Composition and processes of the mantle lithosphere in northeastern Brazil and Fernando de Noronha: evidence from mantle xenoliths     

Giorgio Rivalenti  Maurizio Mazzucchelli  Vicente A.V. Girardi  Riccardo Vannucci  M. Adelaide Barbieri  Alberto Zanetti  Steve L. Goldstein 《Contributions to Mineralogy and Petrology》2000,138(4):308-325

Spinel–peridotite facies mantle xenoliths in Cenozoic alkali basalts of the Pico Cabuji volcano (Rio Grande do Norte State, Northeast Brazil) and the adjacent South Atlantic oceanic island of Fernando de Noronha are studied for: (1) the information they provide on the composition of the lithospheric component in the erupted basalt geochemistry, and (2) to check the effects of the Fernando de Noronha plume track on the mantle lithosphere. Xenoliths from Pico Cabuji are protogranular lherzolites and porphyroclastic harzburgites recording average equilibrium temperatures of 825 ± 116 and 1248 ± 19 °C, respectively. Pressure in the porphyroclastic xenoliths ranges from 1.9 to 2.7 GPa (Ca-in-olivine geobarometer). Both groups show major element chemical variation trends in whole-rock and Ti and HREE (Er, Yb) variations in clinopyroxene consistent with fractional melting and basalt extraction. REE (rare earth element) profiles of clinopyroxenes vary from LREE (La, Ce) enriched (spoon shaped) to LREE depleted in the protogranular group, whereas they are slightly convex upward in most porphyroclastic clinopyroxenes. HFSE (Ti and Zr) negative anomalies are in general modest in the clinopyroxenes of both groups. Xenoliths from Fernando de Noronha have textural variations similar to those of Pico Cabuji. Protogranular and porphyroclastic samples have similar temperature (1035 ± 80 °C) and the pressure is 1–1.9 and 2.3 GPa, respectively. Whole-rock chemical variation trends overlap and extend further than those of Pico Cabuji. The trace element profiles of the clinopyroxenes of the porphyroclastic xenoliths are enriched in La up to 30 × PM and are smoothly fractionated from LREE to HREE, with deep, negative, Zr and Ti anomalies. The geochemical heterogeneities of the xenoliths from both localities are interpreted in terms of reactive porous percolation. The porphyroclastic xenoliths from Pico Cabuji represent the lower part of a mantle column (the head of a mantle diapir, at the transition conductive–adiabatic mantle), where OIB infiltration triggers melting, and the protogranular xenoliths the top of the mantle column, chromatographically enriched by percolation at a low melt/rock ratio. This interpretation may also apply for Fernando de Noronha, but the different geochemical signature recorded by the clinopyroxenes requires a different composition of the infiltrated melt. Nd and Sr isotopes of the Pico Cabuji porphyroclastic clinopyroxenes (¹⁴³Nd/¹⁴⁴Nd= 0.51339–0.51255, ⁸⁷Sr/⁸⁶Sr=0.70275–0.70319) and of Fernando de Noronha (¹⁴³Nd/¹⁴⁴Nd=0.51323–0.51285, ⁸⁷Sr/⁸⁶Sr=0.70323–0.70465) plot on distinct arrays originating from a similar, isotopically depleted composition and trending to low Nd–low Sr (EMI) and low Nd–high Sr (EMII), respectively. Correlation of the isotope variation with geochemical parameters indicates that the isotopic variation was induced by the metasomatic component, of EMI type at Pico Cabuji and of EMII type at Fernando de Noronha. These different components enriched a lithosphere isotopically similar to DMM (depleted MORB mantle) at both localities. At Fernando de Noronha, the isotopic signature of the metasomatic component is similar to that of the ∼ 8 Ma old lavas of the Remedios Formation, suggesting that this is the age of metasomatism. At Pico Cabuji, the mantle xenoliths do not record the high ⁸⁷Sr/⁸⁶Sr component present in the basalts. We speculate that the EMII component derives from a lithospheric reservoir, which was not thermally affected during mantle metasomatism at Pico Cabuji, but was mobilized by the hotspot thermal influence at Fernando de Noronha. This interpretation provides a plausible explanation for the presence of distinct metasomatic components at the two localities, which would be difficult to reconcile with their genetic relationship with the same plume. Received: 12 June 1999 / Accepted: 13 December 1999  相似文献   

Impact of model free parameters and sea-level rise uncertainties on 20-years shoreline hindcast: the case of Truc Vert beach (SW France)     

Maurizio D'Anna  Déborah Idier  Bruno Castelle  Gonéri Le Cozannet  Jeremy Rohmer  Arthur Robinet 《地球表面变化过程与地形》2020,45(8):1895-1907

Shoreline change is driven by various complex processes interacting at a large range of temporal and spatial scales, making shoreline reconstructions and predictions challenging and uncertain. Despite recent progress in addressing uncertainties related to the physics of sea-level rise, very little effort is made towards understanding and reducing the uncertainties related to wave-driven shoreline response. To fill this gap, the uncertainties associated with the long-term modelling of shoreline change are analysed at a high-energy cross-shore transport dominated site. Using the state-of-the-art LX-Shore shoreline change model, we produce a probabilistic shoreline reconstruction, based on 3000 simulations over the past 20 years at Truc Vert beach, southwest France, whereby sea-level rise rate, depth of closure and three model free parameters are considered uncertain variables. We further address the relative impact of each source of uncertainty on the model results performing a Global Sensitivity Analysis. This analysis shows that the shoreline changes are mainly sensitive to the three parameters of the wave-driven model, but also that the sensitivity to each of these parameters is strongly modulated seasonally and interannually, in relation with wave energy variability, and depends on the time scale of interest. These results have strong implications on the model skill sensitivity to the calibration period as well as for the predictive skill of the model in a context of future climate change affecting wave climate and extremes. © 2020 John Wiley & Sons, Ltd.  相似文献   

