Pyribole evolution during tremolite synthesis from oxides
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Krassimir N. Bozhilov
,
David M. Jenkins
Abstract
The formation mechanisms of tremolite in a time series of hydrothermal experiments at 850 °C and 6.1 kbar were studied using transmission electron microscopy (TEM), analytical TEM, and Xray diffraction. The starting materials were unseeded mixtures of reagent-grade oxides. After the first 8 min of reaction, the synthesis products were diopside, enstatite, clinoenstatite, quartz, and minor C-centered and primitive monoclinic amphibole (13 wt% total). The compositions of the firstformed amphiboles vary considerably, from essentially pure cummingtonite (Ca/Mg = 0) to nearly ideal tremolite (Ca/Mg = 0.4). Three groupings of amphiboles with successively higher Ca/Mg ratios were identified, respectively 0.1, 0.22, and 0.35. Over a period of 97 h, the proportions of Mg-rich amphibole gradually decrease, and the average Ca/Mg ratios of all amphiboles steadily increase from about 0.22 to 0.35. Other changes include: (1) a decrease in the aspect ratio of amphibole crystals with increasing time; (2) a decrease in the number of non-amphibole chain multiplicity faults (CMFs), from early A′(2) values as low as 0.81 to a final value of 0.94; and (3) a distinct change in the rate of amphibole growth after 1 h of synthesis. These observations suggest that two mechanisms of amphibole formation are dominant: (1) formation of pyroxene modules with subsequent hydration and arrangement into the double-chain amphibole structure and (2) direct nucleation and growth of amphibole from hydrothermal solution. A third mechanism involving formation of talc-like modules, followed by their breakdown into double-chain modules, incorporation of Ca, and ordering into the amphibole structure, may also occur but probably only at the lamellar or unit-cell scale, because these syntheses were performed outside the stability field of talc.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
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- 2111 biopyribole intermediate between pyroxene and amphibole: Artifact or natural product?
- Coexisting clinopyroxene/spinel and amphibole/spinel symplectites in metatroctolites from the Buck Creek ultramafic body, North Carolina Blue Ridge
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- A kinetic study of the exsolution of pentlandite (Ni,Fe)9S8from the monosulfide solid solution (Fe,Ni)S
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- In situ determination of the compressibility of synthetic pure zircon (ZrSiO4) and the onset of the zircon-reidite phase transition
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- Shirozulite, KMn32+(Si3Al)O10(OH)2, a new manganese-dominant trioctahedral mica: Description and crystal structure
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Articles in the same Issue
- Indialite in xenolithic rocks from Somma-Vesuvius volcano (Southern Italy): Crystal chemistry and petrogenetic features
- Coexisting chromian omphacite and diopside in tremolite schist from the Chugoku Mountains, SW Japan: The effect of Cr on the omphacite-diopside immiscibility gap
- 2111 biopyribole intermediate between pyroxene and amphibole: Artifact or natural product?
- Coexisting clinopyroxene/spinel and amphibole/spinel symplectites in metatroctolites from the Buck Creek ultramafic body, North Carolina Blue Ridge
- The T-X dependence of the isosymmetric displacive phase transition in synthetic Fe3+-Al zoisite: A temperature-dependent infrared spectroscopy study
- A kinetic study of the exsolution of pentlandite (Ni,Fe)9S8from the monosulfide solid solution (Fe,Ni)S
- Single-crystal plagioclase feldspar dissolution rates measured by vertical scanning interferometry
- A simple empirical method for high-quality electron microprobe analysis of fluorine at trace levels in Fe-bearing minerals and glasses
- Constraints on mingling of crystal populations from off-center zoning profiles: A statistical approach
- Pyribole evolution during tremolite synthesis from oxides
- Solution calorimetric determination of the enthalpies of formation of NH4-bearing minerals buddingtonite and tobelite
- Dehydration dynamics of bikitaite: Part I. In situ synchrotron powder X-ray diffraction study
- Dehydration dynamics of bikitaite: Part II. Ab initio molecular dynamics study
- Phosphate mineral associations in the Cañada pegmatite (Salamanca, Spain): Paragenetic relationships, chemical compositions, and implications for pegmatite evolution
- An improved equation for crystal size distribution in second-phase influenced aggregates
- Vibrational spectroscopy of pyrope-majorite garnets: Structural implications
- The modulated crystal structure of antigorite: The m = 17 polysome
- Structural variations in mercurian tetrahedrite
- A computational investigation of the Al/Fe/Mg order-disorder behavior in the dioctahedral sheet of phyllosilicates
- Investigation of Al/Si ordering in tetrahedral phyllosilicate sheets by Monte Carlo simulation
- Equations of state of ZrSiO4phases in the upper mantle
- High pressure behavior, transformation and crystal structure of synthetic iron-free pigeonite
- In situ determination of the compressibility of synthetic pure zircon (ZrSiO4) and the onset of the zircon-reidite phase transition
- Halite-sylvite thermoelasticity
- Spiral growth of grossular under hydrothermal conditions
- Incomplete retention of radiation damage in zircon from Sri Lanka
- Shirozulite, KMn32+(Si3Al)O10(OH)2, a new manganese-dominant trioctahedral mica: Description and crystal structure
- Novel phase transition in orthoenstatite
- In situ observation of the thermal decomposition of weddelite by heating stage environmental scanning electron microscopy
