Instability of Al2SiO5 “triple-point” assemblages in muscovite+biotite+quartz-bearing metapelites, with implications
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David R.M. Pattison
Abstract
This paper uses constraints from experiments, thermodynamic modeling, and natural mineral assemblages to argue that Al2SiO5 “triple-point” assemblages, in which all three Al2SiO5 minerals are in stable equilibrium, are not possible in common muscovite(Ms)+biotite(Bt)+quartz(Qtz)-bearing metapelitic rocks because the reactions that first introduce an Al2SiO5 mineral to these bulk compositions occur at higher temperature than the triple point. Less-common, highly aluminous bulk compositions may develop Al2SiO5 minerals at temperatures below the triple point such that stable triple-point assemblages are theoretically possible. The “invisibility” of the triple-point to common Ms+Bt+Qtz-bearing metapelites calls into question most metapelitic triple-point localities reported in the literature, and carries implications for the topology of the metapelitic petrogenetic grid, the bathozone/bathograd scheme of Carmichael (1978), and the possibility of prograde kyanite → andalusite → sillimanite sequences. Re-examination of reported triple-point localities suggests that in most if not all cases, the Al2SiO5 minerals grew at different times in the metamorphic history of the rock
© 2015 by Walter de Gruyter Berlin/Boston
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Articles in the same Issue
- First-principles modeling of the infrared spectrum of kaolinite
- Determination of the limiting fictive temperature of silicate glasses from calorimetric and dilatometric methods: Application to low-temperature liquid volume measurements
- Enthalpies of formation of tremolite and talc by high-temperature solution calorimetry – a consistent picture
- Evidence for an I2/a to Imab phase transition in the silica polymorph moganite at ~570 K
- Thermal decomposition of rhombohedral KClO3 from 29–76 kilobars and implications for the molar volume of fluid oxygen at high pressures
- High-pressure behavior of clinochlore
- Structure and elasticity of wadsleyite at high pressures
- Determination of the fluid–absent solidus and supersolidus phase relationships of MORB-derived amphibolites in the range 4–14 kbar
- F-rich phlogopite stability in ultra-high-temperature metapelites from the Napier Complex, East Antarctica
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- Stability of osumilite coexisting with spinel solid solution in metapelitic granulites at high oxygen fugacity
- Geikielite exsolution in spinel
- Aeromagnetic anomalies, magnetic petrology, and rock magnetism of hemo-ilmenite- and magnetite-rich cumulate rocks from the Sokndal Region, South Rogaland, Norway
- Minor element chemistry of hemo-ilmenite and magnetite in cumulate rocks from the Sokndal Region, South Rogaland, Norway
- Crystal structure analysis of synthetic Ca4Fe1.5Al17.67O32: A high-pressure, spinel-related phase
- Crystal structure of phase X, a high pressure alkali-rich hydrous silicate and its anhydrous equivalent
- Fluoro-edenite from Biancavilla (Catania, Sicily, Italy): Crystal chemistry of a new amphibole end-member
- Description and crystal structure of turtmannite, a new mineral with a 68 Å period related to mcgovernite
- The crystal structure of low melanophlogite
- Crystal structures of Na and K aluminate mullites
- From mastodon ivory to gemstone: The origin of turquoise color in odontolite
- Letters. Elasticity of single-crystal calcite and rhodochrosite by Brillouin spectroscopy
- Ikaite, CaCO3·6H2O: Cold comfort for glendonites as paleothermometers
