Parvo-mangano-edenite, parvo-manganotremolite, and the solid solution between Ca and Mn2+ at the M4 site in amphiboles
-
Roberta Oberti
,
Fernando Cámara
Abstract
This work reports the crystal-chemical characterization of Mn-rich amphiboles from the Grenville Marble of the Arnold mine, Fowler, St. Lawrence Co., New York (U.S.A.), which were previously described by Benimoff et al. (1991) as “manganoan silicic edenite”. According to the new nomenclature scheme for monoclinic amphiboles (Leake et al. 2004) the ideal composition of reference, ANa B(CaMn) CMg5T(Si7Al)O22(OH)2 with Ca > 1 apfu, is an end-member of the newly defined Group 5, and is named parvo-mangano-edenite. Re-examination of the original rock specimen showed significant inter- and intra-crystalline compositional variations, which can be expressed by the ANa-1TAl-1A⃞ 1TSi1 and BMn2BCa-2 exchange vectors. The first vector leads to parvo-manganotremolite, ideally A⃞ B(CaMn)CMg5TSi8O22(OH)2 with Ca > 1. The second mechanism was never found to reach Mn dominance; however, crystal-chemical analysis does not provide any evidence of structural limits, and thus the magno-calcic counterparts of the Group 5 amphiboles of this work may occur in similar but Mn-richer genetic environments. The presence of Mn at the B site helps to stabilize the charge arrangement of edenite. The parvo-mangano-edenite crystal with composition closest to the end-member, i.e., A(Na0.74 K0.02)B(Ca1.27Mn0.73)C(Mg4.51Mn2+0.28Fe2+0.05Fe3+0.03Al0.12Ti0.01)T(Si7.07Al0.93)O22(OH)2, has a = 9.8260(5), b = 18.0487(9), c = 5.2840(4) Å, β = 104.55(1)º, V = 907.1 Å3 (Z = 2); the calculated density is 3.11 g/cm3. The parvo-mangano tremolite crystal, with composition A(Na0.44K0.01)B(Ca1.13Mn0.83Na0.04)C(Mg4.69Mn2+0.21Fe2+0.03Fe3+0.01Al0.06)T(Si7.52Al0.48)O22 (OH)2, has a = 9.7807(5), b = 18.0548(9), c = 5.2928(4) Å, β = 104.19(1)º, V = 906.1 Å3 (Z = 2); the calculated density is 3.08 g/cm3. The different compositions are virtually indistinguishable under the optical microscope, but can be identified by a measure of their unit-cell parameters. The single-crystal FTIR spectrum of parvo-mangano-edenite in the OH-stretching region shows two main absorptions at 3711 and 3671 cm-1, plus shoulders at 3695, 3660, and 3641 cm-1, respectively. FTIR spectroscopy indicates extensive short-range-order of cations in these amphiboles.
© 2015 by Walter de Gruyter Berlin/Boston
Articles in the same Issue
- Structural model for the biogenic Mn oxide produced by Pseudomonas putida
- Electron-beam (5–10 keV) damage in triplite-group phosphates: Consequences for electron-microprobe analysis of fluorine
- Vacancy defects in MgO at high pressure
- Plastic flow of pyrope at mantle pressure and temperature
- Parvo-mangano-edenite, parvo-manganotremolite, and the solid solution between Ca and Mn2+ at the M4 site in amphiboles
- Reinvestigation of the MgSiO3 perovskite structure at high pressure
- The mechanism and kinetics of α-NiS oxidation in the temperature range 670–700°C
- Influence of charge location on 29Si NMR chemical shift of 2:1 phyllosilicates
- The size distribution of exsolution lamellae in iron-free clinopyroxene
- The high-pressure phase transformation and breakdown of MgFe2O4
- Elastic behavior, phase transition, and pressure induced structural evolution of analcime
- A new chemical etching technique for peridotites using molten anhydrous borax
- Poppiite, the V3+ end-member of the pumpellyite group: Description and crystal structure
- Cation redistribution in the octahedral sheet during diagenesis of illite-smectites from Jurassic and Cambrian oil source rock shales
- A shock-induced polymorph of anatase and rutile from the Chesapeake Bay impact structure, Virginia, U.S.A.
- Water in the interlayer region of birnessite: Importance in cation exchange and structural stability
- In situ HAFM study of the thermal dehydration on gypsum (010) surfaces
- Influence of dehydration kinetics on T-O-T bridge breaking in zeolites with framework type STI: The case of stellerite
- Estimation of volume fractions of liquid and vapor phases in fluid inclusions, and definition of inclusion shapes
- Thermodynamics of uranyl minerals: Enthalpies of formation of uranyl oxide hydrates
- SIMS investigation of electron-beam damage to hydrous, rhyolitic glasses: Implications for melt inclusion analysis
- Synthetic Ag-rich tourmaline: Structure and chemistry
- Genesis and compositional heterogeneity of smectites. Part III: Alteration of basic pyroclastic rocksA case study from the Troodos Ophiolite Complex, Cyprus
- Ganterite, the barium mica Ba0.5K0.5Al2(Al1.5Si2.5)O10(OH)2, from Oreana, Nevada
- Letter. Transformation of pentlandite to violarite under mild hydrothermal conditions
Articles in the same Issue
- Structural model for the biogenic Mn oxide produced by Pseudomonas putida
- Electron-beam (5–10 keV) damage in triplite-group phosphates: Consequences for electron-microprobe analysis of fluorine
- Vacancy defects in MgO at high pressure
- Plastic flow of pyrope at mantle pressure and temperature
- Parvo-mangano-edenite, parvo-manganotremolite, and the solid solution between Ca and Mn2+ at the M4 site in amphiboles
- Reinvestigation of the MgSiO3 perovskite structure at high pressure
- The mechanism and kinetics of α-NiS oxidation in the temperature range 670–700°C
- Influence of charge location on 29Si NMR chemical shift of 2:1 phyllosilicates
- The size distribution of exsolution lamellae in iron-free clinopyroxene
- The high-pressure phase transformation and breakdown of MgFe2O4
- Elastic behavior, phase transition, and pressure induced structural evolution of analcime
- A new chemical etching technique for peridotites using molten anhydrous borax
- Poppiite, the V3+ end-member of the pumpellyite group: Description and crystal structure
- Cation redistribution in the octahedral sheet during diagenesis of illite-smectites from Jurassic and Cambrian oil source rock shales
- A shock-induced polymorph of anatase and rutile from the Chesapeake Bay impact structure, Virginia, U.S.A.
- Water in the interlayer region of birnessite: Importance in cation exchange and structural stability
- In situ HAFM study of the thermal dehydration on gypsum (010) surfaces
- Influence of dehydration kinetics on T-O-T bridge breaking in zeolites with framework type STI: The case of stellerite
- Estimation of volume fractions of liquid and vapor phases in fluid inclusions, and definition of inclusion shapes
- Thermodynamics of uranyl minerals: Enthalpies of formation of uranyl oxide hydrates
- SIMS investigation of electron-beam damage to hydrous, rhyolitic glasses: Implications for melt inclusion analysis
- Synthetic Ag-rich tourmaline: Structure and chemistry
- Genesis and compositional heterogeneity of smectites. Part III: Alteration of basic pyroclastic rocksA case study from the Troodos Ophiolite Complex, Cyprus
- Ganterite, the barium mica Ba0.5K0.5Al2(Al1.5Si2.5)O10(OH)2, from Oreana, Nevada
- Letter. Transformation of pentlandite to violarite under mild hydrothermal conditions
