Kinematics, ages and metallicities of star clusters in NGC 1316: a 3-Gyr-old merger remnant     

Paul Goudfrooij  †  Jennifer Mack  Markus Kissler-Patig  Georges Meylan †  Dante Minniti 《Monthly notices of the Royal Astronomical Society》2001,322(3):643-657

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Opaque phases in type-II chondrules from CR2 chondrites: Implications for CR parent body formation     

Devin L. Schrader  Harold C. Connolly Jr.  Dante S. Lauretta 《Geochimica et cosmochimica acta》2008,72(24):6124-6140

We report the results of a detailed study of sulfide-bearing opaque assemblages from the MAC 87320, EET 92011, and Renazzo CR carbonaceous chondrites. The objectives of this study are to (1) characterize sulfide and associated phases within CR2 chondrites; (2) determine the petrographic relationship between sulfides, metals, and chondrules; (3) constrain the history of type-II chondrules; (4) ascertain the environments in which type-II chondrules formed and were altered; and (5) unravel the formation and alteration history of the CR parent body as recorded in sulfide-bearing assemblages. Sulfide-bearing opaque assemblages occur primarily within type-II (FeO-rich) chondrules. The sulfide assemblages are concentrated near the chondrule edges. Assemblages in MAC 87320 are composed of troilite, phosphate, and Ni-rich metal. EET 92011 contains assemblages composed of pentlandite, troilite, and Ni-rich metal. The assemblages in Renazzo contain tochilinite, magnetite, troilite, pentlandite, and phosphate. In all of the assemblages in Renazzo the tochilinite is fine grained and intimately mixed with troilite, pentlandite, or magnetite. Opaque assemblages in CR chondrites record a complex history that includes both high- and low-temperature processes. The morphology and composition of sulfides in CR2 chondrites suggests that the sulfide-bearing assemblages originally formed in gas-solid reactions in the nebula at temperatures above the Fe-FeS eutectic (988 °C). Many of the assemblages were subsequently aqueously altered on the CR-chondrite parent body to various degrees at temperatures from ∼50 to 200 °C. We combine these observations and interpretations to provide a detailed model of the history of the CR parent body.  相似文献   

What drives visitors’ perceptions in street food events? Potential tools to boost the local and regional development (and how to do it)     

Di Matteo  Dante 《GeoJournal》2021,86(3):1465-1480

The widespread popularity reached by food trucks (FTs) has led to a reshape of many food events into new forms of street food events (SFEs), in which the FTs become the main attractors for the visitors, and not anymore a simple support element to the event making. Such SFEs have rapidly been recognized as a pivotal place marker for attracting visitors from within and beyond the regional boundaries: it is therefore significant to understand visitors’ motivations to attend a SFE, both for addressing policies and for supporting business decision-making processes, since the overall visitors’ perceptions are related to a form of loyalty towards the visited destination, and this linkage might encourage revisit intentions. This study applies an ordered multinomial model to a SFE taking place in Abruzzo region (Italy) and the main findings reveal that visitors’ perceptions tend to strengthen if they find in the event memorable atmospheres and non-routine food specialties, suggesting the search for a hedonic consumption. In these regards, this study provides implications on how SFEs might represent an enhancer for the local and regional development and how SFEs might help preserve the economic and social fabric of smaller and larger communities.

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Asteroid (101955) 1999 RQ36: Spectroscopy from 0.4 to 2.4 μm and meteorite analogs     

Beth Ellen Clark  Richard P. Binzel  Ellen S. Howell  Edward A. Cloutis  Maureen Ockert-Bell  Phil Christensen  Maria Antonietta Barucci  Francesca DeMeo  Dante S. Lauretta  Harold Connolly Jr.  Alicia Soderberg  Carl Hergenrother  Lucy Lim  Josh Emery  Michael Mueller 《Icarus》2011,216(2):462-475

