Metallogenic models and exploration criteria for buried carbonate-hosted ore deposits-a multidisciplinary study in eastem England / Металлогенические модели и критерии разведки залегающих карбонатных рудных месторождений - междисциплинарное исследование

The report that follows presents a first statement of the results of a study sponsored by the European Economic Community and the Department of Trade and Industry as communicated to a meeting of the Institution of Mining and Metallurgy Midlands Section at which the President (Dr A. J. Robinson) and the Section Chairman (Professor N. A. Warner) were present. It was my privilege to attend and to make some concluding remarks; these form the basis of this preface. The Geological Survey, now in its 154th year, has as one of its principal objects the provision of geological maps based on surveying in maximum detail at a scale of 1:10 000. In areas where extractive or other engineering industry is important, the surveys have been revised more than once as new subsurface data became available. The organisation is responsible for a data bank containing about a million borehole records. Since 1960 its surveying methods have been enhanced by the provision of geophysical and geochemical field methods with appropriate laboratory support. Notable examples of the results include the Gravity Map and the Aeromagnetic Map of Britain, for which Dr William Bullerwell had primary responsibility, and the Geochemical Maps, prepared under Dr S. H. U. Bowie and Dr Jane Plant. From all these sources, and from general data derived from information held as Commercial in Confidence, a huge mass of information is available upon any given area such as the East Midlands. The present study is, nevertheless, one of the few cases where a beginning has been made upon the synthesis of the data by digital computer methods with a particular strategic objective in view, in this case the possible existence of concealed metalliferous mineralisation. This move into the field of high technology should be warmly welcomed not merely for what it may eventually lead to in the East Midlands but also because the procedures could form the basis of a service industry applicable anywhere in the world. That mineralisation may occur beneath a cover of younger rocks in the area is a fair conclusion from the existence of great numbers of fissure veins carrying galena, fluorite and baryte that have been exploited in the Southern Pennine Orefield in North Derbyshire. Lead mining there has been carried on since the Roman occupation and may have been practised earlier, and since the later years of the last century the field has been an important source of non-metallics, particularly fluorspar. It is important to be satisfied that an extension or recurrence of this Pennine-type mineralisation would be worth finding, but, unfortunately, past records of production leave much to be desired. Official statistics of lead ore output for 1845 to 1938 show only 0.69 million tonnes (Mt) galena, more than half of which came from one mine, Millclose. Good records prior to 1845 may exist in the archives of the Barmote Courts, which Dr Ford tells me have been in existence for nearly seven centuries, but the task of obtaining the information is formidable and may not be entirely practicable. If argument by analogy from the Northen Pennine Orefield is permissible, here output of 1. 73 Mt for 1845-1938 may be compared with accurate records from the London Lead and W.B. companies and the Devonshire ducal estates that bring the total for 1700-1938 up to 3. 7 Mt, or with the estimated all-time total of 5 Mt. The application of these ratios to Derbyshire would suggest 1.44 or 2.0 Mt, but these figures may still be too low. Official figures for fluorspar output may be interpreted as indicating 4.1 Mt for VII
1880-1977, which must presumably be increased to at least 5 Mt to include recent output. However, the 1880-1938 figure of 0. 78 Mt is almost certainly low, owing to unreported production by small operators. It is fair to estimate the value of the past output at present prices at a figure approaching £1 X 109 (one billion pounds). Certainly it is legitimate to ask: Could there be another equally productive field concealed in the East Midlands? This would become more attractive if the dominant style of mineralisation were widespread limestone replacement as in the Tristate District or the New Lead Belt of Missouri. <...>