Mineralogy and geochemistry of Devonian detrital rocks from the Iberian Range (Spain)

Clay Minerals ◽  
1995 ◽  
Vol 30 (4) ◽  
pp. 381-394 ◽  
Author(s):  
B. Bauluz Lazaro ◽  
M.J. Mayayo Burillo ◽  
C. Fernandez-Nieto ◽  
J.M. Gonzalez Lopez
Keyword(s):  
Chemical Composition ◽  
Clay Minerals ◽  
Source Area ◽  
Weathering Processes ◽  
Marine Deposits ◽  
Mineral Characteristics ◽  
Iberian Range ◽  
Depositional Evolution ◽  
High Degree

AbstractTwo profiles in Devonian marine deposits have been studied, consisting of pelites, subgreywackes, greywackes and quartzites. Quartz and clay minerals are major components and feldspar and calcite are minor ones. Phyllosilicates in the fine fractions are kaolinite and illite; kaolinite has a high degree of ordering; illite is predominantly of a 1Md polytype, with low Na content and poor crystallinity and has a phengitic composition in greywackes, whereas in pelites it is muscovitic in composition. Both phyllosilicates may be inherited from a source area with intensive weathering processes, although illite may also be a diagenetic phase. These mineral characteristics indicate that the Devonian rocks did not reach the anchizone boundary in their post-depositional evolution.The chemical composition of pelites and subgreywackes reveals a high degree of chemical maturity. Chondrite-normalized REE patterns indicate a higher degree of weathering of these Devonian sediments than of Post-Archaean Australian Shales (PAAS), possibly as a consequence of sedimentary recycling processes. The REE patterns of the Devonian rocks in addition to the high Th/Sc, La/Sc and Th/Co ratios suggest a felsic composition of the primitive source area, probably a K-rich granite.

Genesis of kaolinite from Albian sedimentary deposits of the Iberian Range (NE Spain): analysis by XRD, SEM and TEM

Clay Minerals ◽  
2008 ◽  
Vol 43 (3) ◽  
pp. 459-475 ◽  
Author(s):  
B. Bauluz ◽  
M. J. Mayayo ◽  
A. Yuste ◽  
J. M. González López
Keyword(s):  
Source Area ◽  
Weathering Processes ◽  
Sedimentary Deposits ◽  
Iberian Range ◽  
Different Types ◽  
The Matrix ◽  
High Degree ◽  
Feldspar Dissolution ◽  
Ne Spain

AbstractThe kaolinite from Albian sedimentary deposits (Escucha and Utrillas Formations) of the Iberian Range (Spain) have been investigated. This research has shown the presence of different types of kaolinites (detrital and diagenetic) along with micaceous phases in these deposits. Detrital kaolinites show anhedral morphology, low crystallinity and a degree of ordering as well as the presence of interstratified smectite layers. They constitute the matrix of the claystones and siltstones and were probably formed as a consequence of intense weathering processes in the source area during the warm period of the early Cretaceous. Diagenetic kaolinites have been recognized in the sandstones and siltstones, with kaolinite growing between ‘expanded’ mica flakes and vermiform and euhedral kaolinite forming the matrix. They have euhedral morphologies, high crystallinity and a high degree of ordering. They grewin situas a response to incipient diagenesis by K-feldspar dissolution and/or organic acid-rich fluids derived from the maturation of organic matter in shales.

scholarly journals PESTRÉ SEDIMENTY OTTNANGU V BRNĚ-KOHOUTOVICÍCH

2018 ◽  
Vol 25 (1-2) ◽  
Author(s):  
Pavla Tomanová Petrová ◽  
David Buriánek ◽  
Karel Kirchner ◽  
Oldřich Krejčí ◽  
František Laufek ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Clay Minerals ◽  
Heavy Fraction ◽  
Parent Rock ◽  
Fine Grained ◽  
Sediment Layers

