Petrografia szarogłazów sylurskich okolic Niewachlowa

Abstract

PETROGRAPHY OF SILURIAN GREYWACKES FROM NIEWACHLÓW REGION

The Silurian greywackes of the Kielce syncline were investigated as to their petrography in 1957-1960. These rocks are developed as greywacke slates and as fine- and mediumgrained greywackes. These greywackes of the Niewachlów region (in the northwestern part of the Kielce syncline) are characterized by the following mineralogical composition (tabulated in the order from youngest to oldest):

1. The olive-green greywacke slates - angular quartz, showing no wavy light extinction, with rare ingrowths (of apatite); fresh feldspar, often showing albite twinning; muscovite; the cementing mass is a very fine-blastic substance with high interference colours - sericite. Sporadically epidote grains are found in the cementing mass. The texture of the rock is slightly shaly.

2. The finegrained greywacke - angular quartz showing no wavy light extinction; feldspar - orthoclase with up to 25% An; rarely biotite appears. The cementing mass of the rook is limonite with sericite. There are also found fragments of serkitic schist, quartzites, lydites, more rarely greenstones formed from effusive rocks, as well as glauconite.

3. The mediumgrained greywacke - here quartz maybe divided into two groups, a larger one (0.090-0.720 mm.), very well rounded, and a smaller-angular one. The quartz shows no wavy light extinction; feldspars - plagioclases with 4-15% An, pure albite. The fragments of older rocks found here are mostly baisic effusive rocks, finegrained, of green colour. There are also found sericitic schists, hornfelses, metamorphic quartzites and lydites.

On the basis of the examinations as reported above it is a difficult matter to draw conclusions as to the palaeogeographical character of these rocks. It can only be asserted that the massif, eroded during the Silurian, supplied material not only from sedimentary rocks but also from effusive rocks such as diabases. The latter were partly altered due to subsequent albite-quartz solutions, yielding hornfelses. These we find in the greywackes of the Niewachlów region.

The comparison of the greywacke rocks of the Niewachlów region with those appearing in the southeastern part of the syncline (Niestachów-Mójcza; research is under way) is made difficult by the fad that the examined greywackes occur in different stratigraphical horizons of the Silurian. Even so, it should be remembered that in the southeastern part of the syncline, amidst fragments of rocks occurring in the greywacke, we find lamprophyres whereas hornfelses, as are found in the greywacke rocks of the Niewachlów region, are absent here.