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Petrogenesis of oceanic plagiogranites by partial melting of gabbros: an experimental study


Koepke, J and Feig, ST and Snow, J and Freise, M, Petrogenesis of oceanic plagiogranites by partial melting of gabbros: an experimental study, Contributions to Mineralogy and Petrology, 146, (4) pp. 414-432. ISSN 0010-7999 (2004) [Refereed Article]

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Copyright 2003 Springer-Verlag

DOI: doi:10.1007/s00410-003-0511-9


We performed hydrous partial melting experiments at shallow pressures (0.2 GPa) under slightly oxidizing conditions (NNO oxygen buffer) on oceanic cumulate gabbros drilled by ODP (Ocean Drilling Program) cruises to evaluate whether the partial melting of oceanic gabbro can generate SiO2-rich melts with compositions typical of oceanic plagiogranites. The experimental melts of the low-temperature runs broadly overlap those of natural plagiogranites. At 940 °C, the normalized SiO2 contents of the experimental melts of all systems range between 60 and 61 wt%, and at 900 °C between 63 and 68 wt%. These liquids are characterized by low TiO2 and FeOtot contents, similar to those of natural plagiogranites from the plutonic section of the oceanic crust, but in contrast to Fe and Ti-rich low-temperature experimental melts obtained in MORB systems at ∼950 °C. The ∼1,500-m-long drilled gabbroic section of ODP Hole 735B (Legs 118 and 176) at the Southwest Indian Ridge contains numerous small plagiogranitic veins often associated with zones which are characterized by high-temperature shearing. The compositions of the experimental melts obtained at low temperatures match those of the natural plagiogranitic veins, while the compositions of the crystals of low-temperature runs correspond to those of minerals from high-temperature microscopic veins occurring in the gabbroic section of the Hole 735B. This suggests that the observed plagiogranitic veins are products of a partial melting process triggered by a water-rich fluid phase. If the temperature estimations for high-temperature shear zones are correct (up to 1,000 °C), and a water-rich fluid phase is present, the formation of plagiogranites by partial melting of gabbros is probably a widespread phenomenon in the genesis of the ocean crust.

Item Details

Item Type:Refereed Article
Keywords:oceanic plagiogranite, gabbro, partical melting, experiment, oceanic crust
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and metamorphic petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding knowledge
Objective Field:Expanding knowledge in the earth sciences
UTAS Author:Feig, ST (Dr Sandrin Feig)
ID Code:76518
Year Published:2004
Web of Science® Times Cited:224
Deposited By:Central Science Laboratory
Deposited On:2012-03-07
Last Modified:2012-05-24
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