO2 N ratios (0.040 in the compact limonite, 0.033–0.053 in the siderites). Pulverized limonite shows remarkably different REE patterns and the highest REE concentrations, (up to 6 to 13 times higher relatively to the other samples). Its REE fractionation pattern ((La/Sm) N = 3.68, (Gd/Yb) N = 1.58, (La/Yb) N = 9.41, Eu/Eu* = 1.10 and Ce/Ce*= 0.81) is very similar to those in the carbonate shale, identifying it as the possible protolith of pulverized limonite. The same is valid for the Zr/TiO ratios (0.025 in pulverized limonite and 0.017 in carbonate shale). The REE pattern of fine grained ankerite ((La/Yb) 2 N = 2.15, Eu/Eu* = 1.95, Ce/Ce* = 0.78) and its Zr/TiO ratio (0.030) are similar to those in siderite, and could, assuming extensive contamination of pulverized limonite, also represent its protolith. However, the REE patterns of coarse grained ankerite exhibit remarkable depletion of LREE over HREE and a strong reverse LREE pattern ((La/Yb) N =0.05–0.20, (La/Sm) N = 0.04–0.10, (Gd/Yb) N 2 = 1.77–1.91). They have (similar to the other studied samples), a positive Eu anomaly (Eu/Eu* = 2.16–2.75) and negative Ce anomaly (Ce/Ce* = 0.32–0.83). Their Zr/TiO ratio (0.004–0.010) excludes coarse grained ankerite as the possible protolith of pulverized limonite.

Early diagenetic siderite in the Panorama Point Beds (Radok Conglomerate, Early to Middle Permian), Prince Charles Mountains, East Antarctica

The Panorama Point Beds represent a subfacies of the Early to Middle Permian Radok Conglomerate, which is the oldest known sedimentary unit in the Prince Charles Mountains, MacRobertson Land, East Antarctica. This unit records clastic sedimentation in fresh−water depositional system during the early stages of development of the Lambert Graben, a major structural valley surrounded by crystalline highlands in the southern part of Gondwana. It contains common siderite precipitated through early diagenetic processes in the swamp, stagnant water, and stream−flow environments. There are two types of siderite in the Panorama Point Beds: (1) disseminated cement that occurs throughout the sedimentary suc− cession; and (2) concretions that occur at recurrent horizons in fine−grained sediments. The cement is composed of Fe−depleted siderite (less than 90 mol % FeCO3) with an elevated con− tent of magnesium, and trace and rare earth elements. It has negative 13 CVPDB values (−4.5 to −1.5‰). The concretions are dominated by Fe−rich siderite (more than 90 mol % FeCO3), with positive 13 CVPDB values (+1 to +8‰). There are no noticeable differences in the oxygen ( 18 OVPDB between −20 and −15‰) and strontium ( 87 Sr/ 86 Sr between 0.7271 and 0.7281) iso− topic compositions between the siderite types. The cement and concretions developed in the nearsurface to subsurface environment dominated by suboxic and anoxic methanic degrada− tion of organic matter, respectively. The common presence of siderite in the Panorama Point Beds suggests that fresh−water environments of the Lambert Graben were covered by vegeta− tion, starting from the early history of its development in the Early Permian.

Evolution of chemical composition of rock-forming carbonates in Sallanlatvi carbonatites, Kola Peninsula, Russia

