Microbialitos da formação Codó (Aptiano Superior) às margens do rio Tocantins em São Miguel do Tocantins (TO)

The southwestern region of the São Luís-Grajaú Basin has a rare outcrop of the Codó Formation (upper Aptian) with seven outstanding microbialite bioherms along the left margin of the Tocantins river, near Imperatriz (MA). Resting on sandstones of the Grajaú Formation, the Codó Formation presents: 1) a 20 cm thick basal calcilutite with gypsite pseudomorphs and some fossil tree stems; 2) metric dark shales with carbonate nodules and thin intercalated carbonate layers, enclosing some microbial laminites; 3) a 2 cm thick upper breccia composed of microbialite fragments and other carbonate clasts, with halite hoppers on the top; 4) the carbonate bioherms, which partially overlie the extensive shales and interrupt them laterally, as well as the breccia. The bioherms in the northern part of the outcrop are thicker (<2 m) and have interbedded dark shales, whereas the southern are thinner and continuous in the vertical direction. In general, they are composed of irregular gently to strongly wavy microbial laminites, sometimes with pseudocolumnar to conical lamination. All microbialites with highest synoptic relief (<20 cm) look like columnar stromatolites on weathered lateral expositions. In plan view, the horizontal sections of these microbialites are circular to slightly elliptic, sometimes forming very small channels (N60W) filled with fine breccia. The highest bed of the northern bioherm has mixed microbial laminites and columnar stromatolites, where intercolumnar spaces were filled with microbialite clasts, fish bones, plant fragments and very small probable crustacean coprolites. Several fractures and deformation in this upper bed indicate an initial brecciation process probably caused by subaerial exposure. In microscopic scale, the lamination is smooth, diffuse, defined by subtle granulation differences of very fine granular calcite crystals within micrite, but oxide levels, dissolution surfaces or thin precipitated calcite veneers...

Caracterização petrográfica estrutural e metamorfica das rochas da região de Indiara (GO)

The region Indiara (GO) is located in southwestern of São Francisco Craton in the Internal Zone of the Brasília Belt, western part of the Tocantins Province. In this locality outcrop rocks of the Goiás Magmatic Arc. These rocks are muscovite gneiss with biotite, muscovite-biotite gneiss, biotite gneiss with muscovite and garnet, biotite-muscovite gneiss, muscovite porfiroclastic gneiss, biotite porfiroclastic gneiss, muscovite-quartz schists, garnetquartz schists, and metamafic rock (hornblende schists) as metric or kilometric lenses. The gneisses have granodioritic composition, granoblastic texture, with some portions with lepidoblastic texture, constituting a discontinuous centimeter to millimeter banding; the structure is anisotropic, marked by the preferred orientation of all the minerals. These gneisses are leucocratic, generally are inequigranular and fine to medium grained. The hornblende schists have nematoblastic texture, are inequigranular and fine to medium grained and have anisotropic structure that is given by a foliation, marked by a strong preferential orientation of the crystals of amphibole and other minerals present in the rock. The gneisses of the area are composed of plagioclase (oligoclase/andesine), quartz, microcline, muscovite, biotite, epidote, apatite, zircon, garnet, kyanite, oxides and hydroxides of iron and opaque minerals. And the metamafic rocks of Indiara region are composed mainly of amphibole, plagioclase (oligoclase/andesine), quartz, titanite, biotite, allanite, garnet, oxides and hydroxides of iron, apatite, epidote, rutile, muscovite and opaque minerals. At least three phases of deformation were observed in the rocks of area of study (Dn-1, Dn and Dn +1). The Dn phase and represented by a well-marked foliation Sn having low dip angle (average dip of 20 °) and dip direction to SW (210/21) and to NE (18/20); the Dn-1 phase is represented by a compositional banding (Sn- 1), this banding is generally...

