Remarkably uniform oxygen isotope systematics for co-existing pairs of gem-spinel and calcite in marble,with special reference to Vietnamese deposits     

Anthony E. Fallick  Gaston Giuliani  Thomas Rigaudier  Adrian J. Boyce  Van Long Pham  Vincent Pardieu 《Comptes Rendus Geoscience》2019,351(1):27-36

Oxygen isotope systematics for co-existing pairs of gem-spinel and calcite in marble from Vietnam and other worldwide deposits have been determined in order to characterize the O-isotope fractionation between calcite and spinel. In Vietnam, the Δ¹⁸O_cc–sp (= 3.7 ± 0.1‰ for six samples from the An Phu and Cong Troi deposits) is remarkably constant. The combination of these data with those obtained on calcite–spinel pairs of Paigutan (Nepal, n = 2), Ipanko (Tanzania, n = 1), and Mogok (Myanmar, = 2) are also consistent with an overall Δ¹⁸O_cc–sp of 3.6 ± 0.3‰ for all the spinel samples (n = 11). The straight line correlation δ¹⁸O_cc = 0.96 δ¹⁸O_sp + 4.4 is excellent despite their worldwide geographic spread. The increment method of calculating oxygen isotope fractionation gave a geologically unreasonable temperature of formation for both minerals at 1374 °C when compared to temperatures obtained by mineral assemblage equilibrium of these marble type deposits, between 610 and 750 °C. The constant Δ¹⁸O_cc–sp reflects a constant temperature for this amphibolite facies assemblage, whose current best estimate is calculated at 620 ± 40 °C, but unquantified uncertainties remain.  相似文献   

Origin of emerald deposits of Brazil     

G. Giuliani  L. J. H. D. Silva  P. Couto 《Mineralium Deposita》1990,25(1):57-64

Precambrian emerald deposits of Brazil are found in a typical geologic setting with Archean basement and supracrustal, ultramafic, granitoid and rocks. Volcano-sedimentary series occur as imbricated structures or as bodies affected by complex folding and deformation. Emerald mineralization belongs to the classic biotite-schist deposit, which formed by the reaction of pegmatitic veins within ultrabasic rocks. At the same time, pegmatite-free emerald deposits linked to ductile shear zones are also known. Emerald formation is attributed to infiltrational metasomatic processes provoking a K-metasomatism of the ultrabasic rocks and also a desilication of the pegmatites. A new classification based on the geological setting, structural features, and ore paragenesis is proposed.  相似文献   

Co-seismic displacements associated to the Molise (Southern Italy) earthquake sequence of October–November 2002 inferred from GPS measurements     

R. Giuliani  M. Anzidei  L. Bonci  S. Calcaterra  N. D'Agostino  M. Mattone  G. Pietrantonio  F. Riguzzi  G. Selvaggi 《Tectonophysics》2007,432(1-4):21-35

The 2002 earthquake sequence of October 31 and November 1 (main shocks Mw = 5.7) struck an area of the Molise region in Southern Italy. In this paper we analyzed the co-seismic deformation related to the Molise seismic sequence, inferred from GPS data collected before and after the earthquake, that ruptured a rather deep portion of crust releasing a moderate amount of seismic energy with no surface rupture. The GPS data have been reduced using two different processing strategies and softwares (Bernese and GIPSY) to have an increased control over the result accuracy, since the expected surface displacements induced by the Molise earthquake are in the order of the GPS reliability. The surface deformations obtained from the two approaches are statistically equivalent and show a displacement field consistent with the expected deformation mechanism and with no rupture at the surface. In order to relate this observation with the seismic source, an elastic modeling of fault dislocation rupture has been performed using seismological parameters as constraints to the model input and comparing calculated surface displacements with the observed ones. The sum of the seismic moments (8.9 × 10¹⁷ Nm) of the two main events have been used as a constraint for the size and amount of slip on the model fault while its geometry has been constrained using the focal mechanisms and aftershocks locations. Since the two main shocks exhibit the same fault parameters (strike of the plane, dip and co-seismic slip), we modelled a single square fault, size of 15 km × 15 km, assumed to accommodate the whole rupture of both events of the seismic sequence. A vertical E–W trending fault (strike = 266°) has been modeled, with a horizontal slip of 120 mm. Sensitivity tests have been performed to infer the slip distribution at depth. The comparison between GPS observations and displacement vectors predicted by the dislocation model is consistent with a source fault placed between 5 and 20 km of depth with a constant pure right-lateral strike-slip in agreement with fault slip distribution analyses using seismological information. The GPS strain field obtained doesn't require a geodetic moment release larger than the one inferred from the seismological information ruling out significant post-seismic deformation or geodetic deformation released at frequencies not detectable by seismic instruments. The Molise sequence has a critical seismotectonic significance because it occurred in an area where no historical seismicity or seismogenic faults are reported. The focal location of the sequence and the strike-slip kinematics of main shocks allow to distinguish it from the shallower and extensional seismicity of the southern Apennines being more likely related to the decoupling of the southern Adriatic block from the northern one.  相似文献   