The problem of whether calcio, magnesioand ferrocarbonatites are related to each other by fractionation, produced by metasomatic alteration, or derived separately remains central to the understanding of carbonatite petrogenesis. The Sallanlatvi Complex is one of the least well studied alkalinecarbonatite intrusions in the Kola Alkaline Province, but it consists of a simple concentric structure with, in order of intrusion, melteigite, ijolite and then a central carbonatite stockwork containing all of the main types of carbonatite. Calcite, dolomite, magnesite-dolomite and siderite types have all been distinguished (Subbotina and Subbotin, 1990). The authors have studied the composition of the rockforming carbonates in order to determine their relationships. Calcite, major in calcite carbonatite, is also an accessory in the other types of carbonatites. It contains minor Mn, Sr, Fe, Mg and Ba, of which Sr and Mn are the most abundant. The Sr contents range from 0.0-I .O wt% SrO, and MnO contents range from 0.0-1.4 wt%. In fresh carbonatite, zoned crystals of calcite are common and have centres with high SrO (1 .O wt%) and low MnO (<0.3 wt%). From the centre to the rim, SrO content decreases (to 0.2 wt%), whilst MnO increases slightly (up to 0.4 wt%). In altered carbonatites, secondary calcite is developed along cleavages in primary calcite and is characterised by high MnO (up to 1 .I wt%) and low SrO (up to 0.2 wt%). Calcite, which recrystallised accompanying the formation of chlorite and carbonate-apatite, also has the same composition. Calcite from cavities, where it is associated with barite, Ba zeolites, strontianite and ancylite, is very poor in SrO (0.1-0.2 wt%) and rich in MnO (up to 0.9 wt%). In dolomite carbonatites, calcite is observed as inclusions in pyrite and has high MgO (2.1-2.3 wt%), whereas in siderite carbonatites the mineral forms thin veins cutting siderite and has high Fe0 (0.7-I .8 wt%).

Geology of the B baseline zone, Walton Cu-Pb-Zn-Ag-Ba deposit, Nova Scotia, Canada

The Walton Ba-Cu-Pb-Zn-Ag deposit, Nova Scotia (production 4.5 million metric tons (Mt) >90% BaSO 4 and 412,850 t0.52% Cu, 4.28% Pb, 1.29% Zn, and 350 g/t Ag), is hosted by Visean age carbonate rocks of the Macumber Formation and its associated breccia. The Macumber Formation in the Walton area is divided into two units, the lower Macumber, a laminated carbonate unit 9 to 12 m thick and the upper Macumber, a synsedimentary carbonate slump breccia that forms two mounds up to 21 m thick.Outside the immediate mine area the carbonate is either limestone or dolostone; the Macumber Formation surrounding the deposit has been altered to manganiferous siderite. Although three textural types of siderite are recognized, little variation in bulk chemical composition is evident among them.Minerals were deposited in the sequence: barite, pyrite-marcasite, sphalerite, galena, tennantite, chalcopyrite, and (para)rammelsbergite. Each mineral replaces earlier minerals to varying degrees.Based on barite and metal content two main ore types are defined. Type I, with a bulk composition of 0.3 percent Cu, 2.5 percent Pb, 0.2 percent Zn, and 31.2 percent BaSO 4 , comprises barite and variable sulfide contents. Type II, comprised of sulfides only, has a composition of 0.5 percent Cu, 0.5 percent Pb, 0.1 percent Zn, 51 g/t Ag, and no barite. Type I ore forms a roughly conformable sheet which straddles the upper Macumber-lower Macumber contact and contains lenses of Pb- and Cu-rich ore. Type II ore is most commonly associated with the upper Macumber mounds where it forms large pods which cut the type I ore zone. Type II ore also occurs within the underlying Horton Group sandstones but only where the upper Macumber mounds have developed. There is also a stratigraphic zonation in metal content inasmuch as all metals are higher, on average, in the lower Macumber relative to the upper Macumber.The host stratigraphy is steeply dipping and faulted and both features are considered to be postore events. Karsting, which also postdates mineralization and probably folding, has removed portions of the stratigraphic upper parts of the deposit. The cavities produced by this process are now partially filled with sand and limestone breccia.

