Open Access Repository

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


Downloads per month over past year

Koepke, J, Feig, ST, Snow, J and Freise, M 2004 , 'Petrogenesis of oceanic plagiogranites by partial melting of gabbros: an experimental study' , Contributions to Mineralogy and Petrology, vol. 146, no. 4 , pp. 414-432 , doi: 10.1007/s00410-003-0511-9.

[img] PDF
Koepke_et_al_20...pdf | Request a copy
Full text restricted
Available under University of Tasmania Standard License.


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 hightemperature
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 Type: Article
Authors/Creators:Koepke, J and Feig, ST and Snow, J and Freise, M
Keywords: oceanic plagiogranite, gabbro, partical melting, experiment,oceanic crust
Journal or Publication Title: Contributions to Mineralogy and Petrology
ISSN: 0010-7999
DOI / ID Number: 10.1007/s00410-003-0511-9
Additional Information:

The original publication is available at

Item Statistics: View statistics for this item

Actions (login required)

Item Control Page Item Control Page