granite, garnet-biotite gneiss and biotitesillimanite schist compose the lower part of the drilled section down to the limiting depth.
The igneous bodies are heterogeneous and a petrological zoning can be usually established from the margin to the centre (Bastida et al., 1989): a) chilled margin facies, b) central facies and c) pegmatoid
Overlying the banded ironstone is a coarse-grained, black pegmatoid
consisting of augite and inverted pigeonite with minor plagioclase and olivine.
The granites are mainly massive, pegmatoid
texture is common, gneissic varieties are rare, while porphyraceous texture occurs very seldom.
and gabbroid layers in Jurassic Preakness and Hook Mountain basalts, Newark Basin, New Jersey.
Typical fabrics include a weak to strong foliation trending ENE, gradational contacts and metasomatic changes to pegmatoid
and mylonitic rock types.
Such variations can be explained by the change in the petrophysical properties of rocks when passing from biotite gneiss to pegmatoid
granite at depths below 2.0 km.