Prof Gary Stevens
Professor in Experimental Petrology
Director Central Analytical Facilities
(021) 808 3127, Fax (021) 808 3129
(Hons) University of Johannesburg (RAU)
University of Johannesburg (RAU)
University of Manchester
current projects relate to several main themes that are generally
interlinked through the concepts of the response of the crust
to high temperature processes and the evolution of crustal melts.
These are: 1.
Studies of metamorphism, magmatism and partial melting in the
rocks associated with the Barberton greenstone belt. These studies
aim to better understand the geodynamic and chemical evolution
of Earth’s young crust and the nature of the tectonic
processes relevant to this crust. Papers 3, 4, 6, 7, 8, 9, 10,
11, 16 and 17 in the list below relate to this work. On my current
students, Jeanne Taylor, Cynthia Sanchez-Garrido and Angelique
Laure are involved in this work. Richard Armstrong (ANU), Alex
Kisters, JF Moyen, John Clemens, Hervé Martin (Université
Blaise Pascal) and Régis Doucelance (Université
Blaise Pascal) are important collaborators. 2.
S-type granite petrogenesis and the anatexis of metapelitic/psammitic
rocks. These studies aim to better understand how the metasedimentary
crust melts, how melts and magmas excape their anatectic source
and how the resultant accumulations of granitic magma evolve.
To date this work has focussed on the Damara belt in Namibia
and the S-type granites of the Cape Granite suite. Rob Ward
and Arnaud Villaros are current students involved in this work
and papers 1, 5, 13 and 14 in the lists below give an insight
into the nature of this research. There is a crossover between
this theme and the one above in that the metasedimentary granulites
of the ancient gneiss complex in Swaziland (Jeanne Taylor’s
project) fit equally well in both areas. John Clemens, Ian Buick
and Alex Kisters and important collaborators in this work. 3.
Experimental investigations of the behaviour of sulphide minerals
and melts during high temperature processes. These studies have
focussed on the anatexis of Broken Hill type massive sulphide
ores, the solubility of gold in S-bearing granitic magmas and
the behaviour of gold and platinum group elements during partial
melting of sulphide assemblages. Papers 12 and 15 in the lists
below are relevant to this work. Each
of these themes is fascinating provides wonderful opportunities
for training. Whilst we have made very important advances in
each area over the past few years, a huge amount remains to
be done. Thus, my research activities for the next few years
will be more or the same. Importantly, we are very close to
critical breakthroughs in several projects and there are tremendous
opportunities for students to involve themselves in truly exciting
science. In the case of advanced students and post-doctoral
researchers seeking academic careers, there are unique opportunities
inherent to some of these projects currently available.
R., Stevens, G. and Kisters, A.F.M. 2008. Fluid
and deformation induced partial melting and melt volumes in
low-temperature granulite-facies metasediments, Damara Belt,
Namibia. LITHOS, doi 10.1016/j.lithos.2008.04.0 Fagereng,A.,
Harris, C., La Grange, M. and Stevens, G. 2008.
Stable isotope study of the archaean rocks of the vredefort
impact structure, central Kaapvaal craton, South Africa. Contributions
to Mineralogy and Petrology, 155: 63-78. Stevens,
G. and Moyen, J-F. (2007). Metamorphism in the Barberton
granite greenstone terrain: a record of Paleoarchaean accretion.
Developments in Precambrian Geology (Eds van Kranendonk M.J.,
Smithies, R.H. and Bennett, V.C. S Ed Condie K.C.). 15. Elsevier.
J-F, Stevens, G., Kisters, A.F.M. and Belcher,
R. (2007). TTG plutons of the Barberton granitoid-greenstone
terrain, South Africa. Developments in Precambrian Geology (Eds
van Kranendonk M.J., Smithies, R.H. and Bennett, V.C. S Ed Condie
K.C.). 15. Elsevier. Amsterdam. Stevens
G., Villaros, A. and Moyen, J-F. (2007). Experimental
melt compositions as an aid to understanding S-type granite
petrogenesis. GEOLOGY, 35: 9-12. Dziggel,
A., Stevens, G., Poujol, M. and Armstrong,
R. (2006). Contrasting source components of clastic metasedimentary
rocks in the lowermost Formations of the Barberton greenstone
belt. In: Reimold, W.U. and Gibson, R.L., eds., Processes on
the Early Earth: Geological Society of America Special Paper,
405, 157-172. Moyen,
J-F., Stevens, G. and Kisters, A.F.M. (2006).
