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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That unconfined aquifer is an aquifer where the water table is exposed to the atmosphere through openings in the overlying materials.?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for petrography (Keyword) returned 24 results for the whole karstbase:
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Regional dolomitization of subtidal shelf carbonates: Burlington and Keokuk Formations (Mississippian), Iowa and Illinois, 1987, Harris David C. , Meyers William J. ,
Cathodoluminescent petrography of crinoidal limestones and dolomites from the Mississippian (Osagean) Burlington and Keokuk Formations in Iowa and Illinois has revealed a complex diagenetic history of calcite cementation, dolomitization, chertification and compaction. Dolomite occurs abundantly in subtidal, open-marine facies throughout the study area. Three luminescently and chemically distinct generations of dolomite can be recognized regionally. Dolomite I, the oldest generation, is luminescent, thinly zoned, and occurs mainly as a replacement of lime mud. Dolomite II has dull red unzoned luminescence, and occurs mainly as a replacement of dolomite I rhombs. Dolomite III is non-luminescent, and occurs as a syntaxial cement on, and replacement of, older dolomite I and II rhombs. Petrography of these dolomite generations, integrating calcite cement stratigraphy, chertification and compaction histories has established the diagenetic sequence. Dolomites I and II pre-date all calcite cements, most chert, intergranular compaction and styloites. Dolomite III precipitation occurred within the calcite cement sequence, after all chert, and after at least some stylolitization. The stratigraphic limit of these dolomites to rocks older than the St Louis Limestone (Meramecian) suggests that dolomitization took place before or during a regional mid-Meramecian subaerial unconformity. A single dolomitization model cannot reasonably explain all three generations of dolomite in the Burlington and Keokuk limestones. Petrographic and geochemical characteristics coupled with timing constraints suggest that dolomite I formed in a sea water-fresh water mixing zone associated with a meteoric groundwater system established beneath the pre-St Louis unconformity. Dolomite II and III may have formed from externally sourced warm brines that replaced precursor dolomite at shallow burial depths. These models therefore suggest that the required Mg for dolomite I was derived mainly from sea water, whereas that for dolomites II and III was derived mainly from precursor Burlington--Keokuk dolomites through replacement or pressure solution

LATE-STAGE DOLOMITIZATION OF THE LOWER ORDOVICIAN ELLENBURGER GROUP, WEST TEXAS, 1991, Kupecz J. A. , Land L. S. ,
Petrography of the Lower Ordovician Ellenburger Group, both in deeply-buried subsurface cores and in outcrops which have never been deeply buried, documents five generations of dolomite, three generations of microquartz chert, and one generation of megaquartz. Regional periods of karstification serve to subdivide the dolomite into 'early-stage', which predates pre-Middle Ordovician karstification, and 'late-stage', which postdates pre-Middle Ordovician karstification and predates pre-Permian karstification. Approximately 10% of the dolomite in the Ellenburger Group is 'late-stage'. The earliest generation of late-stage dolomite, Dolomite-L1, is interpreted as a precursor to regional Dolomite-L2. L1 has been replaced by L2 and has similar trace element, O, C, and Sr isotopic signatures, and similar cathodoluminescence and backscattered electron images. It is possible to differentiate L1 from L2 only where cross-cutting relationships with chert are observed. Replacement Dolomite-L2 is associated with the grainstone, subarkose, and mixed carbonate-siliciclastic facies, and with karst breccias. The distribution of L2 is related to porosity and permeability which focused the flow of reactive fluids within the Ellenburger. Fluid inclusion data from megaquartz, interpreted to be cogenetic with Dolomite-L2, yield a mean temperature of homogenization of 85 6-degrees-C. On the basis of temperature/delta-O-18-water plots, temperatures of dolomitization ranged from approximately 60 to 110-degrees-C. Given estimates of maximum burial of the Ellenburger Group, these temperatures cannot be due to burial alone and are interpreted to be the result of migration of hot fluids into the area. A contour map of delta-O-18 from replacement Dolomite-L2 suggests a regional trend consistent with derivation of fluids from the Ouachita Orogenic Belt. The timing and direction of fluid migration associated with the Ouachita Orogeny are consistent with the timing and distribution of late-stage dolomite. Post-dating Dolomite-L2 are two generations of dolomite cement (C1 and C2) that are most abundant in karst breccias and are also associated with fractures, subarkoses and grainstones. Sr-87/Sr-86 data from L2, C1, and C2 suggest rock-buffering relative to Sr within Dolomite-L2 (and a retention of a Lower Ordovician seawater signature), while cements C1 and C2 became increasingly radiogenic. It is hypothesized that reactive fluids were Pennsylvanian pore fluids derived from basinal siliciclastics. The precipitating fluid evolved relative to Sr-87/Sr-86 from an initial Pennsylvanian seawater signature to radiogenic values; this evolution is due to increasing temperature and a concomitant evolution in pore-water geochemistry in the dominantly siliciclastic Pennsylvanian section. A possible source of Mg for late-stage dolomite is interpreted to be from the dissolution of early-stage dolomite by reactive basinal fluids