SIDERITE AS A CONSTRAINT ON DEPOSITIONAL AND EARLY DIAGENETIC HISTORY: EXAMPLES FROM BARROW SUB-BASIN, NORTH WEST SHELF, WESTERN AUSTRALIA

Siderite cement is one of the most volumetrically important diagenetic minerals in the Late Triassic to Early Cretaceous sandstones of the Barrow Sub-basin. It constitutes up to 60 per cent of the rock volume, and where abundant, occludes the primary intergranular porosity. Petrogriiphic, chemical and isotopic studies indicate the early precipitation of much of this siderite prior to significant compaction. Siderite samples and concretions were taken from a variety of depositional environments ranging from fluvial to deep marine from Late Triassic to Early Cretaceous sequences.Of the early phases, three distinct siderite types were recognised and vary according to depositional environment. The first type, mostly collected from fluvial deposits, is Fe-rich with a mean composition of (Fe96.3 Mg1.8 Ca0.9 Mn1.0) C03. The second type of siderite cement is relatively Mg-rich, Ca-poor and has a higher Mn content, with a mean composition of (Fe87.1 Mg9.6 Ca1.2 Mn2.1) C03. The third type of siderite cement is typically Mg−, Ca-rich, with a low Mn content and an average composition of (Fe78.7 Mg12.4 Ca8.4 Mn0.5) C03. The second and third siderite cements occur in marine facies. The δ13C and δ180 values for siderite cements range from −2.8 to −14.3 %. PDB and 17.4 to 28.2 %. SMOW, respectively.Petrographic and chemical isotopic studies and other sedimentological data from siderite can be used to distinguish between different depositional environments. Chemical and isotopic compositions of the early authigenic siderites indicate precipitation from fluids with significant meteoric input. Siderite cements formed during sulphate reduction and early methanogenesis from mixed marine and meteoric pore-waters at temperatures below 30°C. While an influx of meteoric water to the fluvial and deltaic sediments of the Triassic Mungaroo Formation is easily envisaged, the siderites show that some mixing of sea water is also required. The concept of introduction of meteoric water to the marine sediments of the Birdrong Formation requires an appreciation of the sea level fluctuations at the time. In these situations, the recognition of meteoric or marine input to an early siderite cement can assist in the determination of sea level fluctuations.

The nature and origin of sideritic ironstone bands in the Tertiary Lowmead and Duaringa Basins, Queensland

Sideritic ironstones in Tertiary lacustrine oil shale from the Lowmead and Duaringa Basins in Queensland, contain two distinctive types of siderite in the ironstone bands: sphaerosiderite in the mudstone and coal, and finely crystalline siderite in the lamosite. The petrological evidence indicates that the siderite in the ironstone bands formed eogenetically by growing displacively within the soft sediment. Chemically the siderite is very pure though the sphaerosiderite sometimes shows compositional zoning. Stable oxygen and carbon isotope analyses of the siderite show a wide range of values from ‐12.8‰ to ‐2.4 %0 δ18O (PDB) and ‐5.5‰ to +12.9‰ δ13C (PDB) for the Lowmead Basin; and ‐9.6‰ to ‐1.2‰ δ18O (PDB) and ‐18.6‰ to +16.4‰ δ13C (PDB) for the Duaringa Basin. The oxygen isotope data indicate that the siderite formed in freshwater environments but not in isotopic equilibrium with the formation waters. Kinetic factors offer the most plausible explanation for the anomalously light δ18O values of many of t...

Mineralogical-genetic types of siderite from Kremikovci deposit

Three polygenic and polychronous siderite mineralizations were established in Kremikovci deposit: syn-diagenetic, hydrothermal and supergenetic, represented by 7 mineralogicalgenetic types of siderite. The syn-diagenetic siderites (I-III types) are micro- to fine-grained, with massive and rare finely-banded and organogenic structures. They are distinguished for relative uniformity and wide variations in grains' composition. They pertain to the magnesian-manganoan (I-II types) and manganoan-magnesian (III type) varieties. During the process of diagenesis the MgC03 content increases. Siderite II is the most widespread type in the deposit. The hydrothermal (veined and metasomatic) siderites form their own sideritic formation (IV type) or attendant the sulphide-barite mineralization (V-VI types). They are coarser-grained, predominantly idiomorphic and with zonal composition. They are represented by magnesian-calcian-manganoan to calcian-magnesian-manganoan (IV type) and magnesian-manganoan to manganoan-magnesian (V-VI types) varieties. The spherulites of siderite VII are distinguished by their maximum values of CaC03 and low quantities of MnCO3 caused by the geochemical separation of Mn and Fe during the supergenetic processes. The XRD studies show that changes in compositions influence the major d1014 reflex being of the following values for the different siderite types: I-III - 2.79 Å; V-VI - 2.80-2.81 Å; IV – 2.81-2.82 Å; VII - over 2.82 Å. The new data presented on the siderite mineralogy support the hypothesis of polygenic and polychronous genesis of the Kremikovci deposit.