Petrologia e geoquímica das rochas graníticas do maciço do Capão Bonito, SP

The granitic massif Capão Bonito is located in the southwest of the State of São Paulo and is associated with Neoproterozoic evolution of Central Mantiqueira Province. Its rocks outcrop along the edge of the Paraná Basin in a body with elongated shape whose major axis has a general NE-SW, covering an area of approximately 110km2. Occurs in intrusive epimetamorphic rocks of Votuverava Formation, Acungui Group and granitic rocks of the Três Córregos Complex and their placement is related to a brittle tectonics of NE-SW direction shear zones. In metasediments, when preserved from deformational features imposed by mylonitic deformation, preserve up textures and mineralogy of contact metamorphism with development of mineral in albite-epidote and hornblende hornfels facies. The Massif Capão Bonito consists of red syenogranites, holo-leucocratic with biotite and rare hornblende, medium to coarse inequigranulars and isotropic lightly mylonitic and / or cataclastic in marginal regions. Commercially are called Vermelho Capão Bonito and for export as Ruby Red Granite. Rocks belonging to the calcium-alkaline high potassium to shoshonitic series or the series subalkaline potassic and metaluminous to peraluminous character. The magmatism is compatible with granite type A, tardi-orogenic to anorogenic of intraplate environment, from the crust material with lower melting emplacement associated with correlated transtensive structure to shear zones in an extensional environment at the end of collisional event of Orogênese Ribeira. Metamorphism occurred in the region in the greenschist facies, low to medium, generating quartzites, phyllites, schists, and calcium-silicate metabasics

Laminitos microbiais no membro Crato (Neoaptiano), bacia do Araripe, nordeste do Brasil

Pós-graduação em Geociências e Meio Ambiente - IGCE

Sulfate Mineral Paragenesis in Pennsylvanian Rocks and The Occurrence of Slavikite in Nebraska

The acid weathering of pyrite-bearing Pennsylvanian clastic sedimentary rocks in southeastern Nebraska locally produces the secondary sulfate minerals alunogen, copiapite, epsomite, felsobanyaite/basaluminite, gypsum, halotrichite, jarosite, rozenite, and slavikite. Of these mineral occurrences, four are first-time discoveries in the state or the surrounding region. Slavikite (NaMg2Fe5 (S04)7 (OH) 6• 33H20), which has been reported only once before in North America and from a handful of sites in Europe and South America, was found in abundance at an outcrop at Brownville, NE. The pH values in 1:1 solutions of deionized water of the studied minerals, excluding epsomite, range from 1.94 to 4.82. Therefore, segregations of secondary minerals in themselves are significant microenvironmental reservoirs of acid that can be mobilized during precipitation events. Because of its role in liberating and concentrating ions such as Al3+, Fe2+, Fe3+, Mg3+, and SO42-, acid rock weathering should be considered in local to regional assessments of surface-water and groundwater chemistry. Observations also suggest that rock weathering by the growth of sulfate salts is a potential factor in local hillslope development, one that has not previously been considered in the study area.

Laminitos microbiais no membro Crato (Neoaptiano), bacia do Araripe, nordeste do Brasil

Pós-graduação em Geociências e Meio Ambiente - IGCE

Integration of spatial and temporal models to predict extreme water table depths

The objective of this work was to evaluate extreme water table depths in a watershed, using methods for geographical spatial data analysis. Groundwater spatio-temporal dynamics was evaluated in an outcrop of the Guarani Aquifer System. Water table depths were estimated from monitoring of water levels in 23 piezometers and time series modeling available from April 2004 to April 2011. For generation of spatial scenarios, geostatistical techniques were used, which incorporated into the prediction ancillary information related to the geomorphological patterns of the watershed, using a digital elevation model. This procedure improved estimates, due to the high correlation between water levels and elevation, and aggregated physical sense to predictions. The scenarios showed differences regarding the extreme levels - too deep or too shallow ones - and can subsidize water planning, efficient water use, and sustainable water management in the watershed.