Carbonate Petrography: Grains, Textures Case Studies, 1996,

Ground-water silicifications in the calcareous facies of the Tertiary piedmont deposits of the Atlas Mountain (Hamada du Guir, Morocco), 1997, Thiry M. , Benbrahim M. ,
The Tertiary piedmont deposits (Hamada Formations), on the southern edge of the Haut-Atlas mountains, form extensive tablelands in the Boudenib area. They consist of two main sedimentary sequences, the Hamada de Boudenib and the Hamada du Guir, of Eocene and Miocene age. Both sequences show elastic facies at their base (conglomerates, calcareous sandstones, silty clays) and end with thick lacustrine limestones and pedogenic calcretes are characterised by rather confined facies, palygorskite-rich, with some gypsum in the second sequence. The recent evolution of the region is marked by the dissection of the tableland that is lined with high cliffs. The water flaw is mainly through wide karst features as there is no major river on the tableland. Silicifications which affect the different facies, form pods of various shape and size, and show an erratic spatial distribution. In the calcareous sandstones, there are irregularly shaped tubules of about 5 cm in diameter, more planar bodies from 5 to 50 cm thick, which frequently display voids lined with translucent silica concretions. The conglomerates display relatively few silicifications, the more characteristic ones consist of a silica cortex on some Limestone pebble and silica plates fitting closely the base of the pebbles. The lacustrine limestones and the calcretes from the upper part of the formation show frequently well developed silicifications. These show very variable shapes; horizontally stretching layers, interconnected or isolated amoeba-like bodies, thin slabs, karst micro-breccia, with frequent concretionnary structures, and quartz crystallisations. Limestone nodules remain often included in these silicifications. The more argillaceous facies display either small tubules or thin plates formed of translucent concretionnary silica. As a rule, the importance of the voids and related structures (concretions, drusy crystals) has to be noticed in all these silicifications, sometimes they are also linked with fractures or karst pipes. Petrography of the silica minerals, their relation with the primary structures. their distribution and their succession, give invaluable information on the silicification processes. Microcrystalline and fibrous quartz are the most common silica minerals, including minor amounts of opal and euhedral quartz. But micrographic arrangements show clearly that primary opal deposits have been more extensive and have recrystallized into chalcedony, microcrystalline quartz, or even ''flame-like'' quartz. Silica deposits in voids make up an important part of the silica pods. The tubules and thin plates of translucent silica of the argillaceous facies are formed of laminar chalcedony deposited around voids. Silica deposits in voids are also particularly obvious in the sandstones. The pores between the quartz grains are then cemented by fibrous quartz and little opal. Some samples show very large cemented voids that cannot be related to the primary porosity of the sandstone. These large voids correspond to the dissolution of the primary calcareous cement, which even led to the collapse of the sandstone fabric. In the limestones, there are silicified micro-karst breccia with a very high primary porosity cemented by quartz crystals, and even in the large microcrystalline quartz zones there are numerous void fillings, the primary porosity often exceeding 50%. There is obviously the alternation of silica deposits and calcite dissolution. Beside the void filling, silicifications comprise also matrix epigenesis, that is replacement of the carbonate by silica with preservation of most of the limestone structures, without development of voids. Nevertheless, the epigenesis of the limestone matrix is restricted to the vicinity of the voids. The silicifications relate to diagenetic processes. The main part of the silica is formed of void deposits and matrix replacement (epigenesis) on the edge of the voids. These void deposits give evidence of the feeding solutions. The regularity of the deposits all around the voids point out to a hydrologic regime characterised by a ground-water our now. Silica originates most probably from alteration of the magnesian clay minerals along the ground-water path. Regarding the low solubility of silica in surficial waters, high flows are needed in order to renew continuously the silica precipitated from solution. This points to a relatively humid climate at time of silicification, and to relief and incised landscapes to bring about these high flows