Real-time assimilation of streamflow observations into a hydrological routing model: effects of model structures and updating methods   总被引：1，自引：1，他引：0  

Maurizio Mazzoleni  Haksu Lee  Yuqiong Liu  Dong-Jun Seo  Alessandro Amaranto 《水文科学杂志》2018,63(3):386-407

This paper comparatively assesses the performance of five data assimilation techniques for three-parameter Muskingum routing with a spatially lumped or distributed model structure. The assimilation techniques used include direct insertion (DI), nudging scheme (NS), Kalman filter (KF), ensemble Kalman filter (EnKF) and asynchronous ensemble Kalman filter (AEnKF), which are applied to river reaches in Texas and Louisiana, USA. For both lumped and distributed routing, results from KF, EnKF and AEnKF are sensitive to the error specification. As expected, DI outperformed the other models in the case of lumped modelling, while in distributed routing, KF approaches, particularly AEnKF and EnKF, performed better than DI or nudging, reflecting the benefit of updating distributed states through error covariance modelling in KF approaches. The results of this work would be useful in setting up data assimilation systems that employ increasingly abundant real-time observations using distributed hydrological routing models.  相似文献   

Geoprospecting Survey in the Archaeological Site of <Emphasis Type="Italic">Aquinum</Emphasis> (Lazio,Central Italy)     

Maurizio Lazzari  Lara De Giorgi  Giuseppe Ceraudo  Raffaele Persico 《Surveys in Geophysics》2018,39(6):1167-1180

In this paper, the results of a ground penetrating radar (GPR) prospecting survey performed in the Roman archaeological site of Aquinum are shown. The prospecting was performed in two distinct areas. The first one was close to the remains of the ancient thermal baths, where a public project intends to build a car park. The second area is close to an apsidal Roman building, and it was of interest to establish whether, and possibly up to what extent, the remains of this partially revealed structure continue, or maybe whether meaningful further structures are present.  相似文献   

Revised seismotectonic model of NE Italy and W Slovenia based on focal mechanism inversion     

Gianni Bressan  Carla Barnaba  Pierluigi Bragato  Maurizio Ponton  Andrea Restivo 《Journal of Seismology》2018,22(6):1563-1578

The study is focusing on the stress and strain inversions from focal mechanisms in a revised seismotectonic zonation of northeastern Italy and western Slovenia. The recent increase of monitoring capability of the local seismic network, the updated geological-structural model of the area, and the novelties emerged from studies on the spatial organization of the seismicity allowed a redefinition of the seismotectonic zones. The stress and strain tensors inversion is inferred from 203 focal mechanisms, corresponding to earthquakes occurred between 1984 and 2016 with coda-duration magnitude range from 2.0 to 5.6. The inverted stress domains reveal an articulated picture of the interaction of the Adria microplate with the Eurasian plate. A dominant strike-slip stress field characterizes the eastern part of the area, while the seismotectonic zones of the central part are undergoing to thrusting regime. The stress pattern inferred in the western part of the study area outlines a complex picture with prevailing strike-slip regime and dominant compression only in a seismotectonic zone. The comparison of stress and strain tensor orientations evidences a relative uniformity of the crustal strength in the eastern and northwestern zones of the study area. The central and western zones appear to be characterized by planes of mechanical weakness not favorably oriented for failure with respect to the stress tensor.  相似文献   

Influence of spatial distribution of sensors and observation accuracy on the assimilation of distributed streamflow data in hydrological modelling     

Maurizio Mazzoleni  Leonardo Alfonso  Dimitri Solomatine 《水文科学杂志》2017,62(3):389-407

The aim of this study is to assess the influence of sensor locations and varying observation accuracy on the assimilation of distributed streamflow observations, also taking into account different structures of semi-distributed hydrological models. An ensemble Kalman filter is used to update a semi-distributed hydrological model as a response to measured streamflow. Various scenarios of sensor locations and observation accuracy are introduced. The methodology is tested on the Brue basin during five flood events. The results of this work demonstrate that the assimilation of streamflow observations at interior points of the basin can improve the hydrological models according to the particular location of the sensors and hydrological model structure. It is also found that appropriate definition of the observation accuracy can affect model performance and consequent flood forecasting. These findings can be used as criteria to develop methods for streamflow monitoring network design.  相似文献   

From flood risk mapping toward reducing vulnerability: the case of Addis Ababa     

De Risi  Raffaele  Jalayer  Fatemeh  De Paola  Francesco  Carozza  Stefano  Yonas  Nebyou  Giugni  Maurizio  Gasparini  Paolo 《Natural Hazards》2020,100(1):387-415

Natural Hazards - Flood risk maps for the built environment can be obtained by integrating geo-spatial information on hazard, vulnerability and exposure. They provide precious support for strategic...  相似文献