Magnetic fabrics and their relationship with the emplacement of the Piracaia pluton, SE Brazil

Magnetic fabric and rock-magnetism studies were performed on the four units of the 578 +/- 3-Ma-old Piracaia pluton (NW of Sao Paulo State, southern Brazil). This intrusion is roughly elliptical (similar to 32 km(2)), composed of (i) coarse-grained monzodiorite (MZD-c), (ii) fine-grained monzodiorite (MZD-f), which is predominant in the pluton, (iii) monzonite heterogeneous (MZN-het), and (iv) quartz syenite (Qz-Sy). Magnetic fabrics were determined by applying both anisotropy of low-field magnetic susceptibility (AMS) and anisotropy of anhysteretic remanent magnetization (AARM). The two fabrics are coaxial. The parallelism between AMS and AARM tensors excludes the presence of a single domain (SD) effect on the AMS fabric of the units. Several rock-magnetism experiments performed in one specimen from each sampled units show that for all of them, the magnetic susceptibility and magnetic fabrics are carried by magnetite grains, which was also observed in the thin sections. Foliations and lineations in the units were successfully determined by applying magnetic methods. Most of the magnetic foliations are steeply dipping or vertical in all units and are roughly parallel to the foliation measured in the field and in the country rocks. In contrast, the magnetic lineations present mostly low plunges for the whole pluton. However, for eight sites, they are steep up to vertical. Thin-section analyses show that rocks from the Piracaia pluton were affected by the regional strain during and after emplacement since magmatic foliation evolves to solid-state fabric in the north of the pluton, indicating that magnetic fabrics in this area of the pluton are related to this strain. Otherwise, the lack of solid-state deformation at outcrop scale and in thin sections precludes deformation in the SW of the pluton. This evidence allows us to interpret the observed magnetic fabrics as primary in origin (magmatic) acquired when the rocks were solidified as a result of magma flow, in which steeply plunging magnetic lineation suggests that a feeder zone could underlie this area.

Sedimentological and provenance response to Cambrian closure of the Clymene ocean: The upper Alto Paraguai Group, Paraguay belt, Brazil

Final Gondwana amalgamation was marked by the closure of the Neoproterozoic Clymene ocean between the Amazonia craton and central Gondwana. The events which occurred in the last stage of this closure were recorded in the upper Alto Paraguai Group in the foreland of the Paraguay orogen. Outcrop-based fades analysis of the siliciclastic rocks of upper Alto Paraguai Group, composed of the Sepotuba and Diamantino Formations, was carried out in the Diamantino region, within the eastern part of the Barra dos Bugres basin, Mato Grosso state, central-western Brazil. The Sepotuba Formation is composed of sandy shales with planar to wave lamination interbedded with fine-grained sandstone with climbing ripple cross-lamination, planar lamination, swaley cross-stratification and tangential to sigmoidal cross-bedding with mud drapes, related to marine offshore deposits. The lower Diamantino Formation is composed of a monotonous, laterally continuous for hundreds of metres, interbedded siltstone and fine-grained sandstone succession with regular parallel lamination, climbing ripple cross-lamination and ripple-bedding interpreted as distal turbidites. The upper part of this formation consists of fine to medium-grained sandstones with sigmoidal cross-bedding, planar lamination, climbing ripple cross-lamination, symmetrical to asymmetrical and linguoid ripple marks arranged in lobate sand bodies. These fades are interbedded with thick siltstone in coarsening upward large-scale cycles related to a delta system. The Sepotuba Formation characterises the last transgressive deposits of the Paraguay basin representing the final stage of a marine incursion of the Clymene ocean. The progression of orogenesis in the hinterland resulted in the confinement of the Sepotuba sea as a foredeep sub-basin against the edge of the Amazon craton. Turbidites were generated during the deepening of the basin. The successive filling of the basin was associated with progradation of deltaic lobes from the southeast, in a wide lake or a restricted sea that formed after 541 +/- 7 Ma. Southeastern to east dominant Neoproterozoic source regions were confirmed by zircon grains that yielded ages around 600 to 540 Ma, that are interpreted to be from granites in the Paraguay orogen. This overall regressive succession recorded in the Alto Paraguai Group represents the filling up of a foredeep basin after the final amalgamation of westem Gondwana in the earliest Phanerozoic. (C) 2011 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.

