Abstract

Three borehole sections in the Traboe area provide a partial section through a layered basic-ultrabasic complex, previously referred to as the Traboe hornblende schists. This complex, though dismembered into thrust sheets, shows an overall NE-dipping stratigraphy with a generalized upward sequence from dunite and pyroxenite to gabbro and anorthosite. The bulk composition of the ultramafic rocks is quite different from the dominantly lherzolitic composition of the main Lizard peridotite. The composition of the basic rocks is also markedly different from that of the Landewednack hornblende schists with which they have previously been correlated. The deformation and recrystallization of the rocks has been complex and locally intense, producing a fine granular fabric in many rock types. Amphibolitization has affected many rock types to give assemblages dominated by hornblende. Mineral composition varies with position in the stratigraphic sequence and is consistent with crystallization of the complex from differentiating basic magma pulses.

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