We present reflectance spectra from 0.4 to 2.4 μm of Asteroid (101955) 1999 RQ36, the target of the OSIRIS-REx spacecraft mission. The visible spectral data were obtained at the McDonald Observatory 2.1-m telescope with the ES2 spectrograph. The infrared spectral data were obtained at the NASA Infrared Telescope Facility using the SpeX instrument. The average visible spectrum is combined with the average near-infrared wavelength spectrum to form a composite spectrum. We use three methods to constrain the compositional information in the composite spectrum of Asteroid (101955) 1999 RQ36 (hereafter RQ36). First, we perform a least-squares search for meteorite spectral analogs using 15,000 spectra from the RELAB database. Three most likely meteorite analogs are proposed based on the least-squares search. Next, six spectral parameters are measured for RQ36 and their values are compared with the ranges in parameter values of the carbonaceous chondrite meteorite classes. A most likely meteorite analog group is proposed based on the depth of overlap in parameter values. The results of the least-squares search and the parametric comparisons point to CIs and/or CMs as the most likely meteorite analogs for RQ36, and COs and CHs as the least likely. RQ36 has a spectrally “blue” continuum slope that is also observed in carbonaceous chondrites containing magnetite. We speculate that RQ36 is composed of a “CM1”-like material. Finally, we compare RQ36 to other B-type asteroids measured by Clark et al. (Clark, B.E. et al. [2010]. J. Geophys. Res. 115, E06005). The results of this comparison are inconclusive. RQ36 is comparable to Themis spectral properties in terms of its albedo, visible spectrum, and near-infrared spectrum from 1.1 to 1.45 μm. However, RQ36 is more similar to Pallas in terms of its near-infrared spectrum from 1.6 to 2.3 μm. Thus it is possible that B-type asteroids form a spectral continuum and that RQ36 is a transitional object, spectrally intermediate between the two end-members. This is particularly interesting because Asteroid 24 Themis was recently discovered to have H₂O ice on the surface (Rivkin, A., Emery, J. [2010]. Nature 464, 1322–1323; Campins, H. et al. [2010a]. Nature 464, 1320–1321).  相似文献   

The Fountain Hills unique CB chondrite: Insights into thermal processes on the CB parent body     

Dante S. LAURETTA  Julia S. GOREVA  Dolores H. HILL  Marvin KILLGORE  Alyssa R. La BLUE  Andrew CAMPBELL  R. C. GREENWOOD  A. B. VERCHOVSKY  Ian A. FRANCHI 《Meteoritics & planetary science》2009,44(6):823-838

Abstract— We report the results of an extensive study of the Fountain Hills chondritic meteorite. This meteorite is closely related to the CB_a class. Mineral compositions and O‐isotopic ratios are indistinguishable from other members of this group. However, many features of Fountain Hills are distinct from the other CB chondrites. Fountain Hills contains 23 volume percent metal, significantly lower than other members of this class. In addition, Fountain Hills contains porphyritic chondrules, which are extremely rare in other CB_a chondrites. Fountain Hills does not appear to have experienced the extensive shock seen in other CB chondrites. The chondrule textures and lack of fine‐grained matrix suggests that Fountain Hills formed in a dust‐poor region of the early solar system by melting of solid precursors. Refractory siderophiles and lithophile elements are present in near‐CI abundances (within a factor of two, related to the enhancement of metal). Moderately volatile and highly volatile elements are significantly depleted in Fountain Hills. The abundances of refractory siderophile trace elements in metal grains are consistent with condensation from a gas that is reduced relative to solar composition and at relatively high pressures (10^?3bars). Fountain Hills experienced significant thermal metamorphism on its parent asteroid. Combining results from the chemical gradients in an isolated spinel grain with olivine‐spinel geothermometry suggests a peak temperature of metamorphism between 535 °C and 878 °C, similar to type‐4 ordinary chondrites.  相似文献   

Ferric iron in mantle-derived pyroxenes and a new oxybarometer for the mantle   总被引：2，自引：0，他引：2  

