Suchergebnisse

Samples were obtained in the framework of TASYO (MAR-98-0209), MOUNDFORCE—EUROCORE-EUROMARGINS 01-LEC-EMA06F and INDEMARES-LIFE projects, on board of RVs Hespérides and Cornide de Saavedra. The authors thank M. Mar Abad of the Centro de Instrumentación Científica (CIC) of Granada, Andalusian project RNM-1897 and PAIDI-groups RNM-328 and RNM-363 of the Andalusia Government for the financial support, as well as the Supercomputational Center of the Granada University (UGRGRID), the Centro Técnico de Informática of CSIC and the Spanish institute of Oceanography for providing samples of mud volcanoes. We acknowledge the Arizona State University National SIMS Facility supported by the US National Science Foundation grant (EAR-0948878). ; Clay dehydration at great depth generates fluids and overpressures in organic-rich sediments that can release isotopically light boron from mature organic matter, producing 10B-rich fluids. The B can be incorporated into the tetrahedral sites of authigenic illite during the illitization of smectite. Therefore, the crystal-chemical and geochemical characterization of illite, smectite or interlayered illite–smectite clay minerals can be an indicator of depth (temperature) and reactions with the basin fluids. The aim of this study was to determine the detailed clay mineralogy, B-content and isotopic composition in illite–smectite rich samples of mud volcanoes from the Gulf of Cádiz, in order to evaluate interactions of hydrocarbon-rich fluids with clays. Molecular modeling of the illite structure was performed, using electron density functional theory (DFT) methods to examine the phenomenon of B incorporation into illite at the atomic level. We found that it is energetically preferable for B to reside in the tetrahedral sites replacing Si atoms than in the interlayer of expandable clays. The B abundances in this study are high and consistent with previous results of B data on interstitial fluids, suggesting that hydrocarbon-related fluids approaching temperatures of methane generation (150 °C) are the likely source of B-rich illite in the studied samples. ; CADHYS project RNM-3581 ; Doctoral scholarship of the Junta de Andalucia (Spain)

The present work is conducted on the Paleozoic (Ordovician) Khabour and the (Silurian) Akkas shales in the Akkas-1 well of western Iraq. The study is aiming to determine the implications of clay mineral transformation, organic mineral distribution and maturity of hydrocarbon generation, using X-ray diffraction (XRD), scanning electron microscopy (SEM) in addition to organic matter concentrations. In the shale of the Khabour Formation, amorphous organic matter is common and includes various Tasmanite-type organic matter, vitrinite, inertinite, and bituminite. The main clay minerals observed include illite, chlorite, kaolinite, in addition to mixed-layer illite-smectite and rare smectite. In Silurian shale, high content of organic matter is recorded in addition to abundant vitrinite and low content of grainy organic matter (Tasmanites) and pyrite. Illite and kaolinite are commonly found in addition to chlorite and illite-smectite clay minerals. Conversion of smectite to mixed-layer illite-smectite (I-S) and an increase in vitrinite reflectance are commonly observed below 2500 m depth in the studied formations, which coincides with oil and gas generation. These results could be used as an indication of higher maturity and hydrocarbon generation in the deeply buried shale of the Khabour and Akkas formations in western Iraq.

AbstractThe paper discusses the mineralogical and chemical stability of the Oxford Clay as a landfill liner for the containment of domestic waste. The results from a series of batch equilibrium experiments with the mudrock and a synthetic leachate are compared with samples of a liner cored from a 15‐year‐old site in the Formation. The effects of leachate on the Clay include mineral dissolution, exchange of cations, particle‐size reduction and collapse of illite‐smectite. In situ mixed‐assemblage mineral liners, such as the Oxford Clay, are capable of attenuating leachate components and buffering acid leachates whilst the predominant clay minerals, i.e. illite and kaolinite, remain stable. Alterations to the mineralogy and chemistry of the samples resulting from both short‐term and long‐term exposure to leachate are discussed with reference to the implications to landfill practice.

