105 research outputs found
Tectonic control on hydrothermal circulation and fluid evolution in the Pietratonda-Poggio Peloso (southern Tuscany, Italy) carbonate-hosted Sb-mineralization
No full textThis paper deals with the development of an exhumed Sb-ore deposit associated with Neogene-Quaternary magmatism of Southern Tuscany. This epithermal mineralization represents a fossil hydrothermal system that was probably active during the volcanic activity that produced rhyolitic lava flows (~2.3Ma), presently exposed close to the study area (Roccastrada volcanic complex). Volcanism was coeval with strike-/oblique-slip and normal faults that controlled the hydrothermal circulation. Faults were active until the Pleistocene. Our study, based on fluid inclusion and structural data, demonstrates that fluids were channeled in damage zones of the Pliocene-Quaternary strike-/oblique-slip and normal faults and permeated within damage zones of Middle-Late Miocene extensional detachments, consisting of fractured carbonate rock masses sandwiched between successions with very low permeability. Fluids produced a diffuse hydrothermal alteration both in the cataclasite and in carbonate damage zones where jasperoid strata bounds developed. Fluid inclusion investigation allowed tracing the evolution of the hydrothermal fluids that is interpreted in terms of a progressive cooling of the hydrothermal system. Such evolution could be related to large infiltration of shallow waters from the early mineralizing stage (fluids at about 200-225°C, salinity around 3 wt.% NaClequiv.) down to the later post-ore stages, characterized by more diluted fluids (salinity of about 2.1 wt.% NaClequiv) having lower temperatures (Th around 155°C). The latest hydrothermal activity in the area is indicated by fluid inclusions hosted in late calcite veins that are characterized by Th values of about 125°C. This fossil hydrothermal system may provide a close analogue to the active geothermal systems occurring in southern Tuscany, thus the results are useful for better understanding the relationships between brittle structures and fluids migration
Development and fast exhumation of a geothermal system in the resurgent caldera environment of Ischia island (Italy).
No full textHydrothermal fluid evolution in the "Botro ai Marmi" quartz-monzonitic intrusion (Campiglia Marittima, Tuscany, Italy). Evidence from a fluid inclusion investigation
No full textAbstract:
The quartz-monzonitic intrusion of "Botro ai Marmi" (Tuscany, Italy) can be considered to be a typical example of an intrusion-centered magmatic hydrothermal system. The evolution of hydrothermal fluids in the "Botro ai Marmi" intrusion was investigated using fluid inclusion analyses to provide suitable physico-chemical constraints on the fluids involved in the late- to postmagmatic hydrothermal activity that affected the intrusion, providing inferences on their origin and variations of temperature and pressure with time.
This work demonstrates that the earliest fluids circulating in the "Botro ai Marmi" intrusion were high-temperature brines exsolved directly from the crystallizing magma. This fluid circulated in the intrusion under lithostatic conditions (P > 90 MPa, T > 540°C). A second evolutionary stage of the magmatic hydrothermal system is marked by the transition from lithostatic (>90 MPa) to
hydrostatic dominated conditions (50 to 10 MPa). In this stage the fluids are also interpreted to be mainly orthomagmatic in origin but unmixed in a high-salinity brine and in a low-salinity vapor aqueous phase, at a temperature ranging from about 500°C to 300°C. These fluids were responsible for the potassic alteration facies. At a later stage of hydrothermal evolution, abundant meteoric dominated fluids entered the system and are associated with propylitic alteration. This event marks the transition from a magmatic-hydrothermal system to a typical hydrothermal (“geothermal”) system, which can be assumed to be similar to some extent to the nearby active high-enthalpy geothermal system of Larderello. Low-temperature and low-salinity meteoric water-dominated fluids characterize the latest stage of the "Botro ai Marmi" hydrothermal system
The feeding system of 1944 eruption of Vesuvius: melt inclusion data from dunitic nodules
No full textGlass-bearing felsic nodules from the crystallizing sidewalls of the 1944 Vesuvius magma chamber
No full textCombined treatment with renin-angiotensin system blockers and polyunsaturated fatty acids in proteinuric IgA nephropathy: a randomized controlled trial.
