Search results for " Geology"

Rare earth elements and hydrothermal ore formation processes

1992

Abstract The geochemical behaviour of REE is influenced by nearly all important hydrothermal ore formation processes including fluid-rock interactions, fluid precipitations, adsorption and scavenging onto particles, and changes in fluid temperature, pressure, pH, Eh, alkalinity and ligand concentration. Destabilization of REE complexes in response to these physicochemical changes and possible chemical-crystallographic controls determine the concentration and distribution of REE within hydrothermal minerals, mineraloids and amorphous phases. Alteration assemblages of intrusive related mineralisations may exhibit a wide range of REE distributions and REE fractionation trends. The REE distribu…

The Potential Geosite of the “Libeccio Antico” Quarries: a Sedimentological and Stratigraphic Characterisation of Ornamental Stone from Mt Cocuccio, …

2018

The Custonaci marble district of western Sicily is known for the production of a valuable ornamental stone that has been, and nowadays is exploited due to its suitable properties and aesthetic qualities. The “Libeccio Antico” was, among the “marbles”, the most appreciated ornamental stone during the Baroque Age (the XVII–XVIII centuries), due to its strong polychrome contrasts from ivory to yellow, green or dark red. This polychrome pattern is the result of dissolution processes that involved an Upper Triassic peritidal limestone. The varicoloured sediments in paleocavities, collapse breccias, paleosols and neptunian dykes that occur in the “Libeccio Antico” represent the peculiar character…

Mining indigenous territories: Consensus, tensions and ambivalences in the Salar de Atacama

2022

Lithium mining in Chile’s Salar de Atacama (SdA) has a relatively long and controversial history, especially when it comes to the local Indigenous peoples. In this context, this paper looks at the ways mining activities, and different visions of territory and indigeneity co-produce each other in the particular context of the SdA. For this, we use historical and ethnographic methods and draw on studies in anthropology and geography. We aim to escape simplistic images of Indigenous peoples’ reactions to mining as reflecting victimhood, resistance, or strategic pragmatism, and show instead how individuals and groups organize and express themselves in ambivalent ways, maintaining complex relati…

STOP 2: Late-glacial and postglacial environmental changes, Lake Āraiši, Vidzeme Upland

2014

STOP 5: Veselava end moraine, north-western Vidzeme Upland

2014

STOP 3: Late-glacial and early postglacial environmental processes and the history of the River Triečupīte valley and surroundings, in the foreland o…

2014

STOP 8: Morphology and arrangement of glaciokarst kettles at Vietalva village

2014

Turmoil at Turrialba Volcano (Costa Rica): Degassing and eruptive processes inferred from high-frequency gas monitoring.

2016

Abstract Eruptive activity at Turrialba Volcano (Costa Rica) has escalated significantly since 2014, causing airport and school closures in the capital city of San José. Whether or not new magma is involved in the current unrest seems probable but remains a matter of debate as ash deposits are dominated by hydrothermal material. Here we use high‐frequency gas monitoring to track the behavior of the volcano between 2014 and 2015 and to decipher magmatic versus hydrothermal contributions to the eruptions. Pulses of deeply derived CO2‐rich gas (CO2/Stotal > 4.5) precede explosive activity, providing a clear precursor to eruptive periods that occurs up to 2 weeks before eruptions, which are acc…

Contrasting Styles of Inter-Caldera Volcanism in a Peralkaline System: Case Studies from Pantelleria (Sicily Channel, Italy)

2022

The recent (<190 ka) volcanic history of Pantelleria is characterized by the eruption of nine peralkaline ignimbrites, ranging in composition from comenditic trachyte to comendite to pantellerite. The ~46 ka Green Tuff (GT) was the last of these ignimbrites, which was followed by many effusive and explosive low-volume eruptions of pantellerite from vents within the caldera moat and along the caldera rim. Although recent studies have shed additional light on the age, petrochemistry, and volcanology of the older ignimbrites, there is very little knowledge of magmatism that occurred between these older ignimbrites, primarily due to the very scarce exposures. In this paper, we present new fi…

Onset of the Messinian Salinity Crisis: Sedimentological, petrographic and geochemical characterization of the pre-salt sediments from a new core (Ca…

2022

The present study aims to reconstruct the environmental changes leading to the Messinian Salinity Crisis during the transition from the Tortonian-Messinian marine conditions to the Messinian evaporitic environments. The core 3AGN2S04, recently drilled in the Caltanissetta Basin (Sicily), was analyzed to reveal the petrographic, mineralogical and geochemical characteristics of the late Tortonian – early Messinian pre-salt sediments. In particular, the facies characterization of the carbonates and organic-rich shales of the Calcare di Base (CdB) member allowed to understand its significance in the paleoenvironmental evolution towards salt deposition and to the reconstruct the brecciation proc…