Stratigraphy and mineralogy of Unit H, Nagoorin South oil shale deposit

Mineralogical and chemical analyses are presented for a continuous sequence of samples over Unit H, Nagoorin South oil shale deposit. X-ray diffractometry and electron microprobe analysis were used to determine the mineralogy and the composition of carbonate minerals. The mineralogy and geochemistry are similar to those of other Tertiary oil shales, except that the composition of siderite-type minerals is unusually variable with stratigraphic depth. The stratigraphy is defined in Unit H and the subunits are characterized. Three types of siderite are recognized, depending upon the subunit and conditions during deposition and diagenesis. Magnesian siderites range in composition from 13 to 53% magnesium carbonate.

Eogenetic siderites in lacustrine oil shales from Queensland, Australia, a stable isotope study

Tertiary lacustrine oil shales from the Lowmead and Duaringa Basins in Queensland, Australia, contain siderite as a ubiquitous minor phase and in ironstone bands within the sequence. There are two distinctive types of siderite in the ironstone bands: sphaerosiderites and finely crystalline siderites. Petrological evidence indicates that the sphaerosiderites in the ironstone bands formed eogenetically by growing displacively within the soft sediment. The geological setting of the basin and the sedimentological evidence indicate a lacustrine environment. The deposition of siderite is therefore considered to be controlled by processes in the lacustrine water body and sediments. The maximal burial depth is estimated to be 1400 m and consequently the oil shales have not undergone any advanced thermal alteration. Stable oxygen and carbon isotope analysis of the siderites show a wide compositional range: δ 18O = −12.8 to − 2.4% vs. PDBG and δ 13C = −5.5 to + 12.9% vs. PDB for the Lowmead Basin: δ 18O = −9.6 to 1.2% vs. PDB and δ 13C = −18.6 to + 16.4% vs. PDB for the Duaringa Basin. The oxygen isotope compositions indicate that the siderite formed in a to + 16.4% vs. PDB for the Duaringa Basin. The oxygen isotope compositions indicate that the siderite formed in a freshwater environment but generally show a range more negative than the expected equilibrium composition with coeval meteoric waters. The carbon isotope composition may reflect deposition within the bacterial oxidation and fermentation zones. The shallow-lake setting with high productivity results in siderite precipitation under high pH either at the water-sediment interface or within the sediment. The δ 13C of the dissolved carbonate will be elevated by intense photosynthesis. Under these conditions of CO 2-depletion/high-pH isotopic disequilibrium during siderite formation will result in δ 13C and δ 18C lower than the equilibrium composition, in agreement with the recorded isotopic data.

Siderite decomposition in retorting atmospheres

This work extends the characterization of siderites found in Tertiary Australian oil shales by investigating their decomposition in atmospheres resembling retorting conditions. The decomposition of mineral siderite samples and selected oil shale samples with high siderite contents, representing the four types of siderites most commonly found, were studied by thermogravimetry in controlled carbon dioxide-nitrogen-water vapour atmospheres. The decomposition temperature of each of the siderite types increased with increasing partial pressure of carbon dioxide, and decreased with increasing partial pressure of water vapour. Both effects were non-linear: larger temperature changes were observed at lower partial pressures. This study makes it possible to predict the amount of siderite decomposition under typical retorting conditions and the consequences for both the retorting and combustion stages during oil shale processing.

