A comment on “Calcic amphibole equilibria and a new amphibole — plagioclase geothermometer” by J.D. Blundy and T.J.B. Holland (Contrib Mineral Petrol (1990) 104: 208–224)     

Stefano Poli  Max W. Schmidt 《Contributions to Mineralogy and Petrology》1992,111(2):273-278

Conclusions The calibration by Blundy and Holland is not a calibration of the reaction albite + tremolite = edenite + 4quartz, because the Al^IV content of amphiboles is a combined result of substitutions.The requirements for a calibration of any of these substitutions are: (1) an amphibole-activity model unequivocally accounting for each substitution and (2) a data-set, wherein all amphiboles are buffered by the same assemblages.  相似文献   

Anatexis and fluid regime of the deep continental crust: New clues from melt and fluid inclusions in metapelitic migmatites from Ivrea Zone (NW Italy)     

Bruna B. Carvalho  Omar Bartoli  Fabio Ferri  Bernardo Cesare  Silvio Ferrero  Laurent Remusat  Luca S. Capizzi  Stefano Poli 《Journal of Metamorphic Geology》2019,37(7):951-975

We investigate the inclusions hosted in peritectic garnet from metapelitic migmatites of the Kinzigite Formation (Ivrea Zone, NW Italy) to evaluate the starting composition of the anatectic melt and fluid regime during anatexis throughout the upper amphibolite facies, transition, and granulite facies zones. Inclusions have negative crystal shapes, sizes from 2 to 10 μm and are regularly distributed in the core of the garnet. Microstructural and micro‐Raman investigations indicate the presence of two types of inclusions: crystallized silicate melt inclusions (i.e., nanogranitoids, NI), and fluid inclusions (FI). Microstructural evidence suggests that FI and NI coexist in the same cluster and are primary (i.e., were trapped simultaneously during garnet growth). FI have similar compositions in the three zones and comprise variable proportions of CO₂, CH₄, and N₂, commonly with siderite, pyrophyllite, and kaolinite, suggesting a COHN composition of the trapped fluid. The mineral assemblage in the NI contains K‐feldspar, plagioclase, quartz, biotite, muscovite, chlorite, graphite and, rarely, calcite. Polymorphs such as kumdykolite, cristobalite, tridymite, and less commonly kokchetavite, were also found. Rehomogenized NI from the different zones show that all the melts are leucogranitic but have slightly different compositions. In samples from the upper amphibolite facies, melts are less mafic (FeO + MgO = 2.0–3.4 wt%), contain 860–1700 ppm CO₂ and reach the highest H₂O contents (6.5–10 wt%). In the transition zone melts have intermediate H₂O (4.8–8.5 wt%), CO₂ (457–1534 ppm) and maficity (FeO + MgO = 2.3–3.9 wt%). In contrast, melts at granulite facies reach highest CaO, FeO + MgO (3.2–4.7 wt%), and CO₂ (up to 2,400 ppm), with H₂O contents comparable (5.4–8.3 wt%) to the other two zones. Our results represent the first clear evidence for carbonic fluid‐present melting in the Ivrea Zone. Anatexis of metapelites occurred through muscovite and biotite breakdown melting in the presence of a COH fluid, in a situation of fluid–melt immiscibility. The fluid is assumed to have been internally derived, produced initially by devolatilization of hydrous silicates in the graphitic protolith, then as a result of oxidation of carbon by consumption of Fe³⁺‐bearing biotite during melting. Variations in the compositions of the melts are interpreted to result from higher T of melting. The H₂O contents of the melts throughout the three zones are higher than usually assumed for initial H₂O contents of anatectic melts. The CO₂ contents are highest at granulite facies, and show that carbon‐contents of crustal magmas are not negligible at high T. The activity of H₂O of the fluid dissolved in granitic melts decreases with increasing metamorphic grade. Carbonic fluid‐present melting of the deep continental crust represents, together with hydrate‐breakdown melting reactions, an important process in the origin of crustal anatectic granitoids.  相似文献   

