Siderite Deposits Research Articles

Rancieite crystals from Friesach, Carinthia, Austria

Rancieite from Friesach, Carinthia, Austria, is described from an oxidation zone of a small (Mn-bearing) siderite deposit. This mineral is associated with “buserite-(Ca)”, hollandite, braunite, romanechite, todorokite, cryptomelane, pyrolusite, manganite, nsutite, goethite, lepidocrocite, and calcite. Rancieite rarely forms small purple-silver grey crystals with a bright metallic luster. Single crystals are up to 200 μm in length and ∼0.1 μm in thickness and exhibit well-formed crystal faces in some cases. The foliated habit of these crystals may be due to rapid growth on the plane of fissure. For the first time a relatively large number of X-ray powder diffraction lines (19 lines) of rancieite are described. Structure modeling, by the Rietveld method and with difference-Fourier summations shows, that rancieite is most probably trigonal in structure, in contrast to the monoclinic structure of birnessite. The layers of the (Mn 4+ ,Mn 3+ )O 6 octahedra, arranged parallel to (00.1), are intercalated predominantly by Ca atoms and water molecules, which are in a statistic and disordered arrangement. The powder pattern of this rancieite was indexed on a trigonal cell, space group P 3 [147], with a = 2.845(1) and c = 7.485(1) A, a:c = 1: 2.632, Z = 1. The unit formula can be written as (Ca 0.85 Mn 2+ 0.06 K 0.05 Mg 0.02 Fe 3+ 0.01 Ba 0.01 ) (Mn 4+ 3.60 Mn 3+ 0.40 )O 9 ·∼ 2.8 H 2 O (calculated on the basis of O = 9; water and the valence states of Mn were calculated), or as Ca 0.19 Mn 2+ 0.01 K 0.01 (Mn 4+ 0.80 Mn 3+ 0.09□0.11 )O 2 ·∼ 0.6 H 2 O (calculated on the basis of O = 2).

“Siderite mineralization of the Gemericum superunit (Western Carpathians, Slovakia): review and a revised genetic model” [Ore Geology Reviews 24, 267–298]—a discussion

Radvanec et al. (2004) provided a revised version of their metamorphic-hydrothermal model for siderite and associated mineral deposits of the Western Carpathians. Compared to the previous version (Grecula, 1995; Grecula et al., 1996), the upgraded model emphasizes the dominant role of retrograde Variscan metamorphic processes and admits remobilization of the Variscan siderite and other ore components during the Alpine orogenic cycle. Similar to the previous versions, the Variscan ore-forming processes genetically related to metamorphism are believed to dominate not only in the siderite vein and metasomatic deposits, but also in the superimposed vein sulphides (p. 292). The revised model is unsustainable in light of recent knowledge. The major pitfalls are summarized and commented as follows.

Siderite mineralization of the Gemericum superunit (Western Carpathians, Slovakia): review and a revised genetic model

