HTLP metamorphism and fluid-fluxed melting during multistage anatexis of continental crust (N Sardinia,Italy)     

Leonardo Casini  Matteo Maino  Antonio Langone  Giacomo Oggiano  Stefania Corvò  Joan Reche Estrada  Montserrat Liesa 《Journal of Metamorphic Geology》2023,41(1):25-57

The Variscan high-grade metamorphic basement of northern Sardinia and southern Corsica record lower Carboniferous anatexis related to post-collisional decompression of the orogen. Migmatites exposed in the Punta Bianca locality (Italy) consist of quartz + biotite + plagioclase + K-feldspar orthogneisses, garnet and cordierite-bearing diatexite and metatexites, derived from metasediments. Field evidence, petrographic observations, ELA-ICP-MS zircon and monazite dating and pseudosection modelling suggest that anatexis was apparently episodic involving two main stages of partial melting. Using pseudosection modelling, we infer that the first stage of partial melting is in the upper amphibolite facies (~0.45 GPa at ~740°C). Cordierite overgrowths replacing sillimanite, combined with the composition of plagioclase and K-feldspar, suggest decompression followed cooling below the solidus at low pressures of ~0.3 GPa. The age of the first anatectic event is not precisely constrained because of extensive resetting of the isotopic systems during the second melting stage, yet few zircons preserve a lower Carboniferous age which is consistent with the regional dataset. This lower Carboniferous migmatitic fabric is offset by a network of pseudotachylyte-bearing faults suggestive of cooling to greenschist facies conditions. Garnet/cordierite-bearing diatexites incorporate fragments of pseudotachylite-bearing orthogneiss and metatexites. Pseudosection modelling indicates nearly isobaric re-heating up to ~750°C, followed by further cooling below the solidus. The inferred P–T path is consistent with decompression and cooling of the Variscan crust through post-collisional extension and collapse of the thickened orogenic crust, followed by nearly isobaric re-heating at low pressures (~0.3 GPa) yielding to a second melting stage under LP-HT conditions. U/Th-Pb monazite ages for diatexite migmatites indicate an upper bound of 310–316 Ma for the second melting stage, suggesting that the second melting stage is coincident with the regional phase of crustal shearing. The cause of the high geothermal gradient required for re-heating during the second melting stage is unknown but likely requires some heat source that was probably related to dissipation of mechanical work within crustal-scale shear zones. According to this interpretation, some upper Carboniferous peraluminous granite precursors of the Corsica–Sardinia Batholith could be the outcome rather than the cause of the late-Variscan high-T metamorphism.  相似文献   

Phylogeography of the bluespotted cornetfish,Fistularia commersonii: a predictor of bioinvasion success?          下载免费PDF全文

Alexis M. Jackson  Kimberly Tenggardjaja  Gerardo Perez  Ernesto Azzurro  Daniel Golani  Giacomo Bernardi 《Marine Ecology》2015,36(4):887-896

Biological invasions result in huge ecological and economic impacts; therefore, a great amount of effort is dedicated to predicting the potential success of newly established or candidate bioinvaders. Thus far, over 90 species of fish have entered the Mediterranean Sea via the Suez canal, the so‐called Lessepsian bioinvaders. The bluespotted cornetfish, Fistularia commersonii, is remarkable in its ability to disperse within the Mediterranean and has been dubbed ‘the Lessepsian sprinter’. In just a few years, starting in 2000, it expanded over the entire area, from the Suez Canal to Gibraltar. Theoretical predictions correlate the dispersal capabilities of an invader in its native range (using the population genetic metrics, F_st, as a proxy) with its dispersal capability in its invading area (continuous extent of spread, CES). Here, we estimated the population genetic characteristics of Indo‐Pacific native populations of F. commersonii in order to determine if this Lessepsian ‘sprinter’ fits the predictive model of dispersal. Indeed, we found that even in the case of such a very rapid range expansion, the predicted relationship between F_st and CES is fulfilled in F. commersonii.  相似文献   