Geomorphology of a modern carbonate slope system and associated sedimentary processes: Example of the giant Great Abaco Canyon,Bahamas     

Audrey Recouvreur  Natacha Fabregas  Thierry Mulder  Vincent Hanquiez  Kelly Fauquembergue  Elsa Tournadour  Herv Gillet  Jean Borgomano  Emmanuelle Poli  Jean‐Baptiste Kucharski  Stanislas Wilk 《Sedimentology》2021,68(1):266-293

The large acoustic data set acquired during the Carambar cruises is composed of high resolution bathymetry, backscatter data and very‐high resolution seismic lines which allow for an overview of the morphology and sediment transfer processes from the shallow upper slope to the abyssal plain of a modern carbonate system: the north‐eastern slope of the Little Bahama Bank. Surficial distribution of the acoustic facies and echofacies reflects a wide variety of sedimentary processes along and across the slope. The western sector of the Little Bahama Bank is dominated by depositional processes whereas its eastern sector, which is incised in the lower slope by giant canyons, is affected by erosion and bypass processes. Datasets suggest that currents play an important role both in along‐slope sedimentary processes and in the abyssal plain. The Antilles Current appears to affect a large part of the middle and lower slopes. The absence of sizeable present‐day channel/levée complexes or lobes at the mouth of the canyon – revealed by the bathymetric map – indicates that the southward flowing Deep Western Boundary Current influences modern abyssal sediment deposition. Based on depositional processes and indicators of canyon maturity observed in facies distribution, the current study proposes that differential subsidence affects the eastern versus western part of the bank. The morphology of the Great Abaco Canyon and Little Abaco Canyon, which extend parallel to the platform, and the Little Bahama Bank slope appears to be related to the Great Abaco Fracture Zone.  相似文献   

Depuration dynamics of oysters (Crassostrea gigas) artificially contaminated by Salmonella enterica serovar Typhimurium     

de Abreu Corrêa A  Albarnaz JD  Moresco V  Poli CR  Teixeira AL  Oliveira Simões CM  Monte Barardi CR 《Marine environmental research》2007,63(5):479-489

The State of Santa Catarina produces the greatest quantity of edible mollusks in Brazil. To guarantee sanitary qualify, mollusk cultures should be monitored for contamination by pathogenic microorganisms. A self-purification or "depuration" system that eliminates Salmonella enterica serovar Typhimurium contamination from oysters has been developed and evaluated. The depuration process occurred within a closed system, in which 1000 L of water was recirculated for 24 h. The water was sterilized with ultraviolet (UV) light, chlorine, or both together. Oysters (Crassostrea gigas) artificially contaminated with S. typhimurium were harvested every 6 h. Samples of oyster tissue were excised and both the presence and numbers of bacteria were determined. Combined UV light and chlorine treatments resulted in total elimination of bacteria within 12 h. Polymerase chain reaction detected bacteria in water exposed to the three treatments. This pioneering study is the first of its kind in Brazil and represents a major contribution to commercial mollusk culture in this country.  相似文献   

Observations of Comet 9P/Tempel 1 around the Deep Impact event by the OSIRIS cameras onboard Rosetta     

Horst Uwe Keller  Sonia Fornasier  Stubbe F. Hviid  Jörg Knollenberg  Miriam Rengel  Gabriele Cremonese  Detlef Koschny  Ekkehard Kührt  Holger Sierks  Cesare Barbieri  Hans Rickman  Michael F. A'Hearn  Maria-Antonella Barucci  Vania da Deppo  Björn J.R. Davidsson  Stefano Debei  Fritz Gliem  José J. Lopez Moreno  Giampiero Naletto  Angel Sanz Andrés 《Icarus》2007,187(1):87-103