No full textBackground. Currently, several therapeutic protocols exist for IgA nephropathy (IgAN); results in slowing the progression to end-stage renal disease (ESRD) are variable, but ∼30–40% of patients require replacement therapy (dialysis or renal transplantation) by 20 years from the onset. The adverse effects brought by the chronic assumption of drugs can be a potential limit. Actually, the most used therapies for IgAN are renin–angiotensin system blockers (RASB), glucocorticoids and immunosuppressive agents. Trials with polyunsaturated fatty acids (PUFA) in IgAN have been done since the first successful attempt by Hamazaki in 1984, resulting in alternate answers, but no trials have ever been done testing the efficacy of combined therapy with RASB and PUFA. Methods. We tested the effect of a 6-month course of PUFA (3 grams/day) in a group of 30 patients with biopsy-proven IgAN and proteinuria already treated with RASB randomized to receive PUFA supplementation or to continue their standard therapy. The primary end-point was the percent reduction of proteinuria from the baseline. Secondary end-points were modifications in glomerular filtration rate (GFR), blood pressure, serum triglycerides and erythrocyturia. Results. At the end of the 6-month trial, the percent reduction of proteinuria was 72.9% in the PUFA group and 11.3% in the RASB group ( P < 0.001). A reduction of ≥50% of baseline proteinuria was achieved in 80.0% of PUFA patients and 20.0% of RASB patients ( P = 0.002). Erythrocyturia was significantly lower in the PUFA group ( P = 0.031). No significant changes in renal function, blood pressure and triglycerides were observed. Conclusions. PUFA associated with RASB reduced proteinuria in patients with IgAN more than RASB alone
Rare element minerals’ assemblage in El Quemado pegmatites (Argentina): insights for pegmatite melt evolution from gahnite, columbite-group minerals and tourmaline chemistry and implications for minerogenesis
No full textThe pegmatite district of El Quemado (NW Pampean Ranges, NW Argentina) hosts several Ordovician pegmatite bodies of theLCT (Li, Cs, Ta) type. We present paragenetic assemblages for a set of samples from two of the El Quemado pegmatite groups,Santa Elena and Tres Tetas, and mineral chemistry analyses for gahnite, columbite-group minerals, tourmaline, micas, albite,microcline, and discuss the relation between their major element composition and the degree of evolution of pegmatite melts. Thechemical composition of rare element minerals allows recognizing an evolutive trend reaching highly differentiated compositions, with complex paragenetic assemblages including Li-, Zr-, U-, Zn-, P-, Mn- and Ta-bearing minerals. The temperature ofcrystallization during the magmatic phase was below 400 °C. Non-pervasive hydrothermal alteration, testified by a moderatepresence of phyllosilicates, affected the pegmatite bodies. Chlorite geothermometry indicates that the circulation of postmagmatic hydrothermal fluids occurred at a temperature ranging between 200 °C and 250 °C. The mineralogical featuresrecognized in the El Quemado pegmatite rocks have implications for the metallogenesis of the region, suggesting that thepegmatites potentially contributed to the genesis of Ta-Nb oxide placer mineralizations.Fil: López, Vanina Lucrecia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto Superior de Correlación Geológica. Grupo Vinculado al INSUGEO- Centro de Estudios Geológicos Andinos; ArgentinaFil: Fulignati, Paolo. Universita Degli Studi Di Pisa. Dipartimento Di Scienze Della Terra; ItaliaFil: Gioncada, Anna. Universita Degli Studi Di Pisa. Dipartimento Di Scienze Della Terra; ItaliaFil: Azarevich, Miguel Basilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tucumán. Instituto Superior de Correlación Geológica. Grupo Vinculado al INSUGEO- Centro de Estudios Geologicos Andinos; Argentin
Evidence of continuous immiscibility within magmatic fluids (79AD eruption of Mt Vesuvius)
No full textTracking mineral evolution and element mobility during albitisation and subsequent kaolinisation of phyllite rocks: A case study from the Verrucano of Monti Pisani, Tuscany, Italy
No full textThis work describes the first occurrence of albitite rocks in the Middle Triassic Verruca Formation, Monti Pisani, Northern Apennines, northern Tuscany, Italy. The albitite formed by Na-metasomatism of phyllites ('potassic white mica' + quartz + 'chlorite' + hematite + albite) in an amagmatic environment. The albitisation process took place after the Miocene main phases of Apenninic deformation and was followed by the formation of veins of Fe-carbonate + quartz. Hydrothermal alteration progressed with the ingression, possibly favoured by the increase of permeability due to albitisation, of a slightly acidic, oxidising, aqueous fluid that led to the pervasive kaolinisation of the albitite and to the complete transformation of the Fe-carbonate of the veins into Fe-hydroxides. This stage was followed by supergene alteration that led to the formation of a pervasive network of halloysite veinlets and colloform (P-Al-Si)-bearing Fe-hydroxides. Finally, the hydrothermally altered rock underwent a localised brittle fracturing without new minerals being formed. The prominent compositional changes occurring during this multi-stage hydrothermal process were the inversion of the Na2O/K2O ratio of the whole rock (from 0.07 in the pristine phyllite to up to 200 for the kaolinised albitite), the loss of Fe and Mg, and the enrichment of Sb. The MREE were partially lost, whereas LREE and HREE behaved conservatively. Though pervasive hydrothermal alteration occurrences are common in central-southern Tuscany, mostly related to the post-collisional extensional regime, lithospheric thinning and emplacement of magmatic bodies in the crust, the rare Monti Pisani kaolinised albitite described in this investigation expands the effects of post-collisional hydrothermal activity in Tuscany northwards, far from potential magmatic sources
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