Ultra-reducing conditions in average mantle peridotites and in podiform chromitites: a thermodynamic model for moissanite (SiC) formation     

Anastasia Golubkova  Max W. Schmidt  James A. D. Connolly 《Contributions to Mineralogy and Petrology》2016,171(5):41

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Dario Grana,Tapan Mukerji,and Philippe Doyen: Seismic Reservoir Modeling: Theory,Examples, and Algorithms     

Connolly  Patrick Alexander 《Mathematical Geosciences》2021,53(7):1697-1698

Mathematical Geosciences -  相似文献   

Compositional evolution of the protoplanetary disk: Oxygen isotopes of type-II chondrules from CR2 chondrites     

Harold C. Connolly Jr.  Gary R. Huss 《Geochimica et cosmochimica acta》2010,74(8):2473-325

Chondrules are the dominant component of chondritic meteorites and attest to high-temperature transient heating events within the protoplanetary disk. They provide valuable constraint on the disk environments in which they formed and potentially the evolution of primitive planetary materials in the disk. The oxygen isotopic composition of CR2 chondrite type-II chondrules was investigated. Our data show significant variation in the isotopic compositions of the chondrules with no petrographic or geochemical means to identify what chondrule will plot where on a three-isotope diagram. Although we cannot rule out that these chondrules may have come from another chondrite-forming region, we argue in context of type-I chondrules from CR2 chondrites that CR2 type-II chondrules record changes in solid and gas composition during formation due to the vaporization of icy bodies in localized regions of the inner disk.  相似文献   

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 effect of large-scale structure on the SDSS galaxy three-point correlation function     

R. C. Nichol  R. K. Sheth  Y. Suto  A. J. Gray  I. Kayo  R. H. Wechsler †  F. Marin  G. Kulkarni  M. Blanton  A. J. Connolly  J. P. Gardner  B. Jain  C. J. Miller  A. W. Moore  A. Pope  J. Pun  D. Schneider  J. Schneider  A. Szalay  I. Szapudi  I. Zehavi  N. A. Bahcall  I. Csabai  J. Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,368(4):1507-1514

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Metamorphism and phase relations in carbonate rocks from the Nevado-Filábride Complex (Cordilleras Béticas, Spain): application of the Ttn + Rt + Cal + Qtz + Gr buffer     

V. López Sánchez-Vizcaíno  J. A. D. Connolly  M. T. Gómez-Pugnaire 《Contributions to Mineralogy and Petrology》1997,126(3):292-302

Phase relations and metamorphic conditions have been studied in metacarbonate rocks from the Nevado-Filábride Complex (Cordilleras Béticas) through forward modeling. In many rock samples, the assemblage titanite + rutile + calcite + quartz + graphite buffered the composition of the C-O-H fluid present during metamorphism. Over a wide range of P-T conditions, fluid compositions computed for this buffer are essentially binary H₂O-CO₂ mixtures. This buffer also constrains the chemical potentials of TiO₂, CaO and SiO₂. Consequently it is possible to make a thermodynamic projection through these components to predict the stable phase relations consistent with the buffer. Using this method, phase relations have been analyzed in a rock containing the buffer assemblage and paragonite, albite, phengite, epidote, and chlorite. The equilibrium P-T conditions for this assemblage are constrained, by minimization of the differences between predicted and observed mineral compositions, to be 560 ± 15 °C and 9.5 ± 1 kbar. Conditions obtained compare well with those estimated from other studies in different lithologic units. The inferred metamorphic fluid composition is H₂O-rich (). Received: 11 October 1995 / Accepted 5 August 1996  相似文献   

Review of nekton patterns and ecological processes in seagrass landscapes   总被引：1，自引：0，他引：1  

Rod M. Connolly  Jeremy S. Hindell 《Estuarine, Coastal and Shelf Science》2006,68(3-4):433

We reviewed seagrass landscape studies on nekton (fish and larger mobile crustaceans) to summarise: (1) patterns of nekton abundance in relation to patch attributes; and (2) models used to explain processes underpinning observed patterns. The response of nekton to landscape attributes is highly variable. Different taxa showed increasing densities with: increasing and decreasing patch size (12 and 11 taxa, respectively), increasing and decreasing proximity within a patch to edge (9, 14), increasing and decreasing distances from nearest seagrass patch (4, 11), and with patches perpendicular and parallel to currents (1, 2). The majority of taxa (213 out of 281, or 82%) showed no relationships. Landscape scale patterns are important for some species but evidence so far does not demonstrate major landscape effects overall. The lack of pattern might reflect the overriding importance of other factors such as within-patch characteristics, water depth or position within an estuary. It might also result from measurements at the wrong scale. The rigour of surveys can be improved by avoiding confounding of patch attributes by other factors, increasing awareness of statistical power, and more considered survey designs for attributes such as edge effects. The predation model is the most frequently invoked and tested model. Other explanatory models are based on disturbance, rates of encounter, food availability, larval supply, migration and reproductive success, but in many cases are not based on observed patterns. The best experimental work has been done on nekton species for which landscape studies have been built on a detailed understanding of the ecology of the species, such as for blue crabs (Callinectes sapidus). As this basic ecological platform is laid for more species, the landscape approach will become increasingly fruitful.  相似文献   

