Abstract
Minerals of the amphibole group are found in igneous rocks on Earth and other rocky bodies. Since the O(3) site of amphibole can contain OH, O2-, F, and Cl, amphibole composition provides important information about water and halogen contents, oxidation state, and other features of its formation and alteration environments. However, the complexity of amphibole crystal chemistry means this information is difficult to extract. Furthermore, it has been regular practice in the era of the electron microprobe to neglect H and Fe3+ analyses for amphibole, critically reducing the amount of information available in amphibole analyses in the literature.
We have assembled models and insights from previous work to create a methodology that allows the estimation of magmatic H2O and Cl contents from existing amphibole analyses. Since the methodology requires use of a cation norm, we begin with a deeper investigation of the consequences of different cation normalization schemes for amphibole analyses, and provide grounds for deciding which scheme best fits a given amphibole analysis. We then show how the existing model of Popp and coworkers can be reversed to estimate the OH and [O(3)]O2- contents of amphiboles in synthesis experiments. Using a synthetic data set collected from the literature (39 amphibole analyses), we calibrate a partitioning model for the OH/Cl competition on the O(3) site of igneous amphiboles
KCl = (XCl/XOH)amphibole/([Cl]/[OH])melt
ln KCl = 6.59 K/(Na + [A]□) - 0.679 Mg + 0.487 [6]Fe where X signifies a mole fraction of an anion on the O(3) site; [Cl] and [OH] signify melt mole fractions of the anion in question on a one-oxygen (Stolper-Zhang) basis; K, Na, [A]o, Mg, and [6]Fe signify the amount of each component in the amphibole in atoms per amphibole formula unit, with [A]□ denoting vacancies on the amphibole A site.
We then combine the Popp et al. model with our new model to link the occupancy of the amphibole O(3) site and other crystal chemical parameters to the Cl and H2O content of melts crystallizing amphibole. The competition between OH and Cl for this site can be used to calculate the melt and amphibole OH/H2O contents, as well as the speciation of Fe in amphibole, provided that the Cl content of both the amphibole and its coexisting melt is known, without analyzing either phase for H or Fe3+/Fe2+.
While the models in this paper should be recalibrated using future experimental data, this work shows that considerably more information about the volatile contents of magmas can be gleaned from amphibole than previously shown and provides additional information about the crystal chemistry of amphibole and how it affects Cl partitioning into minerals of this group.
© 2014 by Walter de Gruyter Berlin/Boston
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Artikel in diesem Heft
- New data on lunar magmatic processes
- Thermodynamic approach provides insights into the aging process of biological apatite
- Effects of chemical composition and temperature on transport properties of silica-rich glasses and melts
- Speciation of and D/H partitioning between fluids and melts in silicate-D-O-H-C-N systems determined in-situ at upper mantle temperatures, pressures, and redox conditions
- Effect of oxalate and pH on chrysotile dissolution at 25 °C: An experimental study
- Gabbroic Shergottite Northwest Africa 6963: An intrusive sample of Mars
- Césarferreiraite, Fe2+Fe23+(AsO4)2(OH)2·8H2O, from Eduardo mine, Conselheiro Pena, Minas Gerais, Brazil: Second arsenate in the laueite mineral group
- Atomic structure and formation mechanism of (101) rutile twins from Diamantina (Brazil)
- Mathesiusite, K5(UO2)4(SO4)4(VO5)(H2O)4, a new uranyl vanadate-sulfate from Jáchymov, Czech Republic
- Comparison of metal enrichment in pyrite framboids from a metal-enriched and metal-poor estuary
- Chemistry of bone mineral, based on the hypermineralized rostrum of the beaked whale Mesoplodon densirostris
- Allendeite (Sc4Zr3O12) and hexamolybdenum (Mo,Ru,Fe), two new minerals from an ultrarefractory inclusion from the Allende meteorite
- Hutcheonite, Ca3Ti2(SiAl2)O12, a new garnet mineral from the Allende meteorite: An alteration phase in a Ca-Al-rich inclusion
- Infrared absorption spectroscopy of SiO2-moganite
- Kaolinite transformation into dickite during burial diagenesis
- Effect of clays and metal containers in retaining Sm3+ and ZrO2+ and the process of reversibility
- Solid solutions and phase transitions in (Ca,M2+)M2+Si2O6 pyroxenes (M2+ = Co, Fe, Mg)
- Further complexities of the 10 Å phase revealed by infrared spectroscopy and X-ray diffraction
- Solid phases of FeSi to 47 GPa and 2800 K: New data
- In-situ infrared spectra of hydroxyl in wadsleyite and ringwoodite at high pressure and high temperature
- Experimental and infrared characterization of the miscibility gap along the tremoliteglaucophane join
- A calorimetric and thermodynamic investigation of the synthetic analogs of cobaltomenite, CoSeO3·2H2O, and ahlfeldite, NiSeO3·2H2O
- Arsenate partitioning from ferrihydrite to hematite: Spectroscopic evidence
- Pressure-induced phase transitions in coesite
- Qingsongite, natural cubic boron nitride: The first boron mineral from the Earth’s mantle
- Phase relations in the system FeCO3-CaCO3 at 6 GPa and 900–1700 °C and its relation to the system CaCO3-FeCO3-MgCO3
- In-situ high-temperature emissivity spectra and thermal expansion of C2/c pyroxenes: Implications for the surface of Mercury
- Thallium geochemistry in the metamorphic Lengenbach sulfide deposit, Switzerland: Thallium-isotope fractionation in a sulfide melt
- Fluorowardite, NaAl3(PO4)2(OH)2F2·2H2O, the fluorine analog of wardite from the Silver Coin mine, Valmy, Nevada
- Correianevesite, Fe2+Mn22+(PO4)2·3H2O, a new reddingite-group mineral from the Cigana mine, Conselheiro Pena, Minas Gerais, Brazil
- Structural complexity of lead silicates: Crystal structure of Pb21[Si7O22]2[Si4O13] and its comparison to hyttsjöite
- A high-resolution powder neutron diffraction study of the crystal structure of neighborite (NaMgF3) between 9 and 440 K
- Geothermometric study of Cr-spinels of peridotite mantle xenoliths from northern Victoria Land (Antarctica)
- Crystal chemistry of the ulvöspinel-qandilite series
- Quantitative models linking igneous amphibole composition with magma Cl and OH content
- Chromium solubility in perovskite at high pressure: The structure of (Mg1–xCrx)(Si1–xCrx)O3 (with x = 0.07) synthesized at 23 GPa and 1600 °C
- New Mineral Names
- Errata