Pennine Orefield Research Articles

The Westgarth Forster Fault models

Four wooden models to illustrate slips in mineral veins were donated to the Geological Society of London in 1830. Labelled Fo(r)ster models, they are considered to represent two directions of faulting: moderately inclined mineral veins traversed by steep cross veins. Through an ingenious method of construction involving two sheets of wood joined by dovetail slides, one vein direction can be faulted by sliding the two sheets of the other fault one over the other. Two of the models, Nos. II and IV, can be related unequivocally to the ENE productive veins and the cross veins in the Northern Pennine orefield. The other pair of models, Nos. I and III, can be arranged as combinations of the NNW trending Slitt Vein and the ENE Veins. Models I and III would then represent conditions as found in the Weardale area east of the Burtreeford disturbance, whereas Models II and IV refer to the Nenthead district to the west. The models are probably contemporaneous with Thomas Sopwith's early experimentation with models to illustrate faulted strata in the same orefield although his models were not issued for sale until 1841. From the date of accession of the fault models, it is likely that they were made after the issue in 1821 of the second edition of Forster's very practical book: ‘A Treatise on a Section of the Strata from Newcastle upon Tyne to the Mountain of Cross Fell’.

Sphalerite mineralogy and trace element geochemistry in the South Pennine Orefield

SUMMARY Sphalerite has a restricted distribution mainly along the eastern margin of the South Pennine Orefield. The main microscopic inclusions in sphalerite are pyrite, chalcopyrite, galena and calcite. Alteration of sphalerite to smithsonite is generally extensive and is usually accompanied by formation of covellite and goethite as copper and iron are released from the sphalerite lattice. Sphalerite, like galena and pyrite, has a very strong preference for association with calcite in the South Pennine Orefield. The low concentrations of iron and silver in the analysed sphalerites indicate a low formation temperature. Bivariate and multivariate analyses of sphalerite analytical data show that, although complex relationships exist among the trace elements in sphalerite, there are only five factors that account for all the variance in the distribution of the trace elements. The co-existence of galena and sphalerite in the orefield does not have any apparent effect on the partition of the trace elements.

The distribution of barytocalcite and alstonite in the Northern Pennine Orefield

SUMMARY The rare minerals barytocalcite and alstonite, the dimorphs of barium calcium carbonate, are shown to be of widespread occurrence in the barium-bearing deposits of the outer zone of the Northern Pennine Orefield where they generally accompany witherite. Barytocalcite in particular is present in much greater abundance than hitherto supposed and in several deposits is shown to be the dominant barium mineral. Both minerals are abundant only in deposits within a limestone wall rock and are considered to be the products of reaction between late-stage mineralising fluids and the wall rock.

A HYDROGEOCHEMICAL AND STREAM SEDIMENT SURVEY OF THE ASKRIGG BLOCK IN THE NORTHERN PENNINE OREFIELD

SUMMARY A regional hydrogeochemical reconnaissance survey of the southern part of the northern Pennine orefield (Askrigg Block) was undertaken at a sampling density of 1 per 2km 2 . For comparison a stream sediment survey using a sample density of 1 per 7km 2 was also conducted. The water samples were analysed for Na, K, Ca, Mg, Fe, Mn, Sr, Zn, Cu, Ag, Pb, Cd, Co, and Ni by atomic absorption spectrophotometry. Colourimetric methods were used to determine NO 2 , B, and Si, and Fe, NO 2 and pH were analysed by a specific ion analyser. Li was determined by flame photometry and standard wet chemical methods were employed in the determination of SO 4 , Cl, CO 2 , Fe 2+ and Fe 3+ . The stream sediments were analysed by X-ray fluorescence spectrometry. The analytical results (>10,000) were interpreted using multivariate statistical techniques. Examples of geochemical patterns and anomalies related to geology, pollution and mineralisation are identified. Silica analyses have delineated the Namurian outcrop. Certain Pb, Zn, Cu, V, Na and Cl anomalies are attributed to pollution from agricultural fertilisation and old smelting and/or dressing sites. Zn, F, Pb, Cu, Ni, Co and Ba anomalies are coincident with known mineralisation as well as, as yet, unproven ore deposits.