Petrography, strontium, barium and uranium concentrations, and strontium and uranium isotope ratios in speleothems as palaeoclimatic proxies: Soreq Cave, Israel, 1999, Ayalon A, Barmatthews M, Kaufman A,
The reconstruction of the palaeoclimate of the eastern Mediterranean region for the last 60 ka BP is based on the delta(18)O and delta(13)C variations of speleothems from Soreq Cave, Israel. Climatic conditions during most of the rime interval between 60 and 17 ka BP (the period equivalent to the last glacial) were relatively cold and dry, while they were warmer and wetter from 17 ka BP to the present. At similar to 17 ka BP, there was a major climatic change with a sharp increase in annual rainfall and temperature and a very wet period occurring between 8.5 and 7.0 ka BP. During the colder and drier period, large, detritus-free, preferentially oriented calcite crystals were deposited from slow-moving water. As a result of a sharp change in the hydrological regime at similar to 17 ka BP, fast-moving water started entrainment of the soil and carrying detrital material into the cave, and the calcite crystals deposited became small and anhedral. Coinciding with the petrographic and isotopic changes, a sharp drop occurred in the concentrations of strontium, barium and uranium, and in the ratios Sr-87/Sr-86 and (U-234/U-238)(0), which reached mini mum values during the wettest period. This drop reflects enhanced weathering of the soil dolomite host rock. During colder and drier periods, higher trace-element concentrations and higher isotopic ratios reflect an increase in the contribution of salts derived from exogenic sources (sea spray and aeolian dust), and a reduced contribution of weathering from the host dolomites

LOW-TEMPERATURE ACID WEATHERING IN NEWHAVEN, SUSSEX, UNITED KINGDOM, AND ITS APPLICATION TO THEORETICAL MODELING IN RADIOACTIVE WASTE-DISPOSAL SITES, 2000, De Putter T, Bernard A, Perruchot A, Nicaise D, Dupuis C,
Tertiary weathered sediments located immediately to the west of the harbor at Newhaven, Sussex, UK, were investigated by examination of major and trace elements by scanning electron microscope (SEM), microprobe, and inductively coupled plasma mass spectrometer (ICP-MS), and the mineralogy was studied by optical petrography, X-ray diffraction (XRD), transmission electron microscope (TEM), selective leaching, and thermodynamic modeling. Studied outcrops experienced acid leaching by sulfuric acid percolating downward through Tertiary sediments overlying Cretaceous chalk. The progressive neutralization of the percolating acid fluids resulted in 'sequentially' layered neoformation of minerals: jarosite, iron oxides, aluminous minerals (sulfates, oxyhydroxides), gypsum, and Fe-Mn oxides. Substantial agreement was found between field observations and mineral assemblages obtained by modeling with the program CHILLER. These results suggest that the initial assumptions on the weathering process and mechanisms are correct. The relevance and implications of this study in the modeling of future denudation and weathering processes of radioactive waste-disposal sites (both deeply buried sites for high-level waste and surface sites for low-level waste) are discussed. Neoformed phases, such as jarosite, aluminous minerals, and silico-aluminous gels may play a significant role in the efficient trapping of mobilized pollutant radionuclides

