The Occurrence of Native Copper in the Tertiary Basalts of Co. AntrimAuthor(s): Peter FrancisSource: The Irish Naturalists' Journal, Vol. 17, No. 8 (Oct., 1972), pp. 274-276Published by: Irish Naturalists' Journal Ltd.Stable URL: http://www.jstor.org/stable/25537604 .

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274

Stone alignment in the study pits shows that their long axis is downhill as

though they had moved by solifluction or by flooding. There are no water channels near to indicate that flood water may have been responsible so that the sandstone must have moved downhill by solifluction.

That the proportions of sandstone is very high is borne out by a study of a

series of pits in the Ballylanders Series at 600 to 700 feet which show that the

proportion of shale varies from 80% to 96%. lt would seem, therefore, that the small areas of Knockastanna series found

below 900 feet within the Ballylanders series are due to higher than normal percentages of Old Red Sandstone, which has been locally soliflucted downslope. The Old Red Sandstone of Clare, Limerick and Tipperary area is an acidic, quartzitic parent material

which forms podzols down to 300 or 400 feet in this area. As its proportion rises in the

dominantly shale soils, the acidity also rises and the likelihood of podzol formation increases.

The factor mainly responsible, therefore, in producing the lower level areas of

podzol is the increasing acidity of the parent material and this in turn is produced by solifluction processes. The low level occurrences of the Knockastanna Series

throughout Clare, Limerick, Tipperary and Waterford can frequently be explained in this manner.

Agricultural Institute, Kinealy, Dublin 5.

THE OCCURRENCE OF NATIVE COPPER IN THE TERTIARY BASALTS OF CO. ANTRIM

Peter Francis

Native Copper has been recorded as occurring as a trace mineral in Co. Antrim

by several authorities. Walker (1959) for instance, records its occurrence in minute

amounts, accompanying zeolite minerals within the gmelinite zone, along the east

coast of Antrim. Various specimens have also been presented to the Ulster Museum

and the Geology Department of Queen's University from localites at Woodburn Glen, Magheramorne and Glenarm.

The largest of these samples, from the Woodburn Glen locality, weighed 58.7 grams, with virtually no matrix, but this was exceptional, most examples being

minute. The copper usually accompanies amygdale minerals, zeolites and montmoril

lonoid clays, in the basalt lava flows, although it may also be found with flint from the clay-with-flint horizon below the basalts. Even in the relatively rich native copper zones, it is sparsely distributed and very localized in occurrence. In form

it is most often anhedral, but euhedral dendrites, as films or wires up to 3 cms long, may occur in basalt or in flint.

Two other copper minerals are associated with the native copper. The first,

cuprite, is invariably present. This is the red oxide of copper (CuO), and is usually found as a dark or black coating on the metal. Secondly malachite, the basic copper carbonate (CuC03Cu(OH)2), may occur as a coating or stain on associated minerals.

This latter mineral, with its bright turquoise colouration, makes even minute traces

of copper readily visible and recognizable. The associated amygdale minerals are mainly zeolites, natrolite and analcite

being the most common. However gmelinite and thomsonite have also been identified, and the one specimen found at an inland locality is on gismondine. (The actual locality of this specimen was at Bruslee Quarry, Ballyclare [J 308892], and the mineral identification was check by X-Ray diffraction photograph). The first three of these

zeolites are sodium varieties. Calcite and montmorillonite may also be present. Most of the specimens of copper-bearing amygdales exhibit a clear order of

mineral deposition. Firstly, the original cavity was invariably lined with montmoril lionite and then followed crystallization of zeolite and native copper. In some cases the copper was wholly embedded in the zeolite but most often the copper lay partially exposed. This denotes deposition at various stages of zeolitization but there appears to be no correlation between this and locality. Often both orders occurred in rock from the same locality, but specimens in situ were too scant to offer any clue. However,

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275

it is fairly reasonable to assume, that both zeolite and native copper originated in the same hydrothermal solutions. Calcite is usually the last mineral to have crystallized.

