Petedunnite (CaZnSi2O6): Stability and phase relations in the system CaO-ZnO-SiO2
-
Alexandra L. Huber
,
Soraya Heuss-Aßbichler
Abstract
The phase relations of petedunnite [CaZnSi2O6 (pd)] were determined experimentally at P-T conditions up to 2.5 GPa and 1100 °C. Single-phase petedunnite is formed at high pressures (P > 0.8 GPa). Reversed experiments show that at lower pressures and temperatures >650 °C petedunnite decomposes to willemite [Zn2SiO4 (wil)], hardystonite [Ca2ZnSi2O7 (har)], and quartz [SiO2 (qtz)] according to the reaction 4 pd = wil + 2 har + 3 qtz. The boundary curve for this equilibrium reaction is given by P (GPa) = -0.093 (0.029) + 0.0014 (0.0003) T (°C), by disregarding the phase transition of quartz. The stability field of wil + har + qtz is restricted toward lower temperatures by zinc-feldspar [CaZn- Si3O8 (zfsp)] according to the known reaction: wil + 2 har + 7 qtz = 4 zfsp. These reactions intersect at 650(1) °C/0.78(0.01) GPa, generating an invariant point Ipd. Additionally, petedunnite-breakdown reaction is intersected by the low/high-quartz phase transition curve, generating an invariant point Ipdqtz at ~840 °C, 1.04 GPa. At temperatures <650 °C, further reactions occur in the system CaO-ZnOSiO2 including the doubly degenerate reaction zfsp = pd + qtz and 3 pd = har + wil + zfsp, which also intersect the invariant point Ipd. All reactions involving petedunnite display shallow positive slopes within the P/T-field, indicating that the crystallization of petedunnite is highly pressure sensitive over a wide temperature range. This means that an increasing petedunnite component in pyroxene shifts its stability field to higher pressures, similar to the effect of a jadeitic component.
The study of natural clinopyroxene and the correlation of its zinc content with published P-T conditions of these mineral assemblages confirmed a significant relationship between extraordinary high-zinc concentrations in pyroxene and high-metamorphic pressure conditions. In addition, the petedunnite component is obviously sensitive to the prevailing fluid conditions in terms of the fugacity ratio fS2/fO₂. Furthermore, a distinct temperature dependency of the zinc component was observed in the range of trace element concentration. In consequence, Zn turns out to be a key element with regard to its implementation as a sophisticated petrogenetic indicator of metamorphic conditions. Therefore, routine measurement of zinc in element analyses of clinopyroxenes is strongly recommended.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Veatchite: Structural relationships of the three polytypes
- Falsterite, Ca2MgMn2+2 (Fe2+0.5Fe3+0.5)4Zn4(PO4)8(OH)4(H2O)14, a new secondary phosphate mineral from the Palermo No. 1 pegmatite, North Groton, New Hampshire
- Pavlovskyite Ca8(SiO4)2(Si3O10): A new mineral of altered silicate-carbonate xenoliths from the two Russian type localities, Birkhin massif, Baikal Lake area and Upper Chegem caldera, North Caucasus
- Zaccagnaite-3R, a new Zn-Al hydrotalcite polytype from El Soplao cave (Cantabria, Spain)
- Incorporation of Si into TiO2 phases at high pressure
- TOF-SIMS and electron microprobe investigations of zoned magmatic orthopyroxenes: First results of trace and minor element analysis with implications for diffusion modeling
- Titanium in muscovite, biotite, and hornblende: Modeling, thermometry, and rutile activities of metapelites and amphibolites
- Polysaccharide-catalyzed nucleation and growth of disordered dolomite: A potential precursor of sedimentary dolomite
- High-pressure and high-temperature phase transitions in FeTiO3 and a new dense FeTi3O7 structure
- Compressibility and thermal expansion of hydrous ringwoodite with 2.5(3) wt% H2O
- Vibrational and elastic properties of ferromagnesite across the electronic spin-pairing transition of iron
- Electronic spin states of ferric and ferrous iron in the lower-mantle silicate perovskite
- Experimental VNIR reflectance spectroscopy of gypsum dehydration: Investigating the gypsum to bassanite transition
- Nature of rehydroxylation in dioctahedral 2:1 layer clay minerals
- Thermal behavior of afghanite, an ABABACAC member of the cancrinite group
- Experimental incorporation of Th into xenotime at middle to lower crustal P-T utilizing alkali-bearing fluids