Dolomitization and Dolomite Neomorphism: Trenton and Black River Limestones (Middle Ordovician) Northern Indiana, U.S.A, 2000, Yoo Chan Min, Gregg Jay M. , Shelton Kevin L. ,
The Trenton and Black River Limestones are dolomitized extensively along the axis of the Kankakee Arch in Indiana, with the proportion of dolomite decreasing to the south and southeast of the arch. Planar and nonplanar dolomite replacement textures and rhombic (type 1) and saddle (type 2) void-filling dolomite cements are present. Three stages of dolomitization, involving different fluids, are inferred on the basis of petrographic and geochemical characteristics of the dolomites. Nonferroan planar dolomite has relatively high {delta}18O values (-1.8 to -6.1{per thousand} PDB) and has 87Sr/86Sr ratios (0.70833 to 0.70856) that overlap those of Middle Ordovician seawater. Petrography, geochemistry, and the geometry of the dolomitized body suggest that the planar dolomite was formed in Middle and Late Ordovician seawater during the deposition of the overlying Maquoketa Shale. Ferroan planar and nonplanar dolomite occurs in the upper few meters of the Trenton Limestone, confined to areas underlain by planar dolomite. This dolomite contains patches of nonferroan dolomite with cathodoluminescence (CL) characteristics similar to underlying planar dolomite. Ferroan dolomite has relatively low {delta}18O values (-5.1 to -7.3{per thousand} PDB) and has slightly radiogenic 87Sr/86Sr ratios (0.70915 to 0.70969) similar to those obtained for the overlying Maquoketa Shale. These data indicate that ferroan dolomite formed by neomorphism of nonferroan planar dolomite as fluids were expelled from the overlying Maquoketa Shale during burial. The absence of ferroan dolomite at the Trenton-Maquoketa contact, in areas where the earlier-formed nonferroan planar dolomite also is absent, indicates that the fluid expelled from the overlying shale did not contain enough Mg2 to dolomitize limestone. Type 1 dolomite cement has isotopic compositions similar to those of the ferroan dolomite, suggesting that it also formed from shale-derived burial fluids. CL growth zoning patterns in these cements suggest that diagenetic fluids moved stratigraphically downward and toward the southeast along the axis of the Kankakee Arch. Type 2 saddle dolomite cements precipitated late; their low {delta}18O values (-6.0 to -7.0{per thousand} PDB) are similar to those of the type 1 dolomite cement. However, fluid-inclusion data indicate that the saddle dolomite was precipitated from more saline, basinal fluids and at higher temperatures (94{degrees} to 143{degrees}C) than the type 1 cements (80{degrees} to 104{degrees}C). A trend of decreasing fluid-inclusion homogenization temperatures and salinities from the Michigan Basin to the axis of Kankakee Arch suggests that these fluids emerged from the Michigan Basin after precipitation of type 1 cement

Diagenesis and porosity evolution of the Upper Silurian-lowermost Devonian West Point reef limestone, eastern Gaspe Belt, Quebec Appalachians, 2001, Bourque Pa, Savard Mm, Chi G, Dansereau P,
Diagenetic analysis based on cathodoluminescence petrography, cement stratigraphy, carbon and oxygen stable isotope geochemistry, and fluid inclusion microthermometry was used to reconstruct the porosity history and evaluate the reservoir potential of the Upper Silurian-Lower Devonian West Point limestone in the eastern part of the Gaspe Belt. The West Point limestone was investigated in two areas: 1) In the Chaleurs Bay Synclinorium, the limestone diagenesis of the lower and middle complexes of the Silurian West Point Formation was affected by repeated subaerial exposure related to late Ludlovian third-order eustatic low-stands, which coincided with the Salinic block tilting that produced the Salinic unconformity. The Anse McInnis Member (middle bank complex) underwent freshwater dissolution, and mixed marine and freshwater cementation during deposition. Concurrently, the underlying Anse a la Barbe and Gros Morbe members (lower mound and reef complex) experienced dissolution by fresh water percolating throughout the limestone succession. Despite this early development of karst porosity, subsequent meteoric-influenced cementation rapidly occluded all remaining pore space in the Gros Morbe, Anse a la Barbe, and Anse McInnis limestones. In contrast, the overlying Colline Daniel Member limestone (upper reef complex) does not show the influence of any freshwater diagenesis. Occlusion of its primary porosity occurred during progressive burial and was completed under a maximum burial depth of 1.2 kin. 2) In the Northern Outcrop Belt, the diagenesis of the Devonian pinnacle reefs of the West Point Formation followed a progressive burial trend. The primary pores of the reef limestone were not completely occluded before the reefs were buried at a significant depth (in some cases, to 6 km). Therefore, hydrocarbon migration in subsurface buildups before primary porosity occlusion might have created reservoirs. Moreover, the presence of gaseous hydrocarbons in Acadian-related veins attests to a hydrocarbon source in the area

