Basic Regional Crustal Setting And Superimposed Local Pluton-Intrusion-Related Tectonics In The Larderello-M Amiata Geothermal Province, From Integrated Crop Seismic Data

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Journal Article: Basic Regional Crustal Setting And Superimposed Local Pluton-Intrusion-Related Tectonics In The Larderello-M Amiata Geothermal Province, From Integrated Crop Seismic Data

Abstract
The Larderello-M. Amiata geothermal province has been explored by two transcrustal seismic sections of the CROP Project: CROP-18A across the Larderello area and CROP-18B across the M. Amiata and SE Larderello area. in this paper the author presents and describes the results of a new carefully conducted interpretation of the CROP-18 sections and of other integrating seismic lines, stressing the importance of the CROP project also for geothermal exploration-exploitation activity. The purpose of the work is the reconstruction of the crustal tectono-stratigraphic setting of the area extending from the Tyrrhenian coast to the A Cetona thrust. The results obtained are very important and decisely innovative as regard to the definition of predicted geothermal magmatic bodies. In fact, for the first time two big plutons intruded in the deep upper crust are seismically imaged in a clear manner. Both the plutons are characterized by marked negative Bouguer gravity anomalies and are associated with anti-Apennine transcurrent (transfer) faults through which the magma flowed during the plutonic emplacement. The lower crust and basal upper crust, beneath the plutons, give rise to a marked synclinal fold. Immediately over the pluton a highly reflective K-interval is evident, very likely represented by foliation or thin lamination saturated by fluids. The above-pluton upper crust forms an anticlinal fold on both the plutons. Finally, this new reconstruction of the plutons' setting demonstrates, very clearly, that the high-angle normal faults are not generated by crustal distension, but are pluton-intrusion-related collapse faults, absent outside the plutons' area. Lack of Tuscan units over the Triassic evaporite (or even of both evaporite and cover) is not due to distension but to tectonic detachment and outward transportation. According to this new careful seismic control that has been carried out, no significant crustal distension is seismically acceptable from the Tyrrhenian coast to the A Cetona thrust. Continuing pluton accretion dynamics, active since Pliocene, preserves high temperatures and long-term geothermal resources, keeping tectonically open the ways of hot fluids ascent. As occurred in the hydrocarbon history, also in the geothermal exploration-exploitation a ne v stage of systematic employment of advanced seismic techniques is essential for discovery of new resources marked by drastic reduction of unsuccessful boreholes and production costs.

Author 
I. R. Finetti








Published Journal 
Bollettino Della Societa Geologica Italiana, 2006





DOI 
Not Provided
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Citation

I. R. Finetti. 2006. Basic Regional Crustal Setting And Superimposed Local Pluton-Intrusion-Related Tectonics In The Larderello-M Amiata Geothermal Province, From Integrated Crop Seismic Data. Bollettino Della Societa Geologica Italiana. (!) .