Research: Melt Generation Processes in the Earth’s Crust and Mantle

My research incorporates both field and laboratory (petrological, experimental, geochemical and geophysical) investigations in order to understand melt generation processes in the Earth’s crust and mantle. Current research is focused on the formation of:

Ocean Islands

Ocean islands are sites of some of the world’s most active volcanism. Research on basaltic lavas from the islands of Tristan da Cuhna and Trindade in the South Atlantic has provided constraints on the role of recycled delaminated subcontinental lithosphere in the genesis of ocean-island basalts.

A recent detailed investigation of alkaline and tholeiitic lavas from Santiago in the Galápagos has revealed that their compositions are as diverse as for any other island in the archipelago or indeed any other ocean island. Our research has led to an understanding of the causes of widespread active volcanism throughout Galápagos: significant lithospheric thinning in the NE of the archipelago explains the generation of volcanism away from the main axis of the Galápagos plume. Santiago resides on the margin of this zone of thin lithosphere. 

 

Gibson & Geist 2010

Research in Galápagos was initiated in 2007 in collaboration with D. Geist, G. Estes, T. Grant, D. Norman and S. Herbert. The main focus of this research was to establish Darwin’s route on Santiago (formerly known as James Island) in 1835: this is the island where he made some of his most significant observations on volcanic rocks and led to his theory of gravitational settling as a cause of magmatic diversity (Gibson, 2009). 

The James Bay laval flow, Island of Santiago, Galapagos The Santiago expedition group on the vessel Pirata. July 2007

  Santiago coastal trekHerbert et al. (2009)

   

Large Igneous Provinces

These represent the most voluminous emplacements and outpourings of magma that have occurred on Earth’s during its 4.5 billion year evolution. They frequently coincide with the break-up of supercontinents (e.g. the Paraná-Etendeka and Deccan flood-basalt provinces) and are formed by the arrival of a large, up to 2000 km in diameter, thermal anomaly on the base of Earth’s lithosphere. These so-called mantle plumes are thought to be derived from thermal boundary layers deep within the Earth, such as the 2700 km core-mantle boundary. Our recent geochemical studies and high pressure and temperature experiments on high Fe-picrites (undertaken in collaboration with E. Takahashi, Tokyo; J. Tuff, Oxford) have shown that garnet pyroxenite, probably derived from subducted lithospheric mantle, is present within upwelling mantle plumes. Our research has also recently documented the longevity of volcanism associated with the initial impact of the Tristan mantle plume and it’s role in the opening of the South Atlantic.


Etendeka flood basalts, NW Namibia Cuillin Hills, Skye: fossilized magma chambers

 

Mantle Peridotites

On-going studies of mantle xenoliths are providing important insights in to the formation of the Earth’s lithosphere. In particular, we have used laser ablation (LA-ICP-MS) techniques to determine concentrations of low-abundance trace-elements in mantle phases (e.g. garnet and clinopyroxene). These small-scale determinations (< 100 microns) of mineral chemistry provide important clues of the large-scale geodynamic processes that have been involved in the creation and evolution of the Earth’s lithosphere.

LA-ICP-MS craters in diopside from a spinel peridotite, Antarctic Peninsula. Each crater has a diameter of ~80 microns LA-ICP-MS craters in garnet and Cr-diopside in a garnet lherzolite from the Kaapvaal craton. Each crater has a diameter of ~80 microns


Publications: 