Diffusion-controlled development of silica-undersaturated domains in felsic granulites of the Bohemian Massif (Variscan belt of Central Europe)   总被引：2，自引：0，他引：2  

Lucie Tajčmanová  Jiří Konopásek  James A. D. Connolly 《Contributions to Mineralogy and Petrology》2007,153(2):237-250

Plagioclase rims around metastable kyanite crystals appear during decompression of high-pressure felsic granulites from the high-grade internal zone of the Bohemian Massif (Variscan belt of Central Europe). The development of the plagioclase corona is a manifestation of diffusion-driven transfer of CaO and Na₂O from the surrounding matrix and results in isolation of kyanite grains from the quartz- and K-feldspar-bearing matrix. This process establishes Si-undersaturated conditions along the plagioclase–kyanite interface, which allow crystallization of spinel during low-pressure metamorphism. The process of the plagioclase rim development is modeled thermodynamically assuming local equilibrium. The results combined with textural observations enable estimation of equilibration volume and diffusion length for Na and Ca that extends ∼400–450 and ∼450–550 μm, respectively, around each kyanite crystal. Low estimated bulk diffusion coefficients suggest that the diffusion rate of Ca and Na is controlled by low diffusivity of Al across the plagioclase rim.  相似文献   

On type B CAI formation: experimental constraints on fO₂ variations in spinel minor element partitioning and reequilibration effects     

Harold C Connolly Jr.  D.S Burnett 《Geochimica et cosmochimica acta》2003,67(22):4429-4434

We report data from a series of dynamic crystallization experiments that focus on determining the partition coefficients (D’s) for V and Ti in the spinel + liquid system of an average type B1 CAI bulk composition for three different fO₂ conditions. Partitioning data for Ca and Si are also obtained. We show that the D’s for V and Ti are fO₂ dependent with D_Ti decreasing at low oxygen fugacity due to the presence of Ti³⁺. D_V is essentially 0 in air, rises to 2.2 at the Fe-FeO buffer and drops to 1.4 at the C-CO buffer. This indicates that V³⁺ is highly compatible in spinel and that higher and lower valence states are much less compatible. We also report data from isothermal experiments that determine diffusion times for V and Ti in same system at a temperature close to the T_max for type B1 CAIs. Diffusion of these elements between spinel and liquid is surprisingly rapid, with essentially total equilibration of Ti and V between spinel and liquid in 90 h run duration. Lack of equilibration of Cr, Si, and Ca shows that the Ti and V equilibration mechanism was diffusion and not dissolution and reprecipitation. Our experimental run durations set an upper limit of a few tens of hours on the time that type B1 CAIs were at their maximum temperature. Based on our data we argue that subsolidus reequilibration between spinel inclusion and host-silicate phases within type B CAIs likely explains the observed range of V and Ti concentrations in spinels which are inclusions in clinopyroxene.  相似文献   

Growth of myrmekite coronas by contact metamorphism of granitic mylonites in the aureole of Cima di Vila, Eastern Alps, Italy   总被引：2，自引：1，他引：2  

B. Cesare  C. Marchesi  J. A. D. Connolly 《Journal of Metamorphic Geology》2002,20(1):203-213

In the contact aureole of the Oligocene granodiorite of Cima di Vila, granitic pegmatites of Variscan age were strongly deformed during eo‐Alpine regional metamorphism, with local development of ultramylonites. In the ultramylonite matrix, consisting of quartz, plagioclase, muscovite and biotite, microstructures show grain growth of quartz within quartz ribbons, and development of decussate arrangements of mica. These features indicate that dynamic recrystallization related to mylonite development was followed by extensive static growth during contact metamorphism. K‐feldspar porphyroclasts up to 1.5 cm are mantled by myrmekite that forms a continuous corona with thickness of about 1 mm. In both XZ and YZ sections, myrmekite tubules are undeformed, and symmetrically distributed in the corona, and oligoclase‐andesine hosts have random crystallographic orientation. Myrmekite development has been modelled from the P–T–t evolution of the ultramylonites, assuming that the development of the ultramylonites occurred during eo‐Alpine metamorphism at c. 450 °C, 7.5 kbar, followed by contact metamorphism at c. 530 °C, 2.75 kbar. Phase diagram pseudosections calculated from the measured bulk composition of granitic pegmatite protolith indicate that the equilibrium assemblage changes from Qtz–Phe–Ab ± Zo ± Cpx ± Kfs during the ultramylonite stage to Qtz–Pl(An_30–40)–Ms–Kfs–Bt(Ann₅₅) during the contact metamorphic stage. The thermodynamic prediction of increasing plagioclase mode and anorthite content, change of white mica composition and growth of biotite, occurring during the end of the heating path, are in agreement with the observed microstructures and analysed phase compositions of ultramylonites. Along with microstructural evidence, this supports the model that K‐feldspar replacement by myrmekite took place under static conditions, and was coeval with the static growth accompanying contact metamorphism. Myrmekite associated with muscovite can develop under prograde (up‐temperature) conditions in granites involved in polymetamorphism.  相似文献