Clay minerals in the veins of the North Pennine Orefield, UK

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Low-temperature mineralization

Report of the Mineral Deposits Studies Group Sixth Annual General Meeting held at St. Peter’s College, University of Aston in Birmingham, 17–19 September 1980. The Conference, ably organized by Dr R. A. Ixer with the co-operation of the University and the Department of Geological Sciences, to whom the Mineral Deposits Studies Group extend their thanks, was subdivided into 3 sections. The first day was devoted to a number of papers which covered varied aspects. Isotopic studies on the mineralization of the Ophir Valley, Colorado (Jackson), and the Ba-Zn deposit at Aberfeldy (Willan) were presented together with 2 papers on U mineralization in Namibia (Marlow and Clemmy). Ineson and Walters indicated the problems of correlating horizons and interpreting the attendant alteration associated with the igneous rocks in the South Pennine Orefield, while Alabaster & Pearce described the geological setting of the sulphide deposits in the Oman ophiolite complex. For this type of meeting, an unusual but interesting contribution by Broadbent et al. reviewed European Pb-Zn production and indicated recent research into new recovery processes for Pb, Zn and Cu as well as improving hydrometallurgical techniques. Well over 100 people attended the second day, and were no doubt attracted by a number of papers related to Permo-Triassic mineralization. A review of the Permo-Triassic rocks and related mineralization was given by Clarke who, in proposing new genetic models, caused some disquiet amongst the audience. On a more localized scale, isotopic evidence indicating possible inter-relationships was presented by Harwood & Coleman, while Turner &

An Account of a Small Nineteenth-Century Lead Mining Company on Alston Moor

Abstract Thanks to the efforts of Hunt, Raistrick & Jennings and others, working on the records of the Beaumonts, the London Lead Company and the Greenwich Hospital, the affairs of the large and successful mining companies working on the Northern Pennine Orefield are well known. However little has been written of the numerous small mining enterprises that flourished on Alston Moor in the eighteenth and nineteenth centuries. Because of this, the finding of a bundle of documents concerning the running of a small, and unsuccessful nineteenth-century mine is of considerable interest. Greenends was at one time the residence of the Waltons, who had interest in the local mines and the documents probably owe their survival to the fact that Jacob Walton of Greenends was the agent for the company concerned, the Nentsberry Green Lead Mine Co., from 1839 to 1841. Included in the bundle were rough accounts, bills and letters for the periods 1822-9 and 1839-41, as well as an account book for 1829-39. In the back of the...

An Account of a Small Nineteenth-Century Lead Mining Company on Alston Moor

Thanks to the efforts of Hunt, Raistrick & Jennings and others, working on the records of the Beaumonts, the London Lead Company and the Greenwich Hospital, the affairs of the large and successful mining companies working on the Northern Pennine Orefield are well known. However little has been written of the numerous small mining enterprises that flourished on Alston Moor in the eighteenth and nineteenth centuries. Because of this, the finding of a bundle of documents concerning the running of a small, and unsuccessful nineteenth-century mine is of considerable interest. Greenends was at one time the residence of the Waltons, who had interest in the local mines and the documents probably owe their survival to the fact that Jacob Walton of Greenends was the agent for the company concerned, the Nentsberry Green Lead Mine Co., from 1839 to 1841. Included in the bundle were rough accounts, bills and letters for the periods 1822-9 and 1839-41, as well as an account book for 1829-39. In the back of the Account Book are further detailed accounts of mine costs for the period 1830-3. Using the new information in conjunction with Greenwich Hospital documents etc., a fairly detailed picture of the Nentsberry Green Lead Mine Company has been constructed.

HYDROGEOCHEMICALLY ANOMALOUS AREAS IN THE ASKRIGG BLOCK OF THE NORTHERN PENNINE OREFIELD

SUMMARY A regional hydrogeochemical reconnaissance survey of the southern part of the northern Pennine orefield (Askrigg Block) was undertaken with a sample density of one sample per two square kilometres. 370 water samples, each with 30 analytical determinations necessitated the use of various multivariate statistical interpretation techniques. After due consideration for pollution and possible contamination, it is concluded that in the Litton and Dent areas undiscovered mineral deposits may be present.

