Formation of Faden Quartz Druses in Mid-Carboniferous Sandstones of the Donetsk Basin

2018 ◽  
pp. 155-162
Author(s):  
Oleg Krisak ◽  
Vyacheslav Bezrukov
Keyword(s):  
Conceptual Framework ◽  
Fluid Inclusions ◽  
Sedimentary Rocks ◽  
Peculiar Feature ◽  
Donetsk Basin ◽  
Tectonic Regime ◽  
Two Stages ◽  
Mechanism Of Growth

The chapter addresses the mechanism of growth of druses of faden quartz in a tectonically deformed sandstone. A peculiar feature of this type of quartz, the so-called “white tape” represented by fine subparallel cracks with fluid inclusions, appears highly informative about the genesis of the mineral and tectonic regime of its growth. Two stages of formation of druses of faden quartz are recognized. The suggested mechanism is checked for contradictions by means of the event bush method. The proposed event bush model appears to describe a wider range of quartz formation environments and therefore may serve as a conceptual framework for various models of quartz growth in sedimentary rocks.

Past hot fluid flows in limestones detected by Δ47–(U-Pb) and not recorded by other geothermometers

Geology ◽  
2020 ◽  
Vol 48 (9) ◽  
pp. 851-856 ◽  
Author(s):  
Benjamin Brigaud ◽  
Magali Bonifacie ◽  
Maurice Pagel ◽  
Thomas Blaise ◽  
Damien Calmels ◽  
...  
Keyword(s):  
Fluid Inclusions ◽  
Thermal History ◽  
Vitrinite Reflectance ◽  
Fluid Flows ◽  
Aqueous Fluid ◽  
Rift System ◽  
History Of ◽  
Clumped Isotope ◽  
Two Stages ◽  
Rock Eval

Abstract Geothermometers are commonly used to reconstruct the diagenetic and thermal history of rocks. However, characterizing the timing, origin, and temperature of paleofluid flow remains challenging because it must be assessed indirectly through the analysis of microscopic cements that precipitate and fill intergranular spaces during fluid circulation. Here, we measure both the clumped isotope (Δ47) temperature and in situ U-Pb age of individual diagenetic calcite cements within a sedimentary section of the Paris Basin (France), whose thermal history has been previously inferred to be <60 °C. We show that cementation occurred during two stages associated with major events at the western European lithospheric scale: (1) the Bay of Biscay rifting (Late Jurassic–Early Cretaceous), and (2) north-south Pyrenean compression (Eocene) followed by east-west extension during the European Cenozoic rift system event (Oligocene). Related to both events, we report unexpectedly hot fluids, up to 110 °C, contrasting with the lower temperatures inferred from other geothermometers (e.g., fluid inclusions, clay minerals, apatite fission tracks, maturity of organic matter by Rock-Eval pyrolysis, or vitrinite reflectance). These high temperatures (>70 °C) have been measured for calcite cements containing single-phase aqueous fluid inclusions, challenging the commonly accepted assertion that the absence of nucleation of a vapor phase indicates crystallization at low temperature (∼<70 °C). We suggest that the kinetics of mineralization events prevented the recording of short-lived hot fluid flows by other geothermometers.

scholarly journals Microthermometry and Raman spectroscopy of fluid inclusions from El Vapor gold mineralizations, Colombia

2018 ◽  
Vol 22 (3) ◽  
pp. 151-158
Author(s):  
Camilo E. Dorado ◽  
Juan C. Molano
Keyword(s):  
Raman Spectroscopy ◽  
Fluid Inclusions ◽  
Gold Mineralization ◽  
Sedimentary Rocks ◽  
Gold Deposition ◽  
Type I ◽  
Fluid Mixture ◽  
Quartz Crystals ◽  
Type Iv ◽  
Isothermal Fluid

