Search results for "Hydrothermal alteration"
showing 6 items of 6 documents
Spectral, mineralogical, and geochemical variations across Home Plate, Gusev Crater, Mars indicate high and low temperature alteration
2009
Over the last ~3 years in Gusev Crater, Mars, the Spirit rover observed coherent variations in color, mineralogy, and geochemistry across Home Plate, an ~80 m-diameter outcrop of basaltic tephra. Observations of Home Plate from orbit and from the summit of Husband Hill reveal clear differences in visible/near-infrared (VNIR) colors between its eastern and western regions that are consistent with mineralogical compositions indicated by Mössbauer spectrometer (MB) and by Miniature Thermal Emission Spectrometer (Mini-TES). Pyroxene and magnetite dominate the east side, while olivine, nanophase Fe oxide (npOx) and glass are more abundant on the western side. Alpha Particle X-Ray Spectromet…
Fumarolic alteration products at Sousaki (Greece) : occurrence and environmental impact
2009
Fumarolic alteration crusts and efflorescences have been sampled at the Sousaki solfataric field. Samples have been analysed for mineralogical (XRD) and chemical composition (HNO3 digestion and leaching with distilled water). Results show that mineralogical and chemical compositions (major, minor and trace metals) are controlled by microenvironmental conditions. The sample collected in the anoxic part of a cave is composed almost exclusively by native sulfur. The samples collected in the oxidizing part of the cave and outside in relatively sheltered position are mainly composed by very soluble sulfates. Chemical composition evidence strong enrichments in Al, Ca, Cr, Fe, Mg and Ni which are …
Fumarolic alteration products of three hydrothermal areas of Greece: Chemical characterization and environmental impact.
2018
Samples of efflorescences and encrustations of hydrothermal origin have been collected at three fumarolic areas in Greece. The three sites are Sousaki, Thiafi (Methana) and Kokkino Nero (Kos) and all belong to the South Aegean Active Volcanic Arc. Samples were analysed for their mineralogical (XRD and SEM-EDS) and chemical composition. Solutions obtained from both mineralization with HNO3 and leaching with distilled water, were analysed for major (ICP-OES), minor and trace metals (ICP-MS) and for sulfate contents (IC). Results show that their composition is mainly controlled by the petrological composition of the substrate (ultramafic rocks at Sousaki, felsic volcanic rocks at Methana and l…
Impact of hydrothermal alteration processes on element mobility and potential environmental implications at the Sousaki solfataric field (Corinthia -…
2020
Abstract Samples of efflorescences and encrustations of hydrothermal origin were collected at Sousaki (Greece) and analysed for their mineralogical (XRD) and chemical composition. Solutions obtained both from mineralization with HNO3 and from leaching with deionised water were analysed for major (ICP-OES), minor and trace metals (ICP-MS) and sulfate contents (IC). Results evidence the dependence of the chemical and mineralogical composition on micro-environmental conditions i.e. humidity, oxygen-rich or -poor environment, exposed or sheltered from meteoric agents. In fact, the presence of highly soluble sulfate minerals with elevated contents of many metals (e.g. Mg, Al, Fe, Mn, Cr, Ni, etc…
CHLORITE/SMECTITE - ALKALI FELDSPAR METASOMATIC XENOLITHS FROM HYBLEAN MIOCENIC DIATREMES (SICILY, ITALY): EVIDENCE FOR EARLY INTERACTION BETWEEN HYD…
2006
Upper-Miocene tuff-breccia pipes from the Hyblean area (south-eastern Sicily) bear a number of ultramafic and mafic xenoliths (spinel-peridotites, pyroxenites, gabbroic rocks) whose study has led to conclude that the Meso-Caenozoic carbonatic and volcanic succession stands upon a fossil oceanic core-complex, probably connected with the adjacent Ionian crust. Evidence for hydrothermal metasomatism is common in the Hyblean ultramafic and mafic xenoliths. In some cases, extreme metasomatic transformation and shearing have deleted original mineralogy and textures yielding unusual rocks, hereafter called “metasomatites”. These rocks generally exhibit cataclastic texture, their hydrothermal miner…
Alteration-Induced Volcano Instability at La Soufrière de Guadeloupe (Eastern Caribbean)
2021
International audience; Volcanoes are unstable structures that deform laterally and frequently experience mass wasting events. Hydrothermal alteration is often invoked as a mechanism that contributes significantly to volcano instability. We present a study that combines laboratory experiments, geophysical data, and large-scale numerical modeling to better understand the influence of alteration on volcano stability, using La Soufrière de Guadeloupe (Eastern Caribbean) as a case study. Laboratory experiments on variably altered (advanced argillic alteration) blocks show that uniaxial compressive strength, Young's modulus, and cohesion decrease as a function of increasing alteration, but that …