Current research on fluid inclusions and on mineral deposits

T he principal theme of this three-and-a-half-day conference (13–17 December 1976) at Durham University was the value of fluid inclusion studies in investigations into the origin of mineral deposits and rocks. Other sessions covered opaque mineralogy, studies on natural and synthetic sulphide systems and various other aspects of ore geology. For this conference the Mineral Deposits Studies Group joined forces with the Applied Mineralogy Group of the Mineralogical Society. There was also official participation by representatives from the Groupe Inclusions of the Société Française de Minéralogie et de Cristallographie and from C.N.R.S. centres at Paris and Nancy. Fluid inclusion papers were mainly concerned with studies of economic mineral deposits. It was stressed (Deicha) that they can now yield valuable data on the genesis of minerals formed over the full range of temperatures from magmatic (Althaus) to sedimentary (Sabouraud et al .). Four papers were concerned with fluid inclusions in fluorite. In one, P. J. Rogers showed that fluids in Derbyshire fluorites have similar salinities to those from the northern Pennine orefields, but a lower K/Na ratio. In another, F. W. Smith demonstrated how homogenization temperatures could be used to reconstruct the distribution of isothermal surfaces in veins so as to outline flow paths and calculate cooling gradients. There have been far too few intensive investigations of this sort on single veins. Such studies combined with Conolly diagrams could become important exploration tools and it is to be hoped that other workers will follow this lead. In work on other vein deposits

Supergene native copper in the Northern Pennine Orefield

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Isotopic age determinations on clay minerals from lavas and tuffs of the Derbyshire orefield

SummaryEpisodic hydrothermal mineralization has previously been recognized in the northern section of the Pennine orefield. Igneous rocks from the southern section (the Derbyshire orefield) have yielded isotopic ages, some of which are thought to represent ages of hydrothermal metasomatism (deuteric or subsequent). In order to ascertain whether epicyclic hydrothermal events gave rise to the Derbyshire mineral deposits, samples of highly altered doleritic lava and pumice tuff were collected adjacent to areas of mineralization. Clay-mineral concentrates from 34 samples were dated by the potassium–argon method. The conclusions drawn from these analyses support a hypothesis of repeated hydrothermal alteration of the clay minerals, reflecting at least two episodes of mineralization, one about 270 m.y., the other about 235 m.y. The geo-chronological significance of these and other results is considered.

The geochronological significance of argon-40/argon-39 age determinations on White Whin from the northern Pennine orefield

Controversy regarding the age and character of mineralization in the northern Pennine orefield is reviewed in the context of recent geological and geochronological research in the region, and a number of the unresolved problems are tabulated. A new method of potassium-argon radioisotopic age determination which utilizes the conversion of the natural isotope 39 K in a rock or mineral to the isotope 39 Ar by neutron irradi­ation is described in outline. This method avoids some of the limitations of conventional potassium-argon age determination, and, among other advantages, makes the measurement of the radioages of clay minerals possible. A geochronological and petrological investigation of White Whin samples from the northern Pennine orefield is reported in full, and eighteen new age determinations, mostly upon clay mineral concentrates are presented. The conclusions that can be drawn from this work support a hypothesis of repeated hydrothermal mineralizations within the area of the northern Pennine orefield: the first within the period 284 ± 40 My with subsequent maxima of hydrothermal activity occurring at intervals. At least two of these subsequent episodes have been identified: one around a minimum age of 230 My and another, very important episode occurring around 170 My. Comparison of these results with histograms of (1) all radio­ages of British rocks and (2) radioages from British dolerites and basalts only, suggests that episodic hydrothermal alteration of pre-existing rocks may be a widespread phenomenon in Britain.

Ore genesis in the North Pennine orefield, in the light of fluid inclusion studies

The temperature range of mineral deposition was as follows--quartz from more than 200 degrees C-125 degrees C, fluorite 200 degrees C-100 degrees C, and barite 130 degrees C-50 degrees C. On the basis of associations with these minerals, the minimum temperature of pyrrhotite deposition was 165 degrees C; the range for galena and sphalerite was 200 degrees C to less than 100 degrees C. Richly mineralized areas were hot spots. Salinity, determined by freezing, was rather uniformly high. Na/K ratios of 6.2-12.4 in the fluorite zone (heart of the ore district) are notably lower than the 29 of sea water. Later-stage barite has ratios of 15.3-46. These compositions and spatial relations suggest that hydrothermal solutions from a deep source, rather than connate waters, deposited the fluorine and base metals.

