1,721,031 research outputs found
Skarn formation and alteration-mineralization phenomena at Funtana Raminosa (Central Sardinia, Italy). Reconstruction of the thermal history from fluid inclusions
No full textThe study of fluid inclusions trapped in minerals of the Funtana Raminosa ore district permit reconstruction of the quite complex history of thermal metamorphic and hydrothermal events that preceded and accompanied ore deposition. On this basis, we have recognized a first thermal metamorphic, isochemical event, which produced garnet-pyroxene skarns in the Silurian rocks, followed by a long-lasting hydrothermal circulation. The latter caused the retrocession of anhydrous skarn parageneses, the ore deposition and the intricate relationships existing among the different alteration assemblages that affected magmatites and surrounding rocks in the area
Hydrothermal alteration and fluid evolution in the Mo-Deposit of Perda Lada (SW Sardinia, Italy)
No full textMinor and trace elements in different honey types produced in Siena County (Italy)
No full textThe concentrations of 23 chemical elements (Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Na, Ni, Pb, Sb, Se, Sr, Th, Tl, U, Zn) were determined in 51 honey samples of different botanical origin produced in Siena County (Italy). K, Ca, Na and Mg were the most abundant elements, with mean contents of 1195, 257, 96.6 and 56.7 mg/kg, respectively. The Fe, Zn and Sr contents generally ranged from 1 to 5 mg/kg. Except for Ba, Cu, Mn and Ni, the trace element contents were below 100 μg/kg. The analytical data indicated a good level of quality of the honeys, especially with regard to the concentrations of toxic trace elements, such as As, Cd, Pb and Sb, and suggested a significant influence of the botanical origin on the element composition. Some local geological and geochemical features also seemed to affect the chemistry of the honey
Assessing Geobiosphere Work of Generating Global Reserves of Coal, Crude Oil, and Natural Gas
No full textRelationship between soil geochemistry and grape composition in Tuscany (Italy)
No full textThe concentrations of 13 trace elements were determined in soils and Sangiovese grapes collected in vineyard zones of Tuscany (Italy). The purpose was to establish a correspondence among the chemical composition of grape, the geochemistry of vineyard soil and the geolithological features of cultivation zone, and determine the provenance of the grapes by means of their chemical fingerprints. Statistical analysis of Ba, Rb and Sr concentrations distinguished three classes of grapes according to the geochemical and geopedological characteristics of the soils. Grapes with the highest Sr levels grew on high-Sr soils derived from calcareous, calcareousmarly and marly-clayey rocks, whereas the most elevated Rb concentrations characterized the berries cultivated on soils formed from clayey-marly and sandy-marly lithologies. Grapes with the highest Ba concentrations grew on soil derived from arenaceous rocks and carbonate lithologies of evaporitic origin. These findings suggested that Ba, Rb and Sr could be used as fingerprints
for the chemical traceability of Sangiovese grapes
High contents of rare earth elements (REEs) in stream waters of a Cu-Pb-Zn mining area
No full textStream waters draining an old mining area present very high rare earth element (REE) contents, reaching 928 μg/l as the maximum total value (ΣREE). The middle rare earth elements (MREEs) are usually enriched with respect to both the light (LREEs) and heavy (HREEs) elements of this group, producing a characteristic “roof-shaped” pattern of the shale Post-Archean Australian Shales-normalized concentrations. At the Fenice Capanne Mine (FCM), the most important base metal mine of the study area, the REE source coincides with the mine tailings, mostly the oldest ones composed of iron-rich materials. The geochemical history of the REEs released into Noni stream from wastes in the FCM area is strictly determined by the pH, which controls the REE speciation and in-stream processes. The formation of Al-rich and mainly Fe-rich flocs effectively scavenges the REEs, which are readily and drastically removed from the solution when the pH approaches neutrality. Leaching experiments performed on flocs and waste materials demonstrate that Fe-oxides/oxyhydroxides play a key role in the release of lanthanide elements into stream waters. The origin of the “roof-shaped” REE distribution pattern as well as the peculiar geochemical behavior of some lanthanide elements in the aqueous system are discussed