Record of an Archaean subduction zone: 3.2 Ga high-pressure,
low-temperature metamorphism in the Barberton terrain, South
Africa. Nature, 442: 559-562.
J.D., Yearron, L.M. and Stevens, G. (2006).
Barberton (South Africa) TTG magmas: Geochemical and experimental
constraints on source-rock petrology, pressure of formation
and tectonic setting. Precambrian Research, 151: 53-78.
J., Kisters, A.F.M., Poujol, M. and Stevens, G.
(2005). Transcurrent shearing, granite sheeting and the incremental
construction of the tabular, 3.1 Ga Mpuluzi batholith, Barberton
granite-greenstone terrain, South Africa. Journal of the Geological
Society of London, 162, 373-388. Diener,
J.F.A., Stevens, G. Kisters, A.F.M., Poujol,
M. (2005). Metamorphism and exhumation of the basal parts of
the Barberton greenstone belt, South Africa: Constraining the
rates of Mesoarchaean tectonism. Precambrian Research 143, 87-112 Diener,
J.F.A., Stevens, G. Kisters, A.F.M. (2005).
High-pressure low-temperature metamorphism in the southern Barberton
granitoid greenstone terrain, South Africa: a record of overthickening
and collapse of Mid-Archaean continental crust. American Geophysical
Union Special Publication (in press). Stevens,
G., Prins, S. and Rozendaal, A. 2005. Partial melting
of the assemblage sphalerite + galena + pyrrhotite + chalcopyrite
+ sulfur: Implications for high-grade metamorphosed massive
sulfide deposits. Economic Geology, 100: 106-110. Buick,
I.S., Stevens, G. and Gibson, R.L. (2004).
The role of water retention in the anatexis of metapelites in
the Bushveld Complex aureole, South Africa: An experimental
study. Journal of Petrology, 45: 1777-1797.
E.M., Stevens, G. and Buick, I.S. (2004). The
low-pressure partial-melting behavior of natural metapelites
from the Mt Stafford area, Central Australia; including the
role of boron as a possible melt fluxing agent. Contributions
to Mineralogy and Petrology, 148: 131-152. Stevens,
G., Przybylowicz, W.J. and Martin, L.E. (2004). Micro-PIXE
studies of low-level gold solubility in natural magmas: Experiments
on two felsic compositions. X-Ray Spectrometry, 33: 216-221.
A.F.M., Stevens, G., Dziggel, A., Armstrong,
R.A. (2003). Extensional detachment faulting and core-complex
formation at the base of the Barberton greenstone belt: evidence
for a 3.2 Ga orogenic collapse. Precambrian Research 127,
G., Droop, G.T.R., Armstrong, R.A., and Anhaeusser,
C.R. 2002. The Schapenburg schist belt: Amphibolite facies Archaean
metasediments of the Figtree Group, Barberton greenstone belt,
South Africa. South African Journal of Geology, 105: To appear
in December 2002 issue.
R.F., Stevens, G. and McCarthy, T.S. 2002.
Fluid compositions in equilibrium with silica-undersaturated
magmas in the system Na2O-Al2O3-SiO2-H2O: Clues to the composition
of fenitizing fluids. Contributions to Mineralogy and Petrology,
Manuscript: 0414. DOI: 10.1007/s00410-002-0414-1. Printed
version to appear December 2002 Murphy,
P.J., Stevens, G. and La Grange, M.S. 2000.
Gold-chloride speciation in hydrothermal fluids: a Raman spectroscopic
study at geologically relevant pressures and temperatures. Geochemica
Cosmochemica Acta, 64: 479-494. Stevens,
G., Clemens, J.D. and Droop, G.T.R. 1997. Migmatites,
granites and granulites: The data from experiments on "primitive"
metasedimentary protoliths. Contributions to Mineralogy and
Petrology, 128: 352-370.