Iron-deficient Low-temperature Pyrrhotite

IN a recent communication1, Sawkins, Dunham and Hirst discussed the occurrence of pyrrhotite in low-temperature veins in the northern Pennine orefield. They found that, on experimental inversion and application of the hexagonal pyrrhotite–pyrite solvus curve2, monoclinic pyrrhotite in these deposits yields temperatures of deposition markedly in excess of those indicated by fluid inclusion studies. Gronvold and Haraldsen3, however, have demonstrated that at temperatures below c. 300° C the stable phases in the iron-rich part of the FeS–S system include troilite, intermediate hexagonal pyrrhotite (Fe0.936–0.900S), and monoclinic pyrrhotite (Fe∼0.877S). These three phases have very restricted ranges of composition, although the compositions of the iron-deficient synthetic phases differ somewhat from those observed in nature4. In the light of these relations it seems unreasonable to expect that primary monoclinic pyrrhotite of low-temperature origin co-existing with pyrite will show an iron-deficiency related to temperature of formation by the hexagonal pyrrhotite-pyrite solvus (which probably terminates at some temperature between 250° and 300° C). In the absence of very iron-deficient hexagonal pyrrhotite, the occurrence of troilite and intermediate pyrrhotite, with or without associated monoclinic pyrrhotite, in pyrite-bearing ores may be accepted as evidence that either the initial crystallization or the re-equilibration of the assemblage occurred at temperatures below c. 250° C. I have recently described5,6 the pyrrhotite assemblages in the Ylojarvi copper–tungsten deposit, Finland, and have suggested that cooling of hexagonal pyrrhotite from 500° to 565° C to below 300° C resulted in the inversion of much of the pyrrhotite to the monoclinic + hexagonal and monoclinic forms7, the formation of hexagonal pyrrhotites having compositions in the range Fe0.887–0.907S, and the development of troilite and intermediate hexagonal pyrrhotite (Fe0.912S). The last-mentioned two phases form characteristic lamellar intergrowths showing transitions to granular aggregates and monomineralic patches and vein-lets. The formation of mackinawite8 (tetragonal FeS), largely by replacement of magnetite and iron- and copper-sulphides, apparently postdated the crystallization of troilite. In this deposit, the monoclinic and monoclinic + hexagonal pyrrhotites have compositions in the narrow range, Fe0.869–0.873S. If inversion from the hexagonal form was iso-chemical, these compositions would indicate temperatures of formation of 510°–515° C. Because natural monoclinic pyrrhotite shows little departure from the composition, Fe0.875S, however, the close coincidence of the crystallization temperatures deduced from the compositions of the co-existing hexagonal and mono-clinic pyrrhotites may be fortuitous9. In other sulphide deposits, low-temperature re-equilibration of hexagonal pyrrhotite has resulted in the formation of monoclinic and monoclinic + hexagonal-pyrrhotite, and hexagonal pyrrhotite having a composition in the approximate range Fe0.896–0.899S. Intermediate pyrrhotite (Fe0.912S) and, especially, troilite may be subordinate or absent in such assemblages (unpublished work).

Geology of the Northern Pennine Orefield. Volume 1. Tyne to Stainmore. By K. C. Dunham. Memoir Geological Survey of Great Britain, pp. 357, with 33 text-figures and 4 folding plates. 1948. Price 17s. 6d.

Geology of the Northern Pennine Orefield. Volume 1. Tyne to Stainmore. By K. C. Dunham. Memoir Geological Survey of Great Britain, pp. 357, with 33 text-figures and 4 folding plates. 1948. Price 17s. 6d. - Volume 86 Issue 5

Ankerites and chalybites from the northern Pennine orefield and the north-east coalfield

Ankerites from the Northumberland coalfield were first described, with chemical analyses, some ten years ago (Hawkes and Smythe, 1935), when it was found that examples from veins exposed on the coast near Hartley and from sludge from nearby coal-washeries showed a remarkable uniformity in composition. The operations of the collieries concerned cover an area roughly 6 × 6 miles, and range from the Beaumont to the High Main Seam. In order to ascertain whether this uniformity is maintained over a wider area, five additional samples of ankerite from veinlets in rocks of Coal Measure age, and one from partings in the Lower Carboniferous Scremerston coal have been examined. The Coal Measure rocks cut by the veinlets have been proved to contain substantial proportions of ferriferous carbonates, while for comparative purposes two examples of rocks of similar age with carbonate but unaccompanied by ankerite veinlets have been investigated. The range in composition of ankerites in the coalfield has proved to be small.