Magmatism and hydrothermal processes in the Funtana Raminosa ore district (Central Sardinia, Italy): petrographic and geochemical features
No full textA petrographic and geochemical study, centered on the numerous subvolcanic bodies cropping out as stocks, sills and dykes in the Funtana Raminosa ore field, is reported. Particular attention has been devoted to the widespread hydrothermal alteration phenomena involving such magmatites. The research has allowed us to recognize magmatic typologies, from andesites s.l. to dacites and rhyolites, likely connected with the Hercynian post-orogenic volcanism. The imprint of different types of hydrothermal alteration processes on these rocks and their temporal succession have been reconstructed. In addition, the results as a whole have allowed us to determine the intrusive sequence of the different magmatic products and their different styles of intrusion, which require a coupled structural evolution of the area. Finally, as regards a possible link between magmatism and mineralization, the study indicates that conditions suitable to ore deposition were limited to the first magmatic phase characterized by andesitic s.l. products
Mineral assemblages, stable isotopes and fluid inclusions in ore veins from the Macigno Formation at Calafuria (Livorno Mountains, northern Tuscany, Italy)
No full textThe present paper deals with an integrated geological, mineralogical and geochemical study on mineralized faults and fractures recognized in the Macigno Formation at Calafuria in the Livorno Mountains of northern Tuscany. In the field, two main different systems of faults were recognized: an earlier one related to a compressive phase with NE-SW and N-S trending faults, and a younger one related to a relaxation phase with NW-SE trending faults. They distinguish for specific mineral assemblages, consisting mainly of quartz in the former, and barite-marcasite-pyrite in the latter. Minerals were analyzed for fluid inclusions and isotopic composition. Data on fluid inclusions indicate that three main mineralizing episodes affected the fault systems. In the first episode, the fluids deposited quartz in the fault systems related to the compressive phase. The second episode was the main one, and led to the deposition of euhedral quartz in the NE-SW faults, and barite, maracasite and pyrite essentially in the N-S and NW-SE faults. The fluid evolution ended with the deposition of calcite, dolomite and a series of supergene minerals originated by alteration of Fe-sulfides.
The sulfur isotopic composition of minerals (–6.3 to 25.1‰) would seem to exclude a magmatic origin of the sulfur, favoring instead a sedimentary origin. Moreover, a temperature of about 400°C is estimated by sulfur isotope thermometry for the second stage of mineralization. Owing to pressure effects, the homogenization temperature given by the fluid inclusions for this stage of mineralization is considerably lower that the isotopic one.
A lithostatic pressure of 125 MPa is estimated for the barite and sulfide mineralization, this corresponding to a depth of 5 Km. Finally, a post-Middle Pliocene age is proposed for the ore veins at Calafuria, that may have formed during tectonic relaxation events from hydrothermal fluids rich in CO2 and H2S, as are observed in the Larderello geothermal area at present
The W-Mo deposit of Perda Majori (SE Sardinia, Italy): a fluid inclusion study of ore and gangue minerals
No full textThe W-Mo deposit of Perda Majori (SE Sardinia) consists of a NW-SE trending quartz vein that crops out for about 500 m in the Salto di Quirra region.
Hercynian low-grade metamorphic rocks, which host the orebody, largely dominate the geology of the area and are themselves intruded and contact metamorphosed by late Hercynian leucogranites and leucogranite porphyries.
Field evidence supports a genetic link between the orebody and the emplacement of the leucogranites.
The ore paragenesis consists chiefly of wolframite, molybdenite, scheelite, pyrite and calcopyrite, while the gangue is formed of quartz, K-feldspar, albite, topaz, micas, fluorite and calcite.
The highest Th (320-420-degrees-C) were found in coarse-grained quartz (Qz I) which also records signs of boiling. Inclusions found in wolframite, giving Th 310-330-degrees-C and the highest recorded salinities (6-7 wt.% NaCl eq.), suggest that ore deposition closely followed the boiling
Mineral assemblages, stable isotopes and fluid inclusions in ore veins from the Macigno Formation at Calafuria (Livorno Mountains, northern Tuscany, Italy)
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