U-Pb zircon ages of orthogneisses and supracrustal rocks of the Cariris Velhos belt: Onset of Neoproterozoic rifting in the Borborema Province, NE Brazil

New geochronological and geochemical constraints on Precambrian sedimentary and volcanic successions exposed in the western part of the Central Domain of the Borborema Province, NE Brazil, indicate the presence of two distinct tectono-stratigraphic complexes: Riacho Gravata and Sao Caetano. Both complexes and associated orthogneisses are referred in the literature as the Cariris Velhos belt, having depositional, extrusive, or intrusive ages within the interval 985-913 Ma. The Riacho Gravata complex consists of bimodal (but mostly felsic) volcanic and volcanoclastic rocks, muscovite+/-graphite schists, quartzites, and marble with local occurrences of banded-iron-formation. The Sao Caetano complex mainly consists of metagreywackes, marbles, calc-silicate rocks, and rare meta-mafic rocks. Meta-mafic rocks from both complexes have geochemical signatures similar to those of continental flood basalts, with epsilon Nd (1.0 Ga) values ranging from -1.0 to -2.8. Felsic volcanic rocks from the Riacho Gravata complex show epsilon Nd (1.0 Ga) values ranging from -1.0 to -7.4 and geochemical signatures similar to A(2)-type granitoids. New SHRIMP U-Pb zircon data from felsic volcanic rocks within the Riacho Gravata complex yielded ages of 1091 +/- 13 Ma and 996 +/- 13 Ma. In contrast, meta-graywackes from the Sao Caetano complex show a maximum deposition age of ca. 806 Ma in the northern part and ca. 862 Ma in the southern part of the outcrop area. The orthogneisses show epsilon Nd (1.0 Ga) values ranging from 1.0 to -4.2 with U/Pb TIMS and SHRIMP ages ranging from 960 to 926 Ma and geochemical signatures of A(2)-type granitoids. The data reported in this paper suggest at least two periods of extension within the Central Domain of the Borborema Province, the first starts ca. 1091 Ma with magmatism and deposition, creating the Riacho Gravata basin and continued intrusion of A-type granites to 920 Ma. A second rift event, which reactivated old faults, generated a basin with a maximum deposition age of ca. 806 Ma. Furthermore, the oldest granitoids cutting these metasedimentary rocks have crystallization ages of ca. 600 Ma. This suggests that the second rift event could be early Brasiliano in age. The resulting Sao Caetano basin received detritus from a variety of sources, although detritus from the Riacho Gravata complex dominated. Deposition ages of the Riacho Gravata and the Sao Caetano complexes are coeval with deposits in other basins of the Borborema Province (Riacho do Tigre in the Central Domain; Macurure and Maranco in the Sergipano Belt of the Southern domain). The Macaubas Group from SE Brazil and its counterparts in Africa, the Zadanian and Mayumbian Groups, in the western edge of the Congo Craton are also coeval. Closure of the Riacho Gravata and Sao Caetano basins occurred during the Brasiliano convergence (705-600 Ma). During the last stage of convergence, ca. 612 Ma, pull-apart basins were created and filled; final basin closure took place 605-592 Ma, after deposition ceased. (C) 2011 Elsevier B.V. All rights reserved.

Morphogenesis of the Ourense plains:(NW of Spain)

[EN] We present a geomorphological analysis of Ourense Province (NW Spain) characterized by: a general narrowing of the fluvial network, highlands with smooth reliefs partially eroded and lowlands with residual reliefs, several extensive plains of erosion frequently limited by fractures -among which Tertiary grabens are inserted-, some ?Hollow Surface?-type morphology, absence of sedimentary deposits outside the grabens, and a generalized outcrop of the Hercynian Massif substratum. Traditionally, this ?piano?s keyboard morphology? has been interpreted as expression of block tectonics in tensile regimen; instead we suggest the existence of: an isostatic upheaval simultaneous to a sequence of tectonic pulses of compressive regimen with activity in favour of transcurrent faults, a General Surface (R600), several plains that present a ?Hollow Surface?-type morphology (R1600 R1400 R1000), a generalized alteration that correspond to a same process of decomposition associated to fluctuating conditions of redox equilibrium, a erosional terraces related principaly to the palaeo-fluvial nets; moreover, we propose the existence of two morphoestructural lineament: the first one represented by the Fault of Vila Real (NE-SW) -a ramification of the ?Basal Pyrenean Overthrust?-, that would have been active at an early moment of the tectonic sequence with a left transcurrent fault, secondly the lineament represented by the Fault of Maceda (NNW-SSE) that would be related to the ?Fault System NW-SE? and would have produced a right transcurrent fault during a late tectonic pulse.