The Gemericum is a segment of the Variscan orogen subsequently deformed by the Alpine–Carpathian orogeny. The unit contains abundant siderite–sulphide and quartz–antimony veins together with stratabound siderite replacement deposits in limestones and stratiform sulphide mineralization in volcano-sedimentary sequences. The siderite–sulphide veins and siderite replacement deposits of the Gemericum represent one of the largest accumulations of siderite in the world, with about 160 million tonnes of mineable FeCO 3. More than 1200 steeply dipping hydrothermal veins are arranged in a regional tectonic and compositional pattern, reflecting the distribution of regional metamorphic zones. Siderite–sulphide veins are typically contained in low-grade (chlorite zone) sedimentary, volcano-sedimentary or volcanic Lower and Upper Paleozoic rocks. Quartz–antimony veins are hosted by higher-grade units (biotite zone). Siderite–sulphide veins are dominated by early siderite followed by a complex set of stages, including quartz–sulphide (chalcopyrite, tetrahedrite), barite, tourmaline–quartz, and sulphide-remobilization stages. The temporal evolution of these stages is difficult to study because of the widespread and repeated tectonic processes, within-vein replacement and recrystallization. Siderite–sulphide veins show considerable vertical (up to 1200 m) and lateral (up to 15 km) extent, and a thickness typically reaching several metres. Carbonate-replacement siderite deposits of the Gemericum are hosted by a Silurian limestone belt and are similar to stratabound siderite deposits of the Eastern Alps (e.g., Erzberg, Austria). Based on a review of geological, petrological and geochronological data for the Gemericum, and extensive stable and radiogenic isotope data and fluid inclusion data on hydrothermal minerals, the siderite–sulphide veins and siderite replacement deposits are classified as metamorphogenic in a broad sense. The deposits were formed during several stages of regional crustal-scale fluid flow. Isotope (S, C, Sr, Pb) fingerprinting identifies the metamorphosed rock complexes of the Gemericum as a source of most components of hydrothermal fluids. Fluid inclusion and stable isotope data evidence the participation of several contrasting fluid types, and the existence of contrasting P– T conditions during vein evolution. A high- δ 1 8O, medium- to high-salinity, H 2O-type fluid is the most important component during siderite deposition, whereas H 2O–CO 2-type fluid inclusion containing dense liquid CO 2 and corresponding to minimal pressures between 1 and 3 kbar were found in a younger tourmaline–quartz stage. Younger quartz–ankerite(±siderite)–sulphide stages are characterized by high-salinity (17 to 35 wt.% NaCl equivalent) and low-temperature ( T h=90 to 180 °C) H 2O-type fluids. The vein deposits are interpreted as a result of multistage hydrothermal circulation, with Variscan and Alpine mineralization phases. Based on available indirect data, the most important mineralization phase was related to regional fluid flow during the uplift of a Variscan metamorphic core complex, producing siderite–sulphide (±barite) mineralization, while tourmaline–quartz stage and sulphide remobilization stages are related to Alpine processes. Two phases of vein evolution are evident from two groups of 87Sr/ 86Sr isotope ratios of Sr-rich, Rb-poor hydrothermal minerals: 0.71042–0.71541 in older barite and 0.7190–0.7220 in late-stage celestine and strontianite.

Lower riphean low-carbonaceous shales in the southern urals: Raw material for the manufacture of porous rubble

A property of swelling on heating to yield firm lightweight granules has first been revealed for lowcarbonaceous shales (LCS) from the Riphean stratotype in the Bashkirian Megaanticlinorium, Southern Urals. These granules possess all technological properties of “keramzite” or claydite (an artificial, expanded clayey material) and can successfully substitute this material. Moreover, the procedure of their manufacture, analogous to the manufacture of “shungizite” (an artificial carbonaceous-clayey material) from Lower Proterozoic clayey rocks of Karelia, is more economical than that for keramzit. Productive beds of the homogeneous LCS make up extended bodies tens of meters thick. At the present time, they can be used as cover rocks during the exploitation of the Bakal siderite deposits. The LCS represent fine-grained quartz-chlorite-sericite aggregates (with variable relationships between the major components), bearing fine-dispersed shungite in amounts of 0.5–1.0%. High-quality raw material of this kind is characterized by a fine-dispersed admixture of a mixed-layer clayey material bearing montmorillonite and vermiculite. Geological, lithological, mineralogical, and chemical prognostic criteria have been developed for the shungizite raw material. It has been concluded that this construction material, new for the Urals, is promising for industrial use

Geology, Geochemistry, and Evolution of the Divrigi and Kuluncak Ophiolitic Melanges, with Reference to Serpentinites in East-Central Turkey

The Divrigi and Kuluncak ophiolitic mélanges are located in central Anatolia in the Tauride ophiolite belt. The stratigraphic sequence in the Divrigi ophiolitic mélange includes, from bottom to top, the Upper Jurassic-Lower Cretaceous Akdag limestone, Upper Cretaceous Çalti ultramafic rocks, and the Curek listwaenite. The Divrigi ophiolitic mélange is intruded by the Late Cretaceous-Eocene Murmano pluton. The above stratigraphic sequence is followed by the Eocene-Paleocene Ekinbasi metasomatite and the Quaternary Kilise Formation. The oldest sequence of rocks in Kuluncak ophiolitic mélange in the GuvenÇ area is the Karadere serpentine/ultramafic body overlain successively by the Kurtali gabbro, Gundegcikdere radiolarite, the GuvenÇ listwaenites, and the Buldudere Formation. All of these units are Late Cretaceous in age. The Karamagra siderite deposit in the Hekimhan area probably was formed in the Lower Cretaceous at the contact between Çalti ultramafic rocks and the Buldudere Formation. The Kuluncak ophiolitic mélange was intruded by a subvolcanic trachyte in the Late Cretaceous. The Eocene-Paleocene Konukdere metasomatite, the Miocene Yamadag volcanic rocks, and Quaternary slope deposits are late in the stratigraphic sequence in the GuvenÇ area. The Kuluncak ophiolitic mélange in the Karakuz area is similar to that at GuvenÇ; however, gabbro, radiolarite, and Miocene volcanic rocks are not present. The Miocene is represented by the Ciritbelen Formation at Karakuz and the Karakuz iron deposit is hosted by a Late Cretaceous subvolcanic trachyte. The rareearth and trace-element concentration of serpentinite in the Divrigi and Kuluncak ophiolitic mélanges indicate that all of the ultramafics and their alteration products were derived from a MORB, which was depleted in certain elements and oxides. The results expressed in this study support the idea that the Divrigi and Kuluncak ophiolitic mélanges within the Tauride ophiolite belt originated from Northern Tauride oceanic lithosphere (Poisson, 1986), instead of a northern branch of Neo-Tethys (Sengor and Yilmaz, 1981).