Laboratory simulation of photometric light curves of the asteroids     

M. A. Barucci  R. Casacchia  M. Fulchignoni  R. Burchi  A. Dipaoloantonio  C. Giuliani  L. Milano  F. Scaltriti  V. Zappala 《Earth, Moon, and Planets》1982,27(4):387-395

We report laboratory simulations of asteroid observations obtained using a specially designed apparatus SAM (the acronym stands for System for Asteroid Models).The aim of the experiment was to assess the geometrical and physical characteristics of an asteroidal body which may affect the shape of its light curve; and, in particular, the parameters which define asteroid orientation with respect to the observer, and the shape and surface morphology of the asteroids.The design and operation of the SAM is described in some detail and the first results obtained with models having a regular shape are presented and discussed.Istituto di Astrofisica Spaziale del CNR  相似文献   

Major zircon megacryst suites of the Indo-Pacific lithospheric margin (ZIP) and their petrogenetic and regional implications     

Lin Sutherland  Ian Graham  Gregory Yaxley  Richard Armstrong  Gaston Giuliani  Paul Hoskin  Victor Nechaev  Jon Woodhead 《Mineralogy and Petrology》2016,110(2-3):399-420

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Gem corundum deposits of Madagascar: A review     

Amos Fety Michel Rakotondrazafy  Gaston Giuliani  Daniel Ohnenstetter  Anthony E. Fallick  Saholy Rakotosamizanany  Alfred Andriamamonjy  Thogne Ralantoarison  Madison Razanatseheno  Yohann Offant  Virginie Garnier  Henri Maluski  Christian Dunaigre  Dietmar Schwarz  Voahangy Ratrimo 《Ore Geology Reviews》2008,34(1-2):134

Madagascar is one of the most important gem-producing countries in the world, including ruby and sapphires. Gem corundum deposits formed at different stages in the geological evolution of the island and in contrasting environments. Four main settings are identified: (1) Gem corundum formed in the Precambrian basement within the Neoproterozoic terranes of southern Madagascar, and in the volcano-sedimentary series of Beforona, north of Antananarivo. In the south, high-temperature (700 to 800 °C) and low-pressure (4 to 5 kbar) granulites contain deposits formed during the Pan-African orogenesis between 565 and 490 Ma. They accompany mafic and ultramafic complexes (ruby deposits of the Vohibory group), skarns at the contact between Anosyan granites and the Proterozoic Tranomaro group (sapphire deposits of the Tranomaro–Andranondambo district), and shear-zone corridors cross-cutting feldspathic gneisses, cordieritites and clinopyroxenites in the Tranomaro, Vohimena and Androyan metamorphic series (biotite schist deposits of Sahambano and Zazafotsy, cordieritites of Iankaroka and Ambatomena). The circulation of fluids, especially along discontinuities, allowed in-situ alkaline metasomatism, forming corundum host rocks related to desilicified granites, biotitites, “sakenites” and “corundumites”. (2) Gem corundum also occurs in the Triassic detrital formations of the Isalo group, as giant palaeoplacers in the Ilakaka–Sakaraha area. Here, sapphires and rubies may come from the metamorphic granulitic terranes of southern Madagascar. (3) Gem corundum deposits occur within the Neogene-Quaternary alkali basalts from Ankaratra (Antsirabe–Antanifotsy area) and in the Ambohitra Province (Nosy Be, Ambato and Ambondromifehy districts). Primary deposits are rare, except at Soamiakatra where ruby in gabbroic and clinopyroxenite xenoliths within alkali-basalts probably derive from mantle garnet peridotites. The blue-green-yellow sapphires typical of basaltic fields are always recovered in palaeoplacer (in karst formed upon Jurassic limestones from the Montagne d'Ambre, Antsiranana Province) and alluvial and soil placers (Ankaratra volcanic massif). (4) Deposits occur within Quaternary eluvial, colluvial and alluvial concentrations, such as high-quality rubies from the Andilamena and Vatomandry deposits.  相似文献   