Epigenetic El Vapor gold mineralization is hosted by the Segovia batholith and sedimentary rocks at both sides of El Nús fault, in the eastern flank of the Colombian Andes central cordillera. Gold mineralization is composed by continuous and discontinuous sigmoidal and stockwork veins and veinlets from a few centimeters to two meters of thickness and by hydrothermal breccias. Ore mineralogy includes Pyrite + Galena + Sphalerite + Chalcopyrite + Pyrrhotite + Proustite - Pyrargyrite. Gold is recognized as inclusions within pyrite, between quartz crystals and as fractures filled within pyrite at a late stage of mineralization. The fluid inclusions in quartz veins occur as clusters of primary inclusions and alignments of secondary and pseudo-secondary inclusions. Based on petrography and Raman spectroscopy, four types of fluid inclusions could be recognized: (1) Type I inclusions, biphasic, liquid-rich, with CO2 (v) + N2 (v) + CH4 (v) + KCl + NaCl + H2O(L), primary inclusions, (2) Type II inclusions, multi-volatile, CO2(V) + CO2(L) + N2(V) + CH4(V) + KCl + NaCl + H2O(L), primary to pseudo-secondary inclusions, (3) biphasic, liquid-rich inclusions, composed of H2O(v) +H2O(L)+KCl+NaCl with secondary origin and two different times of formation (IIIA and IIIB) (4) Type IV inclusions, very rare, three-phasic, secondary inclusions and composed by S+H2O(V)+H2O(L)+KCl+ NaCl. The microthermometric and spectroscopic analysis of fluid inclusions indicates that fluids associated with the first event of mineralization identified in El Vapor have low to moderate salinities (3.5-9.2 wt%NaCl equiv.), with trapping temperatures between 214°C and 350°C and pressures between 0.5kbar and 2.9kbar. There is evidence of the isothermal fluid mixture, and fO2 changes per reaction of fluids in the carbonaceous shales of the Segovia sedimentary rocks could influence the process of gold deposition. Hydrothermal fluids from El Vapor were near neutrality and reduced; similar features have been found in orogenic deposits hosted by turbidite sequences around the world.

HYDROCARBON INCLUSIONS IN CEMENTS OF SEDIMENTARY ROCKS AND IN VEIN MINERALS – CHARACTERISTICS AND SIGNIFICANCE

2016 ◽  
pp. 87-102 ◽  
Author(s):  
Katarzyna JARMOŁOWICZ-SZULC
Keyword(s):  
Ultraviolet Light ◽  
Fluid Inclusions ◽  
Sedimentary Rocks ◽  
Geological History ◽  
History Of ◽  
Homogenization Temperatures ◽  
Two Phases

Characteristics and results of microthermometric studies of fluid inclusions which occur in the cements of sedimentary rocks of various ages (from Cambrian through Permian to Paleogene) and filled with hydrocarbons (HCFI) are presented. The inclusions are primary and secondary in origin. They display one or two phases and fluorescence in white-blue (oil) or dull blue (methane) colours, sometimes yellow or red. Based on the fluorescence colour in the ultraviolet light a character of hydrocarbons that fill these inclusions and migrate in the rocks of the region can be estimated. The inclusions are filled with palaeofluids of different compositions. The homogenization temperatures, which correspond to the minimum estimation of the trapping temperatures in minerals, show variability with respect to the geological history of the study area. The hydrocarbon inclusions are often accompanied by brine inclusions. Wider interpretation of all microthermometric analyses was enabled due to the combination of studies on hydrocarbon and aqueous inclusions. The presence of hydrocarbons in inclusions is a proof of their occurrence and/or migration in the rocks of the regions studied.

scholarly journals Linking Alpine deformation in the Aar Massif basement and its cover units – the case of the Jungfrau–Eiger mountains (Central Alps, Switzerland)

Solid Earth ◽  
2018 ◽  
Vol 9 (5) ◽  
pp. 1099-1122 ◽  
Author(s):  
David Mair ◽  
Alessandro Lechmann ◽  
Marco Herwegh ◽  
Lukas Nibourel ◽  
Fritz Schlunegger
Keyword(s):  
Sedimentary Rocks ◽  
Structural Data ◽  
Brittle Deformation ◽  
Basement Rocks ◽  
Deformation Stages ◽  
Metamorphic Temperature ◽  
Aar Massif ◽  
Multiple Deformation ◽  
Two Stages ◽  
Peak Metamorphic Temperature

Abstract. The northwest (NW) rim of the external Aar Massif was exhumed from  ∼ 10 km depth to its present position at 4 km elevation above sea level during several Alpine deformation stages. Different models have been proposed for the timing and nature of these stages. Recently proposed exhumation models for the central, internal Aar Massif differ from the ones established in the covering Helvetic sedimentary units. By updating pre-existing maps and collecting structural data, a structural map and tectonic section were reconstructed. Those were interpreted together with microstructural data and peak metamorphic temperature estimates from collected samples to establish a framework suitable for both basement and cover. Deformation temperatures range between 250 and 330 °C, allowing for semi-brittle deformation in the basement rocks, while the calcite-dominated sedimentary rocks deform in a ductile manner at these conditions. Although field data allow to distinguish multiple deformation stages before and during Aar Massif's exhumation, all related structures formed under similar P, T conditions at the investigated NW rim. In particular, we find that the exhumation occurred during two stages of shearing in Aar Massif's basement, which induced in the sedimentary rocks first a phase of folding and then a period of thrusting, accompanied by the formation of a new foliation.

