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.

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

/pdf/nomenclature-of-amphiboles-report-of-the-subcommittee-on-2t3q4lqqz2.pdf

Nomenclature of amphiboles; report of the subcommittee on amphiboles of the International Mineralogical Association, Commission on New Minerals and Mineral Names

A set of thermodynamic models is presented that, for the first time, allows partial melting equilibria to be calculated for metabasic rocks. The models consist of new activity–composition relations combined with end-member thermodynamic properties from the Holland & Powell dataset, version 6. They allow for forward modelling in the system Na (Formula presented.) O–CaO–K (Formula presented.) O–FeO–MgO–Al (Formula presented.) O (Formula presented.) –SiO (Formula presented.) –H (Formula presented.) O–TiO (Formula presented.) –Fe (Formula presented.) O (Formula presented.). In particular, new activity–composition relations are presented for silicate melt of broadly trondhjemitic–tonalitic composition, and for augitic clinopyroxene with Si–Al mixing on the tetrahedral sites, while existing activity–composition relations for hornblende are extended to include K (Formula presented.) O and TiO (Formula presented.). Calibration of the activity–composition relations was carried out with the aim of reproducing major experimental phase-in/phase-out boundaries that define the amphibolite–granulite transition, across a range of bulk compositions, at ≤13 kbar.

Activity–composition relations for the calculation of partial melting equilibria in metabasic rocks

The origin of cratonic diamonds — Constraints from mineral inclusions

Both highand medium-pressure granulites have been found as because of the absence of modal minerals. The combination of petrographic textures, mineral compositions, metamorphic reaction enclaves and boudins in tonalitic–trondhjemitic–granodioritic gneisses in the Hengshan Complex. Petrological evidence from these history, petrogenetic grids and thermobarometric data defines a nearrocks indicates four distinct metamorphic assemblages. The early isothermal decompressional clockwise P–T path for the Hengshan prograde assemblage (M1) is preserved only in the high-pressure granulites, suggesting that the Hengshan Complex underwent initial granulites and represented by quartz and rutile inclusions within crustal thickening, subsequent exhumation, and cooling and retrothe cores of garnet porphyroblasts, and omphacite pseudomorphs gression. This tectonothermal path is considered to record a major that are indicated by clinopyroxene + sodic plagioclase symplectic phase of collision between two continental blocks, which resulted in intergrowths. The peak assemblage (M2) consists of clinopyroxene the final assembly of the North China Craton at >1·8 Ga. + garnet + sodic plagioclase + quartz ± hornblende in the high-pressure granulites and orthopyroxene + clinopyroxene + garnet + plagioclase + quartz in the medium-pressure granulites.

/pdf/high-pressure-granulites-retrograded-eclogites-from-the-3bjfg8bfft.pdf

High-Pressure Granulites (Retrograded Eclogites) from the Hengshan Complex, North China Craton: Petrology and Tectonic Implications

A simple general equation is presented for estimating the Fe 3 § concentrations in ferromagnesian oxide and silicate minerals from microprobe analyses. The equation has been derived using stoichiometric criteria assuming that iron is the only element present with variable valency and that oxygen is the only anion. In general, the number of Fe 3 + ions per X oxygens in the mineral formula, F, is given by; F = 2X(1 - T/S) where T is the ideal number of cations per formula unit, and S is the observed cation total per X oxygens calculated assuming all iron to be Fe 2 § Minerals for which this equation is appropriate include pyralspite and ugrandite garnet, aluminate spinel, magnetite, pyroxene, sapphirine and ilmenite. The equation cannot be used for minerals with cation vacancies (e.g. micas, maghemite) unless, as in the case of amphiboles, the number of ions of a subset of elements in the formula can be fixed. Variants of the above equation are presented for some of the numerous published schemes for the recalculation of amphibole formulae. The equation is also inappropriate for minerals showing SP += 4H § substitution (e.g. staurolite, hydrogarnet), minerals containing an unknown proportion of an unanalysed element other than oxygen (e.g. boron-bearing kornerupine) and minerals containing two or more elements with variable valency.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/5B6FB5CD4245697A1FAA86E0B2309379/S0026461X00021769a.pdf/div-class-title-a-general-equation-for-estimating-fe-span-class-sup-3-span-concentrations-in-ferromagnesian-silicates-and-oxides-from-microprobe-analyses-using-stoichiometric-criteria-div.pdf

G. T. R. Droop

Papers

A general equation for estimating Fe3+ concentrations in ferromagnesian silicates and oxides from microprobe analyses, using stoichiometric criteria