Petrographic and Geochemical Screening of Speleothems for U-series Dating: An Example from Recrystallized Speleothems from Wadi Sannur Cavern, Egypt, 2002, Railsback, L. B. , Dabous, A. A. , Osmond, J. K. , Fleisher, C. J.
Petrographic and geochemical analyses of four speleothems from Wadi Sannur Cavern in eastern Egypt show that petrography and geochemistry can provide a useful way to screen speleothems prior to dating via U-series analysis. The speleothems vary from inclusion-rich zoned calcite to clear featureless calcite. U concentrations (ranging from 0.01-2.65 ppm) and Sr concentrations (ranging from 0.00-0.11 wt%) are greater in inclusion-rich zoned calcite. U concentrations are also greater in speleothems with small (<1.2 mm wide) columnar calcite crystals than in speleothems with larger crystals. Mg concentrations in the speleothems range from 0.2 to 2.3 mol% MgCO3 and show no significant relationship to petrography at the microscopic scale. Geochemical considerations suggest that the Wadi Sannur speleothems were originally mostly aragonite, and that all four have undergone recrystallization. More generally, they suggest that coarse clear columnar calcite and large (>1.0 ppm) ranges of U concentration are warning signs of recrystallization and U loss. However, even finer grained, inclusion-rich columnar calcite may be the result of recrystallization while retaining U contents less depleted than those of associated clear calcite.

Sedimentologic, diagenetic and tectonic evolution of the Saint-Flavien gas reservoir at the structural front of the Quebec Appalachians, 2003, Bertrand R, Chagnon A, Malo M, Duchaine Y, Lavoie D, Savard Mm,
The Beekmantown Group (Lower Ordovician) of the Saint-Flavien reservoir has produced 162x106 m3 (5.7 bcf) of natural gas between 1980 and 1994. The conversion of the field into gas storage was initiated in 1992 and the pool became operational in 1998. Integration of structural and sedimentologic features, carbonate and organic matter petrography and geochemistry for 13 drill holes is used to define a tectonic-sedimentologic-diagenetic model for porosity evolution in these reservoir dolostones. The Beekmantown Group consists of numerous fifth-order shallowing-upward cycles 1.0 to 7.0 m thick (average of 2.4 m). Each cycle consists of a basal shale deposited during the initial flooding of the platform which was subsequently covered by a shoaling succession of subtidal and intertidal limestones to intertidal dolostones. Early dolomitization has produced intercrystalline porosity and preserved some moldic pores in the intertidal facies. Near surface, post-dolomite karstification has created vugs that were subsequently filled by early marine calcite fibrous cement based on the {delta}18O and {delta}13C ratios of calcite. Early burial elements consist of horizontal stylolites, pyrite and sphalerite. Late migrated bitumen was thermally altered or vaporized as native coke under deep burial conditions exceeding 240{degrees}C, partly due to overthrusting of Appalachian nappes. Under these conditions, breccias and fractures were generated and subsequently filled with K-feldspar, quartz, illite, and xenomorphic and poikilotopic calcite. The {delta}18O of the poikilotopic calcite and homogenization temperature of coeval fluid inclusions indicate formation under high temperatures (Th about 260{degrees}C). Horizontal shear zones and marcasite-rich vertical stylolites were produced during folding and thrusting. Dissolution has preferentially affected late fracture-filling calcite and generated most of the actual porosity during or soon after the Taconian Orogeny. The relationship between the occurrence of smectite and this type of porosity indicates the low temperature condition of this dissolution (T <100{degrees}C). Porosity in the Saint-Flavien reservoir has been mostly produced by fracture-controlled, late to post-Taconian dissolution of early to late calcite in the intertidal dolomitic slightly porous facies at the top of rhythmic cycles that compose the Beekmantown Group

