School of Geography, Earth Science and Environment


Dr. Holger Sommer

Contact Information

Email: sommer_h(at) info(at) somhol(at)
Phone: +679 323 1507
Office: Room 4, SGESE Building, Lower Campus

Research Interests

Dr. Holger Sommer undertakes research within the areas of petrology, mineralogy, geochemistry and fluid rock interaction. His work on metamorphic and igneous petrology deals with the formation and recycling of continental and oceanic crust from the microscale to the macroscale. This work employs analytical facilities including SHRIMP, EPMA and LA-ICPMS, and software such as PerPleX and TWQ. His mineralogical work assesses components of the planetary volatile cycle, including water and carbon dioxide. He uses Synchrotron Based FTIR with a micrometre-scale resolution to determine the distribution of volatiles in Nominally Anhydrous Minerals. His geochemical interests lie in understanding the distribution of REE, LREE and HREE in the granulite-eclogite facies transition zone. His studies regarding fluid rock interaction includes the investigations of hot springs and their interaction with the upper crust in combination with formation of ore deposits and the use of geothermal power. Holger Sommer has undertaken research in the USA, Greenland, Germany, Morocco, Tanzania, Botswana, Namibia, Lesotho, South Africa, Antarctica and Fiji.

Selected publications (articles referenced: 504; H-factor: 11)

  • Sommer. H., Kröner. A., 2019. Igneous petrology, zircon geochronology and geochemistry of multiply emplaced granitoid bodies from the Palaeoproterozoic Usagaran domain in central Tanzania. Journal of African Earth Sciences 150, 626-656.

  • Sommer. H., Kröner. A., Lowry. J., 2017. Neoproterozoic eclogite- to high-pressure granulite-facies metamorphism in the Mozambique belt from east-central Tanzania: A petrological, geochemical and geochronological approach. Lithos 284, 266-290.   

  • Sommer. H., Jacob. D. E., Stern. R.A., Petts, D., Mattey. D.P., Pearson. D.G., (2017). Fluid-induced transition from banded kyanite- to bimineralic eclogite and implications for the evolution of cratons. Geochimica et Cosmochimica Acta 207, 19-42.     
  • Sommer, H., Rao, B., Naco, S., 2014. Report on International Meeting on Subduction, Volcanism and the Evolution of Oceanic and Continental Crust. Episodes 37. 2. 129-130.   
  • Sommer, H., Wan, Y., Kroener, A., Xie, H., Jacob, J. E., 2013. SHRIMP zircon ages and petrology of lower crustal xenoliths from the Letseng-la-Terae kimberlite, Lesotho: Further evidence for a Namaqua-Natal connection, South African Journal of Geology, 116, 183-198  
  • Sommer, H., Kroener, A., 2013. Ultra high-temperature granulite-facies metamorphic rocks from the Mozambique belt of SW Tanzania, Lithos, 170-171, 117-143       

  • Sommer, H., Regenauer-Lieb, K., Gasharova, B., Jung, H., 2012. The formation of volcanic centers at the Colorado Plateau as a result of the passage of aqueous fluid through the oceanic lithosphere and the subcontinental mantle: New implications for the planetary water cycle in the Western United States. Journal of Geodynamics, 61, 154-171

  • Sommer, H., Gauert C., 2011, Hydrating laterally extensive regions of continental lithosphere by flat subduction, Journal of Geodynamics, 144, 17-24       

  • Sommer, H., 2009 “Wet” low angle subduction: A possible mechanism below the Tanzania craton 2 Ga ago, Mineralogy and Petrology, 96, 113-120     
  • Sommer, H., Regenauer-Lieb, K., Gasharova, B. Siret, D., 2008 Grain boundaries: A possible water reservoir in the Earth's mantle? Mineralogy and Petrology, 94, 1-8

