Topic
Hydrogrossular
About: Hydrogrossular is a research topic. Over the lifetime, 78 publications have been published within this topic receiving 1924 citations.
Papers published on a yearly basis
Papers
Journal Article•
TL;DR: In this article, the tetrahedral site occupation of three titanian andradites (San Benito County, California) and a synthetic deuterated hibschite was determined by using X-ray single-crystal and neutron powder data, respectively.
Abstract: Tetrahedral-site occupations were determined for three titanian andradites (San Benito County, California) and a synthetic deuterated hibschite by using X-ray single-crystal and neutron powder data, respectively. Site refinements reveal the presence of tetrahedral vacancies (4-14%) in all three andradites. Infrared absorption spectra measured for the same material used in the X-ray analysis indicate structurally bound water (as OH^-) in
amounts of 0.8 to 5. 7 wt% OH, which is in good agreement with water contents derived from the refinements. These data confirm that the tetrahedral site is not fully occupied
and that charge balance can be achieved by the substitution (O_4H_4)^(4-) = (SiO_4)^(4-). The proton position could not be determined because of the small amount of H present.
Diffraction maxima in the neutron profile for hibschite exhibited small, well-defined shoulders related to chemical inhomogeneity. The data were fit using multiphase Rietveld
techniques assuming four phases with slightly different Si/D ratios. Structural parameters [ɑ= 12.0105(3) A; O(x,y,z) = 0.03561(14), 0.04653(12), 0.64957(12); d site= 0.767(6) Si] refined for the major phase [62(3)% mole fraction) were consistent with X-ray refinements of natural hydrogrossulars. The deuterium atom [0.0965(5), 0.0520(4), 0.6600(5)] was located (ΔF map) outside the tetrahedral volume near the position reported for the Si-free end-member. A significant improvement in R factor was obtained after refinement of a split-atom model to describe the oxygen positional disorder. The short O-D distance
[0.744(6)] calculated for the ordered (average) structure can be interpreted within the context of this model.
Distance-least-squares (DLS-76) calculations were used to simulate the effect of the (O_4H_4)^(4-) = (SiO_4)^(4-) substitution on the grossular structure. If the tetrahedral d-O distance, calculated from vacancy concentration, is weighted heavily in the geometric refinement, structural
variations in the hydrogrossular series [Ca_3Al_2(SiO_4)_(3-)Ca_3Al_2(O-4H_4)_3] can be predicted.
Application of DLS to other garnet structures suggests that mantle garnets (rich in pyrope component) may contain only very limited amounts of water.
137 citations
TL;DR: Isometric tricalcium aluminate hexahydrate, one of the well-established products of hydration of portland cement, forms complete solid solutions with the corresponding ferrite, 3CaO.AhOa.3Si02 as discussed by the authors.
Abstract: Isometric tricalcium aluminate hexahydrate, one of the well-established products of hydration of portland cement, forms complete solid solutions with the corresponding ferrite, 3CaO.Fe20a.6H20, with grossularite garnet, 3CaO.AhOa. 3Si02, and with andradite garnet, 3CaO.Fe20a.3Si02. Members of this solidsolution series were synthesized by hydrothermal methods, and X-ray determinations were made of their crystal structures. To the series belong: (1) The mineral plazolite, 3CaO.AhOa.2Si02.2R20, (2) the major product of hydration of the glass phase in portland cement clinker at elevated temperatures and pressures, and (3) one of the major products of hydration of tetracaleium aluminoferrite.
76 citations
TL;DR: In this paper, the stability of grossularite has been investigated in relation to the progressive metamorphism of a limestone containing clay impurities, and the range of stability has been outlined indirectly from field and laboratory data.
Abstract: Exploratory experiments have been conducted to determine the stability range of grossularite garnet, $$Ca_{3}Al_{2}(SiO_{4})_{3}$$ Grossularite probably has a field of stability at atmospheric pressure; although the garnet does not require pressure for its formation, pressure should favor its formation. Grossularite may form by reaction of its components in the solid state; the intermediate products obtained are presumed to be meta-stable. The majority of garnets described as grossularite are probably members of the hydrogrossular series as defined by Hutton. Pressure, in addition to temperature and time, determines the stable member of the hydrogarnet series. It is believed that the dry end member, grossularite, exists but that it cannot exist in the presence of water at elevated temperatures. The range of stability of grossularite is outlined indirectly from field and laboratory data in relation to the progressive metamorphism of a limestone containing clay impurities. Grossularite has, as yet, not been...
70 citations
TL;DR: In this article, the phase relations in eclogite facies metarodingites have been explored in terms of T-XCO2, T-μ(SiO2), μ(Cal)−μ( SiO2) and P-T sections.
Abstract: Eclogite facies metarodingites occur as deformed dykes in serpentinites of the Zermatt-Saas ophiolite (Western Alps). They formed during the subduction of the Tethys oceanic lithosphere in the Early Tertiary. The metarodingites developed as a consequence of serpentinization of the oceanic mantle. Three major types of metarodingites (R1, R2 & R3) can be distinguished on the basis of their mineralogical composition. All metarodingites contain vesuvianite, chlorite and hydrogrossular in high modal amounts. In addition they contain: R1 – diopside, tremolite, clinozoisite, calcite; R2 – hydroandradite, diopside, epidote, calcite; and R3 – hydroandradite. Both garnets contain a small but persistent amount of hydrogarnet component. The different metarodingites reflect different original dyke rocks in the mantle. In each group of metarodingite, textural relations suggest that reactions adjusted the assemblages along the P–T path travelled by the ophiolite during subduction and exhumation. Reactions and phase relations derived from local textures in metarodingite can be modelled in the eight-component system: SiO2-Al2O3-Fe2O3-FeO-MgO-CaO-CO2-H2O. This permits the analysis of redox reactions in the presence of andradite garnet and epidote in many of the rocks. Within this system, the phase relations in eclogite facies metarodingites have been explored in terms of T–XCO2, T–μ(SiO2), μ(Cal)–μ(SiO2) and P–T sections. It was found that rodingite assemblages are characterized by low μ(SiO2) and low XCO2 conditions. The low SiO2 potential is externally imposed onto the rodingites by the large volume of antigorite-forsterite serpentinites enclosing them. Moreover, μ(SiO2) decreases consistently from metarodingite R1 to R3. The low μ(SiO2) enforced by the serpentinites favours the formation of hydrogarnet and vesuvianite. Rodingite formation is commonly associated with hydrothermal alteration of oceanic lithosphere at the ocean floor, in particular to ocean floor serpentinization. Our analysis, however, suggests that the metarodingite assemblages may have formed at high-pressure conditions in the subduction zone as a result of serpentinization of oceanic mantle by subduction zone fluids.
61 citations
TL;DR: In this paper, the authors classified rodingite dykes into two types: prehnite and vesuvianite, and showed that the latter is more abundant than the former.
57 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2021 | 4 |
| 2019 | 3 |
| 2018 | 3 |
| 2017 | 3 |
| 2016 | 1 |
| 2015 | 2 |