Manganoan kinoshitalite in Mn-rich marble and skarn from Virginia
-
Robert J. Tracy
and
James S. Beard
Abstract
A new locality for the Ba-rich trioctahedral mica, kinoshitalite [Ba(Mg,Mn,Fe,Al)3Si1.9-2Al2- 2.2O10(OH,F)2], has been found in a metamorphosed manganoan marble from Pittsylvania County, Virginia. Metamorphic grade is middle amphibolite facies, with documented P and T of 400 MPa and 575 °C. The locality is along strike not far from the well known Bald Knob, North Carolina, Mn-mineral locality, and appears to represent a silica-poorer analog of Bald Knob. The kinoshitalite occurs in a single layered hand sample containing both skarn and marble layers, and it shows significant compositional contrasts between the two lithologies. Kinoshitalite is scarce and fine-grained in manganoan marble and coexists with kutnahorite, manganoan calcite, fluorian alleghanyite, fluorian sonolite, aluminous jacobsite, and alabandite. Kinoshitalite is both more abundant and coarser-grained in skarn where it coexists with kutnahorite, tephroite, fluorian manganhumite, spessartine, jacobsite, and manganoan magnetite. A-sites in kinoshitalite in skarn are about 3/4 occupied by Ba (with the remainder mostly K), whereas in marble, Ba occupancy of A-sites exceeds 90% and most of the remainder is Ca. XMg in octahedral sites is >0.6 and is higher in marble than in skarn, whereas XMn is significant (>0.2) and is higher in skarn than in marble. The VIAl is significantly higher in skarn kinoshitalite, as is total Tschermak content. The total Tschermak content of these barian micas (VIAl + Ti + Fe3+) is typical of all previously reported kinoshitalites and is significantly lower than that of clintonite and biotite. The XF of kinoshitalite in marble is significantly higher than that in skarn.
The petrogenesis of kinoshitalite at the Hutter Mine locality is unclear due to the lack of context for the single mine-dump sample in which the mineral was found and the absence of textural evidence for reactions. However, the two likeliest source minerals for Ba that have been found in the deposit are barite and BaCa(CO3)2 (probably barytocalcite). One hypothetical reaction to produce kinoshitalite involves decarbonation, in which BaCa(CO3)2, rhodochrosite, Mn-garnet, and aqueous fluid react to form kinoshitalite, tephroite (or an Mn-humite), calcite, and CO2. A second potential reaction to form kinoshitalite involves barite, Mn-garnet, tephroite, and aqueous fluid as reactants, and kinoshitalite, alabandite, jacobsite, SiO2, and O2 as products.
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- TEM study of mullite growth after muscovite breakdown
- The reduction of aqueous Au3+ by sulfide minerals and green rust phases
- Manganoan kinoshitalite in Mn-rich marble and skarn from Virginia
- Expandability of anchizonal illite and chlorite: Significance for crystallinity development in the transition from diagenesis to metamorphism
- X-ray absorption spectroscopy of silicates for in situ, sub-micrometer mineral identification
- Radiation damage in zircon
- Neutron and temperature-resolved synchrotron X-ray powder diffraction study of akaganéite
- Li-rich zincostaurolite and its decompression-related breakdown products in a diaspore-bearing metabauxite from East Samos (Greece): An EMP and SIMS study
- Olivine from planetary basalts: Chemical signatures that indicate planetary parentage and those that record igneous setting and process
- Observations on the relationship between crystallographic orientation and biasing in apatite fission-track measurements
- Borocookeite, a new member of the chlorite group from the Malkhan gem tourmaline deposit, Central Transbaikalia, Russia
- New thermochemical evidence on the stability of dickite vs. kaolinite
- Thermodynamics of Fe oxides: Part I. Entropy at standard temperature and pressure and heat capacity of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
- Thermodynamics of Fe oxides: Part II. Enthalpies of formation and relative stability of goethite (α-FeOOH), lepidocrocite (γ-FeOOH), and maghemite (γ-Fe2O3)
- An in situ neutron diffraction study of cation disordering in synthetic qandilite Mg2TiO4 at high temperatures
- Peristeritic plagioclase in North Sea hydrocarbon reservoir rocks: Implications for diagenesis, provenance and stratigraphic correlation
- Incorporation of Ni into natural goethite: An investigation by X-ray absorption spectroscopy
- Characterization of an early metamorphic stage through inclusions in zircon of a diamondiferous quartzofeldspathic rock from the Erzgebirge, Germany
- Gersdorffite (NiAsS) chemical state properties and reactivity toward air and aerated, distilled water
- The concentration and speciation of hydrogen in feldspars using FTIR and 1H MAS NMR spectroscopy
- The significance of mineral inclusions in large diamonds from Yakutia, Russia
- Letters. Evidence from surface phonons for the (2 × 1) reconstruction of the (101̄4) surface of calcite from computer simulation
- Transformation of SiO2 to the amorphous state by shearing at high pressure