  • Sommer, H., Kroener, A., Muhongo, S., Hauzenberger, C A., 2008 Isothermal decompression history in the “Western Granulite” terrain, central Tanzania: Evidence from reaction textures and trapped fluids in metapelites. Journal of African Earth Science, 51, 123-144
  • Hauzenberger, C A., Sommer, H., Fritz H, Bauernhofer A, Hoinkes G, Wallbrecher, E, Kroener, A, Martin Thoeni, 2007. New Zircon SHRIMP ages from Taita hills and Tsavo National Park in southwest Kenya., in Journal of Geological Society of London, 164, 189-201      
  • Vogt, M., Kröner, A., Poller, U., Sommer, H., Muhongo., S., Wingate, M., 2006. Archaean and Palaeoproterozoic gneisses reworked during a Neoproterozoic (Pan-African) event in the Mozambique belt of East Africa: structural relationships and zircon ages from the Kidatu area, central Tanzania. Journal of African Earth Sciences, 45, 139-145   
  • Sommer, H., Kroener, A., Muhongo, S., Hauzenberger, C. A., 2005, Reworking of Archaean and Palaeoproterozoic crust in the Mozambique belt of central Tanzania as documented by SHRIMP zircon geochronology, Journal of African Earth Sciences, 43, 145 – 167     
  • Sommer, H., Kroener, A., Muhongo, S., Hauzenberger, C A., 2005, SHRIMP zircon ages for post-Usagaran granitoid and rhyolitic rocks from then Palaeo-proterozoic terrain of southwestern Tanzania, Journal of South African Geology, 108, 243 – 252 
  • Sommer, H., Kroener, A., Hauzenberger. C A., Muhongo. S., Wingate, T D., 2003, Metamorphic petrology and zircon geochronology of high-grade rocks from the central Mozambique belt of Tanzania: Crustal recycling of Archaean and Palaeoproterozoic material during the Pan-African orogeny, Journal of Metamorphic Geology, 21, 915-934

  • Markl, G., Abart, R., Vennemann, T., Sommer, H., 2003, Mid-crustal metasomatic reaction veins in a spinel peridotite, Journal of Petrology, 44, 1097-1120    

  • Muhongo, S., Hauzenberger, C A., Sommer, H., 2003, Vestiges of the Mesoproterozoic events in the Neoproterozoic Mozambique Belt; the East African perspective in the Rodinia puzzle, Gondwana Research, 6, 409-416

  • Muhongo, S., Kroener, A., Wallbrecher, E., Tuisku, P., Hauzenberger, C., Sommer, H., 2001, Cross-section through the Mozambique Belt of EastAfrica and implications for Gondwana assembly, Gondwana Research, 4, 709-71

  • Markl, G., Marks, M., Schwinn, G., Sommer, H., 2001, Phase equilibrium constraints on intensive crystallization parameters of the Ilimaussaq Complex, South Greenland, Journal of Petrology, 42, 2231-2258 

  • “1st International Conference on Subduction, Volcanism and the Evolution of Oceanic and Continental Crust (SVEOCC 2014)" Editor: Holger Sommer, Gondwana Research, Conference Series 17, pages 1-65 
    Ongoing Projects
  • Clean geothermal power for developing countries. Klaus Regenauer-Lieb, Stuart Walsh, Holger Sommer, Hui Tong Chua, Graham Wragg, Selina Leo (UN DESA project)

  • “Win – Win” situation between landowners, government and the mining industry in the South Pacific”. Holger Sommer (SRT project, University of the South Pacific,)

  • The Supercontinent cycle. Holger Sommer (FSTE project, University of the South Pacific)

  • Subduction Dynamics and Seismic Hazards in Fiji. Holger Sommer and Bhaskar Rao   (FSTE project, University of the South Pacific)

  • Measuring H2O and CO2 along grain boundaries and totally embedded cracks in nominally anhydrous minerals olivine and pyroxenes (Neil Kumar, Holger Sommer, Dorrit Jacob, Australian Synchrotron project M12642)

  • Nitrogen concentration in micro-diamonds from the Roberts Victor diamond mine, South Africa (Holger Sommer, Dorrit Jacob, Neil Kumar, Australian Synchrotron project M12600)

  • Volatiles around micro cracks and fluid inclusions (Holger Sommer, Dorrit Jacob, Neil Kumar, Australian Synchrotron project M11682)

  • H2O and CO2 distribution along grain boundaries (Holger Sommer, Dorrit Jacob, Neil Kumar, Australian Synchrotron project M10939)

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School of Geography, Earth Science and Environment
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The University of the South Pacific
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