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http://journals.cambridge.org Downloaded: 25 Jan 2012 IP address: 129.240.87.90 Geol. Mag. 128 (3), 1991, pp. 207-226. Printed in Great Britain 207
 

Summary: http://journals.cambridge.org Downloaded: 25 Jan 2012 IP address: 129.240.87.90
Geol. Mag. 128 (3), 1991, pp. 207-226. Printed in Great Britain 207
Melt-enhanced deformation during emplacement of gabbro
and granodiorite in the Sunnhordland Batholith,
west Norway
T O R G E I R B.ANDERSEN, PETER NIELSEN, E R L I N G R Y K K E L I D & HANNE S 0 L N A
Geological Institute, University of Oslo, P.O. Box 1047, 0316 Blindern Oslo 3, Norway
(Received 6 September 1990; accepted 15 November 1990)
Abstract - The Caledonian Sunnhordland Batholith comprises calc-alkaline plutons that have been
assigned to three units according to their relative age and composition: a gabbro-diorite unit, a
granodiorite unit and a later granodiorite-granite unit. The batholith was emplaced into an envelope
including ophiolite and island-arc complexes, sediments and volcanites of early Ordovician age that
were developed in a zone of plate convergence. Continued convergence resulted in the formation of
a mature magmatic arc and a thickened crust; the late granitoids (unit 3), which commenced their
crystallization at pressures around 6 to 7 kb, rose as permitted diapiric intrusions. The ingress and
ascent of the magmas in this setting is considered to have been facilitated by the presence of major
shear zones developed in relation to plate convergence. In this model, plastic instabilities were formed
in an otherwise elastic middle and upper crust. Non-coaxial deformation was accelerated by the
emplacement of magmas and the formation of abundant partial melts in water-rich sediments of the
envelope. The deformation, which was accelerated by magma and melt lubrication in aureoles,

  

Source: Andersen, Torgeir Bjørge - Centre for Physics of Geological Processes & Department of Geosciences, Universitetet i Oslo

 

Collections: Geosciences