Nomenclature of amphiboles Report of the Subcommittee on Amphiboles of the International Mineralogical Association Commission on New Minerals and Mineral Names;Nomenclature of amphiboles Report of the Subcommittee on Amphiboles of the International Mineralogical Association Commission on New Minerals and Mineral Names
TL;DR: The International Mineralogical Association's approved amphibole nomenclature has been revised to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely, and include new amphibole species discovered and named since 1978, when the previous scheme was approved.
Abstract: The International Mineralogical Association's approved amphibole nomenclature has been revised to simplify it, make it more consistent with divisions generally at 50%, define prefixes and modifiers more precisely, and include new amphibole species discovered and named since 1978, when the previous scheme was approved. The same reference axes form the basis of the new scheme and most names are little changed, but compound species names like tremolitic hornblende (now magnesiohornblende) are abolished, as are crossite (now glaucophane or ferroglaucophane or magnesioriebeckite or riebeckite), tirodite (now manganocummingtonite), and dannemorite (now manganogrunerite). The 50% rule has been broken only to retain tremolite and actinolite as in the 1978 scheme; the sodic-calcic amphibole range has therefore been expanded. Alkali amphiboles are now sodic amphiboles. The use of hyphens is defined. New amphibole names approved since 1978 include nyboite, leakeite, kornite, ungarettiite, sadanagaite, and cannilloite. All abandoned names are listed. The formulae and source of the amphibole end-member names are listed and procedures outlined to calculate Fe (super 3+) and Fe (super 2+) where not determined by analysis.
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TL;DR: In this article, a rigorous analysis of the physical-chemical, compositional and textural relationships of amphibole stability and the development of new thermobarometric formulations for amphibole-bearing calc-alkaline products of subduction-related systems is presented.
Abstract: This work focuses on a rigorous analysis of the physical–chemical, compositional and textural relationships of amphibole stability and the development of new thermobarometric formulations for amphibole-bearing calc-alkaline products of subduction-related systems Literature experimental results (550–1,120°C, 021) and are inferred to represent xenocrysts of crustal or mantle materials Most experimental results on calc-alkaline suites have been found to be unsuitable for using in thermobarometric calibrations due to the high Al# (>021) of amphiboles and high Al2O3/SiO2 ratios of the coexisting melts The pre-eruptive crystallization of consistent amphiboles is confined to relatively narrow physical–chemical ranges, next to their dehydration curves The widespread occurrence of amphiboles with dehydration (breakdown) rims made of anhydrous phases and/or glass, related to sub-volcanic processes such as magma mixing and/or slow ascent during extrusion, confirms that crystal destabilization occurs with relatively low T–P shifts At the stability curves, the variance of the system decreases so that amphibole composition and physical–chemical conditions are strictly linked to each other This allowed us to retrieve some empirical thermobarometric formulations which work independently with different compositional components (ie Si*, AlT, Mg*, [6]Al*) of a single phase (amphibole), and are therefore easily applicable to all types of calc-alkaline volcanic products (including hybrid andesites) The Si*-sensitive thermometer and the fO2–Mg* equation account for accuracies of ±22°C (σest) and 04 log units (maximum error), respectively The uncertainties of the AlT-sensitive barometer increase with pressure and decrease with temperature Near the P–T stability curve, the error is 35%) and lower-T magmas, the uncertainty increases up to 24%, consistent with depth uncertainties of 04 km, at 90 MPa (~34 km), and 79 km, at 800 MPa (~30 km), respectively For magnesiohornblendes, the [6]Al*-sensitive hygrometer has an accuracy of 04 wt% (σest) whereas for magnesiohastingsite and tschermakitic pargasite species, H2Omelt uncertainties can be as high as 15% relative The thermobarometric results obtained with the application of these equations to calc-alkaline amphibole-bearing products were finally, and successfully, crosschecked on several subduction-related volcanoes, through complementary methodologies such as pre-eruptive seismicity (volcano-tectonic earthquake locations and frequency), seismic tomography, Fe–Ti oxides, amphibole–plagioclase, plagioclase–liquid equilibria thermobarometry and melt inclusion studies A user-friendly spreadsheet (ie AMP-TBxls) to calculate the physical–chemical conditions of amphibole crystallization is also provided
865 citations
TL;DR: In this article, a new classification and nomenclature scheme for the amphibole-supergroup minerals is described, based on the general formula AB 2 C 5 T 8 O 22 W 2.