2006 - Present 

2000-2005 Publications

  1. Gibson, S.A., Thompson, R.N., Day, J., Humphris, S.E., Dickin, A.P. 2005. Melt generation processes associated with the Tristan mantle plume: constraints on the origin of EM-1.Earth and Planetary Science Letters 237, 744-767
  2. Tuff, J., Takahashi, E. & Gibson, S.A., 2005. Experimental Constraints on the Role of garnet pyroxenite in the genesis of high-Fe mantle plume derived melts. Journal of Petrology 46, 2023-2058
  3. Thompson, R.N., Ottley, C.J., Smith, P.M., Pearson, D.J., Morrison, M.A., Leat, P.T. & Gibson, S.A., 2005. The puzzle of OIB-like continental alkalic magmatism: Quaternary alkalic basalts, picrites and basanites of the Potrillo Volcanic Field, New Mexico, USA. Journal of Petrology 46, 1603-1643.
  4. Johnson, J., Gibson, S.A., Thompson, R.N. & Nowell, G.M., 2005.Volcanism in the Vitim Field, Siberia: geochemical evidence for a mantle plume beneath the Baikal Rift Zone. Journal of Petrology 46, 1309-1344
  5. Chalpathi Rao, N. V., Gibson, S. A., Pyle, D. M., Dickin, A. P., 2004. Petrogenesis of Proterozoic lamproites and kimberlites from the Cuddapah Basin and Dharwar Craton, Southern India. Journal of Petrology 45, 907-948
  6. Anand, M. , Gibson, S. A., Subbarao, K. V., Kelley, S. P., Dickin, A. P. 2003. Early Proterozoic melt generation processes beneath the intra-cratonic Cuddapah Basin, Southern India. Journal of Petrology, 44, 2139-2171
  7. Thompson, R. N., Smith, P. M., Gibson, S. A., Mattey, D. P., Dickin, A. P., 2002. Ankerite carbonatite from Swartbooisdrif, Namibia: the first evidence for magmatic ferrocarbonatite. Contributions to Mineralogy and Petrology 143, 377-395
  8. Gibson, S.A., Major element heterogeneity in Archean to recent mantle plume starting-heads. Earth and Planetary Science Letters 195, 59-74.
  9. Thompson, R.N., Gibson, S.A., Dickin, A.P. & Smith, P., 2001. Early Cretaceous basalt and picrite dykes of the Southern Etendeka region, NW Namibia: windows into the role of the Tristan mantle plume in Paraná-Etendeka magmatism. Journal of Petrology 42, 2049-2081.
  10. Thompson, R.N. & Gibson, S.A., 2000. Transient high temperatures in mantle plume heads inferred from magnesian olivines in Phanerozoic picrites. Nature 407, 502-505.
  11. Mahotkin, I. L. Gibson, S.A., Thompson, R. N, Zhuravlev, D. Z. & P. U.Zherdev, 2000. Late Devonian Diamondiferous Kimberlite and Alkaline Picrite (Proto-kimberlite?) Magmatism in the Arkhangelsk Region, NW Russia. Journal of Petrology 41, 201-227.
  12. Gibson, S.A., Thompson, R.N. & Dickin, A.P., 2000. Ferropicrites: geochemical evidence for Fe-rich streaks in upwelling mantle plumes. Earth and Planetary Science Letters 174, 355-374

Older Publications by Dr Sally Gibson

 

Current Additional Posts Held

2001 – : ICP-MS Lab Manager, Department of Earth Sciences, University of Cambridge

2009 – : Trustee Cambridge Arctic Shelf Project (CASP)

2010 – : Member of Council, Geological Society of London

2010 – : Honorary Curator in Petrology, University of Cambridge

2011 – : Teaching Accreditation Panel for UK Earth Sciences, Geological Society of London

 

Membership of Professional Organisations

American Geophysical Union (since 1991)

Geological Society of London (since 1985)

Mineralogical Society of Great Britain & Ireland (since 1998)

 

Past & Current PhD Students

  • J.A. Brod (University of Durham): Petrogenesis of the Tapira and Salitre carbonatite complexes, SE Brazil. 1994 –1998
  • N.V.C. Rao: Petrogenesis of the Proterozoic kimberlites and lamproites from the Cuddapah Basin and Dhawar Craton, South India. 1995 –1997
  • M. Anand: Tectonomagmatic evolution of the Cuddapah Basin, India. 1997 –2001
  • P. Smith: Magmatic insights into lithospheric behaviour during varying styles of continental extension. 1997 –2001
  • J.C. Greenwood: Geochemical evolution of the Trindade mantle plume. 1996 –2001
  • M. Roberts: Quaternary volcanism in the East African Rift. 1998 – 2002
  • J. Garner: Mantle melting and lithospheric extension beneath the Baikal Rift, Siberia. 1999 –2002
  • J. Tuff: Compositional heterogeneity of the Earth’s mantle. 2002- 2005.
  • L. Gibson: Composition and evolution of the Antarctic mantle. 2008 – present

 

Past MPhil Students

  • T. Brod (University of Durham) - Petrogenesis of plume-related potassic mafic magmas in central Brazil. 1996 –1999.

Publications: 2006-Present

Last updated on 14-Sep-11 11:39