Robert W. Luth  Dante Canil 《Contributions to Mineralogy and Petrology》1993,113(2):236-248

Ferric iron contents of coexisting ortho- and clinopyroxene from spinel lherzolite xenoliths were measured with Mössbauer spectroscopy and found to be significant. In orthopyroxene, the range in Fe³⁺/Fe is from 0.04 to 0.14; in clinopyroxene, the range is from 0.12 to 0.24. Reactions involving coexisting olivine, orthopyroxene, and clinopyroxene, where either the esseneite (CaFe³⁺ AlSiO₆) or the acmite (NaFe³⁺Si₂O₆) component in the clinopyroxene is considered, are used to calculate oxygen fugacities. These oxygen fugacities agree well with those calculated with the olivine-orthopyroxene-spinel oxybarometer. Because these reactions do not involve garnet, spinel, or plagioclase, they may be applied to lherzolites to give internally-consistent oxygen fugacities across the pressure-dependent facies boundaries between plagioclase, spinel, and garnet lherzolite. Another application of this method is to predict the Fe³⁺/Fe in clinopyroxene coexisting with olivine and orthopyroxene given pressure, temperature, , and the compositions of the coexisting phases in either experimental or natural assemblages. At values of equal to those of the synthetic fayalite-magnetite-quartz buffer, for example, 15–35% of the iron in the clinopyroxenes from these xenoliths would be ferric. The simplifying assumption that all Fe is divalent in silicate phases at geologically — reasonable oxygen fugacities must be re-evaluated.  相似文献   

An experimental calibration of the “Nickel in Garnet” geothermometer with applications     

Dante Canil 《Contributions to Mineralogy and Petrology》1994,117(4):410-420

The partitioning of Ni between olivine and garnet in two multi-component compositions was studied as a function of temperature and pressure in a 6–8 type multi-anvil apparatus. Weighted least squares regression of the experimental results for both compositions give a temperature dependence for Ni partitioning between olivine (Ol) and garnet (Gt) of the form: T=–10210(±114)/[lnD _Gt/Ol ^Ni –3.59(±67)] where DGt/Ol/Ni=Ni content of Gt/Ni content of olivine (by weight) and Tis in Kelvin. The pressure effect on Ni exchange between olivine and garnet is estimated to be 0.13 J/bar, and should therefore have a negligible effect on the geothermometer, as is demonstrated in the experiments. The experimentally derived Ni in Gt geothermometer is in agreement with an extant empirical version between 1100 to 900°C, but the two thermometers produce significantly different results outside of this temperature range.  相似文献   

Experimental evidence for the exsolution of cratonic peridotite from high-temperature harzburgite     

Dante Canil 《Earth and Planetary Science Letters》1991,106(1-4)

Phase equilibrium experiments were performed on typical ‘oceanic’ and ‘cratonic’ peridotite compositions and a Ca, Al-rich orthopyroxene composition, to test the proposal that garnet lherzolites exsolved from high-temperature harzburgites, and to further our understanding of the origin of ancient cratonic lithospheres. ‘Oceanic’ peridotites crystallize a garnet harzburgite assemblage at pressures above 5 GPa in the temperature range 1450–1600°C, but at 5 GPa and temperatures less than 1450°C, crystallize clinopyroxene to become true lherzolites. ‘Cratonic’ peridotites crystallize a garnet harzburgite assemblage at pressures above 5 GPa in the temperature range 1300–1600°C. Garnet-free harzburgite crystallizes from both ‘cratonic’ and ‘oceanic’ peridotite at temperatures above 1450°C and pressures below 4.5–5 GPa. Phase relations for the high Ca, Al-rich orthopyroxene composition essentially mirror those for ‘oceanic’ peridotite.The complete solution of garnet and clinopyroxene into orthopyroxene observed in all three starting compositions at temperatures near or above the mantle solidus at pressures less than 6 GPa supports the hypothesis that garnet lherzolite could have exsolved from harzburgite. The inferred cooling path for the original high-temperature harzburgite protoliths of garnet lherzolites differs depending on bulk composition. The precursor harzburgite protoliths of garnet lherzolites and harzburgites with ‘cratonic’ bulk compositions apparently experienced simple isobaric cooling from formation temperatures near the peridotite solidus to those at which most of these peridotites were sampled in the mantle (< 1200°C). The cooling histories for harzburgite protoliths of sheared garnet lherzolites with ‘oceanic’ compositional affinity are speculated to have involved convective circulation of mantle material to depths deeper than those at which it was originally formed.Phase equilibria and compositional relationships for orthopyroxenes produced in phase equilibrium experiments on peridotite and komatiite are consistent with an origin for ‘cratonic’ peridotite as a residue of Archean komatiite extraction, which has since cooled and exsolved clinopyroxene and garnet to become the common low-temperature, coarse-grained peridotite thought to comprise the bulk of the mantle lithosphere beneath the Archean Kaapvaal craton.  相似文献   

