PhD thesis

Dipl.-Geol. Philipp Brandl is writing his PhD-thesis in the group of Endogene Geodynamics (Dr. Marcel Regelous and Prof. Dr. Karsten Haase). He started his thesis within the project "Chemical and thermal evolution of the upper mantle; implications for Earth's climate and biosphere and the nature of mantle convection" in January 2010 (DFG grant RE3020/1-1). This project is part of the DFG priority program 527: "Infrastructure - Integrated Ocean Drilling".

Project summary:

The chemistry of mid-ocean ridge basalts (MORB) can be used to infer the temperature of the upper mantle, and ancient seafloor lavas preserve a record of mantle temperature and crustal thickness variations since the Mesozoic. Existing chemical data for old seafloor suggest that before 80 Ma the upper mantle was 60°C hotter than today. Mantle temperature variations on this scale impact on global climate and the biosphere. It has been argued that the Cretaceous greenhouse climate and sea-level highstand was triggered by higher than normal rates of oceanic crust production, due to higher mantle temperatures.

However, there are presently very few chemical data for older oceanic crust, and most existing analyses were carried out on highly altered, phenocryst-rich, whole-rock samples. We will determine the changes in MORB chemistry over the past 170 Ma in each of the major ocean basins, avoiding the effects of alteration by analysing fresh basaltic glass using microanalytical techniques. Suitable samples for this study are available from the numerous DSDP/ODP sites drilled on old oceanic crust in the Pacific, Atlantic and Indian Oceans. The results will be used to examine the implications for the scale of mantle convection, and effects on sea-level, seawater chemistry and climate on timescales of 1-10 Ma.

Further research interests

Awards

March 2009: Member of Leonardo-Kolleg of the FAU Erlangen-Nürnberg

September 2011: Fellowship of the Erika Gierhl-Foundation

Publications (peer-reviewed)

P.A. Brandl, M. Regelous, C. Beier, and K.M. Haase (2013): High mantle temperatures following rifting caused by continental insulation. Nature Geoscience, Vol. 6(5): 391-394, doi:10.1038/ngeo1758.

F.S. Genske, C. Beier, K.M. Haase, S.P. Turner, S. Krumm, and P.A. Brandl (2013): Oxygen isotopes in the Azores islands: Crustal assimilation recorded in olivine. Geology, Vol. 41(4), 491-494, doi:10.1130/G33911.1 (open access).

O. Lehnert, S. Stouge, and P.A. Brandl (2013, in press): Conodont biostratigraphy in the Early to Middle Ordovician strata of the Oslobreen Group in Ny Friesland, Svalbard. ZDGG (German Journal of Geosciences), Vol. 164 (1) doi: 10.1127/1860-1804/2013/0003.

C. Beier, J. Mata, F. Stöckhert, N. Matielli, P.A. Brandl, P. Madueira, F.S. Genske, S. Martins, J. Madeira, and K.M. Haase (2012): Geochemical evidence for melting of carbonated peridotite on Santa Maria Island, Azores. Contributions to Mineralogy and Petrology, published online, doi:10.1007/s00410-012-0837-2.

P.A. Brandl, C. Beier, M. Regelous, W. Abouchami, K.M. Haase, D. Garbe-Schönberg, and S.J.G. Galer (2012), Volcanism on the flanks of the East Pacific Rise: quantitative constraints on mantle heterogeneity and melting processes, Chemical Geology, Vol. 298-299, 41-56, doi:10.1016/j.chemgeo.2011.12.015.

K.M. Haase, M. Regelous, R.A. Duncan, P.A. Brandl, N. Stroncik, and I. Grevemeyer  (2011), Insights into mantle composition and mantle melting beneath mid-ocean ridges from postspreading volcanism on the fossil Galapagos Rise, Geochem. Geophys. Geosyst., Vol. 12, Q0AC11, doi:10.1029/2010GC003482.