Building the thermodynamic framework for modelling the Earth

Viscous relaxation of grain-scale pressure variations

M Dabrowski, R Powell, Y Podladchikov

2015-10-01

In the presence of grain-scale pressure variations, there will be a natural tendency for deformation to flatten pressure gradients..

The effect of subduction on the sulphur, carbon and redox budget of lithospheric mantle

KA Evans, R Powell

2015-08-01

Subduction of hydrated lithospheric mantle introduces H2O, ferric iron, oxidized carbon and sulphur to the subduction zone system...

Using calculated chemical potential relationships to account for replacement of kyanite by symplectite in high pressure granulites

JA Baldwin, R Powell, RW White, P Stipska

2015-04-01

Calculated mineral equilibria are used to account for the formation of sapphirine-plagioclase, spinel-plagioclase and corundum-pla..

Interpreting zirconium-in-rutile thermometric

K Taylor-Jones, R Powell

2015-02-01

At first sight, experimental results and observations on rocks suggest that the Zr content in rutile, where equilibrated with quar..

Phase equilibria constraints on the melt fertility of crustal rocks: the effect of subsolidus water loss

G Webb, R Powell, S McLaren

2015-02-01

During regional prograde metamorphism, H2O generated by ongoing dehydration reactions is likely to be continuously lost from a roc..

The effect of Mn on mineral stability in metapelites revisited: new a-x relations for manganese-bearing minerals

RW White, R Powell, TE Johnson

2014-10-01

The a-x relations recently presented in White et al. (, Journal of Metamorphic Geology, 32, 261-286) are extended to include MnO. ..

Intermediate granulite produced by transformation of eclogite at a felsic granulite contact, in Blansk y les, Bohemian Massif

P Stipska, R Powell, M Racek, O Lexa

2014-05-01

Layers or bodies of intermediate granulite on scales from a centimetre to a hundred metres occur commonly within the felsic granul..

Rare eclogite-mafic granulite in felsic granulite in Blansk y les: precursor of intermediate granulite in the Bohemian Massif?

P Stipska, R Powell, M Racek

2014-05-01

Mafic granulite, generated from eclogite, occurs in felsic granulite at Kleť, Blanský les, in the Bohemian Massif. This is signifi..

A new thermodynamic model for sapphirine: calculated phase equilibria in K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-Fe2O3

CJ Wheller, R Powell

2014-04-01

The activity-composition (a-x) relations of sapphirine are re-evaluated in the light of a recent new internally-consistent data se..

New mineral activity-composition relations for thermodynamic calculations in metapelitic systems

RW White, R Powell, TJB Holland, TE Johnson, ECR Green

2014-04-01

New activity-composition (a-x) relations for minerals commonly occurring in metapelites are presented for use with the internally ..

On parameterizing thermodynamic descriptions of minerals for petrological calculations

R Powell, RW White, ECR Green, TJB Holland, JFA Diener

2014-04-01

A new regularization approach, termed micro-φ{symbol}, is outlined for parameterizing activity-composition (a-x) relations and oth..

Magmatism, orogeny and the origin of high-heat-producing granites in Australian Proterozoic terranes

Sandra McLaren, Roger Powel

2014-03-01

Temperature-dependent processes such as magmatism and orogeny provide key insights into the Earth's thermal state. We propose an i..

Grain-scale pressure variations and chemical equilibrium in high-grade metamorphic rocks

L Tajcmanova, Y Podladchikov, R Powell, E Moulas, JC Vrijmoed, JAD Connolly

2014-02-01

In the classical view of metamorphic microstructures, fast viscous relaxation (and so constant pressure) is assumed, with diffusio..

HIGH-PRESSURE METAMORPHISM OF SERPENTINIZED CHROMITITE AT LUOBUSHA (SOUTHERN TIBET)

Meng-xi Huang, Jian-jun Yang, Roger Powell, Xuanxue Mo

2014-01-01

Podiform chromitite with a dunite envelope occurs in harzburgite in the Luobusha ophiolite in the Yarlung-Zangbo suture zone, Tibe..

New Thermodynamic Models and Calculated Phase Equilibria in NCFMAS for Basic and Ultrabasic Compositions through the Transition Zone into the Uppermost Lower Mantle

Tim JB Holland, Neil FC Hudson, Roger Powell, Ben Harte

2013-09-01

Phase equilibria calculated with THERMOCALC for simplified mantle ultrabasic and basic bulk compositions in Na2O-CaO-FeO- MgO-Al2O..

Using equilibrium thermodynamics in the study of metasomatic alteration, illustrated by an application to serpentinites

KA Evans, R Powell, BR Frost

2013-05-01

Metasomatic rocks, in which mineralogical change is driven by infiltration of an externally-derived fluid, are challenging for the..

Garnet and spinel lherzolite assemblages in MgO-Al2O3-SiO2 and CaO-MgO-Al2O3-SiO2: thermodynamic models and an experimental conflict

ECR Green, TJB Holland, R Powell, RW White

2012-08-01

The recent publication of an updated thermodynamic dataset for petrological calculations provides an opportunity to illustrate the..

Revised activity-composition models for clinopyroxene and amphibole

JFA Diener, R Powell

2012-02-01

Recent activity-composition models for clinopyroxene and amphibole are revised to provide better consistency with observed phase r..

Stability of sapphirine plus quartz in the oxidized rocks of the Wilson Lake terrane, Labrador: calculated equilibria in NCKFMASHTO

FJ Korhonen, R Powell, JH Stout

2012-01-01

The equilibrium coexistence of sapphirine+quartz is inferred to record temperatures in excess of 980°C, based on the stability of ..

An improved and extended internally consistent thermodynamic dataset for phases of petrological interest, involving a new equation of state for solids

TJB Holland, R Powell

2011-04-01

The thermodynamic properties of 254 end-members, including 210 mineral end-members, 18 silicate liquid end-members and 26 aqueous ..

On the interpretation of retrograde reaction textures in granulite facies rocks

RW White, R Powell

2011-01-01

Retrograde reaction textures, such as partial pseudomorphs, coronae and symplectic coronae are a relatively common feature of gran..

Progress in linking accessory mineral growth and breakdown to major mineral evolution in metamorphic rocks: a thermodynamic approach in the Na2O-CaO-K2O-FeO-MgO-Al2O3-SiO2-H2O-TiO2-ZrO2 system

DE Kelsey, R Powell

2011-01-01

Activity-composition (a-x) models have been generated for zirconium-bearing haplogranitic silicate melt and garnet from experiment..

Calculated phase equilibria for a morb composition in a P-T range, 450-650 degrees C and 18-28 kbar: the stability of eclogite

G Rebay, R Powell, JFA Diener

2010-08-01

Lower temperature eclogite (with T = 600 °C) represents a significant part of the occurrences of eclogite in orogenic belts. 'True..

Influence of ferric iron on the stability of mineral assemblages

JFA Diener, R Powell

2010-08-01

Ferric iron is present in all metamorphic rocks and has the ability to significantly affect their phase relations. However, the in..

Retrograde melt-residue interaction and the formation of near-anhydrous leucosomes in migmatites

RW White, R Powell

2010-08-01

Considering physical segregation of melt from its residue, the chemical potentials of the components (oxides) are the same in both..

The stability of sapphirine plus quartz: calculated phase equilibria in FeO-MgO-Al2O3-SiO2-TiO2-O

K Taylor-Jones, R Powell

2010-08-01

The presence in rocks of coexisting sapphirine + quartz has been widely used to diagnose conditions of ultra-high-temperature (UHT..