I. Introduction
Ever since the publication of Teall's description of the Scourie dyke (1885, p. 133) and its passage from a dolerite into a foliated amphibolite by the ordinary processes of metamorphism, petrologists have from time to time directed their researches along modern lines to a study of the metamorphism of basic igneous rocks. No formal review of the literature is necessary owing to the numerous references contained in the following pages, but among the earlier writers Maculloch (1821, p. 298), De la Beche (1834, pp. 298
et seq.
) and Sterry Hunt (1875) may be mentioned. Although frequently the work of these authors was a model of careful observation and accurate description, their inference that hornblendic rocks were chemical precipitates from a thermal ocean can to-day be regarded as of historical interest only. It was thus left for Jukes (1862, pp. 169–72) to suggest that many hornblendic rocks were altered lavas or tuffs. Dealing with amphibblites chiefly from the south-west of England, Allport (1876, p. 422), Phillips(1876, p. 155,and 1878, p.471), and Bonney (1883, p. 14) expressed the opinion that they were metamorphosed igneous rocks. Shortly afterwards, the Scottish Geological Survey (Geikie, 1884, p. 122) in the course of their investigations on the amphibolites of Aberdeenshire and Banffshire came to a similar conclusion.
Lehmann (1884, p. 190) also arrived at this conclusion for the amphibolites from the Saxon Granulitgebirge, when describing the passage of a gabbro into a schistose amphibolite, whilst Lessen (1882–3) studied the contact metamorphism of a diabase
In this study, Central Appalachian coal-derived fly ashes from two power plants were beneficiated in a pilot-scale facility in order to produce a product with a relatively consistent concentration of rare earth elements (REE). The <200-mesh final fly ash product was produced by removing the carbon- and Fe-rich particles prior to screening at 200 mesh (75 µm). The Plant D fly ash had high concentrations of CaO and SO3, which were diminished through the two months when the ash was being beneficiated, representing a consequence of the heat, humidity, and excessive rainfall in the Kentucky summer. The high CaO and SO3 concentrations through the early runs likely contributed to the lower REE in the <200-mesh products of those runs. Of the non-REE minor elements, Ba, V, Mn, Zn, and As showed the greatest between-run variations within the runs for each plant. The overall REE concentrations proved to be similar, both on a between-run basis for the individual fly ash sources and on a between-plant basis. Variations in fly ash quality will occur in larger-scale operations, so on-going attention to the fly ash quality and the response of the fly ash to beneficiation is necessary. Changes in the Plant D fly ash with time imply that both the freshness of the original ash and the length and conditions of its storage at the site of beneficiation could be factors in the quality and consistency of the processed fly ash.
During the course of the John Murray Expedition some 22,000 miles of the floor of the Arabian Sea and the neighbouring areas of the Indian Ocean were mapped by means of the Echosounding apparatus. The region between India and Africa was crossed four times, namely:(i) from Aden to Karachi,(ii) from Bombay to Mombasa,(iii) from Zanzibar to Colombo, and(iv) from Colombo to Aden,while more detailed surveys were carried out in the Gulf of Aden, the Gulf of Oman, and the region off Zanzibar.
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