Origin of giant stratabound deposits of magnesite and siderite in Riphean carbonate rocks of the Bashkir mega-anticline, western Urals

In the Bashkir mega-anticline (western Urals) stratabound magnesite, siderite, fluorite and base-metal deposits are hosted by a sequence of Riphean sediments with a thickness of more than 12 km. The giant deposits of siderite (Bakal) and sparry magnesite (Satka) belong to the largest known mineral deposits of this type on Earth but are still disputed with respect to their origin. Both the Fe- and Mg-carbonate ores are clearly characterized by mimetic preservation of sedimentary and diagenetic textures of the host carbonate sediments, giving evidence of epigenetic metasomatic replacement. In the stratiform magnesite deposits of Satka, O- and C-isotopes, REE pattern and the lithostratigraphic position of the ore, point to the reflux of early diagenetic Mg-rich brines being responsible for the selective replacement of brecciated dolomite. The Bakal siderite deposits are hosted by Lower Riphean carbonate rocks and are controlled by a Lower to Middle Riphean unconformity marked by deep erosion and subsequent transgression-related sedimentation of coarse clastics. Their independence of carbonate lithofacies and their trace element distribution are indicative of metasomatic processes. Fe-bearing fluids have probably been generated by low-grade metamorphic (catagenetic) devolatization from underlying argillites, causing the metasomatic formation of large siderite ore bodies in the Bakal carbonates due to the focusing of the fluid flow by the overlying Mid-Riphean coarse clastics.

Forging a future for fossil insects: thoughts on the First International Congress of Paleoentomology

Insects are the most diverse macroorganismic group to ever inhabit the planet, constituting a major share of the animal biomass in terrestrial and freshwater ecosystems. Since their first appearance in the fossil record some 400 million years ago, they have expanded ecologically into almost every niche except the ocean below the photic zone. When fossilized, their chitinous exoskeletons typically are well preserved, as evidenced by a respectable fossil record. They are found notably in lacustrine shales and amber but also occur in siderite nodules, lithographic limestone, sinter deposits, asphalt, and various glacial deposits. Insect fossils are major subjects in phylogenetic studies but are used to a lesser extent in understanding past ecological associations and reconstruction of ancient environments.

Petrographic and geochemical arguments for hydrothermal formation of the Ouenza siderite deposit (NE Algeria)

The Ouenza siderite deposit is located proximal to evaporitic diapirs of Triassic age. Mineralization occurs mainly in Aptian neritic limestones which host important iron concentrations (120–150 MT) and minor Pb, Zn, Cu, Ba and F occurrences. The iron ore consists of iron carbonate minerals which have been oxidized partially to hematite. Fine-grained ankerite and siderite replace limestones, whereas sparry ankerite and siderite were emplaced in veins. Limited variation in the chemical and isotopic compositions of ankerite and siderite were observed, which indicate that they precipitated from the same fluid. Stable isotope compositions (δ18O and δ13C) of iron carbonates and limestones allow estimation of the isotopic composition of the mineralizing fluid and precipitation temperature: δ18O = 7.5‰ SMOW, T = 100–120 °C. Later deposition of Pb, Zn, Cu, Ba and F minerals is controlled by fractures oriented NE–SW and SE–NW. Fluid inclusion studies of quartz yield salinities of 18–22 wt.% equivalent NaCl and homogenization temperatures between 150 and 180 °C. These values are similar to those of Mississippi Valley type deposits which are associated with basinal brines.

