Geochemistry of mafic dykes in the Antarctic Peninsula continental-margin batholith: a record of arc evolution |
| |
Authors: | Jane H Scarrow Philip T Leat Christopher D Wareham Ian L Millar |
| |
Institution: | (1) British Antarctic Survey, NERC, High Cross, Madingley Road, Cambridge CB3 0ET, UK, GB;(2) British Antarctic Survey, c/o NERC Isotope Geosciences Laboratory, Keyworth, Nottingham NG12 5GG, UK, GB |
| |
Abstract: | Mafic dykes of the Antarctic Peninsula continental-margin arc are compositionally diverse, comprising calc-alkaline (dominant),
shoshonite, tholeiite, and OIB-like varieties. Their compositions give information about different mafic magma sources tapped
during arc evolution. The compositional groups represent partial melts of at least five distinct mantle sources: a low-ɛNd
subduction-modified, garnet-bearing, lithospheric mantle (older calc-alkaline); a high-ɛNd subduction-modified, garnet-bearing,
lithospheric mantle (shoshonites); a high-ɛNd subduction-modified, spinel-bearing, asthenospheric mantle (younger calc-alkaline);
E-MORB-like spinel-bearing asthenosphere depleted by a previous melting event (tholeiites); and within-plate non-subduction
modified, garnet- and spinel-bearing, asthenosphere (OIB-like). Slab-derived fluids, subducted sediment, and arc crust also
contributed to the magmas. Consideration of previous work in the light of our new compositional and geochronological data
enables presentation of a summary of arc evolution. For most of the Cretaceous and Tertiary, the tectonic regime of the Antarctic
Peninsula arc was transtensional, and calc-alkaline magmas intruded. An oceanic spreading centre collided with the trench
during the Late Cretaceous and induced tectonic changes which caused tapping of different magma sources. A pulse of shoshonitic,
tholeiitic, and OIB-like mafic magmatism resulted. Three ridge-trench collisions are now recognized during the history of
the arc, in Mid–Late Jurassic, Late Cretaceous, and Early–Mid Tertiary times.
Received: 13 January 1997 / Accepted: 5 December 1997 |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|