The Gabbros and associated Xenolithic Complexes of the Haddo House District, Aberdeenshire

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Abstract
I. Introduction The investigation of the Younger gabbro masses of North-East Scotland was begun in 1914 by W. R. Watt in the Huntly district. Watt described picrite (peridotite), olivine-gabbro, troctolite, and norite, and showed that certain endomorphosed gabbros, such as cordierite-norites, “originated from a magma contaminated by the aluminous material of the phyllites.” After the War, I described the Huntly gabbro mass and portions of the Insch and Cabrach masses. During this work the endomorphosed cordierite-bearing types discovered by Watt were found to have a wide distribution (Read, 1923b). The term “contaminated rock” was introduced to denote a rock resulting from the solidification of a magma which had been modified by reaction with xenoliths, usually of sedimentary origin (Read, 1921). It was suggested that in the formation of these contaminated gabbros a reciprocal reaction between initial magma and sedimentary xenoliths had taken place. Later, additional analyses of xenoliths from contaminated gabbros of the Huntly mass were supplied in support of this view (Read, 1924). Meanwhile, an account of the petrology of the Arnage district in eastern Aberdeenshire had been published in 1923 (Read, 1923a). In this, I held that contamination of gabbros had taken place on a large scale, with the formation of quartz-biotite-felspar-cordierite rocks (Arnage Type) and, as a final product, of a granitic rock (Ardlethen Type). Half a dozen years' work amongst the granitic complexes of Sutherland (Read, 1931a, pp. 99–164; Read & others, 1925, pp. 21–40; 1926, pp. 148–52), and a closer acquaintance with the “Older Magma”

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