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The Parauapebas Formation and Igarapé Cigarra Formation constitute two Neoarchean extrusive units inserted in the metavolcanosedimentary sequence (~2.76 Ga) of the Grão Pará Group, Itacaiúnas Supergroup, being represented by basaltic seeps underlain and overlain by jaspillites, rhyolites, volcanoclastic rocks, and gabbro dikes/sills, thus being inserted in the Serra Sul district in the Mineral Province of Carajás, Pará. This study aimed to understand the igneous processes involved in the genesis of these basalts from both geological formations, supported by field, petrographic, and geochemical data. Inserted in the metavolcanosedimentary sequence of the Grão Pará Group (Carajás Domain), the basalts and basalt andesites, the most abundant types of the Parauapebas and Igarapé Cigarra Formations, occur as successions of massive and amygdaloidal lava flows. The study of core samples from nine stratigraphic holes that intersected basaltic rocks of the two geological formations in body S11D (Serra Sul) showed that these rocks reach thick layers with different characteristics, ranging from aphanitic to phaneritic. The basalts are dark green, aphanitic, phaneritic, thin to medium, and hypocrystalline. They show preserved igneous texture being commonly seriated as inequigranular, intersertal, ophitic, subophytic, intergranular, branching, and swallow tail. Its essential primary constituents are plagioclase, orthopyroxene, and clinopyroxene, and its accessory constituents are titanite and apatite. Chlorite, epidote, quartz, and calcite occur as secondary phases and are interpreted as the products of ocean-bottom hydrothermal alteration and/or incipient metamorphism. In general, the studied volcanic rocks stand out for SiO2 content between 47.00 and 56.04%, high alkali contents (4.70-7.50%), K2O contents between 0.40 and 3.97%, TiO2 (< 1.0%), and MgO between 4.90 and 8.16%. In the classification diagrams, the samples are situated in the fields of basalts, basalt andesites, trachyandesite, and trachybasalt basalts, in the transition of the toleitic and calc-alkaline series. The basalts of the Parauapebas and Igarapé Cigarra Formations were probably formed in an intraplate continental environment influenced by subduction zones. Therefore, the Grão-Pará Basin was probably formed in a convergent regime related to a subduction-type environment. The geochemical data indicate that the studied rocks of the Parauapebas Formation and the Igarapé Cigarra Formation correspond to basalts of calc-alkaline affinity. Two facies were identified in the Parauapebas Formation, namely, the Amendoim and Violão facies. In the Igarapé Cigarra Formation as well, the following facies were identified: Jacaré and Três Marias. Based on the geochemical interpretation, it is assumed that the rocks studied are arc-like continental basalts, which are formed in a subduction environment with influence from a possible asthenospheric source and modified by crustal contamination. [ABSTRACT FROM AUTHOR]

A new mollusc material from the Ilona Valley Section (Mátra Mts, Hungary) is investigated. Strata of the section represent the Ilonavölgy Member of the Pétervására Sandstone Formation. Based on geochemical data and mollusc biostratigraphy these deposits appear to be early Ottnangian in age. The mollusc fauna displays much higher diversity than was recognized in earlier studies from the locality in question and from other Ottnangian sites in the Paratethys. The rich material verifies the extended stratigraphic and palaeogeographic ranges of numerous taxa, and allows of designating 12 new gastropod species: Clanculus s. l. gulyasi n. sp., Gibbula kralli n. sp., Calliostoma nandori n. sp., Ormastralium erazmusi n. sp., Sconsia landaui n. sp., Cirsotrema kokayi n. sp., Ocinebrina deaki n. sp., Calagrassor mathiasi n. sp., Clavatula s. l. barnabasi n. sp., Clavatula s. l. istvani n. sp., Dentimargo barnai n. sp., Solatisonax pozsgayae n. sp. With 106 figures and 1 table. [ABSTRACT FROM AUTHOR]

