Monte Amiata Research Articles

Behaviour of trace elements during magmatic processes in the crust: Application to acidic volcanic rocks of Tuscany (Italy)

Plio-Quaternary acidic rock suites from three volcanic centres of Tuscany (Italy) — San Vincenzo, Roccastrada and Monte Amiata — are composed predominantly of rhyolitic and rhyodacitic ignimbrites. The rocks are characterized by distinct enrichments, particularly of K and Rb, and display considerable compositional differences among the various volcanic centres. The volcanic rocks of Roccastrada and most of S. Vincenzo were probably generated by partial melting of metapelitic rocks from the Paleozoic basement of Tuscany, leaving a residue composed of biotite, cordierite and quartz and sometimes plagioclase or garnet. The enrichment of K and related elements can be attributed to selective contamination by fluids. The other volcanic rocks including trachytes of Mt. Amiata have also been affected by interaction with an upper-mantle component, probably K-rich basaltic rocks. A similar petrogenetic model can be applied to the granodiorite pluton of Mt. Capanne (Elba) which belongs to the same magmatic cycle. Since the variation trends observed in the Tuscany volcanic rocks are similar to those reported from many acidic plutons, it appears that crustal anatexis accompanied by interaction with upper-mantle components has frequently played an important role in the genesis of the granitic rocks.

The October 4th, 1983 — Magnitude 4 earthquake in Phlegraean Fields: Macroseismic survey

On Oct. 4th, 1983 the area of Phlegraean Fields, near Naples (Southern Italy) was shaked by an earthquake of magnitude (M L) 4.0 that caused some damage in the town of Pozzuoli and its surroundings. This seismic event was the largest one recorded during the recent (1982–84) inflation episode occurred in the Phlegraean volcanic area, and a detailed macroseismic reconstruction of the event was carried out. Failing macroseismic data on other earthquakes occurred in Phlegraean Fields, the attenuation law of the intensity as a function of the distance as obtained for the Oct. 4th earthquake was compared with those obtained for other volcanic areas in central Italy —i.e., Tolfa, Monte Amiata — in order to check the reliability of the results obtained for Phlegraean Fields. The Blake's model of the earthquake of Oct. 4th, 1983 does not agree with the experimental data because isoseismals contain areas larger than those shown by the model. This result has been interpreted as an effect of energy focusing due to a reflecting layer 6–8 km deep.

Geochronological study of the Monte Amiata Lavas (Central Italy)

K/Ar and fission track age measurements were performed on lava samples of Monte Amiata volcano (Central Italy) which is formed by a sequence of lava flows and lava domes ranging in composition from trachybasalts to high-SiO2 quartzlatites.

A Possible Source of Error in 14C Dates: Volcanic Emanations (Examples from the Monte Amiata District, Provinces of Grosseto and Sienna, Italy)

Wood from regular timbering of a shallow seated mine in Tuscany gave 14C ages of 5730 ± 100 years BP, much too old to be attributed to one of the known civilizations of Italy. This mine is located in a region of declining volcanic activity, noticeable especially through numerous emanations (natural or incidentally induced by drillings). It was suspected that the analyzed wood had grown in an environment where the normal atmosphere had been diluted by volcanic emanations. To check this hypothesis, living plants (trees, bushes and reeds) and volcanic emanations have been sampled and their 14C content measured. All present day plants are depleted in 14C, giving a fictitious age different from 0 (1805, 1820, 2540, 4350 years BP). Of the gaseous emanations sampled, two have a high pressure and show virtually no 14C (>41,000 years BP). Two others have a pressure close to atmospheric, and small amounts of 14C were introduced by atmospheric contamination (22,570 and 30,580 years BP).Conclusion: plants grown in the vicinity of volcanic emanations have 14C activities that are too low because of a natural 14C dilution and yield anomalously high ages. The δ13C values obtained for two of these plants (—27.4‰ and —23.7‰) are close to the average for plants in general (—25‰), whereas the CO2 of mofettes is heavier than atmospheric CO2.

CO 2 distribution in the atmosphere and noise survey after blow-out in alfina 1 well, Northern Latium, Italy

A water-dominated geothermal reservoir, with a gas cap (mainly CO 2) on the reservoir roof, was individualed in Torre Alfina zone, northern Latium, about 30 km south-east of Monte Amiata. The first exploratory well (Alfina 1), drilled in 1973, blew-out spontaneously so that no production casing could be inserted. After well shut-in several surface gas manifestations appeared which were considered of some risk to the environment. This paper describes the methods used to determine the degree of pollution and the total area involved. The study of the gas dispersion in the atmosphere, the noise resulting from production, and the meteorological conditions in the area, was used in drawing up a disposal plant project; this plant will be assembled on future wells as a safety measure where large quantities of fluids are involved.

Application of a Stabilized XRF System in Mercury Determinations of Minerals

This paper describes a system of analysis for the rapid determination of mercury content in samples taken from Monte Amiata mines. The technique is based on the counting of Hg XK-rays excited by a 57Co source. Signal processing unit is characterized by an Automatic Gain Control Amplifier in order to correct pulse amplitude errors caused by detector or main amplifier gain shifts.