Elemental and Isotopic Composition of Siderite in the Kuparuk Formation, Alaska: Effect of Microbial Activity and Water/Sediment Interaction on Early Pore-Water Chemistry

ABSTRACT The Kuparuk Formation (Neocomian) consists of glauconitic sandstones and mudrocks of marine origin. Authigenic siderite is common throughout the formation, either concentrated in distinct layers or as isolated rhombs. Examination of siderite-rich samples with back-scattered electron imaging reveals complex compositional zonation in the siderite. The samples are principally composed of mixtures of relatively early-formed Fe-rich siderite and relatively late-formed Mg-rich siderite, with mean compositions of (Fe77.5Mg13.8Ca7.9Mn0.7 )CO3 and (Fe55.8Mg32.8Ca10.8Mn0.6 )CO3, respectively. Fe-rich siderites are most abundant in glauconitic sandstone intervals, whereas Mg-rich siderit s are most abundant in non-glauconitic sandstones and mudrocks. The whole-rock isotopic composition of the siderite is highly variable, with 13C values ranging from -20.3 to 7.9 PDB, and 18O values from 21.4 to 31.1 SMOW. This variation in isotopic composition correlates with the relative proportions of the two siderite types in a given sample. The Fe-rich siderites have low 13C and high 18O values, whereas the Mg-rich siderites have high 13C and low 18O values. Both the elemental and carbon isotopic compositions of the siderite result from modification of the original marine pore waters during successive stages of microbial decomposition of organic matter. The oxygen isotopic compositions of the siderite indicate that early pore waters were depleted in 18O, perhaps as a result of water/sediment interaction. Authigenic ankerite associated with the siderite-bearing samples is unzoned and has a mean composition of Ca1.11 Fe0.35Mg0.53(CO3)2. The ankerites have higher 13C values and lower 18O values than the Fe-rich siderite, but have 13C values less than and 18O values greater than (with one exception) that of the Mg-rich siderite. The isotopic data suggest that ankerite precipitation began prior to precipitation of Mg-rich siderite and ended subsequent to or during Mg-rich side ite precipitation.

Mineral reactions in the processing of Australian Tertiary oil shales

Mineralogical, mineral characterization and thermogravimetric studies were made of raw and processed shale samples from the most prospective sections of the Rundle, Stuart, Condor, Duaringa, Nagoorin South, Nagoorin, Yaamba and Lowmead oil shale deposits. The effects of processing on minerals were determined in sufficient detail to establish the relevance of the various minerals and their reactions in oil shale processing. Minerals identified as the most significant in processing were smectite, kaolinite, siderite-type minerals and pyrite. Smectite and siderite-type minerals are characteristic of the oil shales of eastern Queensland. Smectites were found to be comparable in the various deposits and to be members of the montmorillonite/nontronite series with unusually low thermal stability. Four types of siderite (siderite, manganoan siderite, magnesian siderite and high magnesian siderite) were found, with progressively increasing decomposition temperatures in the retort. The most important mineral reactions occurring in the preheater, retort and combustor have been identified. Endothermic dehydroxylation and decomposition reactions of smectite, kaolinite, siderite minerals and pyrite influence heat requirements and gaseous products from retorting and combustion. The results indicate the possibility of transferring some of these reactions from the retort to the combustor by control of partial pressures of vapour phases in the retort. A sound basis has been established for future studies of the effects of specific minerals on oil coking reactivity and oil yields in retorting.

Palaeo-environment information from deep water siderite (Lake of Laach, West Germany)

Summary A comparative study from modern and ancient sediments from the Lake of Laach was performed by means of chemical and stable isotope analyses. In the modern environment siderite is precipitated around CO 2 -spring vents. In contrast, siderite from the Pleistocene/Holocene boundary occurs as small layers in a varved sequence. The stable isotope data provide strong evidence for an analogous formation of both types of siderite. The different CO 2 sources of the siderites allow reconstruction of a distinct rise of productivity at the Pleistocene/Holocene transition. It is proposed that siderite may be developed as a useful tool for tracing both palaeo-environmental and early diagenetic processes.