Giovanni Ruggieri

TL;DR: In this article, the authors performed a geochemical and isotopic investigation on granites cored during drilling exploration activity on the Larderello geothermal field. But they did not find any of the typical petrographic features commonly observed in the TMP hybrid granites (enclaves, patchy zoning of plagioclase, amphibole clots).

TL;DR: The Magnesite deposits of Malentrata (Tuscany, Italy) were derived from serpentinite silicification-carbonation of the Ligurian ophiolite, and represent a natural analogue of in situ CO 2 mineral sequestration as mentioned in this paper.

TL;DR: The La Crocetta mine near Porto Azzurro (Elba Island, Tuscany, Italy) is an important producer of raw material for the ceramic industry as discussed by the authors.

Abstract: [1] The He isotope composition of paleofluids entrapped in fluid inclusions of hydrothermal minerals is compared with the present-day fluid composition of the Larderello geothermal field. Almost constant values of (3He/4He)m/(3He/4He)air (=R/Ra) over time indicate that no important changes have occurred in the deep source of gases, at least during the last 3.8 million years. On a regional scale, a correlation has been found between the R/Ra spatial distribution, heat flow, and Bouguer gravity anomaly. High values of R/Ra and heat flow, and low Bouguer anomaly values indicate that the Larderello field is an area of preferential escape for mantle-derived fluids. A positive correlation has also been found between the R/Ra spatial distribution and a major seismic reflector named the “K horizon.” A deep magma source, refilled by periodic gas input from the mantle, is the most likely source of 3He-enriched fluids and the anomalously high heat flow. The nearly constant value of R/Ra clearly indicates that input of fresh mantle material has occurred up to recent times. Clear evidence of mixing between mantle and crustal fluids indicates that the high R/Ra is the lower limit of the actual mantle value, which is suggested to be similar to the subcontinental European mantle. The decrease of R/Ra over time in the peripheral part of the Larderello field indicates that important changes in the feeding fracture system and/or cooling rate have occurred in these areas.

TL;DR: In this article, microprobe analyses have been carried out on chlorite and illite in order to apply several geothermometers and it is found that the temperatures calculated from the chlorite Geothermometer (159-292°C) after Cathelineau and Nieva [Contrib. Mineral. Petrol. 4, 907-919 (1992) indicate thermal stability or slight heating.