Hydrogeochemistry of the region between Monte Amiata and Rome

The study carried out in the region limited by the Mt. Amiata zone to the north, the river Tiber to the east and SE, Rome to the south and the Tyrrhenian sea to the west, is aimed at investigating the thermal and mineral manifestations from the hydrogeological and geochemical point of view. These manifestations (about 200 in all) are distributed over an area exceeding 5000 km 2. The investigation enabled to locate the areas of possible supply of meteoric waters and to determine the pattern of underground circulation down to a depth of approximately 1000–1200 m. Consequently, the most preferential areas as possible reservoirs of hyperthermal fluids have been singled out. In this connection, some ions or compounds such as boron, silica, chlorine, magnesium and sulphates proved to be particularly significant. Generally speaking, thermomineral manifestations represent the surface trace of two essential types of circulation: one, occurring almost exclusively within the volcanic cover (2–300 m at most) and the other, deeper, prevalently involving the calcareous Mesozoic substratum at various levels (6–700 m at least). Because of particular lithological and tectonic situations, more or less marked mixings occur locally between the above-said types of circulation, From such mixings a series of different effluents, which feature chemical and thermal characteristics intermediate between those of the meteoric waters and those of the deep thermomineral waters, originates.

Geothermal gradient and heat flow in the radicofani region (East of Monte Amiata, Italy)

Exploration carried -out in the central-western part of the Monte Amiata region until 1966 confirmed the existence of three producing fields in the areas of Bagnore, Piancastagnaio and Poggio Nibbio. On the contrary, eastwards of Monte Amiata, towards the Radicofani area, the border of the region of potential interest for endogenous fluid exploration had not vet been defined. Geological surveys previously carried out in this area merely pointed to the existence of some favourable factors for preliminary investigations to be continued. The existence of a rather recent volcanic activity (Pliocene) and other general favourable features suggested the advisability of a geothermal prospection in the area of the neogenic Radicofani graben. Such prospection was carried out by means of 61 shallow wells (average depth 33 m) located in an area of about 300 km 2. The prospection was based on temperature measurements by platinum resistance thermometers and on thermal conductivity measurements. The latter were performed by the Von Herzen-Maxwell needle probe method on cores drilled from suitable depths of each well. The iso-gradient and iso-flow maps thus obtained indicate that the surveved region is an area of non-specific anomaly, the values of which merely represent the depletion of the nearby Monte Amiata geothermal anomaly.

Progress report on geothermal development in Italy

This paper deals with geothermal development in Italy from 1960 to 1969. It describes results obtained thanks to technological progress in equipment for geothermal plants and enhancement of research and exploitation of endogenous resources existing in Larderello and Monte Amiata regions. Total capacity installed in Italian geothermal plants has risen from 285,200 kW as of December 1960 to 384,100 kW as of December 1969. In the same period gross geothermal power production has increased from 2103.9 to 2746.8 million kWh. Geothermal prospections prior to 1961 were focused in the Larderello and Monte Amiata regions, but in the period under consideration they have been systematically extended to several other areas of potential interest for endogenous fluids research. Deep exploration of the region of Monte Amiata has been completed and preliminary studies and investigations have started in Viterbo-Monte Cimino, Monti Volsini, Roccamonfina and Naples regions.

Rubidium et caesium dans biotite, sanidine et verre des ignimbrites de Toscane (Italie)

The results are communicated of a study of rubidium, caesium in the biotite and glass of the Tuscany ignimbrites. Rb contents progressively diminish from biotite (575–847 p.p.m.) to glass (395–622 p.p.m.) and to sanidine (328–480 p.p.m.). Cs is essentially concentrated in glass (27–78 p.p.m.) and enters with difficulty into biotite (18–45 p.p.m.) and into sanidine (7–19 p.p.m.). Rb repartition coefficient between biotite-sanidine and between glass-sanidine shows a higher formation temperature in the ignimbrites of Monte Amiata and Monte Cimino than in those of San Vincenzo and Roccastrada. Rb repartition equilibrates between biotite-sanidine and with respect to some exceptions between glass-sanidine. In that second case, equilibrium is connected to the low variation of Rb concentration during the course of crystallization as well as with the low solidification index (approx. 50%). That equilibrium seems less established between glass-biotite, especially in the Monte Amiata and Monte Cimino areas. Because Rb is present, the repartition of Cs between glass-sanidine produces aberrant results with regard to experimental and theoretical data.