The OSIRIS cameras on the Rosetta spacecraft observed Comet 9P/Tempel 1 from 5 days before to 10 days after it was hit by the Deep Impact projectile. The Narrow Angle Camera (NAC) monitored the cometary dust in 5 different filters. The Wide Angle Camera (WAC) observed through filters sensitive to emissions from OH, CN, Na, and OI together with the associated continuum. Before and after the impact the comet showed regular variations in intensity. The period of the brightness changes is consistent with the rotation period of Tempel 1. The overall brightness of Tempel 1 decreased by about 10% during the OSIRIS observations. The analysis of the impact ejecta shows that no new permanent coma structures were created by the impact. Most of the material moved with . Much of it left the comet in the form of icy grains which sublimated and fragmented within the first hour after the impact. The light curve of the comet after the impact and the amount of material leaving the comet ( of water ice and a presumably larger amount of dust) suggest that the impact ejecta were quickly accelerated by collisions with gas molecules. Therefore, the motion of the bulk of the ejecta cannot be described by ballistic trajectories, and the validity of determinations of the density and tensile strength of the nucleus of Tempel 1 with models using ballistic ejection of particles is uncertain.  相似文献   

Intercomparison of two nowcasting methods: preliminary analysis     

V. Poli  P. P. Alberoni  D. Cesari 《Meteorology and Atmospheric Physics》2008,101(3-4):229-244

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FORSAT: a 3D forest monitoring system for cover mapping and volumetric 3D change detection     

Efstratios Stylianidis  Daniela Poli  Martin Hofer  Armin Gruen  Victor Sanchez Martin 《International Journal of Digital Earth》2020,13(8):854-885

ABSTRACT

A 3D forest monitoring system, called FORSAT (a satellite very high resolution image processing platform for forest assessment), was developed for the extraction of 3D geometric forest information from very high resolution (VHR) satellite imagery and the automatic 3D change detection. FORSAT is composed of two complementary tasks: (1) the geometric and radiometric processing of satellite optical imagery and digital surface model (DSM) reconstruction by using a precise and robust image matching approach specially designed for VHR satellite imagery, (2) 3D surface comparison for change detection. It allows the users to import DSMs, align them using an advanced 3D surface matching approach and calculate the 3D differences and volume changes (together with precision values) between epochs. FORSAT is a single source and flexible forest information solution, allowing expert and non-expert remote sensing users to monitor forests in three and four (time) dimensions. The geometric resolution and thematic content of VHR optical imagery are sufficient for many forest information needs such as deforestation, clear-cut and fire severity mapping. The capacity and benefits of FORSAT, as a forest information system contributing to the sustainable forest management, have been tested and validated in case studies located in Austria, Switzerland and Spain.  相似文献   

Monitoring of Short-Term Heavy Metal Deposition by Accumulation in Epiphytic Lichens (Hypogymnia Physodes (L.) Nyl.)     

Poličnik Helena  Batič Franc  Ribarič Lasnik Cvetka 《Journal of Atmospheric Chemistry》2004,49(1-3):223-230

Many lichens are very sensitive to air pollution due to their symbiotic nature. However, they are generally less sensitive to toxic effects of trace elements; therefore they can be used as accumulator organisms for estimating concentrations of these elements in the environment. Heavy metal accumulation in lichens is a commonly used bioindication method for assessing heavy metal ambient levels. An active biomonitoring method was used for the determination of short-term accumulation of zinc, lead, arsenic and cadmium by epiphytic lichens transplanted at different localities in Slovenia polluted by heavy metals. The atomic absorption spectrophotometry method was used for the determination of heavy metal content in lichen thalli. The content of heavy metals in lichens collected in the background area with clean air (Rogla, Pohorje Mountains) was used as the reference value. Lichens were transplanted from Rogla using the branch transplantation technique for a period of 6 months in the surroundings of Slovenian thermal power plants (Velenje, otanj, Zavodnje, Veliki Vrh, Vnajnarje, and Dobovec) and close to the lead and zinc ore smelter at erjav. The monthly accumulation of heavy metals was comparable within years at selected locations. Heavy metal pollution was the highest at erjav despite of remediation of lead and zinc ore smelter. The monthly accumulation of all four heavy metals was statistically significantly higher in lichens exposed at erjav than at other localities.  相似文献   

