One-phase Inclusions Research Articles

Equivalent-inclusion approach and effective medium approximations for elastic moduli of compound-inclusion composites

Effective medium approximations are developed to estimate the elastic moduli of macroscopically isotropic suspensions of compound inclusions in a continuous matrix material. The two-phase compound (coated) inclusions are substituted by equivalent one-phase inclusions, using the respective dilute solution results. Then, the available effective medium approximation schemes for homogeneous-inclusion materials can be applied to the equivalent medium to estimate the effective moduli of original composites. Since the compound-inclusion dilute solution for the shear modulus is rather involved, a simplified approximation is also proposed. Numerical simulations by finite element method in some benchmark examples are compared favorably with the predictions of the scheme.

Equivalent-inclusion approach and effective medium estimates for elastic moduli of two-dimensional suspensions of compound inclusions

An effective medium scheme is developed to estimate the elastic moduli of two-dimensional macroscopically isotropic suspensions of compound inclusions in a continuous matrix material. The two-phase (coated) compound inclusions are substituted by equivalent one-phase inclusions, using dilute solution results. Then, the available effective medium approximations and bounds are applied to the equivalent medium with homogeneous inclusions. Numerical fast Fourier transform simulations in some benchmark examples are compared favourably with the predictions of the scheme.

Equivalent-inclusion approach and effective medium approximations for conductivity of coated-inclusion composites

Effective medium approximations are developed to estimate the macroscopic conductivity of inhomogeneous materials with coated-inclusion inhomogeneities. The two-phase coated inclusions are substituted by equivalent one-phase inclusions, with the help of an analytical dilute solution result. Then the available effective medium estimates can be applied to the simpler equivalent homogeneous-inclusion composites to estimate the effective conductivity of original composites. Numerical finite element results for a number of periodic structures illustrate the efficiency of the approach.

Characterisation of amphibolite-facies fluids of Variscan eclogites from the Orlica-Snieznik dome (Sudetes, SW Poland)

Eclogites from the Orlica-Snieznik dome (Sudetes, SW Poland) exhibit evidence for Variscan high-pressure metamorphism and a subsequent amphibolite-facies overprint. Three main types of fluid inclusions were observed in quartz of partially retrogressed eclogites. Type 1: aqueous inclusions, mostly two-phase inclusions (L + V). Type 2: (a) CO 2 ± N 2 ± CH 4 inclusions, normally one-phase inclusions, some contain graphite as daughter mineral; (b) N 2 ± CH 4 inclusions, one-phase inclusions. Type 3: mixed H 2OCO 2 ± N 2 inclusions, normally two-phase inclusions (LH 2O + LCO 2 ± VCO 2) consisting of 70–80 vol% CO 2. The texturally earliest inclusions are the CO 2 ± N 2 ± CH 4 (type 2a) inclusions, which were followed by H 2OCO 2N 2 (type 3) and H 2O (type 1) inclusions in chronological order. Late aqueous (type 1) and N 2CH 4 (type 2b) inclusions were the last to be trapped. Isochores for fluid inclusions are not conformable with peak-metamorphic conditions which are estimated at temperatures between 640° and 790°C and minimum pressures of >14 kbar. At least three possible explanations must be considered: (1) no fluid phase was present during the eclogite-facies metamorphism; (2) all fluid inclusions which were trapped during the high-pressure event decrepitated during retrogression; (3) only under medium-pressure conditions fluid inclusions were trapped. We did not succeed to identify fluid inclusions which clearly are related to the eclogite-facies metamorphism. However, the isochores derived from microthermometric measurements can be used to constrain the retrograde P-T path. The highest-density isochore of the early CO 2 ± N 2 ± CH 4 inclusions indicates a pressure of 8 kbar at 600°C. The isochores of the H 2OCO 2 ± N 2, the H 2O inclusions and the re-equilibrated CO 2 ± N 2 ± CH 4 inclusions suggest an almost isothermal decompressional uplift to 2 kbar at 600°C, which was followed by isobaric cooling to 200°C. Therefore, the rate of uplift was low relative to the rate of cooling, indicating a relatively long period of tectonic inactivity.

Applications of the laser Raman microprobe RAMANOR U-1000 to hydrothermal ore deposits; Carlin as an example

The laser Raman microprobe has been used effectively in the identification of polyatomic gases, complex ions, and daughter crystals in fluid inclusions in a variety of host rocks (e.g., Dhamelincourt et al., 1979a; Rosasco and Roedder, 1979). This is a generally nondestructive, in situ, semiquantitative analytical technique in which a monochromatic laser beam is focused into a sample. The spectrum resulting from the inelastically scattered radiation indicates the chemical speciation of the irradiated sample. Although laser Raman microprobe analysis is not very effective for brines composed of simple salts, the nonelectrolyte components of hydrothermal fluid inclusions can be readily analyzed. Raman spectroscopy also provides important information, on a microscale, for solid phases in the assemblage. Fluid inclusions in quartz and calcite from several types of samples from the disseminated gold deposit at Carlin, Nevada, were studied petrographically and analyzed by microthermometry and Raman spectroscopy. The laser Raman microprobe was used to scan for CO 2 , CO, N 2 , H 2 S, and CH 4 + or - H 2 O. The semiquantitative microprobe analyses confirmed the presence of three-phase inclusions containing water and different amounts of CO 2 , one-phase inclusions of high-density CH 4 -dominated fluid, and very weak aqueous brines. Very minor H 2 S was detected in a CO 2 -H 2 O inclusion and small amounts of CO 2 were detected in some of the CH 4 -dominated inclusions. These gases may have affected ore deposition. In any event, their identification is necessary for correct estimations of pressure to be derived from homogenization temperatures of the fluid inclusions. The laser Raman microprobe provides more than compositional data. For instance, the exact spectral position and shape of the CH 4 peak indicate the internal pressure, even in inclusions too small ( 2 polymorphs anatase and brookite (both present) in hydrothermal quartz deposits at Magnet Cove, Arkansas. The ability of the laser Raman microprobe to provide pinpoint analyses has many advantages over bulk extraction methods, which mix the volatiles from separate generations of fluids and may also produce chemical artifacts.

Fluid inclusions in quartz from a quartz breccia in the Siljan Ring structure, central Sweden

Abstract The Siljan structure represents a deep erosion level of an astrobleme. Post-impact formation of minerals as various types of vein fillings is common. Non-shocked milky quartz from a large vein revealed fluid inclusions of three types:(1) one-phase, regularly shaped inclusions, < 1 to 10 μm in size, (2) two-phase, regularly to irregularly shaped inclusions, 2 to 7 μm, (3) larger irregular two-phase inclusions, 8–20 μm. The one-phase inclusions dominate; density of inclusion occurrence is estimated at 46 × 104 inclusions per cm2. Melting temperatures indicate a total salinity of 1.0 eq. wt. % NaCl. Homogenization temperatures range between 165 and 309°C. The fluid inclusion data imply a complex origin of the quartz. It consists in part of breccia fragments formed after the impact. The quartz vein was cemented by deep circulating meteoric waters at successively lowered temperatures initially over 300°C.