These metasedimentary rock is a metamorphosed extrusive mafic volcanic of calc alkaline affinity distinct from what has been deduced for amphibolitic
rocks of other parts of the Schist belt of Nigeria.
A zone of amphibolites and amphibolitic
gneiss is encountered in the upper part of the complex.
The veined and brecciated structure undergoes flattening (Figure 2(g)), evolving to a foliated scapolite-bearing amphibolitic
rock (Figure 2(h)).
The composition of rocks and their metamorphic grade change rapidly from granulitic or high-grade amphibolitic
in the PPZ to mainly medium-grade amphibolitic
metasediments and intermediate to felsic metavolcanics, migmatites, and late-orogenic microcline granites in the Tallinn and Alutaguse zones.
The prehnite deposit is enclosed in a north-south strip of amphibolitic
rocks (amphibolite and amphibolite gneiss).
Massive mineralisation is mostly associated with norite and layers of pyroxenite and peridotite, whereas pyroxene and amphibolitic
gabbros contain irregularly distributed mineralisation, either disseminated or semi-massive.
Although amphibole-poor soapstone was quarried at BRQ, artifacts from CW were made of a very amphibolitic
"soapstone." A stepwise discriminant analysis performed on the two quarries' mineral ogies produced statistically significant coefficients (p[less than]0.0005).
The Nagar Parkar Igneous complex comprises a series of late Proterozoic granitic rocks emplaced in a basement of amphibolitic