Petrogenesis of Monte Vulture volcano (Italy): inferences from mineral chemistry,major and trace element data     

M. De Fino  L. La Volpe  A. Peccerillo  G. Piccarreta  G. Poli 《Contributions to Mineralogy and Petrology》1986,92(2):135-145

The paper presents major and trace element data and mineral compositions for a series of foiditic-tephritic to phonolitic rocks coming from Monte Vulture, Southern Italy, and investigates their origin, evolution and relationship with the other centres of the Roman province.Major and trace element variation in the foiditic to tephritic suite agrees with a hypothesis of evolution by simple crystal/liquid fractionation, whereas the early erupted phonolitic trachytes and phonolites have geochemical characteristics which do not support their derivation from tephritic magma by crystal fractionation. Foiditic and phonolitic rocks have mineral compositions which are interpreted as indicating magma mixing. However geochemical evidence shows that this process did not play an important role during the magma evolution.The Vulture rocks have compositional peculiarities such as high abundance of Na₂O, CaO, Cl and S, when compared with other Roman volcanics. Instead, the distribution of incompatible elements is similar to those of Roman rocks, except for a lower content of Rb and K, higher P and lower Th/Ta and Th/Nb ratios which are still close to the values of arc volcanics.The high contents of Na, Ca and of volatile components are tentatively attributed to the interaction of magma with aqueous solutions, rich in calcium sulphate and sodium chloride, related to the Miocene or Triassic evaporites occurring within the sedimentary sequence underlying the volcano. The distribution pattern of the incompatible elements is interpreted as indicative of magma-forming in a subduction modified upper mantle and of the peculiar location of M. Vulture.  相似文献   

Geochemistry of granitic rocks from the Hercynian Sardinia-Corsica batholith: Implication for magma genesis   总被引：5，自引：0，他引：5  

Giampiero Poli  Claudio Ghezzo  Sandro Conticelli 《Lithos》1989,23(4):247-266

The Sardinia-Corsica batholith was structured in the late stage of the Hercynian orogenesis. The granitoids intrude mainly metamorphic complexes grading from zeolite up to amphibolite facies. The batholith is heterogeneous consisting of complexes with different affinity, chemical composition, age and degree of deformation. The present paper reports major-and trace-element data for selected samples coming only from Sardinian outcrops.

The rocks range from gabbro-diorite to tonalite, monzogranite and leucogranite. The two latter lithologies are the most abundant, gabbrodiorites and tonalites occurring in minor amounts and mainly in northern-central Sardinia. Over 75% of the granitoids contain microgranular enclaves of magmatic origin. The age of the rocks falls in the interval between 307 and 281 Ma. Sr isotope initial ratios are high, ranging between 0.7083 and 0.7107.

REE, Rb, Sr, Ba, Zr, Th, Ta, Hf, Co and Sc abundances were determined on selected samples. All elements follow three types of trends vs. CaO, which is used as differentiation index. Two trends show positive and negative correlations while the third one shows a bell-shaped pattern. LREE have different degrees of enrichment (La = 20−120× ch) and HREE show variable fractionation with prevailing (Tb/Yb)_n<1. The two peraluminous samples have very different geochemical characteristics.

From the geochemical point of view all the rocks coming from the Sardinian segment of the batholith display a typical calc-alkaline chemical character showing the imprint of both “normal and mature” continental arc geodynamic environments.

Geochemical trends suggest some petrogenetic constraints. The complete sequence of differentiation can be neither the product of crystal/liquid fractionation processes starting from a single basic parent magma nor the product of an AFC process. On the contrary, a two-stage model can be proposed. In the first stage a mafic melt of subcrustal origin interacted with monzogranitic magmas derived from 25–35% degree of melting of a crustal biotite amphibolitic source. Such a mixing process acted together with a crystal/liquid fractionation process to give tonalites and granodiorites. In the second stage lesser degrees of melting of the same crustal source could give the late-stage leucogranitic masses.

A possible scenario, able to take into account field and geochemical data, can be suggested for the genesis of this suite and we propose it as a working model for future investigations.  相似文献