Project Details
Projekt
The late-stage evolution of oceanic gabbros - Combined experimental and in-situ isotope study on gabbros of the ODP Legs 118/176 drilled at the Southwest Indian Ridge
Applicant
Professor Dr. Jürgen Koepke
Subject Area
Palaeontology
Term
from 2005 to 2012
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 12877566
Gabbroic rocks from Hole 735B at the Southwest Indian Ridge (SWIR; Legs 118 and 176), represent the longest continuous section of in-situ oceanic lower crust ever drilled by ODP (Ocean Drilling Program). About 25% of the core is strongly influenced by late-stage magmatic processes leading to Ferich (ferrogabbros) and Si-rich (plagiogranites) compositions as endmembers. For a comprehensive understanding of the late magmatic processes ongoing in the deep oceanic crust, we present here a new approach, by combining experimental and analytical investigations in natural gabbros from the ~ 1500 m long section drilled at SWIR. In three experimental subprojects we attempt to clarify (1) the phase relations and phase compositions in a typical late-magmatic system, (2) whether liquid immiscibility is an important late-magmatic process, and (3) how percolating late-stage melts influence the just solidified normal gabbro. Particular attention will be given to the oxygen fugacity and the water activity in our experiments, since these volatiles are regarded to play a dominant role during the late-magmatic activity. Since it has been recently discussed whether magmatic late-stage processes can also be the result of hydrothermal circulation in the deep oceanic crust at very high temperatures, we attempt to perform in-situ Sr isotope analyses of late-stage phases in the 735B gabbros for clarifying the nature of these fluids, i.e., whether they are magmatic or seawater-influenced.
DFG Programme
Infrastructure Priority Programmes
Participating Person
Privatdozent Dr. Ingo Horn