Atlantic forcing of Pacific decadal variability   总被引：1，自引：0，他引：1  

Fred Kucharski  Farah Ikram  Franco Molteni  Riccardo Farneti  In-Sik Kang  Hyun-Ho No  Martin P. King  Graziano Giuliani  Kristian Mogensen 《Climate Dynamics》2016,46(7-8):2337-2351

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Hybrid simulation of a partial-strength steel–concrete composite moment-resisting frame endowed with hysteretic replaceable beam splices     

Roberto Andreotti  Giulia Giuliani  Nicola Tondini  Oreste S. Bursi 《地震工程与结构动力学》2023,52(1):51-70

This paper deals with the seismic response assessment of a steel–concrete moment-resisting frame (MRF) equipped with special dissipative replaceable components (DRCs): the dissipative replaceable beam splices (DRBeS), which combine large energy dissipation with ease of replacement. The evaluation of the full potential of DRBeS requires a system-level investigation, that is, a six-story MRF, whereby the hysteretic effects of beam splices partial-strength joints are considered on the global response of the structural system. Therefore, an OpenSees finite element (FE) frame model, based on previous experimental campaigns with cyclic displacements on partial-strength joints, and a Matlab model validated on OpenSees, were used for a more complex experimental activity via hybrid simulation (HS). The aim of the simulations was twofold: (i) to increase knowledge of the non-linear behaviour of steel-concrete composite partial-strength MRFs; and (ii) to study the effectiveness of the DRBeS components for increasing the recovery of functionality after a major seismic event. Therefore, to appreciate the performance of the partial-strength MRF at damage limitation (DL), significant damage (SD) and near collapse (NC) within the performance-based earthquake engineering (PBEE) approach, HSs were carried out. In such instances, the ground floor was physically tested at full scale in the laboratory and the remainder of the structure was numerically simulated. Relevant results showed that the DRBeS were capable of dissipating a significant amount of hysteretic energy and of protecting the non-dissipative parts of partial-strength joints and the overall structure with an ease of replacement.  相似文献   

Seismic response of bridge piers on pile groups for different soil damping models and lumped parameter representations of the foundation     

Francisco González  Luis A. Padrón  Sandro Carbonari  Michele Morici  Juan J. Aznárez  Francesca Dezi  Graziano Leoni 《地震工程与结构动力学》2019,48(3):306-327

This paper presents a wide parametric study aimed at elucidating the influence, on the computed seismic response of bridge piers, of two related aspects of the model: (1) the adoption of the classical hysteretic or the causal Biot's damping models for the soil and (2) the use of two different lumped parameter models of different complexity and accuracy to approximate the impedances of the pile foundation. A total of 2072 cases, including different superstructures, pile foundations, soil deposits, and seismic input signals, are studied. The results are presented so that the influence of the different parameters involved in the analysis can be assessed. From an engineering point of view, both lumped parameter models provide, in general, sufficiently low errors. The choice of the most adequate model for each case will depend not only on the configuration of the structure and the soil-foundation system but also on the assumed soil damping model, whose influence on the computed seismic responses is relevant in many cases. The nonphysical behaviour provided by the classical hysteretic damping model for the soil at zero frequency generates issues in the process of fitting the impedance functions. It is also found that larger deck displacements are predicted by Biot's model due to the higher damping at low frequencies provided by the classical hysteretic damping model.  相似文献   

Distribution of sea urchins living near shallow water CO₂ vents is dependent upon species acid–base and ion-regulatory abilities     

P. Calosi  S.P.S. Rastrick  M. Graziano  S.C. Thomas  C. Baggini  H.A. Carter  J.M. Hall-Spencer  M. Milazzo  J.I. Spicer 《Marine pollution bulletin》2013

To reduce the negative effect of climate change on Biodiversity, the use of geological CO₂ sequestration has been proposed; however leakage from underwater storages may represent a risk to marine life. As extracellular homeostasis is important in determining species’ ability to cope with elevated CO₂, we investigated the acid–base and ion regulatory responses, as well as the density, of sea urchins living around CO₂ vents at Vulcano, Italy. We conducted in situ transplantation and field-based laboratory exposures to different pCO₂/pH regimes. Our results confirm that sea urchins have some ability to regulate their extracellular fluid under elevated pCO₂. Furthermore, we show that even in closely-related taxa divergent physiological capabilities underlie differences in taxa distribution around the CO₂ vent. It is concluded that species distribution under the sort of elevated CO₂ conditions occurring with leakages from geological storages and future ocean acidification scenarios, may partly be determined by quite subtle physiological differentiation.  相似文献