Abstract: A new classification and nomenclature scheme for the amphibole-supergroup minerals is described, based on the general formula AB 2 C 5 T 8 O 22 W 2 , where A = □, Na, K, Ca, Pb, Li; B = Na, Ca, Mn 2+ , Fe 2+ , Mg, Li; C = Mg, Fe 2+ , Mn 2+ , Al, Fe 3+ , Mn 3+ , Ti 4+ , Li; T = Si, Al, Ti 4+ , Be; W = (OH), F, Cl, O 2− . Distinct arrangements of formal charges at the sites (or groups of sites) in the amphibole structure warrant distinct root names , and are, by implication, distinct species; for a specific root name, different homovalent cations (e.g., Mg vs. Fe 2+ ) or anions (e.g., OH vs. F) are indicated by prefixes (e.g., ferro-, fluoro-). The classification is based on the A, B, and C groups of cations and the W group of anions, as these groups show the maximum compositional variability in the amphibole structure. The amphibole supergroup is divided into two groups according to the dominant W species: W (OH,F,Cl)-dominant amphiboles and W O-dominant amphiboles (oxo-amphiboles). Amphiboles with (OH, F, Cl) dominant at W are divided into eight subgroups according to the dominant charge-arrangements and type of B-group cations: magnesium-iron-manganese amphiboles, calcium amphiboles, sodium-calcium amphiboles, sodium amphiboles, lithium amphiboles, sodium-(magnesium-iron-manganese) amphiboles, lithium-(magnesium-iron-manganese) amphiboles and lithium-calcium amphiboles. Within each of these subgroups, the A- and C-group cations are used to assign specific names to specific compositional ranges and root compositions. Root names are assigned to distinct arrangements of formal charges at the sites, and prefixes are assigned to describe homovalent variation in the dominant ion of the root composition. For amphiboles with O dominant at W, distinct root-compositions are currently known for four (calcium and sodium) amphiboles, and homovalent variation in the dominant cation is handled as for the W (OH,F,Cl)-dominant amphiboles. With this classification, we attempt to recognize the concerns of each constituent community interested in amphiboles and incorporate these into this classification scheme. Where such concerns conflict, we have attempted to act in accord with the more important concerns of each community.
856 citations
TL;DR: The 1995-1999 eruption of the Soufriere Hills volcano, Montserrat, has produced a crystal-rich andesite containing quench as discussed by the authors, which was preceded by a pristine and unaltered to strongly oxidized and pseudomorphed by period of seismic swarms, which began in January 1992.
Abstract: The 1995–1999 eruption of the Soufriere Hills volcano, MontINTRODUCTION serrat, has produced a crystal-rich andesite containing quenchThe Soufriere Hills volcano, Montserrat, located in the textured mafic inclusions, which show evidence of having been molten Lesser Antilles island arc in the West Indies, began to when incorporated into the host magma. Individual crystals in the erupt on 18 July 1995, after about 350 years of dormancy andesite record diverse histories. Amphibole phenocrysts vary from (Young et al., 1998b). The eruption was preceded by a pristine and unaltered to strongly oxidized and pseudomorphed by period of seismic swarms, which began in January 1992. anhydrous reaction products. Plagioclase phenocrysts are commonly Previous earthquake crises have occurred on Montserrat reverse zoned, often with dusty sieve textures. Reverse zoned rims are in 1896–1897, 1932–1935 and 1966–1967 (Powell, 1938; also common on orthopyroxene phenocrysts. Pyroxene geothermometry Shepherd et al., 1971). Initial phreatic and phregives an average temperature of 858 ± 20 °C for orthopyroxene atomagmatic activity was followed by extrusion of an phenocryst cores, whereas reverse zoned rims record temperatures andesitic lava dome in November 1995. Pyroclastic flows, from about 880 to 1050 °C. The heterogeneity in mineral rim generated by gravitational collapse of the unstable dome, compositions, zoning patterns and textures is interpreted as reflecting have been the dominant form of activity throughout the non-uniform reheating and remobilization of the resident magma eruption, but periods of explosive activity, producing body by intrusion of hotter mafic magma. Convective remobilization pumice flows and falls, have also occurred (Robertson et results in mixing together of phenocrysts that have experienced al., 1998; Young et al., 1998b). Dome growth ceased different thermal histories, depending on proximity to the intruding suddenly in March 1998 and further activity up to May mafic magma. The low temperature and high crystallinity are 1999 has mainly involved gravitational collapses of the interpreted as reflecting the presence of a cool, highly crystalline dome and periods of ash venting, with some small-scale magma body beneath the Soufriere Hills volcano. The petrological vulcanian explosive events. observations, in combination with data on seismicity, extrusion rate The Soufriere Hills volcano is the only active centre and SO2 fluxes, indicate that the current eruption was triggered by on Montserrat. The volcano is a composite of at least recent influx of hot mafic magma. five andesitic lava domes, flanked by pyroclastic deposits. Rea (1974) identified four other volcanic centres, all
456 citations
TL;DR: In this paper, a systematic classification of tourmaline-group minerals, general formula X Y3 Z6 (Γ6Oi8) (B03)3 V3W, is proposed, based on chemical composition and ordering at the different crystallographic sites of the tourmalines structure.