Laminar Viscous Flowage Structures in Ash-Flow Tuffs from Gran Canaria, Canary Islands: A Discussion

Previous articleNext article No AccessDiscussionLaminar Viscous Flowage Structures in Ash-Flow Tuffs from Gran Canaria, Canary Islands: A DiscussionDonald C. NobleDonald C. Noble Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Journal of Geology Volume 76, Number 6Nov., 1968 Article DOIhttps://doi.org/10.1086/627396 Views: 3Total views on this site Citations: 15Citations are reported from Crossref Copyright 1968 University of ChicagoPDF download Crossref reports the following articles citing this article:Claudia Principe, Luigina Vezzoli Monte Amiata volcano (Tuscany, Italy) in the history of volcanology: 2—its role in the definition of “ignimbrite” concepts and in the development of the “rheoignimbrite” model of Alfred Rittmann, Rendiconti Lincei. Scienze Fisiche e Naturali 31, no.33 (Jul 2020): 539–561.https://doi.org/10.1007/s12210-020-00932-8Steven W. Novak Eruptive History of the Rhyolitic Kane Springs Wash Volcanic Center, Nevada, (Mar 2014): 8603–8615.https://doi.org/10.1002/9781118782095.ch27Howard R. Horgrove, Petro-Lewis Denver, Michael F. Sheridan Welded Tuffs Deformed into Megarheomorphic Folds During Collapse of the McDermitt Caldera, Nevada-Oregon, (Mar 2014): 8629–8638.https://doi.org/10.1002/9781118782095.ch29Philip T Leat, Hans-Ulrich Schmincke Large-scale rheomorphic shear deformation in Miocene peralkaline ignimbrite E, Gran Canaria, Bulletin of Volcanology 55, no.33 (Feb 1993): 155–165.https://doi.org/10.1007/BF00301513Kelsie A. Dadd Structures within large volume rhyolite lava flows of the Devonian Comerong Volcanics, southeastern Australia, and the Pleistocene Ngongotaha lava dome, New Zealand, Journal of Volcanology and Geothermal Research 54, no.1-21-2 (Dec 1992): 33–51.https://doi.org/10.1016/0377-0273(92)90113-RMichael J Branney, Peter Kokelaar A reappraisal of ignimbrite emplacement: progressive aggradation and changes from particulate to non-particulate flow during emplacement of high-grade ignimbrite, Bulletin of Volcanology 54, no.66 (Aug 1992): 504–520.https://doi.org/10.1007/BF00301396Antony John Reedman, Ki Hwa Park, Richard James Merriman, Seon Eok Kim Welded tuff infilling a volcanic vent at Weolseong, Republic of Korea, Bulletin of Volcanology 49, no.33 (Jun 1987): 541–546.https://doi.org/10.1007/BF01080448P.T. Leat Interaction of a rheomorphic peralkaline ash-flow tuff and underlying deposits, Menengai volcano, Kenya, Journal of Volcanology and Geothermal Research 26, no.1-21-2 (Oct 1985): 131–145.https://doi.org/10.1016/0377-0273(85)90049-6Steven W. Novak Eruptive history of the rhyolitic Kane Springs Wash Volcanic Center, Nevada, Journal of Geophysical Research 89, no.B10B10 (Jan 1984): 8603.https://doi.org/10.1029/JB089iB10p08603Howard R. Hargrove, Denver Petro-Lewis, Michael F. Sheridan Welded tuffs deformed into megarheomorphic folds during collapse of the McDermitt Caldera, Nevada-Oregon, Journal of Geophysical Research 89, no.B10B10 (Jan 1984): 8629.https://doi.org/10.1029/JB089iB10p08629J.A. Wolff, J.V. Wright Rheomorphism of welded tuffs, Journal of Volcanology and Geothermal Research 10, no.1-31-3 (May 1981): 13–34.https://doi.org/10.1016/0377-0273(81)90052-4W. D. Birch Petrogenesis of some palaeozoic rhyolites in Victoria, Journal of the Geological Society of Australia 25, no.1-21-2 (Aug 2007): 75–87.https://doi.org/10.1080/00167617808729015R. Macdonald, D. K. Bailey, F. Barberi Recommendations for further studies on the peralkaline oversaturated volcanic rocks, Bulletin Volcanologique 38, no.22 (Jun 1974): 828–860.https://doi.org/10.1007/BF02596910Brian E. Lock Zonal schemes in ancient ignimbrites, Geological Magazine 108, no.22 (May 2009): 103–109.https://doi.org/10.1017/S0016756800051116J.N. Rosholt, D.C. Noble Loss of uranium from crystallized silicic volcanic rocks, Earth and Planetary Science Letters 6, no.44 (Jul 1969): 268–270.https://doi.org/10.1016/0012-821X(69)90166-6

The self-sealing geothermal field

The self-sealing geothermal field

Remarks on the geothermal research in the region of Monte Amiata (Tuscany — Italy)

Remarks on the geothermal research in the region of Monte Amiata (Tuscany — Italy)

Antimony deposits of Tuscany

The principal antimony deposits of Tuscany, Italy, are found in the Manciano district; they form tabular or sheet-like replacement bodies in upper Triassic dolomitic limestones along sedimentary or fault contacts with relatively impermeable Tertiary strata. Antimony is also present in many of the cinnabar deposits of the district, and both ores are believed to be genetically related to the emplacement of the Monte Amiata trachyte dome during the Quaternary.