Application of different instrumental techniques to the selective evaluation of bio-sensible compounds in foodstuff of animal and vegetable origin

This PhD thesis describes the application of some instrumental analytical techniques suitable to the study of fundamental food products for the human diet, such as: extra virgin olive oil and dairy products. These products, widely spread in the market and with high nutritional values, are increasingly recognized healthy properties although their lipid fraction might contain some unfavorable components to the human health. The research activity has been structured in the following investigations: “Comparison of different techniques for trans fatty acids analysis” “Fatty acids analysis of outcrop milk cream samples, with particular emphasis on the content of Conjugated Linoleic Acid (CLA) and trans Fatty Acids (TFA), by using 100m high-polarity capillary column” “Evaluation of the oxidited fatty acids (OFA) content during the Parmigiano-Reggiano cheese seasoning” “Direct analysis of 4-desmethyl sterols and two dihydroxy triterpenes in saponified vegetal oils (olive oil and others) using liquid chromatography-mass spectrometry” “Quantitation of long chain poly-unsatured fatty acids (LC-PUFA) in base infant formulas by Gas Chromatography, and evaluation of the blending phases accuracy during their preparation” “Fatty acids composition of Parmigiano Reggiano cheese samples, with emphasis on trans isomers (TFA)”

Provenienza dei sedimenti arenitici nel bacino di Tracia (eo-oligocene, Turchia nord-occidentale e Grecia nord-orientale)