Abstract: A systematic classification of the tourmaline-group minerals, general formula X Y3 Z6 (Γ6Oi8) (B03)3 V3W, is proposed, based on chemical composition and ordering at the different crystallographic sites of the tourmaline structure. There are currently thirteen accepted tourmaline species. However, based on the actual chemical composi tions of holotype material, several of these species were imprecisely or incorrectly defined. A proper definition of these species is proposed. A crystal-chemical feature that extends the number of possible end-members is the anion occupancy of the W-site (dominated by OH-, F~ or O2-) and the V-site (dominated by OH- or, more rarely, 02~). Thus, based on the W-site alone, there can be hydroxy-, fluor-, or oxy-end-members. Furthermore, the presence of dominant O2- at the W-site commonly requires local cation-ordering at the Y- and Z-sites. The tourmaline-group min erals can be divided into three principal groups based on the dominant species at the X-site: alkali tourmalines (Na), calcic tourmalines (Ca) and X-site-vacant tourmalines (O: vacancy). These groups are further divided, initially based on the W-site occupancy, then by the (actual or inferred) V-site occupancy, next by the (actual or inferred) F-site occupancy and, finally, by the (actual or inferred) Z-site occupancy. A systematic classification procedure is developed that takes into account different levels of knowledge of the chemical composition and site occupancy of the tourmaline. Several examples are used to illustrate the application of this classification procedure.
455 citations
TL;DR: In this article, the authors present constraints of the stability of Mg-rich amphiboles in both calc-alkaline and alkaline magmas, testing of previous thermobarometers, and formulation of new empirical equations that take into consideration a large amount of literature data (e.g. more than one thousand amphibole compositions among experimental and natural crystals).
Abstract: The following article presents constraints of the stability of Mg-rich (Mg/(Mg + Fe2+) > 0.5) calcic amphibole in both calc-alkaline and alkaline magmas, testing of previous thermobarometers, and formulation of new empirical equations that take into consideration a large amount of literature data (e.g. more than one thousand amphibole compositions among experimental and natural crystals). Particular care has been taken in choosing a large number of natural amphiboles and selecting quality experimental data from literature. The final database of experimental data, composed of 61 amphiboles synthesized in the ranges of 800–1,130°C and 130–2,200 MPa, indicates that amphibole crystallization occurs in a horn-like P–T stability field limited by two increasing curves (i.e. the thermal stability and an upper limit), which should start to bend back to higher pressures. Among calcic amphiboles, magnesiohornblendes and tschermakitic pargasites are only found in equilibrium with calc-alkaline melts and crystallize at relatively shallow conditions (P up to ~1 GPa). Kaersutite and pargasite are species almost exclusively found in alkaline igneous products, while magnesiohastingsite is equally distributed in calc-alkaline and alkaline rocks. The reliability of previous amphibole applications was checked using the selected experimental database. The results of this testing indicate that none of the previous thermobarometers can be successfully used to estimate the P, T and fO2 in a wide range of amphibole crystallization conditions. Multivariate least-square analyses of experimental amphibole compositions and physico-chemical parameters allowed us to achieve a new thermobarometric model that gives reasonably low uncertainties (T ± 23.5°C, P ± 11.5%, H2Omelt ± 0.78wt%) for calc-alkaline and alkaline magmas in a wide range of P–T conditions (up to 1,130°C and 2,200 MPa) and ∆NNO values (±0.37 log units) up to 500 MPa. The AK-[4]Al relation in amphibole can be readily used to distinguish crystals of calc-alkaline liquids from those of alkaline magmas. In addition, several chemometric equations allowing to estimate the anhydrous composition of the melts in equilibrium with amphiboles of calc-alkaline magmas were derived.
430 citations
Cites methods from "Nomenclature of amphiboles Report o..."
...Before the application of the proposed internally consistent model of amphibole crystallization, it is necessary to calculate the amphibole formula using the 13-cation method (Leake et al 1997)....
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...The mineral formulas of all the calcic amphiboles were calculated using the 13 cation method (Leake et al. 1997; Ridolfi et al. 2010a), while element oxides (i.e. SiO2, TiO2, Al2O3, total iron content as FeO, MnO, MgO, CaO, Na2O and K2O) of whole-rocks and all glasses were normalized to 100....
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...According to the 13-cation method (e.g. Leake et al. 1997; Ridolfi et al. 2010a), the selected calcic amphiboles (i.e. BCa C 1.5) have Mg/(Mg ?...