The SI,a universal language     

P. Giacomo 《Marine Geodesy》2013,36(4):312-321

Abstract

The SI has inherited and developed the fundamental features of the Systéme Métrique: simplicity, universality, and mainly coherence. It has to adapt itself steadily to the new fields and the increasing demand of accuracy, with the constraints of improving its coherence and universality and maintaining the continuity of measurements. The SI cannot ignore such natural units as the day, the turn, and their usual fractions and multiples; they must be tolerated for general use in spite of their incoherence. Such tolerances must be severely restricted. It is the condition for the SI to become and remain a truly universal language common to all fields and all countries. A few simple rules follow that any scientist should keep in mind.  相似文献   

Spring thermal resources for grapevine in Kőszeg (Hungary) deduced from a very long pictorial time series (1740–2009)     

Simone Gabriele Parisi  Moreno Mauro Antoniazzi  Gabriele Cola  Lorenzo Lovat  Luigi Mariani  Giacomo Morreale  Kiss Zoltan  Antonio Calò 《Climatic change》2014,126(3-4):443-454

Since 1740 until now, the Book of Vine Branches encompasses beautiful pictorial representations of shoots and sprouts, collected every year on April 24th in the vineyards of the Hungarian town of K?szeg. A long time series (1740–2009) of sprouts phenological development coded with the BBCH scale is obtained through paintings visual inspection. Consequently, a model relating sprouts development with thermal resources accumulation is developed on the base of Wien daily air temperature series for the 1857–2009 period. Thermal resources is obtained with the Normal Heat Hours approach, a response curve method that takes into account the nonlinear response of phenological development to temperature. The model, calibrated and validated on the 1930–2009 period, shows an overestimation of thermal resources when applied to the 1857–1929, due to the more advanced phenology of that phase. Since this advance can be ascribed to genetics and management instead of more favorable thermal conditions, model outputs previous to 1930 are decreased by a constant factor. Finally, the 1740–2009 time series of grapevine spring thermal resources is obtained applying the model to the complete phenological time series. The analysis of the series highlights a first phase (1740–1780) characterized by high and stable availability of thermal resources during the 1740–1780, a second phase (1781–1820) with the lowest level of resources, a phase of intermediate availability (1821–1929) and a final present phase (1930–2009) with renewed high availability. The adopted method overcomes the lack of correlation for the post 1960 period shown by previous works.  相似文献   

Review of Modeling Approaches to Groundwater Flow in Deformed Carbonate Aquifers     

Giacomo Medici  Luca Smeraglia  Anita Torabi  Chartlotte Botter 《Ground water》2021,59(3):334-351

We discuss techniques to represent groundwater flow in carbonate aquifers using the three existing modeling approaches: equivalent porous medium, conduit network, and discrete fracture network. Fractures in faulted stratigraphic successions are characterized by dominant sets of sub-vertical joints. Grid rotation is recommended using the equivalent porous medium to match higher hydraulic conductivity with the dominant orientation of the joints. Modeling carbonate faults with throws greater than approximately 100 m is more challenging. Such faults are characterized by combined conduit-barrier behavior. The barrier behavior can be modeled using the Horizontal Flow Barrier Package with a low-permeability vertical barrier inserted to represent the impediment of horizontal flow in faults characterized by sharp drops of the piezometric surface. Cavities can occur parallel to the strike of normal faults generating channels for the groundwater. In this case, flow models need to account for turbulence using a conduit network approach. Channels need to be embedded in an equivalent porous medium due to cavities a few centimeters large, which are present in carbonate aquifers even in areas characterized by low hydraulic gradients. Discrete fracture network modeling enables representation of individual rock discontinuities in three dimensions. This approach is used in non-heavily karstified aquifers at industrial sites and was recently combined with the equivalent porous medium to simulate diffusivity in the matrix. Following this review, we recommend that the future research combines three practiced modeling approaches: equivalent porous medium, discrete fracture network, and conduit network, in order to capture structural and flow aspects in the modeling of groundwater in carbonate rocks.  相似文献   

