Publication Date:
1995-09-01
Description:
Detrital clinopyroxenes occur abundantly in several greywacke formations in the Southern Uplands, both as single grains and within andesite lithoclasts. Compositionally, these pyroxenes fall into two main groups. Those from the oldest unit, the early Caradoc Galdenoch Formation, were derived from a simple tholeiitic volcanic arc. In contrast, the pyroxenes in the younger Portpatrick (late Caradoc) and Glenlee (Ashgill) Formations and the Gala Group (early Llandovery), show initial strongly calc-alkaline affinities, followed by a more complex calc-alkaline to transitional (calc-alkaline to tholeiitic) volcanic arc signature. The latter may be due to a mixture of calc-alkaline and tholeiitic components. A presently exposed source for the andesites has not yet been established, although the Ballantrae Complex is a potential candidate for a tholeiitic component.
Print ISSN:
0016-7568
Electronic ISSN:
1469-5081
Topics:
Geosciences
Permalink