The Thrace Basin is the largest and thickest Tertiary sedimentary basin of the eastern Balkans region and constitutes an important hydrocarbon province. It is located between the Rhodope-Strandja Massif to the north and west, the Marmara Sea and Biga Peninsula to the south, and the Black Sea to the est. It consists of a complex system of depocenters and uplifts with very articulate paleotopography indicated by abrupt lateral facies variations. Its southeastern margin is widely deformed by the Ganos Fault, a segment of the North Anatolian strike-slip fault system . Most of the Thrace Basin fill ranges from the Eocene to the Late Oligocene. Maximum total thickness, including the Neogene-Quaternary succession, reaches 9.000 meters in a few narrow depocenters. This sedimentary succession consists mainly of basin plain turbiditic deposits with a significant volcaniclastic component which evolves upwards to shelf deposits and continental facies, with deltaic bodies prograding towards the basin center in the Oligocene. This work deals with the provenance of Eocene-Oligocene clastic sediments of the southern and western part of Thrace Basin in Turkey and Greece. Sandstone compositional data (78 gross composition analyses and 40 heavy minerals analyses) were used to understand the change in detrital modes which reflects the provenance and geodinamic evolution of the basin. Samples were collected at six localities, which are from west to est: Gökçeada, Gallipoli and South-Ganos (south of Ganos Fault), Alexandroupolis, Korudağ and North-Ganos (north of Ganos Fault). Petrologic (framework composition and heavy-mineral analyses) and stratigraphic-sedimentologic data, (analysis of sedimentologic facies associations along representative stratigraphic sections, paleocurrents) allowed discrimination of six petrofacies; for each petrofacies the sediment dispersal system was delineated. The Thrace Basin fill is made mainly of lithic arkoses and arkosic litharenites with variable amount of low-grade metamorphic lithics (also ophiolitic), neovolcanic lithics, and carbonate grains (mainly extrabasinal). Picotite is the most widespread heavy mineral in all petrofacies. Petrological data on analyzed successions show a complex sediment dispersal pattern and evolution of the basin, indicating one principal detrital input from a source area located to the south, along both the İzmir-Ankara and Intra-Pontide suture lines, and a possible secondary source area, represented by the Rhodope Massif to the west. A significant portion of the Thrace Basin sediments in the study area were derived from ophiolitic source rocks and from their oceanic cover, whereas epimetamorphic detrital components came from a low-grade crystalline basement. An important penecontemporaneous volcanic component is widespread in late Eocene-Oligocene times, indicating widespread post-collisional (collapse?) volcanism following the closure of the Vardar ocean. Large-scale sediment mass wasting from south to north along the southern margin of the Thrace Basin is indicated (i) in late Eocene time by large olistoliths of ophiolites and penecontemporaneous carbonates, and (ii) in the mid-Oligocene by large volcaniclastic olistoliths. The late Oligocene paleogeographic scenario was characterized by large deltaic bodies prograding northward (Osmancik Formation). This clearly indicates that the southern margin of the basin acted as a major sediment source area throughout its Eocene-Oligocene history. Another major sediment source area is represented by the Rhodope Massif, in particolar the Circum-Rhodopic belt, especially for plutonic and metamorphic rocks. Considering preexisting data on the petrologic composition of Thrace Basin, silicilastic sediments in Greece and Bulgaria (Caracciolo, 2009), a Rhodopian provenance could be considered mostly for areas of the Thrace Basin outside our study area, particularly in the northern-central portions of the basin. In summary, the most important source area for the sediment of Thrace Basin in the study area was represented by the exhumed subduction-accretion complex along the southern margin of the basin (Biga Peninsula and western-central Marmara Sea region). Most measured paleocurrent indicators show an eastward paleoflow but this is most likely the result of gravity flow deflection. This is possible considered a strong control due to the east-west-trending synsedimentary transcurrent faults which cuts the Thrace Basin, generating a series of depocenters and uplifts which deeply influenced sediment dispersal and the areal distribution of paleoenvironments. The Thrace Basin was long interpreted as a forearc basin between a magmatic arc to the north and a subduction-accretion complex to the south, developed in a context of northward subduction. This interpretation was challenged by more recent data emphasizing the lack of a coeval magmatic arc in the north and the interpretation of the chaotic deposit which outcrop south of Ganos Fault as olistoliths and large submarine slumps, derived from the erosion and sedimentary reworking of an older mélange unit located to the south (not as tectonic mélange formed in an accretionary prism). The present study corroborates instead the hypothesis of a post-collisional origin of the Thrace Basin, due to a phase of orogenic collapse, which generated a series of mid-Eocene depocenters all along the İzmir-Ankara suture (following closure of the Vardar-İzmir-Ankara ocean and the ensuing collision); then the slab roll-back of the remnant Pindos ocean played an important role in enhancing subsidence and creating additional accommodation space for sediment deposition.

Climate signatures in corals of the tropical-temperate transition zone (Late Miocene, Crete/Greece)

