Research interests

Over the years (60 plus) I have undertaken research in several closely related areas of sedimentary mineralogy/geochemistry dealing mainly with the distribution of elements and the stability of the host minerals. The industrial implications and anthropogenic issues are important components of this work. (Key publications are indicated in brackets)

Early research: My PhD project was under the supervision of Professor L.R. Moore and dealt with the radioactivity of Coal Measures marine mudrocks (3) and the major elements (4). At the same time Charles Curtis was involved in a parallel study involving the trace elements. Both of us at that time had a growing appreciation of the importance of diagenetic reactions and the role of anion availability on mineral stability. What proved to be a key paper was published at that time (10). The Mesozoic ironstones were revisited some years later (58) with a better understanding of the role of organic matter in the diagenetic processes and a greater appreciation of the contributions of Sorby.

Analytical methods used in the early research were time consuming. The major elements were analysed using the so called rapid wet methods and the trace elements with the optical spectrograph, which was also the instrument used by Goldschmidt in his pioneering research. The acquisition of X- ray facilities, XRF and XRD in the late 1960s, and atomic absorption, both flame and furnace in the 1970s greatly extended our analytical capabilities , both in terms of elements and sample throughput. Further enhancement came in the 1990s with the advent of ICP-AES, ICP-MS and laser ablation ICP-MS.

Engineering Geology (1970-81). Following on from my initial research on mudrocks I successfully collaborated with Roy K. Taylor on the influence of mudrock mineralogy and texture on engineering properties. After the Aberfan Disaster in 1966 we were funded by the National Coal Board to study the influence of weathering on mudrocks to assess the long-term stability of colliery discard tips. Formal, and equally rewarding informal collaboration with Roy continued until his untimely death in 1987, exactly 21 years to the day after Aberfan (13,15,19,20 and 38).

Groundwater evolution (1975-1987). The earlier research described above involved mineral stability in the low temperature sedimentary environment. Recharge of aquifers involves similar reactions as water moves through the unsaturated zone. This area of environmental geochemistry featured in several publications (26, 27, 30, 32, 42 and 48). In addition to the elements in the groundwater originating from natural processes the fate of anthropogenic elements from effluent and fertilizers was also investigated (52 and 55). Over a period of ten years there was close collaboration and support from the Water Research Centre, Water Companies and NERC. Because the work involved not only the porewaters in major UK aquifers, but also the enclosing rock/sediment, several papers were generated dealing specifically with the mineralogy and geochemistry of non-Carboniferous rocks (25, 34, and 41).

Mudrock geochemistry/mineralogy (mainly Carboniferous,1960- 1990). This was a continuation of my earlier research and increasingly involved research students from the UK and elsewhere. Although trace elements such as B have been tested unsuccessfully as a palaeosalinity indicator (5, 7), other trace elements do show significant differences between the marine and non-marine mudrocks (36). Research was also directed at other specific elements including Ti (28), Rb/Sr (23) and Fe (10, 58). However, by the mid 1980s, the emphasis of the work had shifted away from the mudrocks and towards the coals in the sequence. This also meant that the trace element analyses of the marine mudrocks were not comprehensive (XRF rather than ICP) and in recent work (124 and 127) this shortcoming was partially corrected thanks to the generosity of Dr Henk Kombrink, who allowed access to analyses of equivalent mudrocks from the Netherlands. Clay minerals dominate these mudrock sequences and based in part on PhD projects the lateral and vertical variations in the Carboniferous clay mineralogy were defined (39, 47, 53, 54, 59). Based in part on these papers an overview account of onshore Carboniferous clay mineralogy in the UK was produced (117).

Tonsteins. Laterally extensive, clay-rich beds in coal-bearing strata composed of kaolinite are now known to have formed from the alteration of a volcanic ash in a freshwater environment. These are tonsteins, which first came to my attention because of their high radioactivity in borehole logs. Many origins had been proposed but by the mid 80` there was a consensus that they were volcanic. The mineralogy and geochemistry provide evidence of the volcanic origin and the relationships with bentonites in marine sequences. These volcanic horizons are of stratigraphic importance and are of interpretative value in understanding geochemical and palaeovolcanic processes. The published work (8, 14, 17, 22, 33, 40, 43, 44, 49, 50, 51, 57, 61, 65, 72, 78, 92, 105 and 110) includes collaborative work with authors in the UK and elsewhere. A comprehensive review of this work was published in 2012 (121). Subsequently, comprehesive analyses were undertaken with Professor Sergey Arbuzov on tonsteins from Siberia in the Russian Far East (126) and representative UK tonsteins (128). where the interest is not only on elements retained in the altered ash but also those captured by the enclosing coal during the alteration of the ash. This, in turn, has led to research on economically important metalliferous coals (129,130).

Coals. By the mid-1980s the emphasis in the coal-bearing sequences had moved from the mudrocks to the coals. This work was intially funded by NERC but with major, longterm support from industry, notably British Coal, CEGB and latterly Rio Tinto. The experience we had gained on the mudrocks in the sequence provided an excellent insight into the mineralogy of the coals themselves. Some outstanding research students and research assistants made important contributions resulting in a significant number of papers. Several papers dealt specifically with minerals within the coal and their chemical analysis by direct and indirect means (53, 56, 60, 62, 64, 68, 69, 70, 71, 79, 80, 82, 91, 93, 94, 95, 98, 99, 100, 101, 107, 108, 119, 120 and 122). Other papers were directed at specific problems such as the forms of Cl in coals and its removal (45, 46 and 115) and the distribution of S in multi-plie seams (83, 87, 97). Increasingly we were looking at the behaviour of the coal in conventional power stations working with Dr Rosa Martinez-Tarazona. Areas of interest included a) the role of minerals and macerals on combustion properties (81, 104 and 118), b) the links between the minerals and phase equilibria at high temperature (86), c) and the distribution of trace elements between combustion residues (84, 88, 89, 96, 102, 112, 113, 116 and 125) and how these residues from combustion, mainly fly ashes, behave in the weathering environment (77, 85, 88, 90, 111 and 114). The release of surface associated trace elements from fly ash into porewaters is closely related to the earlier interest in groundwater evolution. In the last decade trace element distributions within coal were determined directly by laser ablation ICP-MS, mainly of the macerals (119) and indirectly using a statistical approach (120) and sequential leaching (123). An overview paper on the mineralogy and geochemistry of Yorkshire coals was published in 2015 (124). The influence of seawater on the geochemistry of these coals was stressed in 2017 (127), as was the major contribution made by V.M. Goldschmidt nearly a hundred years earlier. Finally, the work on tonsteins with Russian colleagues cited above, has impications for metalliferous coals (129,130). The latter publication deals with economically important Ge coal ores, a possibility envisaged by Goldschmidt so many years ago. Unfortunately, future collaborative research is on hold due to events elsewhere.