Some aspects of the chemistry of the Bodmin Moor granite

Edmondson, Keith

Abstract

Attempts were made to sample the Bodmin Moor pluton, S. W. England, at grid intersections of a plan employing a 1.4 km spacing between grid lines. As a result of poor exposure the collection of material was extended to include sampling within a 0.5 km radius of the grid line intersections although even this could not be maintained at all the localities (circles about the grid intersections).
Major element determinations have been carried out on 34 samples, taken from three localities, to determine local and regional variations. Visual inspection reveals difficulties in locality classification of samples, although statistical analysis indicates a significant regional variation in FeO, CaO, Na2O and K2O.
Na, K, Li, Cu, Zn, Rb, Sr, Y, Zr, Sn, Cs, Ba, La, Ce, Nd, Pb, U and Th determinations have been carried out on 195 samples of granite and associated rook types collected, wherever possible, from the localities on the gridded sampling plan. Computerised process extraction techniques have been employed in the assessment of the analyses and the majority of elements are interpreted as following a "typical" igneous differentiation trend. The metallic elements and K, however, are considered to have been influenced by "post-magmatic" processes.
The Bodmin Moor granite is envisaged as having developed at a low crustal level and intruded at higher levels by passive upward emplacement and stoping. Subsequent tectonic activity, controlled by the regional setting of the S. W. England batholith, is regarded as having influenced the distribution of the metallic elements and K.

Citation

Edmondson, K. (1972). Some aspects of the chemistry of the Bodmin Moor granite