Oxygen and carbon isotopic study on the genesis of the Steirischer Erzberg siderite deposit (Austria)

The carbon and oxygen isotopic composition of Fe-carbonate ore and its calcitic to dolomitic Devonian host rocks at the Steirischer Erzberg siderite deposit (Greywacke zone, Upper Austroalpine Unit) were determined in order to constrain the source and nature of the Fe-rich mineralizing fluid. The δ18O-values obtained for various Fe-carbonate generations and the carbonate host lie within a similar range between + 14.6 and + 21.6‰ (V-SMOW). No good correlation exists between the relative ages of the carbonate phases and their O isotopic composition. The variation in δ18O-values is due to metamorphic recrystallization with locally variable fluid/rock ratios. The average δ13C-value of the carbonate host is +0.5 ± 1.2‰ (PDB) which corresponds well to worldwide Phanerozoic marine carbonate values. The first Fecarbonate generation has slightly lower δ13C-values, on average -1.4 ± 0.8‰ (PDB). Recrystallization of both the carbonate host minerals and the ankerite/siderite led to significantly lower δ13C-values of -4.2 ± 0.6‰ and-4.7 ± 0.7‰, respectively. Within the basal breccia of the post-Hercynian transgression series matrix calcite/ dolomite shows an average δ13C-value of -2.9 ± 0.7‰, and matrix siderite/ankerite an average value of-4.1 ± 0.4‰. These data, together with Sr isotope data published previously, strongly support a late-diagenetic or epigenetic first Fe-mineralization from convecting formation waters. They ascended along extension faults and were driven by an increased heat flow caused by crustal thinning during a Devonian rifting phase that initiated the separation of the Noric terrane from Africa. A potential source of the Fe could have been the underlying Ordovician acid volcanics. Regional metamorphism related to collision tectonics in the Late Carboniferous (Hercynian) and later during the Alpine orogeny, caused intensive recrystallization and partial mobilization of the various carbonate phases.

Minerals Associated with Biofilms Occurring on Exposed Rock in a Granitic Underground Research Laboratory

The concept of disposal of nuclear fuel waste in crystalline rock requires the effects of microbial action to be investigated. The Underground Research Laboratory excavated in a pluton of the Canadian Shield provides a unique opportunity to study these effects. Three biofilms kept moist by seepage through fractures in granitic rock faces of the Underground Research Laboratory have been examined. The biofilms contained a variety of gram-negative and gram-positive morphotypes held together by an organic extracellular matrix. Nutrient levels in the groundwater were low, but energy-dispersive X-ray spectroscopy has shown biogeochemical immobilization of several elements in the biofilms; some of these elements were concentrated from extremely dilute environmental concentrations, and all elements were chemically complexed together to form amorphous or crystalline fine-grained minerals. These were seen by transmission electron microscopy to be both associated with the surfaces of the bacteria and scattered throughout the extracellular matrix, suggesting their de novo development through bacterial surface-mediated nucleation. The biofilm consortia are thought to concentrate elements both by passive sorption and by energy metabolism. By Mössbauer spectroscopy and X-ray diffraction, one of the biofilms showed that iron was both oxidized and precipitated as ferrihydrite or hematite aerobically and reduced and precipitated as siderite anaerobically. We believe that some Archean banded-iron formations could have been formed in a manner similar to this, as it would explain the deposition of hematite and siderite in close proximity. This biogeochemical development of minerals may also affect the transport of material in waste disposal sites.

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.

Origin of siderite deposits from the Lombardy Valleys, northern Italy: a carbon, oxygen and strontium isotope study

In the Lombardy Valleys, siderite mineralization is widespread as stratiform orebodies in Lower Triassic terrigenous-carbonate rocks as well as vein orebodies in Permian volcanics and continental sequences and in the metamorphic basement. A number of these orebodies and host limestone/dolomite rocks have been analysed for C, O and Sr isotope compositions, in order to constrain geochemically the origin of the siderite. The intermediate δ 13C-, δ 18O- and 87 Sr 86 Sr-values of stratiform siderite relative to vein siderite and host limestone and the very good linear correlations between δ-δ and δ- 87 Sr 86 Sr data points concur to support a metasomatic origin for stratiform siderite after calcite. In addition, stratiform and vein siderite should have formed from the same kind of fluids, and possibly are the products of the same mineralizing event. The δ-values of carbonate rocks are discussed in terms of recrystallization/dolomitization effects during diagenesis. These processes occurred earlier than siderite mineralization.