Preliminary investigations into the sorption of boron by clay minerals

Clay Minerals ◽  
1965 ◽  
Vol 6 (1) ◽  
pp. 3-16 ◽  
Author(s):  
M. E. L. Fleet
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Natural Waters ◽  
Boron Content ◽  
Sedimentary Rocks ◽  
Experimental Results ◽  
Unit Weight ◽  
Mineral Sorbent ◽  
Rate Of Sedimentation ◽  
Two Stages

AbstractThe sorption of boron by clay minerals from natural waters has been studied experimentally. The quantity of boron sorbed per unit weight of clay mineral is dependent on both the salinity and the boron content of the solution. Previous work has shown that illite is the best clay mineral sorbent, though kaolinite and montmorillonite do sorb some boron and this is confirmed by the present work. The new experimental results demonstrate that the amount of boron sorbed by illite is not affected by the original boron content of the mineral and suggest that the process of incorporation of boron into the lattice proceeds in two stages. The bearing of these experimental results on the use of boron as a palaeosalinity indicator in sedimentary rocks is discussed and this leads to the conclusion that the rate of sedimentation may also influence the boron content of such rocks.

scholarly journals Gothic-Arch Calcite from Speleothems of the Bohemian Karst (Czech Republic): Its Occurrence, Microscopic Ultrastructure and Possible Mechanism of Growth

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 866
Author(s):  
Václav Suchý ◽  
Kateřina Pachnerová Brabcová ◽  
Jiří Zachariáš ◽  
Ivo Světlík ◽  
Lenka Borecká
Keyword(s):  
Czech Republic ◽  
Fluid Inclusions ◽  
Late Stage ◽  
Hot Springs ◽  
Surface Layers ◽  
Etch Pits ◽  
Bohemian Karst ◽  
Late Pleistocene To Holocene ◽  
Mechanism Of Growth ◽  
Gothic Arch

Gothic arch calcite, a specific crystallographic variety of calcite known from some hot springs and tufa streams, has been newly recognized in the Koněprusy Caves. The gothic-arch calcite occurs on the exteriors of exotic coralloid speleothems where it coexists with scalenohedral (dogtooth) spar crystals. The crystals exhibit microscopic ultrastructural features including deeply eroded topography, etch pits, and spiky and ribbon calcite crystallites, pointing to its extensive natural etching. Many gothic-arch calcites originated as late-stage, secondary overgrowths on older, etched dogtooth calcite crystals. Its characteristic outward curvature resulted from the recrystallization of etching-liberated fine carbonate grains and newly formed needle-fiber calcite laths, which were accumulated and bound on the faces and at the bases of corroded crystals. These intimately coexisting destructive and constructive processes of carbonate crystal corrosion and growth were probably mediated by bacteria, fungi, or other microorganisms. Fluid inclusions embedded in calcite crystals point to a vadose setting and temperatures below ~50 °C. This, combined with the wider geological context, indicates that the gothic arch calcite crystals originated only during the late Pleistocene to Holocene epochs, when the cave, initially eroded by hypogene fluids in the deeper subsurface, was uplifted to the subaerial setting and exposed to the meteoric waters seeping from the topographic surface. The radiocarbon analysis shows that gothic-arch calcite crystals are generally older than ~55,000 years, but the surface layers of some crystals still reveal a weak 14C activity, suggesting that microbiologically mediated alterations of the speleothems may have been occurring locally until now.

Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism

1977 ◽  
Vol 35 ◽  
pp. 162-163
Author(s):  
Thomas R. McKee ◽  
Peter R. Buseck
Keyword(s):  
Crystallite Size ◽  
Sedimentary Rocks ◽  
Carbonaceous Material ◽  
Low Grade ◽  
X Ray ◽  
Graphitized Carbon ◽  
Transmission Electron ◽  
Heat Treated ◽  
Commercial Carbon ◽  
Metamorphic Zone

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).

Altered Fine Structure of B Lymphocytes Correlated with Defective Terminal Differentiation

1973 ◽  
Vol 31 ◽  
pp. 386-387
Author(s):  
Dale E. Bockman ◽  
L. Y. Frank Wu ◽  
Alexander R. Lawton ◽  
Max D. Cooper
Keyword(s):  
Immune Deficiency ◽  
B Lymphocytes ◽  
Plasma Cells ◽  
Present Report ◽  
Specific Antigen ◽  
Terminal Differentiation ◽  
Second Stage ◽  
Two Stages ◽  
Deficiency Diseases ◽  
Cell Line Generation

B-lymphocytes normally synthesize small amounts of immunoglobulin, some of which is incorporated into the cell membrane where it serves as receptor of antigen. These cells, on contact with specific antigen, proliferate and differentiate to plasma cells which synthesize and secrete large quantities of immunoglobulin. The two stages of differentiation of this cell line (generation of B-lymphocytes and antigen-driven maturation to plasma cells) are clearly separable during ontogeny and in some immune deficiency diseases. The present report describes morphologic aberrations of B-lymphocytes in two diseases in which second stage differentiation is defective.

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