Oxidation state of mantle xenoliths from British Columbia,Canada   总被引：3，自引：0，他引：3  

Dante Canil  David Virgo  Christopher M. Scarfe 《Contributions to Mineralogy and Petrology》1990,104(4):453-462

Mössbauer spectra for 17 spinels separated from mantle xenoliths from six different eruptive centers in southern British Columbia, Canada were measured in an effort to accurately determine their Fe³⁺/total Fe ratios, and to examine lateral and vertical variations in oxygen fugacities (f _o2's) calculated for these samples using published thermobarometric methods. Spectra acquired at 298 and 77 K suggest that both Fe²⁺ and Fe³⁺ are tetrahedrally coordinated in lherzolite spinels from this alkaline province. Calculatedf _o2's for spinel lherzolites from British Columbia range from about 0.5 to 1.5 log units below the fayalite-magnetite-quartz (FMQ) oxygen buffer at 15 kbar using the thermobarometric method of O'Neill and Wall. Thesef _o2's are on average more reducing than those reported for the upper mantle beneath the Massif Central and Japanese Arc and fall within the range for fresh MORB glasses and for lherzolite xenoliths from the southwestern United States and Mongolia. Significant variations inf _o2 between samples from different eruptive centers with varying ages are absent, indicating that the oxidation state of the upper mantle was not affected by Cenozoic magmatism within this alkaline province.  相似文献   

Late Holocene sea-surface temperature and precipitation variability in northern Patagonia, Chile (Jacaf Fjord, 44°S)     

Julio Sepúlveda  Silvio Pantoja  Konrad A. Hughen  Sbastien Bertrand  Dante Figueroa  Tania Len  Nicholas J. Drenzek  Carina Lange 《Quaternary Research》2009,72(3):400-409

A high-resolution multi-proxy study including the elemental and isotopic composition of bulk organic matter, land plant-derived biomarkers, and alkenone-based sea-surface temperature (SST) from a marine sedimentary record obtained from the Jacaf Fjord in northern Chilean Patagonia (44°20′S) provided a detailed reconstruction of continental runoff, precipitation, and summer SST spanning the last 1750 yr. We observed two different regimes of climate variability in our record: a relatively dry/warm period before 900 cal yr BP (lower runoff and average SST 1°C warmer than present day) and a wet/cold period after 750 cal yr BP (higher runoff and average SST 1°C colder than present day). Relatively colder SSTs were found during 750–600 and 450–250 cal yr BP, where the latter period roughly corresponds to the interval defined for the Little Ice Age (LIA). Similar climatic swings have been observed previously in continental and marine archives of the last two millennia from central and southern Chile, suggesting a strong latitudinal sensitivity to changes in the Southern Westerly Winds, the main source of precipitation in southern Chile, and validating the regional nature of the LIA. Our results reveal the importance of the Chilean fjord system for recording climate changes of regional and global significance.  相似文献