The geochemistry of actinides under reducing conditions in a deep geological nuclear waste repository is characterized by low solubility and strong sorption to mineral surfaces. The quantification of actinide migration (i.e. diffusion) at resulting concentration levels requires an analytical method able to determine actinide concentrations down to ultra-trace levels (≈fg g−1). In the actual study, such an analytical procedure was tested by using accelerator mass spectrometry (AMS), one of the very few analytical techniques that can presently meet those requirements. Specimens simulating the sample matrix representative for a diffusion experiment in natural clay rock were produced by spiking clay rock powders (Opalinus Clay or Callovo-Oxfordian Clay) and aliquots of corresponding pore waters with the actinide nuclides 233U, 237Np, 244Pu, and 248Cm in amounts ranging from approximately 3 × 10−19 to 5 × 10−15 mol per sample (≈0.07–1000 fg per sample). The actinide nuclides were separated as group via Fe(OH)3 co-precipitation and then analyzed sequentially with AMS. During such analysis a decrease in count rates by up to a factor of 6 was observed in high-matrix clay rock samples compared to low-matrix standard solutions. Since the chemical yield of the actinides in the Fe(OH)3 co-precipitation step prior to analysis turned out to be quantitative, this observation must originate from a reduction of the sputter rate of the actinide nuclides in the AMS ion source, which can be described partly as a dilution effect. By determining chemical-ionization-yield factors, suitable non-isotopic tracers were identified for 237Np and 243Am. This allowed for the concurrent determination of all actinide nuclides at levels down to 3 × 10−19 mol per sample. Different actinides in a deep geological formation may be present in concentration ranges differing by orders of magnitude depending on their chemical form and solubility. Such concentration spreads were simulated by preparing clay rock/pore water samples where each individual sample contained 233U, 237Np, 244Pu, 243Am, and 248Cm at quantities ranging from approximately 3 × 10−19 to 4 × 10−15 mol per sample. The presented sample preparation procedure, in combination with the extraordinary detection sensitivity of AMS allows for the simultaneous determination of diffusion profiles of several actinides at ultra-trace levels within one experiment. [ABSTRACT FROM AUTHOR]

Mapping of regolith is significant to identify and discriminate geomorphic expression, regolith evolution, weathering histories and assistance in clarification of relationships between parent and surface materials. In this research work, the hydrothermally altered regolith of Western Jahajpur Belt, Bhilwara, India is studied using ASTER and AVIRIS imageries by PCA, decorrelation stretching supervised classification image processing methods. Results of decorrelation stretching of ASTER spectral bands 6, 7 and 9 showed the regolith in blue, green and red colour with the associated geological formations. Analyses of VNIR-SWIR spectral bands of ASTER by PCA showed the bed rocks associated to the regolith green, yellow, white and red colours, respectively. The minerals of the regolith and parent geological formations are identified using AVIRIS data by supervised classification and endmember spectral analyses. The study also identified six regolith-landforms which include the regolith (vegetation cover), crop land (vegetation cover), water, crop land with vegetation, alluvium and regolith (ferruginous and calcareous mineral zone). The discrimination of regoliths and geological formations are verified in the field and confirmed by XRF and ICP-MS geochemical analysis of samples. [ABSTRACT FROM AUTHOR]

The hinterland of Campo is marked by Archean, Paleoproterozoic, and Cretaceous geological formations. Petrographic, mineralogical and geochemical analyzes of beach sediment samples were performed to determine the origin, alteration, and paleoclimate of the various coastal sediment layers and to reconstruct the structural context of the source region. The beach sediments are fine to medium-grained in size. Morphoscopic examination showed a predominance of very angular and shiny quartz grains. These data reflect a relatively close source with transport in a fluvial environment. The Chemical Index of Alteration (CIA: average = 79.94%), Plagioclase Index of Alteration (PIA: average = 85.31%), as well as the A–CN–K and (A-K)-C-N triangular diagram, show that the weathering affected the source area rocks. The ratios of SiO 2 /Al 2 O 3 , K 2 O/Na 2 O, and the chemical composition variation index (ICV ∼ 1.32) show that the sediment samples are immature to mature in terms of texture and chemical composition. Al 2 O 3 /TiO 2 ratio values ranged from 3.04 to 33.44, indicating an intermediate to felsic rock signature, confirmed by Zr vs TiO 2 , La/Sc, and Th/Co binary diagrams. Geochemical results reveal a passive marginal continental environment. The passive margin emerged during the opening of the South Atlantic Ocean, which is compatible with the overall geology and structural setting of the studied area. • Campo beach sediment textural vary from clays to silt. • Beach sediments derived from moderate to intense source area weathering. • The source rocks vary from felsic to mafic rocks. • Campo beach sediments are compositionally immature to mature. • The source rock is controlled by sedimentary processes and diagenetic impacts. [ABSTRACT FROM AUTHOR]

La Réunion Island has been considered an attractive target for geothermal exploitation since the 1970s. However, to date, the island's geothermal resources are not being used. Here we use for the first time, a Geographic Information System (GIS) as a decision-making tool to target the most favorable zones for exploitation of moderate and high temperature geothermal resources. All data acquired since the 1970s (geology, geophysics, geochemistry) in addition to environmental constraints such as protection of the National Park that was recently classified as a UNESCO World Heritage Site, were analyzed using the weighted overlay method to delineate favorable areas for local geothermal exploration. Three thematic maps were constructed: geological and structural indicators, thermal indicators, and geophysical indicators. Cross-analysis of these maps highlights two zones that have high geothermal potential; six zones with unconfirmed geothermal potential; and two zones located within the National Park protected area and thus subject to stringent exploitation regulations. It appears that, while thermal anomalies exist in several areas, permeability of the geological formations is low or insufficient for traditional geothermal utilization. Future exploration phases should assess the feasibility of using enhanced geothermal system (EGS) technologies to obtain a satisfactory economic return. [ABSTRACT FROM AUTHOR]