Structural evolution of the '41st parallel zone': Tyrrhenian Sea     

Giacomo Spadini  Forese-Carlo Wezel 《地学学报》1994,6(6):552-562

The present study is based on the interpretation of more than 1300 km of 16 kJ sparker seismic profiles recorded in July 1990, during the Cruise T-41 of the Geological Institute of Urbino. The investigated area extends along the 41st parallel in the central Tyrrhenian Sea between the northern Sardinian margin to the west and the Latium–Campanian margin to the east. This zone, situated on continental crust, marks the boundary between the northern Tyrrhenian and the southern Tyrrhenian domains. A kinematic reconstruction is presented, based on the age-dating of the recognized structures (i.e. normal faults, reverse faults, anticline and flower structures). The evolution of the ‘41st parallel zone’ can be described in terms of polyphase tectonics characterized by different orientations of the stress field during time. The direction of the normal fault-trends, turned clockwise, striking NE–SW in the late Tortonian–Messinian, E–W in the early Pliocene, NNW–SSE in the late Pliocene and N–S during the Quaternary. The concurrence of compressional and strike-slip deformations suggests oblique shear motions across the 41st parallel. The occurrence of late Pliocene–Quaternary tectonic activity in the northern Tyrrhenian Sea, locally characterized by inversion tectonics, suggests active mechanisms (intraplate compression?) superimposed on the post-rift subsidence.  相似文献   

Acoustically estimated size distribution of sperm whales (Physeter macrocephalus) off the east coast of New Zealand     

Giacomo Giorli  Kimberly T. Goetz 《新西兰海洋与淡水研究杂志》2020,54(2):177-188

ABSTRACT

The length-frequency distribution of sperm whales (Physeter macrocephalus) was studied on the east coast of NZ using passive acoustic recorders moored offshore of Kaikoura, Cape Palliser and Castlepoint. Sperm whale’s echolocation signals are unique among odontocete species. Their clicks are composed by multiple pulses resulting from the sound transmission within the whale head. The total length of the whales can be estimated by measuring the time delay between these pulses. A total of 997 length measurements were obtained from click trains using cepstral analysis (mean?=?14.6?m; min?=?9.6?m; max?=?18.3?m; std?=?1?m). The size-frequency distributions at all three locations were similar, although animals smaller than 12?m were not present offshore of Kaikoura. Animals of various sizes appeared to be present all year round, with no apparent seasonality in the occurrence of any size class.  相似文献   

The switching between zonal and blocked mid-latitude atmospheric circulation: a dynamical system perspective     

Davide Faranda  Giacomo Masato  Nicholas Moloney  Yuzuru Sato  Francois Daviaud  Bérengère Dubrulle  Pascal Yiou 《Climate Dynamics》2016,47(5-6):1587-1599

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Eine durch Tiefengesteinskontakt veränderte Uranlagerstätte     

P. Ramdohr  Giacomo Cevales 《Mineralium Deposita》1980,15(3):383-390

Zusammenfassung Die vorliegende Untersuchung befaßt sich mit einer Uranvererzung der permischen Sandsteine, welche sich in unmittelbarer Nähe des granodioritisch-tonalitischen Adamello-Plutons befunden hat. Geographisch liegen diese Vererzungen im westlichen Teil des Massivs, etwa bei 2120 m ü. d. M. In bezug auf den Mineralbestand und die Verwachsungen ist zu betonen, daß eine wohl zu erwartende allgemeine Mobilisierung und Rekristallisation der ursprünglichen Vererzung- — und des Nebengesteins —, zusammen aber mit z. T. auffallend mangelhaften Gleichgewichtseinstellungen vor sich gegangen sind. Bemerkenswert ist u. a. die Neubildung einer noch nicht bekannten Vanadium- und Eisen-Silikat-Verbindung.

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In this paper is investigated a uranium deposit in permian sandstones, which was situated in immediate neighbourhood to the granodioritic-tonalitic Adamello-pluton. The deposit occurs in the western part of the massiv, at an altitude of 2100 meter. With regard to the mineral associations and the related intergrowths it should be pointed out that the obvious phenomena related to the mobilisation and the recrystallisation of the ore — and of the ore bearing rocks —, are sometimes characterized by an evidently uncomplete equilibrium. Remarkable is the formation of a still unknown vanadium- and ironbearing opaque mineral.

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On the efficiency and effectiveness of automatic deep drainage systems during an extreme rainfall event: the Mendatica landslide case study (western Liguria,Italy)     

Pepe  Giacomo  Cevasco  Andrea  Piazza  Michele  Macciò  Roberto  Arrighetti  Fabio  Casagli  Nicola 《Landslides》2021,18(12):3799-3820

Landslides - This study presents the employment of automatic deep drainage systems to stabilize the Mendatica landslide, one of the largest relict landslides of western Liguria (north-western...  相似文献