Silicified conifer forests and potential mining problems in seam M2 of the Gore Lignite Measures (Miocene), Southland, New Zealand

Silicified conifer ( Podocarpus cf. hallii) stumps up to 0.8 m in diameter are present at two levels in seam M2 of the Miocene Gore Lignite Measures, Mataura Coalfield, eastern Southland. The in situ stumps are believed to be the remains of forests which grew during pauses in peat accumulation, when groundwater levels were depressed as a result of climatic change or local basinal processes. Growth-ring measurements show the trees increased in radius between 0.16 and 1 mm per year. In two of six specimens, the growth-rates halved during their final 30–40 years of life; rising water levels may have resulted in less favourable growth conditions. Within the stumps, much of the wood structure is well preserved. Progressive diagenesis involved impregnation of the cell walls by silica, infilling of the cell lumens with length-slow chalcedony and opaline silica, and deposition of opal, length-fast chalcedony, and minor siderite in fractures. Radial and axial parenchyma contain coalified organic material and minor chalcedony. Filaments of wood-rotting fungi and probable root masses of epiphytes are present in some fossil wood. However, by analogy with modern Podocarpus hallii, we maintain the stumps were preserved for later silicification because the wood was highly resistant to fungal and bacterial decay. The stumps presumably functioned as conduits to ascending silica-saturated meteoric groundwater and water released during compaction, because of the contrasts in permeability between the vertical stumps and the surrounding peat.

A new genetic model for the North African metasomatic siderite deposits

Based on published accounts of the diagenetic evolution of evaporite diapirs and geological, preliminary geochemical, and fluid inclusion data a new genetic model is presented for the North African metasomatic siderite deposits.

Hydrothermal alteration of felsic volcanic rocks at the Helen siderite deposit, Wawa, Ontario

Within the footwall volcanic sequence five chemically and mineralogically distinct alteration types have been defined: least altered, sericite, chlorite, chloritoid, and ankerite. An alteration model is proposed in which shallow circulating seawater (1-3 km), heated by a subvolcanic intrusion, encountered rocks of felsic composition within the upper part of the volcanic succession. Seawater-rock reactions evolved an acidic, potassium-rich solution which migrated upward, reacting with overlying felsic rocks, converting plagioclase to sericite and quartz. Porosity of the altered rocks decreased and a widespread sericitic alteration zone formed. At depths greater than 3 km, circulating seawater came into contact with basaltic rocks and ensuing reactions enriched the seawater in Fe, Mg, Mn, Ca, and CO 2 . This second hydrothermal solution moved upward and encountered sericite-rich rocks. Near the sea floor, boiling of the solution and/or mixing with relatively cold seawater rapidly decreased CO 2 solubility causing mass precipitation of iron carbonate. This led to the formation of the ankerite assemblage in the immediate footwall rocks and the siderite iron-formation on the sea floor.--Modified journal abstract.

Applications géologiques des résultats expérimentaux du système FeCOS (+ H 2O)

The experimental results obtained from the study of the FeCOS (+ H 2O) system are applied to four Fe ranges and in more detail to two of them. The Central Labrador Fe formation where the temperature of metamorphism, based on the Fe 2O 3Fe 3O 4 and Fe 2SiO 4SiO 2 assemblages, is in the range 290–350°C. The Michipicoten Fe formation, Ontario, has a temperature of metamorphism in the range from 300 to about 380°C. This is based on the temperature obtained from the univariant FeCOS assemblages and the stability of epidote. It is therefore concluded that the Michipicoten range has a dual origin; sedimentary deposition of siderite, pyrite and little magnetite with later most probably took place in the temperature range 200–270°C. An experimental study of this nature cannot explain in great detail all the physicochemical phenomena influencing the equilibrium or the disequilibrium of the chemical reactions taking place but it gives some information of a more or less quantitative nature related to temperature and pressure conditions, chemical potential of solid-state reactants and products, and fugacity of some important gases partially controlling the equilibrium of solid-state reactions.

