Active plate boundaries

Exchange between seawater, oceanic crust and continental crust

At convergent plate boundaries, oceanic crust is subducted into the mantle and material is transferred from there by active magmatism to the overriding plate. Fluids are released in the subduction system at various depths can either flow along the decollement zone, exit upwards through the upper plate and be expelled by mud volcanoes or modify the compositional and physical properties of the upper mantle and trigger melting beneath the arc and hence arc magmatism. Despite the importance of fluids in subduction zones, the ultimate source and the pathway of the fluids is still not well understood. There is no direct access to the zones of fluid generation and melting, but the subducting oceanic crust including sediments, altered crust and serpentinized mantle as well as the magmatic products in the upper plate can be studied directly, mechanisms e.g. serpentinitization can also be studied in laboratory experiments and fluid flow and water-rock interaction by analyzing fluids from mud volcanoes and drill cores along the active accretionary prism. Our research also focuses on interaction of seawater with source rocks that form at divergent plate boundaries, e.g. serpentinitization of oceanic crust/mantle, fluid generation, flow, and precipitates in the magmatic and sedimentary sections of oceanic crust using Li, B, Sr, Nd and Pb isotopes as potential tracers. The same tracers are used to constrain mass transfer from the melting zone and recycling processes in magmatic rocks of the arc. The Central Andes provide the unique possibility to study magmatic rocks of the arc including dramatic changes of composition and tectonic framework at this old active margin (> 500 Ma), e.g. at the transition from Triassic to the Jurassic arcs.

Selected Related Publications

Wilckens, F.K., Reeves, E.P., Bach, W., Meixner, A., Seewald, J.S., Koschinsky, A., Kasemann, S.A. (2018). The influence of magmatic fluids and phase separation on B systematics in submarine hydrothermal vent fluids from back-arc basins. Geochimica et Cosmochimica Acta, DOI: 10.1016/j.gca.2018.04.023

Hansen, C.T., Meixner, A., Kasemann, S.A., Bach, W. (2017). New insight on Li and B isotope fractionation during serpentinization derived from batch reaction investigations. Geochimica et Cosmochimica Acta 217, 51-79, doi:10.1016/j.gca.2017.08.014

Echaurren, A., Oliveros, V., Folguera, A., Ibarra, F., Creixell, Ch., Lucassen, F. (2017). Early Andean tectonomagmatic stages in north Patagonia: insights from field and geochemical data. Journal of the Geological Society, doi.org/10.1144/jgs2016-087.

Hüpers, A., Kasemann, S.A., Kopf, A.J., Meixner, A., Toki, T., Shinjo, R., Wheat, C.G., You, C.-F. (2016). Fluid flow and water-rock interaction across the active Nankai Trough subduction zone forearc revealed by boron isotope geochemistry. Geochimica et Cosmochimica Acta 193, 100–118, doi.org/10.1016/j.gca.2016.08.014

Jones, R.E., Kirstein, L.A., Kasemann, S.A., Litvak, V.D., Poma, S., Alonso, R.N., Hinton R. (2016). The role of changing geodynamics in the progressive contamination of Late Cretaceous to Late Miocene arc magmas in the southern Central Andes. LITHOS, doi:10.1016/j.lithos.2016.07.002.

Jones, R.E., Kirstein, L.A., Kasemann, S.A., Duhime, B., Elliott, T., Litvak, V., Hinton, R., EIMF. (2015). Geodynamic controls on the contamination of Cenozoic arc magmas in the southern Central Andes: insights from the O and Hf isotopic composition of zircon. Geochimica et Cosmochimica Acta 164, 386–402.

Jones, R.E., De Hoog, J.C., Kirstein, L.A., Kasemann, S.A., Hinton, R., Elliott, T., Litvak, V., EIMF. (2014). Temporal variations in the influence of the subducting slab on Central Andean arc magmas: evidence from boron isotope systematics. Earth and Planetary Science Letters, 408, 390–401.

Jeffcoate, A.B., Elliott, T., Kasemann, S.A., Ionov, D., Cooper, K., Brooker, R. (2007). Lithium isotope fractionation in peridotites and mafic melts. Geochimica Cosmochimica Acta 71, 202-218.

Coogan, L.A., Kasemann, S.A. and Chakraborty, S. (2005). Rates of hydrothermal cooling of new oceanic upper crust derived from lithium-geospeedometry. Earth and Planetary Science Letters 240, 415-424.

Schmitt A.K., Kasemann S., Meixner A., Rhede D. (2002): Boron isotopic composition of Central Andean ignimbrites: implications for crustal boron cycles in active continental margin. Chemical Geology 183, 333-347.

Lucassen F., Becchio R., Harmon R., Kasemann S., Franz G., Trumbull R., Romer R.L., Dulski P. (2001). Composition and density model of the continental crust in an active continental margin – the Central Andes between 18° and 27°S. Tectonophysics 341, 195-223.

Kasemann, S., Erzinger, J., Franz, G. (2000). Boron recycling in the continental crust of the Central Andes from Palaeozoic to Mesozoic, NW Argentina. Contribution to Mineralogy and Petrology 140: 328-343.

Scientific Cooperation

DFG Koselleck Project (Ch. Hansen, W- Bach) Experimental investigations on lithium and boron isotope fractionation during serpentinization and the fundamental feedback mechanisms between permeability and reaction turnover in fluid rock interactions.

IODP/ODP (SPP 527) (A. Hüpers) Chemical hydrology of subduction zones: Processes, signals and fluid flow.

CCP4: Mud volcanic episodity (A. Kopf) Radiogenic and stable isotope analyses of fluids expelled by fluid-flow controlled mud volcanoes.

Projects

DFG EXC 309 The Ocean in the Earth System Research Area GB4 From Element and Energy Fluxes to Vent Ecosystems

CONICYIT - FONDECYT

(CONICYIT (FONDECYT, Chile) (V. Oliveros, F. Lucassen) The initiation of Andean subduction: Triassic to late Jurassic magmatism and basin dynamics in northern Chile (25°30'-31°)

Completed Projects

DFG Initiation of International Collaboration

DFG Initiation of International Collaboration (F. Lucassen) Radiogenic isotope signatures of Triassic to lower Jurassic magmatic rocks emplaced during the transition to the Andean subduction at the Chilean margin.

NERC PhD Studentship

NERC PhD Studentship (R. Jones; Supervisor L. Kirstein & S. Kasemann) Landscape evolution, volcanism and sediment flux along the active Andean margin