- Sol-gel synthesis of nanocrystalline fayalite (Fe2SiO4)
- The heat capacity of fayalite at high temperatures
- Structural trends for celestite (SrSO4), anglesite (PbSO4), and barite (BaSO4): Confirmation of expected variations within the SO4 groups
- The dehydroxylation of serpentine group minerals
- Formation of nanoscale Th-coffinite
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- Crystal structure and thermal expansion of aragonite-group carbonates by single-crystal X-ray diffraction
- The lower-pressure stability of glaucophane in the presence of paragonite and quartz in the system Na2O-MgO-Al2O3-SiO2-H2O
- Coralloite, Mn2+Mn23+(AsO4)2(OH)2·4H2O, a new mixed valence Mn hydrate arsenate: Crystal structure and relationships with bermanite and whitmoreite mineral groups
- The crystal structure of metanatroautunite, Na[(UO2)(PO4)](H2O)3, from the Lake Boga Granite, Victoria, Australia
- Petedunnite (CaZnSi2O6): Stability and phase relations in the system CaO-ZnO-SiO2
- Revision of the crystal structure and chemical formula of weeksite, K2(UO2)2(Si5O13)·4H2O
- Electron backscatter diffraction (EBSD) analyses of phyllosilicates in petrographic thin sections
Articles in the same Issue
- Veatchite: Structural relationships of the three polytypes
- Falsterite, Ca2MgMn2+2 (Fe2+0.5Fe3+0.5)4Zn4(PO4)8(OH)4(H2O)14, a new secondary phosphate mineral from the Palermo No. 1 pegmatite, North Groton, New Hampshire
- Pavlovskyite Ca8(SiO4)2(Si3O10): A new mineral of altered silicate-carbonate xenoliths from the two Russian type localities, Birkhin massif, Baikal Lake area and Upper Chegem caldera, North Caucasus
- Zaccagnaite-3R, a new Zn-Al hydrotalcite polytype from El Soplao cave (Cantabria, Spain)
- Incorporation of Si into TiO2 phases at high pressure
- TOF-SIMS and electron microprobe investigations of zoned magmatic orthopyroxenes: First results of trace and minor element analysis with implications for diffusion modeling
- Titanium in muscovite, biotite, and hornblende: Modeling, thermometry, and rutile activities of metapelites and amphibolites
- Polysaccharide-catalyzed nucleation and growth of disordered dolomite: A potential precursor of sedimentary dolomite
- High-pressure and high-temperature phase transitions in FeTiO3 and a new dense FeTi3O7 structure
- Compressibility and thermal expansion of hydrous ringwoodite with 2.5(3) wt% H2O
- Vibrational and elastic properties of ferromagnesite across the electronic spin-pairing transition of iron
- Electronic spin states of ferric and ferrous iron in the lower-mantle silicate perovskite
- Experimental VNIR reflectance spectroscopy of gypsum dehydration: Investigating the gypsum to bassanite transition
- Nature of rehydroxylation in dioctahedral 2:1 layer clay minerals
- Thermal behavior of afghanite, an ABABACAC member of the cancrinite group
- Experimental incorporation of Th into xenotime at middle to lower crustal P-T utilizing alkali-bearing fluids
- Sol-gel synthesis of nanocrystalline fayalite (Fe2SiO4)
- The heat capacity of fayalite at high temperatures
- Structural trends for celestite (SrSO4), anglesite (PbSO4), and barite (BaSO4): Confirmation of expected variations within the SO4 groups
- The dehydroxylation of serpentine group minerals
- Formation of nanoscale Th-coffinite
- Magnetic and low-temperature structural behavior of clinopyroxene-type FeGeO3: A neutron diffraction, magnetic susceptibility, and 57Fe Mössbauer study
- Crystal structure and thermal expansion of aragonite-group carbonates by single-crystal X-ray diffraction
- The lower-pressure stability of glaucophane in the presence of paragonite and quartz in the system Na2O-MgO-Al2O3-SiO2-H2O
- Coralloite, Mn2+Mn23+(AsO4)2(OH)2·4H2O, a new mixed valence Mn hydrate arsenate: Crystal structure and relationships with bermanite and whitmoreite mineral groups
- The crystal structure of metanatroautunite, Na[(UO2)(PO4)](H2O)3, from the Lake Boga Granite, Victoria, Australia
- Petedunnite (CaZnSi2O6): Stability and phase relations in the system CaO-ZnO-SiO2
- Revision of the crystal structure and chemical formula of weeksite, K2(UO2)2(Si5O13)·4H2O
- Electron backscatter diffraction (EBSD) analyses of phyllosilicates in petrographic thin sections