An Stratigraphische Hiate gebundene Vererzungen in den Tschechoslowakischen Karpaten

During the course of the geotectonic development of the West Carpathians there were ore mineralisation periods, which are associated with different stratigraphical hiatuses. Hematite-magnetite ore was deposited in the first period between the Silurian and the Devonian. In both the Middle and the Upper Carboniferous, some stratiform siderite deposits originated, which were exploited in the vicinity of Dobsina and Mlynky during about the last 100 years. In the Permian, some haematite occurrences, fossil gold placers and uranium-bearing strata were formed, the last of which was exploited. Some minor haematite occurrences are widespread in the Lower Triassic. The same type of occurrence is known in the Upper Triassic and in the Lower Jurassic, too. In the Jurassic, small occurrences of manganese ore are known. Bauxite occurreces were found in the Middle and Upper Cretaceous, but they are very small. More important are the sedimentary manganese deposits, which were deposited in the Middle Eocene. These were exploited during the last 70 years. The fossil gold placers of the east Slovakian, Paleogene flysch series are very interesting from genetic point of view. The small kaoline, bauxite and silicate-nickel occurrences, which are associated with the alteration processes of basic rocks of different age, were found during the Miocene. The Quaternary period is well known for its gold placers, from which those of the Danube river as well as others were exploited in the past.

Geochemistry and Diagenesis of Macrokaolinite

Research Article| July 01, 1973 Geochemistry and Diagenesis of Macrokaolinite WAYNE C. ISPHORDING; WAYNE C. ISPHORDING 1Department of Geology, University of South Alabama, Mobile, Alabama 36608 Search for other works by this author on: GSW Google Scholar WILLIAM LODDING WILLIAM LODDING 2Department of Geology, Rutgers University—The State University of New Jersey, New Brunswick, New Jersey 08903 Search for other works by this author on: GSW Google Scholar Author and Article Information WAYNE C. ISPHORDING 1Department of Geology, University of South Alabama, Mobile, Alabama 36608 WILLIAM LODDING 2Department of Geology, Rutgers University—The State University of New Jersey, New Brunswick, New Jersey 08903 Publisher: Geological Society of America First Online: 01 Jun 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (1973) 84 (7): 2319–2326. https://doi.org/10.1130/0016-7606(1973)84<2319:GADOM>2.0.CO;2 Article history First Online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation WAYNE C. ISPHORDING, WILLIAM LODDING; Geochemistry and Diagenesis of Macrokaolinite. GSA Bulletin 1973;; 84 (7): 2319–2326. doi: https://doi.org/10.1130/0016-7606(1973)84<2319:GADOM>2.0.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract Three stages of diagenesis can be identified in the sediments that form the Alloway Clay Member of the Miocene Kirkwood Formation in New Jersey. Clay- and sand-size muscovite, mixed with woody debris, formed the original sediment. These materials were deposited in restricted lagoons receiving a high amount of fresh water runoff. Transgression of the sea then resulted in the deposition of marine clays above the lagoonal sediments. Following regression, the muscovite was altered to sand-size kaolinite by the action of acidic ground water. This highly permeable unit was locally cemented by deposition of siderite, forming large concretions. Later, all calcareous fossils in the macrokaolinite bed were removed by dissolution, while those inside the siderite concretions were preserved. These diagenetic episodes are controlled by changes in Ca+2 and Fe+2 concentration of the ground water and, significantly, by permeability. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Sur la genese des gites de fer du massif du Mouthoumet (Aude) (a propos d'hypotheses recentes)

Abstract The siderite deposits of the Mouthoumet massif, Aude, France, are of metasomatic origin, like those of the Canigou district. Karstification during Tournaisian (Carboniferous) time occurred after mineralization, and therefore could not have been responsible for it.

The Yorkshire Dogger: III. Upper Eskdale

1. A sequence of strata is determined in the Dogger of Upper Eskdale and its tributary valleys. The rocks fall into three main series, which are subdivided into groups.2. The underlying Yeovilian sediments, originally included with the Dogger, are mapped and briefly described. The unconformity between them and the Dogger is emphasized.3. The Dogger is marine throughout but only the oldest yields an adequate faunal assemblage, similar to that of the Glaisdale Oolite Series (upper opalinum). The greater part of the Dogger of this area is therefore younger than that of the Yorkshire Coast.4. Chemical changes in the sea-water caused the deposition of siderite to characterize the earliest phase (Glaisdale Oolite Series). This was succeeded by a phase of dominantly chamosite deposition (the Chamositic Series) followed by a reversion to siderite deposition (the Ajalon Series).5. Earth-movement controlled sedimentation over the area. During the first phase an eastern tilt to the region held the centre and west above or near sea-level, where it received no sediment. The second phase saw general depression with the accumulation of shallow water sediments. This was followed by uplift and erosion when a broad shallow valley was cut. Partial depression then flooded the valley with derived marine sediments.