Coexisting clinopyroxene/spinel and amphibole/spinel symplectites in metatroctolites from the Buck Creek ultramafic body, North Carolina Blue Ridge
-
Helen M. Lang
,
Aletha J. Wachter
Abstract
Buck Creek metatroctolites preserve evidence of three stages in the geologic history of the region: a relict igneous stage; a high-pressure, granulite-facies metamorphic stage; and a hydrous alteration stage. During high-pressure granulite-facies metamorphism, adjacent olivine and plagioclase reacted to produce complex coronitic textures. Relict olivine is surrounded by radial, columnar orthopyroxene, and plagioclase is rimmed by fine-grained symplectite composed of separate grains of clinopyroxene/ spinel, tschermakitic amphibole/spinel symplectite and minor clinopyroxene/sapphirine symplectite. Examination of textural relationships in back-scattered electron images and X-ray element maps of the symplectites demonstrates that amphibole/spinel and clinopyroxene/spinel symplectites grew simultaneously at high temperature to replace plagioclase in these rocks. Clinopyroxene/sapphirine symplectite grew in the latest stages of plagioclase replacement in some samples.
A successful model for the main corona-forming reaction in sample BC7, 1.00 Pl + 1.72 Ol + 0.17 H2O = 0.59 Di + 0.17 Amp + 0.68 Spl + 0.79 Opx, results only if amphibole is included. The model predicts relative volumes of product clinopyroxene, amphibole and spinel that are generally consistent with the proportions in imaged symplectites. Proportions of clinopyroxene- and amphibole-hosted symplectite appear to have been governed by local mass-balance of Na and Al in plagioclase and/or availability of H2O. The most successful model for formation of the inner clinopyroxene/sapphirine corona, 1.00 Pl + 1.47 Ol + 0.17 H2O = 0.59 Di + 0.17 Amp + 0.30 Spr (10 ox.) + 0.57 Opx, also includes amphibole, which is present in association with clinopyroxene/sapphirine symplectite. Sufficient H2O for formation of symplectic amphibole must have been present in the intergranular fluid of relict igneous troctolites or have infiltrated during metamorphism at high P-T conditions.
© 2015 by Walter de Gruyter Berlin/Boston
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
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
