Intrusive Rocks of the Shelve Area, South Shropshire

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Abstract
Summary The minor intrusions which are emplaced in the folded Ordovician sediments and pyroclastic rocks of the Shelve area are mainly basic in character, but range from picrite to alkali-rich andesite. Their structure and petrology are described and chemical analyses given. The Corndon dolerite phacolith, which occupies a faulted dome in shales near the main anticlinal axis of the area, is the largest of the intrusive masses and is discussed in detail; evidence based on 25–inch mapping of its outcrop and structural features is put forward for a re-interpretation of its form. The related Squilver dolerite and adinolization arising from it are also described in some detail, and other dyke and sill occurrences more briefly. The igneous rocks form a differentiation series with alkaline affinities, and were probably derived from a parent magma whose composition was not far removed from that of plateau-basalt. Folding of the Shelve rocks at the end of Ordovician times was accompanied by emplacement of the intrusions; smaller bodies of syenitic aplite were injected either at the same time or subsequently, and with this possible exception it is believed that all the igneous rocks were intruded before the Valentian submergence of the area. I. Introduction The Ordovician rocks of the Shelve area, which lies to the west of the Longmynd in South Shropshire, occupy some 40 to 50 square miles arid extend from near Minsterley (10 miles west-south-west of Shrewsbury) southward to within two miles of Bishop's Castle. Their eastern boundary is the prominent ridge of

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