Dr. Holger Sommer - Geography
Holger Sommer undertakes research within the areas of petrology, mineralogy and geochemistry. 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. Holger Sommer has undertaken research in the USA, Greenland, Germany, Morocco, Tanzania, Botswana, Namibia, Lesotho, South Africa, Antarctica and Fiji.
Sommer, H., Wan, Y., Kröner, A. and Jacob, D.E. 2013. SHIRIMP zircon ages and petrology of lower crustal granulite 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. and Kröner, 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. and 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. and 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. and Siret, D. 2008. Grain boundaries: a possible water reservoir in the Earth's mantle? Mineralogy and Petrology 94, 1–8.
Sommer, H., Kröner, A., Muhongo, S. and 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 Sciences 51, 123–144.
Hauzenberger, C.A., Sommer, H., Fritz, H., Bauernhofer, A., Kröner, A., Hoinkes, G., Wallbrecher, E. and Thöni, M. 2007. SHRIMP U–Pb zircon and Sm–Nd garnet ages from the granulite-facies basement of SE Kenya: evidence for Neoproterozoic polycyclic assembly of the Mozambique Belt. Journal of the Geological Society 164, 189–201.
Vogt, M., Kröner, A., Poller, U., Sommer, H., Muhongo, S. and 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., Kröner, 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, 447–463.
Sommer, H., Kröner, A., Muhongo, S. and 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. and 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. and Sommer, H. 2003. Mid-crustal metasomatic reaction veins in a spinel peridotite. Journal of Petrology 44, 1097–1120.
Muhongo, S., Hauzenberger, C A. and 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., Kröner, A., Wallbrecher, E., Tuisku, P., Hauzenberger, C. and Sommer, H. 2001. Cross-section through the Mozambique Belt of East Africa and implications for Gondwana assembly. Gondwana Research 4, 709–710.
Markl, G., Marks, M., Schwinn, G. and Sommer, H. 2001. Phase equilibrium constraints on intensive crystallization parameters of the Ilimaussaq Complex, South Greenland. Journal of Petrology 42, 2231–2258.