1,721,053 research outputs found
Constraints on the Equations of State of stiff anisotropic minerals: Rutile, and the implications for rutile elastic barometry
No full textWe present an assessment of the thermo-elastic behaviour of rutile based on X-ray diffraction data and direct elastic measurements available in the literature. The data confirms that the quasi-harmonic approximation is not valid for rutile because rutile exhibits substantial anisotropic thermal pressure, meaning that the unit-cell parameters change significantly along isochors. Simultaneous fitting of both the diffraction and elasticity data yields parameters of KTR0= 205.14(15) GPa, KSR0= 207.30(14) GPa, = 6.9(4) in a 3rd-order Birch-Murnaghan Equation of State for compression, αV0= 2.526(16) × 10-5 K-1, Einstein temperature θE = 328(12) K, Anderson-Grüneisen parameter δT = 7.6(6), with a fixed thermal Grüneisen parameter γ = 1.4 to describe the thermal expansion and variation of bulk modulus with temperature at room pressure. This Equation of State fits all of the available data up to 7.3 GPa at room temperature, and up to 1100 K at room pressure within its uncertainties. We also present a series of formulations and a simple protocol to obtain thermodynamically consistent Equations of State for the volume and the unit-cell parameters for stiff materials, such as rutile. In combination with published data for garnets, the Equation of State for rutile indicates that rutile inclusions trapped inside garnets in metamorphic rocks should exhibit negative residual pressures when measured at room conditions
Elastic geobarometry: How to work with residual inclusion strains and pressures
No full textA continuously increasing number of research groups are adopting elastic geobarometry for retrieving pressures and temperatures of entrapment of inclusions into a host from both natural and experimental samples. However, a few misconceptions of some of the general concepts underlying elastic geobarometry are still widespread. One is the difference between various approaches to retrieve the residual pressures and residual strains from Raman measurements of inclusions. In this paper, the estimation of uncertainties and the validity of some general assumptions behind these methods are discussed in detail, and we provide general guidelines on how to deal with inclusion strain, measurements, inclusion pressure, and their uncertainties
Inclusions in diamonds probe Earth’s chemistry through deep time
Full text linkMost of our knowledge about the chemical composition of the Earth's interior is primarily retrieved by indirect observations, experiments and calculations that are limited to simple compositions. Here, the authors present the investigation of inclusions trapped in super deep diamonds as an alternative source of a wealth of information on the chemical state of the Earth's interior through time
Micropetrology: Are inclusions grains of truth?
No full textInclusions in minerals, whether fluids, melts or crystalline phases, are small pieces of the largescale puzzle of Nature, time-consuming to investigate and often of difficult interpretation. Yet they are windows into the past of their host mineral. Mineral inclusions provide the opportunity to unravel the genesis of their host, and the increasingly refined understanding of their elastic behaviour provides the basis for alternative, equilibrium-independent geobarometry. Fluid and melt inclusions reveal information about material transfer in the Earth system, from shallow mineralization to mantle re-fertilization via subduction. The study of inclusions is thus one of the most intriguing and fertile branches of micropetrology. In this contribution, we focus on two recent developments: the use of elasticity models to extract the formation conditions of the host crystal, and the discovery and investigation of melt inclusions in metamorphic rocks. We also discuss how to evaluate the information provided by inclusions, given that they are no longer at the pressure and temperature conditions of entrapment. We discuss how to understand and quantify the changes undergone during cooling and depressurization, and how metastability-related phenomena in inclusions, such as crystallization of rare polymorphs and preservation of the original content of volatiles in fluid and melt inclusions, provide direct evidence that inclusions represent closed systems. The field of study of inclusions in minerals still has a largely untapped potential. The most fruitful avenues for future research will emerge from continuous technological innovation in analytical and imaging techniques, the application of experimental petrology, and the development and application of new theoretical models for coupled mineral behaviour under changing P-T conditions
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Equation of state of spinel (MgAl2O4): constraints on self-consistent thermodynamic parameters and implications for elastic geobarometry of peridotites and chromitites
No full text"eosFit-Pinc: A simple GUI for host-inclusion elastic thermobarometry" - Reply to Zhong et al
Full text linkWe provide a further algebraic proof that the lines of entrapment conditions for inclusions calculated with the formula of Guiraud and Powell (2006) are not thermodynamic isomekes and therefore do not represent exactly lines of possible entrapment conditions
Commentary on Constraints on the Equations of State of stiff anisotropic minerals: Rutile, and the implications for rutile elastic barometry [Miner. Mag. 83 (2019) pp. 339-347]
No full textThe conclusion of Zaffiro et al. (2019; Constraints on the Equations of State of stiff anisotropic minerals: rutile, and the implications for rutile elastic barometry. Mineralogical Magazine, 83, 339-347) that the Mie-Grüneisen-Debye (MGD) Equation of State (EoS) cannot fit the available data for rutile is shown to be incorrect, even though rutile exhibits significant anisotropic thermal pressure which invalidates the quasi-harmonic approximation used as the basis for the MGD EoS. The refined parameters for the MGD EoS of rutile are: KTR0= 205.05(25) GPa, = 7.2(5), θD = 399(20) K, γ0= 1.40(2) and q = 1.5(7). This EoS predicts volumes, bulk moduli and volume thermal expansion coefficients for rutile at metamorphic conditions that are statistically indistinguishable from those predicted by the 'isothermal' type of EoS reported previously
Stress, strain and Raman shifts
No full textThe concept of the phonon-mode Grüneisen tensor is reviewed as method to determine the elastic strains across crystals from the changes in the wavenumbers of Raman-active phonon modes relative to an unstrained crystal. The symmetry constraints on the phonon-mode Grüneisen tensor are discussed and the consequences for which combinations of strains can be determined by this method are stated. A computer program for Windows, stRAinMAN, has been written to calculate strains from changes in Raman (or other phonon) mode wavenumbers, and vice-versa. It can be downloaded for free from www.rossangel.net
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