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E. Pandeli C. Bartolini A. Dini E. Antolini 《International Journal of Earth Sciences》2010,99(6):1357-1381
In order to add new data to the knowledge of the paleogeography of Southern Tuscany and the Tuscan shelf, a multidisciplinary
study on the petrology and distribution of magmatic clasts of the widely exposed Messinian, Pliocene, and Quaternary sediments
in Southern Tuscany was carried out. The magmatic clasts consist of porphyric aplites and subordinate granite porphyries,
which derive from eroded subvolcanic acidic bodies. The porphyric aplite clasts were analyzed in detail to define their textural,
petrographic, and chemical (major and trace elements, Sr and Nd isotopic composition) features. The porphyric aplite clasts
show strong affinities with the 8.4–7.9 Ma old Capo Bianco aplite, whereas the granite porphyry clasts have affinities with
the Portoferraio porphyry (ca. 8 Ma) which intruded the Cretaceous and Paleogene Flysch Units and the Ophiolitic Unit in central-western
Elba Island (Northern Tyrrhenian Sea). The present outcrops of the Capo Bianco aplite in central Elba Island cannot be considered
as the source rock for the Late Messinian gravels, because at that time such Capo Bianco aplite (located at the lower portion
of the laccolitic stack) was there buried at several kilometers depth. However, other Capo Bianco-like aplitic bodies outcropped
during the latest Miocene in the host rocks above and also around the 6.8 Ma M. Capanne Pluton in the western Elba areas.
The exposure of such bodies was made possible by the activation of the central Elba detachment fault (=CEF), due to the uplift
of the M. Capanne pluton. This uplift displaced a significant portion of the cover (including the upper portion of the laccolithic
stack) of the granitoid body at about 6, 7 Ma, thus allowing the erosion of the lower part of the laccolith complex made up
of the Capo Bianco aplite and of the Portoferraio porphyry and leaving still buried the M. Capanne pluton. The paleogeographic
picture of Southern Tuscany arising from the collected evidences is the following: during Late Messinian, the clasts were
dispersed by a SSW/NNE-trending complex fluvial system in the Colline Metallifere area. The Early Pliocene extensional tectonics
cut off the detrital inputs from the Messinian source areas, because of the onset of the Piombino Channel and of the Campiglia–Gavorrano
Ridge. During the Pliocene, the clasts were cannibalized from the previous sedimentary units and reached the easternmost areas
due the eastward progressive uplift of the Colline Metallifere, likely connected with the coeval magmatic intrusions. Finally,
the Quaternary regional uplift allowed a drainage reversal and a backward displacement of the aplitic clasts toward the Tyrrhenian
coast. These data point to a rapidly evolving drainage pattern in Southern Tuscany during the considered time interval, which
was mostly driven by the intrusion and uplift of the Messinian to Quaternary plutons. The morpho-tectonic evolution is well
framed also within the models since long accepted for the Northern Apennine geodynamics, characterized by an overall eastward
shift of the orogenic front. 相似文献
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Investigation of hydroelastic ship responses has been brought to the attention of the scientific and engineering world for several decades. There are two kinds of high-frequency vibrations in general ship responses to a large ocean-going ship in its shipping line, so-called springing and whipping, which are important for the determination of design wave load and fatigue damage as well. Because of the huge scale of an ultra large ore carrier (ULOC), it will suffer seldom slamming events in the ocean. The resonance vibration with high frequency is springing, which is caused by continuous wave excitation. In this paper, the wave-induced vibrations of the ULOC are addressed by experimental and numerical methods according to 2D and 3D hydroelasticity theories and an elastic model under full-load and ballast conditions. The influence of loading conditions on high-frequency vibration is studied both by numerical and experimental results. Wave-induced vibrations are higher under ballast condition including the wave frequency part, the multiple frequencies part, the 2-node and the 3-node vertical bending parts of the hydroelastic responses. The predicted results from the 2D method have less accuracy than the 3D method especially under ballast condition because of the slender-body assumption in the former method. The applicability of the 2D method and the further development of nonlinear effects to 3D method in the prediction of hydroelastic responses of the ULOC are discussed. 相似文献
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We have examined the data of 600 geothermal wells and re‐interpreted approximately 500 km seismic profiles through the field of Larderello, Italy. We conclude that the two main seismic reflectors present below the geothermal area host two different fluids: (1) superheated steam in the upper H‐horizon (reached by drillholes) and (2) supercritical fluid in the deeper K‐horizon (reached by few unproductive or damaged wells). The superheated steam has the physical and chemical connotation of the geothermal fluid exploited so far at Larderello, whereas the supercritical fluid represents a potential unconventional deep‐seated resource still to be assessed. The high temperatures existing in correspondence of the K‐horizon suggest that the silica‐rich rocks are close to a plastic state and the fluids should remain confined in a medium sealed to the confining rocks, unless occasional fluid overpressure and abrupt high strain rates occur. 相似文献
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