Abstract. Magnetic measurements, mineralogical and geochemical studies were carried out on surface soil samples in order to find possible relationships and to obtain environmental implications. The samples were taken over a square grid (500 × 500 m) near the city of Coimbra, in central Portugal. Mass specific magnetic susceptibility ranges between 12.50 and 710.11 × 10−8 m3 kg−1 and isothermal magnetic remanence at 1 tesla values range between 253 and 18 174 × 10−3 Am−1. Chemical analysis by atomic absorption spectrometry shows that the concentration of various toxic elements was higher than the mean background values for world soils. Higher values of susceptibility and toxic elements content were reported near roads and rivers. Urban pollution and road traffic emission seem to be the main influence for these values. A semi-quantitative X-ray diffraction study has been carried out on a representative set of subsamples, using peak areas. Illite (average 52%), kaolinite (average 55%), chlorite (average 6%) and irregular illite-smectite mixed-layers (average 9%) are the major clay minerals groups identified. Mineral composition of total fraction confirms the presence of magnetite/maghemite. The clay minerals results point to a contrast in the behavior of the main clay minerals: illite, chlorite, and kaolinite (also, smectite in some samples), which are generally in agreement with the magnetic and geochemical data. The results showed that magnetic measurements are a sensitive, fast, inexpensive and robust method, which can be advantageously applied for studying soils affected by urban and road pollution.

rentgenpulverdifrakcija ir viena no galvenajām mālu minerālu polimorfisma pētniecības metodēm. šī pētījuma mērķis ir iegūt neorientētu paraugu difraktogrammas, kurās politipiem atbilstošie maksimumi būtu ar analīzei atbilstošu intensitāti.

Reseña de la comunicación presentada en el EUG VII European Union Geosciences (Estrasburgo, Francia, 4-8 abril 1993) ; Althoug superposition of retrograde metamorphic events on higher, prograde assemblages is universally recognized and accepted for greenschist facies and higher grade metamorphic rocks, clay mineral assemblages are generally interpreted within a prograde setting. ; Finnacial support: Project PB022801, Research Group 4065, NSF Project EAR-9104565 ; Peer reviewed

Elektroniskā versija nesatur pielikumus ; ANOTĀCIJA Disertācijā "Illīta struktūras glacigēnajos nogulumos Latvijā" pētītas dažādas illīta struktūras un to iespējamā pārmantojamība glacigēnajos nogulumos materiāla asimilācijas ceļā. Pētījumā iegūti rezultāti par illīta struktūrām glacigēnajos nogulumos. Diskutēts par iespējamo illīta politipu jutību uz ģeoloģiskās vides apstākļu izmaiņām. Izmantojot rentgenstaru pulverdifrakcijas metodi (XRD), veikta illīta 1Md politipā sastopamo 1M un 2M1 politipu nebazālo refleksu diagnostika. Izvērtētas paraugu frakcionēšanas metodes un paraugu sagatavošanas veidi XRD analīzei, kā arī optimizēti XRD uzņemšanas parametri. Konstatēts, ka detrītiskas cilmes 2M1 illīts ar 1Mcv un 1Mtv politipu piejaukumu ir dominējošais politips 1Md struktūrās glacigēnajos nogulumos, kas ievākti Ulmāles un Kupravas pētījumu rajonos, < 2; 1; 0,4 μm frakcijās. Glacigēnajos un zem tiem paguļošajos nogulumos konstatēta attiecību nevienādība starp 1Mcv un 1Mtv illīta politipiem. ; ANNOTATION Various illite structures and probable inheritance of these structures in glacigenic deposits caused by assimilation of the material have been studied in dissertation "Structures of illite in glacigenic sediments of Latvia". Possible sensitivity of illite polytypes depending on various geological conditions is discussed. Diagnostic of unbasal reflexes of 1M and 2M1 polytypes found in illite polytype 1Md is performed applying x-ray powder diffraction method (XRD). Fractioning methods of the samples and sample preparation for XRD methods are evaluated, as well as XRD recording parameters were optimised. It is found out that detritic origin illite polytype 2M1 with admixture of 1Mcv and 1Mtv polytypes dominates in 1Md structures of glacigenic deposits fractions < 2; 1; 0.4 μm in the samples taken at the Ulmāle and Kuprava study areas. Inconsistency of 1Mcv and 1Mtv polytypes is found in glacigenic and underlying deposits.