Petrography of Finely Crystalline Cenozoic Dolostones as Revealed by Backscatter Electron Imaging: Case Study of the Cayman Formation (Miocene), Grand Cayman, British West Indies, 2003, Jones Brian, Luth Robert W. ,
Finely crystalline Cenozoic island dolostones, like those found in the Cayman Formation on Grand Cayman, are commonly assumed to be petrographically and compositionally homogeneous. Backscatter electron images (BSEI), however, show that the constituent dolomite crystals (< 100 {micro}m long and commonly < 20 {micro}m long) are commonly zoned with respect to their mol % CaCO3 content. Moreover, such images allow (1) depiction of growth patterns in the constituent crystals, irrespective of their origin, (2) recognition of replacive dolomite as opposed to dolomite cement, and (3) delineation of 'stratigraphic packages' in the dolomite cements that reflect different episodes of cementation. Integration of this information forms the basis for paragenetic interpretations of the dolostones. On Grand Cayman, the Miocene Cayman Formation can be divided into friable, high-porosity dolostones and hard, low-porosity dolostones. Backscatter electron images show that the hard dolostones are characterized by complex arrays of zoned dolomite cements that have occluded most of the pores. Caymanite, an internal sediment, has occluded many of the larger cavities. In contrast, the high-porosity dolostones contain little cement and no internal sediments. Precipitation of the cements and the deposition of internal sediments were related to the passage of large volumes of water through some of the dolostones. Thus, the hard, low-porosity dolostones are found in the 'cap rock' of the formation, in coastal locations, and in areas close to solution-widened fractures. Conversely, the friable, high-porosity dolostones form the lower 'porous unit' of the formation in the interior of the island, where the passage of water was more restricted

Hypogene and supergene alteration of the Late Palaeozoic Ratburi Limestone during the Mesozoic and Cenozoic (Thailand, Surat Thani Province). Implications for the concentration of mineral commodities, 2005, Dill H. G. , Botz R. , Luppold F. W. , Henjeskunst F.
An interdisciplinary study of the Upper Carboniferous to Middle Permian Ratburi Group, Peninsular Thailand, is presented. The investigation involved sedimentary petrography, inorganic geochemistry, Sr, C, O isotope analyses, micropalaeontology as well as radio-carbon age dating. Emphasis was placed on the post-depositional evolution of the Ratburi Limestone in the Surat Thani Province. The Holocene chemical residues and the various calcite and dolomite minerals which have formed since the Late Palaeozoic in the Ratburi Limestone are the product of a complex, multistage alteration which is called supergene and hypogene karstifications, respectively. Sedimentation took place in a shelf environment with some reefs evolving during the late Murgabian at the shelf margin. There was no pre-concentration of elements, except for Ca and F during sedimentation. Diagenetic neomorphism and cementation under marine and freshwater conditions caused the Ratburi Limestone to convert into a marble-like rock. Fabric-selective dolomitization is of local scale and has impacted only on part of the Ratburi Limestone during the Lower to Upper Permian. A significant enhancement of pore space and better conduits were generated during the Late Cretaceous epithermal alteration. The most favorable conditions for the accumulation of metals were provided during the high-temperature stage of epithermal alteration when a low-metal concentration with As, Zn, Sb, U, Co and Pb existed. Unlike the other elements, Sb was subject to a multiphase concentration, giving rise to a considerable Sb deposit in the region. The most recent stage of karstification produced numerous caves, dripstones, tufa terraces and encrustations around brine pools in the study area. This alteration originated from per descensum and per ascensum processes which may be traced back to 15,000 years before present. The alteration of the Ratburi Limestone may be subdivided into two parts. The prograde post-depositional alteration, beginning with diagenesis, reached its temperature climax during epithermal subsurface alteration I. The retrograde branch of alteration lasted until the most recent times. The initial stages deposition and diagenesis took place under more or less closed-system conditions relative to the succeeding stages of the prograde alteration which saw the strongest influx of metal-bearing brine during the epithermal stage I. The retrograde branch of alteration is element-conservative.

