Tourmaline of the elbaite-schorl series from the Himalaya Mine, Mesa Grande, California: A detailed investigation
-
Andreas Ertl
,
George R. Rossman
Abstract
Chemical, structural, infrared, optical, and Mössbauer spectroscopic data were obtained on tourmalines from gem pockets in the Himalaya mine, San Diego County, California, including a strongly color-zoned crystal. Calcium and Li abundances increase from core to rim, whereas Mn2+ and F increase, reach a maximum, and then decrease. Upon initiation of crystallization of lepidolite, F contents in tourmaline decrease. The black core is a Mn-bearing “oxy-schorl.” The grayish-yellow, intermediate zone is Mn-rich “fluor-elbaite” that contains a relatively high Mn content with ~6 wt% MnO. The nearly colorless “fluor-elbaite” rim has the highest Li content of all zones. There is an inverse correlation between the lattice parameter a (for values ≥15.84 Å) and the Li content (r2 = 0.96). Mössbauer studies from the different zones within this crystal show that the Fe3+/Fe(total) ratio increases continuously from the Fe-rich core to the Fe-poor near-rim zone, consistent with increasing oxygen fugacity during pegmatite pocket evolution. There is a high positive correlation between lattice parameter a (for values ≥15.84 Å) and (Fe2++Mn2+) content in tourmalines from the elbaite-schorl series (r2 = 0.99). Values lower than 15.84 Å for a are likely a consequence of greater [4]B contents in samples that usually have a (Fe2++Mn2+) content of <0.1 apfu. Positive correlations between Al at the Y site and [4]B (r2 = 0.93), and between (Mn2++Fe2+) and [4]Al (r2 = 0.99) were found in tourmalines from the Himalaya Mine. These correlations indicate that, in the short-range order configurations, YAl is coupled with [4]B, whereas Mn2+ and Fe2+ are coupled with [4]Al.
To obtain the most accurate OH data, different analytical methods were used: SIMS, hydrogen manometry, continuous-flow mass spectrometry, and IR overtone spectroscopy. Some elbaites contain a mixed occupation of F, OH, and O at the W site. Based on these data, the assumption OH = 4 - F appears to be valid only for elbaitic tourmalines with FeO+MnO < 8 wt%.
In terms of the conditions of formation, whether gel or glass, the transition from low to high viscosity of the pocket-forming medium occurs before primary crystallization within the pockets ceased. At the pocket stage, Li contents of residual hydrosilicate melt were evidently high enough to promote a continuous transition from schorl-foitite at the pegmatite margin to elbaite-rossmanite-liddicoatite in the final stages of consolidation of the pegmatite interior.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- Metamorphic ultrahigh-pressure tourmaline: Structure, chemistry, and correlations to P-T conditions
- Slavikite—Revision of chemical composition and crystal structure
- Anisotropic elasticity of jarosite: A high-P synchrotron XRD study
- Tourmaline of the elbaite-schorl series from the Himalaya Mine, Mesa Grande, California: A detailed investigation
- Characterization of Al-Si ordering state in an alkali feldspar using atom location by channeling-enhanced microanalysis (ALCHEMI)
- The relative stability of stoichiometrically related natural and synthetic double salts
- Free energy of formation of zircon based on solubility measurements at high temperature and pressure
- Structure refinement of a synthetic knorringite, Mg3(Cr0.8Mg0.1Si0.1)2(SiO4)3
- A mineral tracer toward high-resolution dust provenance on the Chinese Loess Plateau: SEM, TEM, and sulfur isotopes of sulfate inclusions in biotite
- High-resolution TEM study of jimthompsonite, chesterite, and chain-width disorder in Archean ultramafic rocks from Isua, West Greenland
- Retrograde hydration sequence in disordered Mg amphiboles: A TEM investigation
- Can electron energy-loss spectroscopy (EELS) be used to quantify hydrogen in minerals from the O K edge?
- Texture analysis of a turbostratically disordered Ca-montmorillonite
- Packing systematics of the silica polymorphs: The role played by O-O nonbonded interactions in the compression of quartz
- Calorimetric study of the surface energy of forsterite
- Crystallographic texture of the magnetite-hematite transformation: Evidence for topotactic relationships in natural samples from Quadrilátero Ferrífero, Brazil
- Semi-ordered crystalline structure of the Santa Olalla vermiculite inferred from X-ray powder diffraction
- Stishovite single-crystal growth and application to silicon self-diffusion measurements
- Density of dry peridotite magma at high pressure using an X-ray absorption method
- The crystal-structure and vacancy distribution in 6C pyrrhotite
- Thermal modification of hematite-ilmenite intergrowths in the Ecstall pluton, British Columbia, Canada
- A new Al-rich hydroxylian pseudorutile from Kalimantan, Indonesia
- Lapeyreite, Cu3O[AsO3(OH)]2·0.75H2O, a new mineral: Its description and crystal structure
- High P-T phase relation of magnesian (Mg0.7Fe0.3) staurolite compositon in the system FeO-MgO-Al2O3-SiO2-H2O: Implications for prograde high-pressure history of ultrahigh-temperature metamorphic rocks
- Letter: Hibonite-(Fe), (Fe,Mg)Al12O19, a new alteration mineral from the Allende meteorite
- Letter: Ion irradiation of the TiO2 polymorphs and cassiterite
- Letter: Corundum + orthopyroxene ± spinel intergrowths in an ultrahigh-temperature Al-Mg granulite from the Southern Marginal Zone, Limpopo Belt, South Africa
- Letter: Fe3+ spin transition in CaFe2O4 at high pressure
- Density functional theory and Monte Carlo study of octahedral cation ordering of Al/Fe/Mg cations in dioctahedral 2:1 phyllosilicates