The reddish coloured sediment layers (up to 5 m thick) were found within building pit in the Brno-Kohoutovice on the Libušina třída Avenue (NW part of Brno). These sediments were assigned to the Ottnangian based on characteristic pseudoassociation of microfossils. Smectite or illite/smectite dominates over kaolinite among the clay minerals. Minerals typomorphic for granitoids of the Brno Massif, i.e. epidote, amphibole and altered titanite, absolutely dominate (99 mod. %) within the assemblage of translucent heavy fraction. Minerals like garnet and staurolite which are typical for the Ottnangian sediments in this region, are presented only in accessoric amount. The chemical composition of the studied sediments is located between the chemical composition of granodiorites of the Brno Massif and Neogene clays. Relatively high content of Zr, Hf and HREE, which is interpreted as result of presence of very fine grained zircon in studied sediments, is characteristic. High content of SiO2 and comparatively low contents of Al2O3 and Fe2O3 indicates non-lateritic type of weathering. The chemical composition of studied sediments reflects semiarid to humid paleoclimate that the granitoids of the Brno Massif as parent rock have undergone.

Smectite, chlorite and a regular interlayered chlorite-vermiculite in soils developed on a small serpentinite body Massif Central, France

Clay Minerals ◽  
1976 ◽  
Vol 11 (2) ◽  
pp. 121-135 ◽  
Author(s):  
J. Ducloux ◽  
A. Meunier ◽  
B. Velde
Keyword(s):  
Chemical Composition ◽  
Clay Minerals ◽  
Closed System ◽  
Soil Profile ◽  
Crystalline Rocks ◽  
Soil Profiles ◽  
Massif Central ◽  
Three Stages ◽  
Image Position ◽  
Chemical Migration

AbstractThree soil profiles developed on a serpentinite body (La Rochel'Abeille, near Limoges) show three stages of weathering. All soils contain iron-rich smectites and secondary chlorites. The latter are very silica-rich, more so than 14 Å chlorites from crystalline rocks. In the (B)1g horizon of the hydromorphic profile, these minerals seem to give a reaction of the type:This reaction, typical of a closed system, appears to be operative in a soil profile which is certainly, in part, open to chemical migration. The chemistry of the weathered serpentinite and the chemical composition of newly formed minerals as well as those of the serpentinite are used to indicate the chemiographic relations of clay minerals formed in the weathering profiles.

Analyse et simulation des transferts geochimiques au sein d'un aquifere; la nappe de Beauce et l'alteration des Sables de Fontainebleau

2001 ◽  
Vol 172 (3) ◽  
pp. 367-381 ◽  
Author(s):  
Anne Bariteau ◽  
Medard Thiry
Keyword(s):  
Ground Water ◽  
Mass Balance ◽  
Clay Minerals ◽  
Pyrite Oxidation ◽  
Sandy Soils ◽  
Quaternary Period ◽  
Calcite Dissolution ◽  
Weathering Processes ◽  
Unsaturated Sands ◽  
White Sands