Dolomite formation in breccias at the Musandam Platform border, Northern Oman Mountains, United Arab Emirates, 2006, Breesch L, Swennen R, Vincent B,
The presence of dolomite breccia patches along Wadi Batha Mahani suggests large-scale fluid flow causing dolomite formation. The controls on dolomitization have been studied, using petrography and geochemistry. Dolomitization was mainly controlled by brecciation and the nearby Hagab thrust. Breccias formed as subaerial scree deposits, with clay infill from dissolved platform limestones, during Early Cretaceous emergence. Cathodoluminescence of the dolostones indicates dolomitization took place in two phases. First, fine-crystalline planar-s dolomite replaced the breccias. Later, these dolomites were recrystallized by larger nonplanar dolomites. The stable isotope trend towards depleted values (delta O-18: -2.7 parts per thousand to - 10.2 parts per thousand VPDB and delta C-13: -0.6 parts per thousand to -8.9 parts per thousand VPDB), caused by mixing dolomite types during sampling, indicates type 2 dolomites were formed by hot fluids. Microthermometry of quartz cements and karst veins, post-dating dolomites, also yielded high temperatures. Hot formation waters which ascended along the Hagab thrust are invoked to explain type 2 dolomitization, silicification and hydrothermal karstification. (C) 2006 Elsevier B.V, All rights reserved

Unusual Phosphate Concretions Related to Groundwater Flow in a Continental Environment, 2006, Thiry Medard, Galbois Jean, Schmitt Jean Michel,
Occurrence of phosphate cemented-sandstone concretions in alluvial sand containing archaeological layers implies that they have formed during the last 2000 years. Morphology and petrography of the concretions indicates a relationship with groundwater cementation. The phosphate cement of the concretions consists of concentric isopachous aureoles, about 10 {micro}m thick, that wrap the detrital grains. Aureoles are formed of collophane, the cryptocrystalline or amorphous variety of hydroxyapatite. Geochemical modeling indicates that the apatite cement likely results from the leaching of a preexisting phosphate deposit (bones?) in an acidic soil environment and the precipitation of dissolved phosphate under pH control at the mixing zone of down-moving soil-water with the calcite-saturated groundwater

Evidence against the Dorag (mixing-zone) model for dolomitization along the Wisconsin arch - A case for hydrothermal diagenesis , 2006, Luczaj, J. A.

Ordovician carbonates near the Wisconsin arch represent the type locality in ancient rocks for the Dorag, or mixing-zone, model for dolomitization. Field, petrographic, and geochemical evidence suggests a genetic link between the pervasive dolomite, trace Mississippi Valley–type (MVT) minerals, and potassium (K)-silicate minerals in these rocks, which preserve a regional hydrothermal signature. Constraints were placed on the conditions of water-rock interaction using fluid-inclusion methods, cathodoluminescence and plane-light petrography, stable isotopic analyses, and organic maturity data. Homogenization temperatures of two-phase aqueous fluid inclusions in dolomite, sphalerite, and quartz range between 65 and 120°C. Freezing data suggest a Na-Ca-Mg-Cl-H2O fluid with salinities between 13 and 28 wt.% NaCl equivalent. The pervasive dolomitization of Paleozoic rocks on and adjacent to the Wisconsin arch was the result of water-rock interaction with dense brines at elevated temperatures, and it was coeval with regional trace MVT mineralization and K-silicate diagenesis. A reevaluation of the Dorag (mixing-zone) model for dolomitization, in conjunction with convincing new petrographic and geochemical evidence, has ruled out the Dorag model as the process responsible for pervasive dolomitization along the Wisconsin arch and adds to the abundant body of literature that casts serious doubt about the viability of the Dorag model in general.

John Luczaj is an assistant professor of earth science in the Department of Natural and Applied Sciences at the University of Wisconsin–Green Bay. He earned his B. S. degree in geology from the University of Wisconsin–Oshkosh. This was followed by an M.S. degree in geology from the University of Kansas. He holds a Ph.D. in geology from Johns Hopkins University in Baltimore, Maryland. His recent interests include the investigation of water-rock interaction in Paleozoic sedimentary rocks in the Michigan Basin and eastern Wisconsin. Previous research activities involve mapping subsurface uranium distributions, reflux dolomitization, and U-Pb dating of Permian Chase Group carbonates in southwestern Kansas.


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