Igneous rocks of south-west England by P.A. Floyd, C.S. Exley and M.T. Styles. Chapman & Hall, London, U.K., 1993. Hardcover, XII + 256 pp. Price: £ 65.00 ISBN 0-412-48850-7     

Richard D'Lemos 《Lithos》1994,31(3-4):227-228

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Timing of Cadomian and Variscan tectonothermal activity,La Hague and Alderney,North Armorican Massif: Evidence from 40Ar/39Ar mineral ages     

R. D. Dallmeyer  R. S. D'Lemos  R. A. Strachan 《Geological Journal》1994,29(1):29-44

The La Hague region of northwest France exposes Palaeo-Proterozoic Icartian gneisses which were reworked and intruded by calc-alkaline plutonic rocks during the Cadomian Orogeny (about 700–500 Ma). ⁴⁰Ar/³⁹Ar mineral cooling ages have been determined to clarify the timing of the regional metamorphism of orthogneisses and the emplacement of quartz diorite plutons in this region. Metamorphic amphiboles within Icartian gneisses display discordant ⁴⁰Ar/³⁹Ar apparent age spectra interpreted to result from limited Variscan (about 350–300 Ma) overprinting of intracrystalline argon systems which initially cooled through post-metamorphic hornblende closure temperatures during the Cadomian at about 600 Ma. Igneous hornblendes from the weakly foliated Jardeheu and Moulinet quartz diorites record isotope correlation ages of 599 ± 2 and 561 ± 2 Ma, respectively. Igneous hornblende and biotite from foliated quartz diorite on the nearby Channel Island of Alderney record isotope correlation ages of about 560 Ma. The results imply that metamorphic and plutonic events in the La Hague-Alderney region were approximately contemporaneous with those recorded on Guernsey and Sark, which are thus likely to have formed part of the same tectonic block during the Cadomian Orogeny.  相似文献   

Insights into the collection and emplacement of granitic magma based on 3D seismic images of normal fault-related salt structures     

Quirk  D'Lemos  Mulligan  & Rabti 《地学学报》1998,10(5):268-279

ABSTRACT
3D seismic data from salt structures in the Southern North Sea show how viscous fluids tend to migrate towards and flow upwards along the footwalls of active normal faults where zones of low stress are inherent. This process provides one potential solution for the question of how enough space is created to accommodate large granitic bodies in the crust. During episodes of regional extension, granitic melt may collect in the lower crust below normal detachments in domed areas from which magma may be sourced. Subsequently, in the upper crust, emplacement can occur in fault-bounded laccoliths at rates commensurate with other geological processes.  相似文献