Abstract Ground-water mineralisation results mainly from alteration of the confining aquifer along its flow path. Such alteration may deeply alter the aquifer formations and have to be recognized to avoid misinterpretation of the altered facies. The Beauce ground-water and the Fontainebleau Sands aquifer have been studied to highlight such ground-water/aquifer interactions. The Beauce ground-water is contained in thick limestone series (Oligo-Miocene) interlayered with the Fontainebleau Sands (Stampian). The sands show various facies related to the geomorphology: dark and reduced facies are restricted to the bottom of the formation in the center of the plateaux, oxidized yellowish facies occur in the vadose zone beneath the plateaux, and bleached white facies at the edge of the plateaux. These facies result from modern alternations due to the ground-water and the recharge waters. The water and rock chemistry allows to investigate the diverse stages of the geochemical and weathering processes that occur within the aquifer, and to calculate accurate mass balance of the dissolved and exported elements. Hydrochemistry of the Beauce ground-water: Each compartment of the aquifer can be characterised by one type of water. (1) The aquifer is recharged by two types of water. The waters coming from the limestone plateau are calco-carbonaceous, oxygenated and lightly mineralised, especially in silica; those coming from the sandy soils near the outcropping sand area are more acidic, oxygenated and very lightly mineralised. (2) The ground-water of the limestone aquifer are oxygenated, oversaturated with respect to quartz and near equilibrium with calcite and cristobalite. Silica comes from the alteration of the clay minerals and/or the cherts in the limestones. The ground-waters are of calco-carbonaceous type, have pH values approx 6.5. They are characterised by a relative low mineralisation (average 460 mg.kg (super -1) ), an oversaturation with respect to quartz and the presence of dissolved oxygen (Eh around +450 mV). (3) The ground-water of the dark sands aquifer contains hydrogen sulfur and is oxygen free (Eh around +140 mV), with relatively high Fe and SO 4 contents related to the pyrite oxidation. It is also characterised by a relatively high SiO 2 and cations contents resulting from the alteration of the alumino-silicates. (4) The ground-water of the bleached sands aquifer is strongly diluted by the recharge waters from the sandy soils. It remains oversaturated with respect to quartz and has the ability to hydrolyse the alumino-silicates. Geochemical modelling: The ground-water/aquifer interactions have been modelled. The modelisation takes into account the kinetics of water/rock interactions and was done by successive steps. (1) Alteration of the dark sands by the ground-water leads to dissolution of the pyrite and the calcite. The pyrite oxidation and the "buffering" calcite dissolution directly depend on oxygen availability in the ground-water. Muscovite remains stable, feldspars and glauconite are partially dissolved and Al-smectite forms. The composition of the resulting simulated oxydized sands agrees with the analyses. (2) The leaching of these oxydized sands by the calco-carbonaceous recharge water leads to simulate leached sands of similar composition than the unsaturated sands beneath the plateau. Muscovite remains stable; smectite, kaolinite and hematite form. (3) The final leaching of the former leached sand by the acidic recharge water brings about to simulate bleached sand. The muscovite stability, smectite dissolution and kaolinite precipitation are in conformity with the composition of the white sands. Nevertheless, the modelisation is not fully in agreement with the mass balance calculations. The discrepancy mainly comes from the simulation of excessive amounts of clay minerals and iron oxides. This precipitation excess may be related to the fact that the precipitation kinetics and/or of the organic complexations have not been taken into account in the model. Even if there is discrepancy in the mass balance, the thermokinetic simulations validate the reaction path which leads to the Beauce ground-water mineralisation and the Fontainebleau Sands bleaching. Discussion: Ground-water chemistry thus provides information on the alteration processes and indicates that the alterations are presently active. The white facies results from the progressive alteration of dark primary sands. This bleaching leads to a complete change of the geochemical characteristics of the Fontainebleau Sands. These alterations come with the export of a large amount of material corresponding to a geochemical lowering of the Beauce Plateau of at least 10 m during the Plio-Quaternary period. This example illustrates the importance of the sub-surface alterations due to ground-water flow, that are difficult to gauge from outcrop observation only.

scholarly journals Clay mineral genesis and chemical evolution in the Miocene sediments of Somosaguas, Madrid Basin, Spain

Clay Minerals ◽  
2007 ◽  
Vol 42 (2) ◽  
pp. 187-201 ◽  
Author(s):  
O. Fesharaki ◽  
E. García-Romero ◽  
J. Cuevas-González ◽  
N. López-Martínez
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Clay Minerals ◽  
Analytical Electron Microscopy ◽  
Source Area ◽  
Alluvial Fan ◽  
Granitic Rocks ◽  
Central System ◽  
Transmission Electron ◽  
Spanish Central System