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References
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01 Jan 1966
TL;DR: In this article, the authors define di-and ring silicates: olivine group humite group zircon sphene (titanite) garnet group, vesuvianite sillimanite, mullite, andalusite, kyanite topaz staurolite, chloritoid epidote group lawsonite, pumpellyite melilite group beryl, cordierite, tourmaline axinite.
Abstract: PART 1 ORTHO: Di- and ring silicates: olivine group humite group zircon sphene (titanite) garnet group, vesuvianite sillimanite, mullite, andalusite, kyanite topaz staurolite, chloritoid epidote group lawsonite, pumpellyite melilite group beryl, cordierite, tourmaline axinite. PART 2 CHAIN SILICATES: pyroxene group wollastonite sapphirine amphibole group. PART 3 SHEET SILICATES: mica group stilpnomelane pyrophyllite chlorite serpentine clay minerals apophyllite prehnite. PART 4 FRAMEWORK SILICATES: feldspar group silica minerals nepheline group petalite, leucite sodalite group cancrinite - vishnevite, scapolite analcite, zeolite group. PART 5 NON-SILICATES: oxides hydroxides sulphides sulphates carbonates phosphates halides
5,387 citations
"Nomenclature of amphiboles Report o..." refers background in this paper
...Thorough discussions of the calculation of mineral formulae can be found in the appendices of Deer et al., (1966, 1992) ....
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...Amphiboles that are referred to in numerous mineralogy and optical mineralogy textbooks as 'basaltic hornblende' ( Deer et al., 1966 ), or the kaersutite end member of the IMA amphibole nomenclature can show this type of compositional variation (Dyar et al., 1993)....
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01 Jan 1995
TL;DR: A report about values for the entropy, molar volume, and for the enthalpy and Gibbs energy of formation for the elements and minerals and substances at 298.15 K was given in this paper.
Abstract: A report about values for the entropy, molar volume, and for the enthalpy and Gibbs energy of formation for the elements and minerals and substances at 298.15 K.
3,552 citations
TL;DR: The Na-Ca-Mg-Fe-Mn-Li amphibole group was proposed in this article, which is defined by 0.50 apfu (atoms per formula unit), with members whittakerite and ottoliniite.
Abstract: The introduction of a fifth amphibole group, the Na-Ca-Mg-Fe-Mn-Li group, defined by 0.50 < B(Mg, Fe2+, Mn2+, Li) < 1.50 and 0.50 < = B(Ca, Na) < = 1.50 apfu (atoms per formula unit), with members whittakerite and ottoliniite, has been required by recent discoveries of B(LiNa) amphiboles. This, and other new discoveries, such as sodicpedrizite (which is herein slightly, but significantly changed from the original idealised formula), necessitate amendments to the IMA 1997 definitions of the Mg-Fe-Mn-Li, calcic, sodic-calcic and sodic groups. The discovery of obertiite and the finding of an incompatibility in the IMA 1997 subdivision of the sodic group, requires further amendments within the sodic group. All these changes, which have IMA approval, are summarised.
2,389 citations
TL;DR: In this paper, amphibole thermodynamics are approximated with the symmetric formalism (regular solution model for within-site non-ideality and a reciprocal solution for cross-site terms) in order to formulate improved thermometers for amphibole-plagioclase assemblages.
Abstract: Amphibole thermodynamics are approximated with the symmetric formalism (regular solution model for within-site non-ideality and a reciprocal solution model for cross-site-terms) in order to formulate improved thermometers for amphibole-plagioclase assemblages. This approximation provides a convenient framework with which to account for composition-dependence of the ideal (mixing-on-sites) equilibrium constants for the equilibria:
For A and B all possible within-site and cross-site interactions among the species □−K−Na−Ca−Mg−Fe2+−Fe3+−Al−Si on the A, M4, M1, M3, M2 and T1 amphibole crystallographic sites were examined. Of the 36 possible interaction energy terms, application of the symmetric formalism results in a dramatic simplification to eight independent parameters. Plagioclase nonideality is modelled using Darken's quadratic formalism. We have supplemented an experimental data set of 92 amphibole-plagioclase pairs with 215 natural pairs from igneous and metamorphic rocks in which the pressure and temperature of equilibration are well constrained. Regression of the combined dataset yields values for the eight interaction parameters as well as for apparent enthalpy, entropy and volume changes for each reaction. These parameters are used to formulate two new thermometers, which perform well (±40°C) in the range 400–1000°C and 1–15 kbar over a broad range of bulk compositions, including tschermakitic amphiboles from garnet amphibolites which caused problems for the simple thermometer of Blundy and Holland (1990). For silica-saturated rocks both thermometers may be applied: in silica-undersaturated rocks or magmas thermometer B alone can be applied. An improved procedure for estimation of ferric iron in calcic amphiboles is presented in the appendix.
2,039 citations