Melting relations of basalt-andesile-rhyolite-H2O and a pelagic red clay at 30 kb (original) (raw)

Abstract

An olivine basalt, a tonalite (andesite), a granite (rhyolite), and a red clay (pelagic sediment) were reacted, with known quantities of water in sealed noble metal capsules, in a piston-cylinder apparatus at 30 kb pressure. For the pelagic sediment, with H2O+=7.8% and no additional water, the liquidus temperature is 1240°C, the primary phases are garnet and kyanite. The subsolidus phase assemblage is phengite mica+garnet+clinopyroxene+coesite+kyanite. With 5 wt.% water added, the liquidus temperatures and primary phases for the calc-alkaline rocks are 1280°-1180°-1080°, garnet+clinopyroxene, garnet, and quartz respectively. Garnet and clinopyroxene occur throughout the melting interval of the olivine tholeiite for all water contents. Garnet is joined by clinopyroxene 80° below the andesite plus 5% H2O liquidus, quartz is joined by clinopyroxene 180° below the rhyolite plus 5% H2O liquidus. The subsolidus phase assemblage is garnet+clinopyroxene+coesite+minor kyanite for all the calc-alkaline compositions. We conclude that calc-alkaline andesites and rhyolites are not equilibrium partial melting pruducts of subducted oceanic crust consisting of olivine tholeiite basalt and siliceous sediments. Partial melting in subduction zones produces broadly acid and intermediate liquids, but these liquids lie off the calc-alkaline basalt-andesite-rhyolite join and must undergo modification at lower pressures to produce calcalkaline magmas erupted in overlying island arcs.

Access this article

Log in via an institution

Subscribe and save

Buy Now

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Similar content being viewed by others

References

Download references

Author information

Authors and Affiliations

  1. Department of the Geophysical Sciences, The University of Chicago, 60637, Chicago, Illinois, USA
    C. R. Stern & P. J. Wyllie

Authors

  1. C. R. Stern
    You can also search for this author inPubMed Google Scholar
  2. P. J. Wyllie
    You can also search for this author inPubMed Google Scholar

Rights and permissions

About this article

Cite this article

Stern, C.R., Wyllie, P.J. Melting relations of basalt-andesile-rhyolite-H2O and a pelagic red clay at 30 kb.Contr. Mineral. and Petrol. 42, 313–323 (1973). https://doi.org/10.1007/BF00372609

Download citation

Keywords