AbstractA mineralogical and microtextural study of Somosaguas Miocene deposits, located in the Madrid Basin (western Madrid, Spain), was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and optical microscopy, whereas crystal chemistry data were obtained by analytical electron microscopy-transmission electron microscopy and electron icroprobe analysis. Four stratigraphic sections were studied, compising detrital rocks representing intermediate and distal facies from alluvial fan deposits. The predominant source area of these sediments was the granitic rocks of the Spanish Central System with a lesser contribution of metamorphic rocks. Clayey arkoses are the most abundant rocks of these sections, typical of granite alteration under warm, semi-arid climates. The mineralogy is characterized by phyllosilicates, followed by feldspars and quartz. The data obtained reveal mineral mixtures of detrital (quartz, feldspars, kaolinite, micas and chlorite), transformed (illite and beidellite) and neoformed (montmorillonite) origin. Clay minerals resulted from interactions between detrital minerals and meteoric waters. Two trends of degradation of micas are detected. The first shows a transition from muscovites and dioctahedral illites, to beidellites. The other trend is defined by the biotite degradation to beidellites with different layer charge and octahedral Fe content. Montmorillonites were neoformed from the hydrolysis and weathering of primary minerals (feldspars and muscovite). Magnesian clay minerals such as sepiolite, palygorskite and trioctahedral smectites, extremely abundant in the centre of the basin, were not detected in Somosaguas sediments.

scholarly journals Vertical zonality of fractionated granite plutons reflected in zircon chemistry: the Cínovec A-type versus the Beauvoir S-type suite

2012 ◽  
Vol 63 (5) ◽  
pp. 383-398 ◽  
Author(s):  
Karel Breiter ◽  
Radek Škoda
Keyword(s):  
Czech Republic ◽  
Chemical Composition ◽  
Vertical Section ◽  
Chemical Compositions ◽  
Massif Central ◽  
Intermediate Unit ◽  
Type Granite ◽  
Vertical Changes ◽  
High Degree ◽  
Vertical Zonality

Abstract We studied vertical changes in the chemical composition of zircon from two contrasting Variscan granite systems. The Beauvoir system (Massif Central, France) composed of three successive intrusions (B1, B2, B3) represents typical peraluminous S-type granite extremely enriched in P, F, Li, Rb, Cs, Be, Sn, Nb, Ta, and poor in Zr, Th, REE and Y. The Cínovec system (Krušné hory Mts/Erzgebirge, Czech Republic/Germany) composed of two successive intrusions (protolithionite granite, zinnwaldite granite) is only slightly peraluminous, P-poor, F, Li, Rb, Cs, U, Th, REE, Y, Sc, Sn, W, Nb, Ta-rich granite, which may be classified as A-type. In both localities, the most fractionated intrusions are located on the top of the system. Samples from borehole GPF-1 (Beauvoir) represent an 800 m long vertical section through the entire granite stock, while CS-1 borehole (Cínovec) reached a depth of 1600 m. Chemical compositions of zircons from both granite systems show distinct vertical zonality, but their shape and elemental speciation is highly contrasting. At Beauvoir, zircon shows a remarkable increase in Hf-content from 2-4 wt. % HfO2 (~0.03 apfu Hf) in the deepest B3-unit to 15-19 wt. % HfO2 (up to 0.18 apfu Hf) in the uppermost B1-unit. The highest contents of F, P, and U were detected in the intermediate unit B2 at a depth of 400-600 m. At Cínovec, Hf shows only moderate enrichment from ca. 2 wt. % HfO2 in the deeper protolithionite granite to 5-10 wt. % HfO2 in the uppermost part of the zinnwaldite granite. High contents of Th (3-8 wt. % ThO2) are entirely bound in the uppermost section of the granite copula to a depth of 200 m, but below this level the contents only sporadically exceed 1 wt. % ThO2. Concentrations of U, Y, HREE, Sc and Bi also reach their highest values in the uppermost parts of the zinnwaldite granite, but their decrease downward is much gentler. Extreme enrichment of outer zones of zircon crystals from some granites with Hf or high contents of Th, U, REE, Y, Nb and of some other elements in zircons from other localities is not considered to be a specific phenomenon characterizing melts of A- or S-type granite, but reflects a high degree of fractionation of systems rich in Na and F.

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