The present study describes a Late Miocene (early Tortonian - early Messinian) transitional carbonate system that combines elements of tropical and cool-water carbonate systems (Irakleion Basin, island of Crete, Greece). As documented by stratal geometries, the submarine topography of the basin was controlled by tilting blocks. Coral reefs formed by Porites and Tarbellastrea occurred in a narrow clastic coastal belt along a „central Cretan landmass“, and steep escarpments formed by faulting. Extensive covers of level-bottom communities existed in a low-energy environment on the gentle dip-slope ramps of the blocks that show the widest geographical distribution within the basin. Consistent patterns of landward and basinward shift of coastal onlap in all outcrop studies reveal an overriding control of 3rd and 4th order sea level changes on sediment dynamics and facies distributions over block movements. An increasingly dry climate and the complex submarine topography of the fault block mosaic kept sediment and nutrient discharge at a minimum. The skeletal limestone facies therefore reflects oligotrophic conditions and a sea surface temperature (SST) near the lower threshold temperature of coral reefs in a climatic position transitional between the tropical coral reef belt and the temperate zone. Stable isotope records (δ18O, δ13C) from massiv, exceptionally preserved Late Miocene aragonite coral skeletons reflect seasonal changes in sea surface temperature and symbiont autotrophy. Spectral analysis of a 69 years coral δ18O record reveals significant variance at interannual time scales (5-6 years) that matches the present-day eastern Mediterranean climate variability controlled by the Arctic Oscillation/North Atlantic Oscillation (AO/NAO), the Northern Hemisphere’s dominant mode of atmospheric variability. Supported by simulations with a complex atmospheric general circulation model coupled to a mixed-layer ocean model, it is suggested, that climate dynamics in the eastern Mediterranean and central Europe reflect atmospheric variability related to the Icelandic Low 10 million years ago. Usually, Miocene corals are transformed in calcite spar in geological time and isotope values are reset by diagenetic alteration. It is demonstrated that the relicts of growth bands represent an intriguing source of information for the growth conditions of fossil corals. Recrystallized growth bands were measured systematically in massive Porites from Crete. The Late Miocene corals were growing slowly with 2-4 mm/yr, compatible with present-day Porites from high latitude reefs, a relationship that fits the position of Crete at the margin of the Miocene tropical reef belt. Over Late Miocene time (Tortonian - early Messinian) growth rates remained remarkably constant, and if the modern growth temperature relationship for massive Porites applies to the Neogene, minimum (winter) SST did not exceed 19-21°C.

Weathering of Fe-bearing minerals under extraterrestrial conditions, investigated by Mössbauer spectroscopy

The weathering of Fe-bearing minerals under extraterrestrial conditions was investigated by Mössbauer (MB) spectroscopy to gain insights into the role of water on the planet Mars. The NASA Mars Exploration Rovers Spirit and Opportunity each carry a miniaturized Mössbauer spectrometer MIMOS II for the in situ investigation of Martian soils and rocks as part of their payload. The MER flight instruments had to be modified in order to work over the Martian diurnal temperature range (180 K – 290 K) and within the unique electronic environment of the rovers. The modification required special calibration procedures. The integration time necessary to obtain a good quality Mössbauer spectrum with the MIMOS II flight instruments was reduced by 30 % through the design of a new collimator. The in situ investigation of rocks along the rover Spirit's traverse in Gusev crater revealed weakly altered olivine basalt on the plains and pervasively altered basalt in the Columbia Hills. Correlation plots of primary Fe-bearing minerals identified by MB spectroscopy such as olivine versus secondary Fe-bearing phases such as nanophase Fe oxides showed that olivine is the mineral which is primarily involved in weathering reactions. This argues for a reduced availability of water. Identification of the Fe-oxyhydroxide goethite in the Columbia Hills is unequivocal evidence for aqueous weathering processes in the Columbia Hills. Experiments in which mineral powders were exposed to components of the Martian atmosphere showed that interaction with the atmosphere alone, in the absence of liquid water, is sufficient to oxidize Martian surface materials. The fine-grained dust suspended in the Martian atmosphere may have been altered solely by gas-solid reactions. Fresh and altered specimens of Martian meteorites were investigated with MIMOS II. The study of Martian meteorites in the lab helped to identify in Bounce Rock the first rock on Mars which is similar in composition to basaltic shergottites, a subgroup of the Martian meteorites. The field of astrobiology includes the study of the origin, evolution and distribution of life in the universe. Water is a prerequisite for life. The MER Mössbauer spectrometers identified aqueous minerals such as jarosite and goethite. The identification of jarosite was crucial to evaluate the habitability of Opportunity's landing site at Meridiani Planum during the formation of the sedimentary outcrop rocks, because jarosite puts strong constrains on pH levels. The identification of olivine in rocks and soils on the Gusev crater plains provide evidence for the sparsity of water under current conditions on Mars. Ratios of Fe2+/Fe3+ were obtained with Mössbauer spectroscopy from basaltic glass samples which were exposed at a deep sea hydrothermal vent. The ratios were used as a measure of potential energy for use by a microbial community. Samples from Mars analogue field sites on Earth exhibiting morphological biosignatures were also investigated.