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Kuwait Institute of Scientific Research , Kuwait

ABSTRACT

Detailed petrographic studies on carbonate and terrigenous rocks of Carboniferous age in the South Wales Coalfield have revealed the modification of their fabrics in the western, incipiently metamorphosed part of the coalfield (the anthracite area). Aggrading and degrading recrystallisation and lattice deformation are the main effects of incipient metamorphism in carbonate rocks. In terrigenous rocks, reaction of the matrix with framework grains, deformation of argillaceous rock fragments, and development of deformed fibrous quartz veinlets are the main fabric modifications. These incipient metamorphic fabrics are controlled to some extent by the lithology of the different carbonate and terrigenous rock types. There is a significant relation between fabric modification of the rocks studied and the variation of the fixed carbon ratio of the associated coal seams. The development of the incipient metamorphic fabrics increases progressively towards the western and northwestern parts of the coalfield (the anthracite area). Modification of fabric is first observed in some carbonate rocks in areas where coal seams have more than 80/, fixed carbon and reaches its maximum development, in both carbonate and terrigenous rocks, in northwestern areas where the fixed carbon ratio is 92.5%.