With the exception of the tiny speck from Bruslee (referred to above), all the copper minerals have been found along the east coast of Antrim, and within the first few flows of the Lower Basalts. Magheramorne Quarry [J 435985], near Larne, has yielded most

specimens, usually of better quality, despite the fact that active quarrying has denuded the main copper-rich zone. Broken rock from this locality has fortunately been tipped at the Curran, Larne [D 413015] and this artificial causeway is now the best place to find native copper in Co. Antrim. The associated minerals at Magheramorne are

natrolite, gmelinite, analcite, thomsonite, calcite and montmorillonite. Good specimens have also been found at quarried sections on the Coast Road about half a mile south of Glenarm [D 325153]. Associated minerals are natrolite, gmelinite, analcite,

montmorillionite and calcite.

In past years copper has been found in the quarry on the northern side of Woodburn Glen [J 384895], about 1 mile from Carrickfergus. These outstanding

specimens are now in the Ulster Museum. Unfortunately, this quarry has now been

filled in and no further specimens have been found there.

A BRUSLEE QUARRY I& \ \ J

B WOODBURN GL?M QRY U\j \ ^\

D CURfcAK CAU&tWAY ( \ * >& \^^ E GLCMARM CAUSE.WAY ^"""\ N\ ̂ \^ ,/' MAJOR FAULTS ^t

^\fx/rf\ *&&%?>& jf LIMIT QF^BASAUT V \ Ul7/A XS70%Y/0&.

^f% JS/ / ^\\" <^?&&6\ ^\ ISLAND d/f GMELlWlTe. IQME. / / / Vk\ Nk*^XAs N\ MAG6.E.

] SCAl-g._, / / \ ^ ^

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Jf/ lB \ t> V ? /

If fis^J Cs*~y \AfHlT?H?AD

y'"/ J ^^CACR.tCKPG.RC?US

Fig. I. Map showing relative distribution of native copper outcrops, gmelinite zone, and

major faults.

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276

These native copper-bearing exposures conform remarkably closely to Walker's

gmelinite zone (1959). Walker postulated that gmelinite was formed by the infiltration of sea water into the N-S fault zone between the mainland and Islandmagee. At

Magheramorne, the best copper locality lies closest to the fault zone. Even the

seemingly remote occurrence at Bruslee lies close to the Templepatrick fault, which can be traced to Ballygalley, and therefore must be significant. The Regional Geochemical Reconnaissance (Stream Sediment Survey) of Northern Ireland by the Applied Geochemistry Research Group of Imperial College, London, shows higher copper values along the Templepatrick fault.

Outside Northern Ireland, native copper and associated copper minerals are

found in similar localities, notably in Scotland. Heddle (1901), records them as

occurring in Perthshire, Stirlingshire and Refrewshire, with prehnite, and in Ayrshire with anorthite and pectolite. All are in basalt lavas. In Australia, native copper and

prehnite are again common associates in basalt lavas, and at the best known locality on the Upper Michigan Peninsula region of the U.S.A., native copper in economically workable quantities was mined in a 4 X 100 mile strip of land, in amygdaloidal basalt and underlying conglomerates.

This association of copper minerals with the hydrothermal mineral assemblage in amygdaloidal basalts, offers some clue to their origin.

Most basalt lavas contain trace quantities of copper (30-100 ppm), and

circulating hydrothermal solutions may leach out this constituent and deposit it in the rock cavities in a different form. As mentioned above, Walker has suggested seepage of sea water into a hot lava pile along the east Antrim fault zone, to account for the sodium-rich gmelinite zone of zeolitization. Sea water itself contains only .001-.01 ppm of copper, but the percolating solutions have attacked olivine and feldspar in the basalts, and alteration of the former to montmorillonoid clay minerals may have

released larger quantities of copper.

Alternatively, deeper seated circulation of ground water, affecting the saliferous Triassic marls are found at ddpth in the Carrickfergus-Larne area, may have involved

leaching of a much greater volume of rock. The copper content of evaporite deposits is as low as that of sea water, but so is the observed occurrence of Cu in the basalts.

Since copper minerals have been found only in the lower flows of the lower basalts, this could mean either an exceptional copper content for these early lavas, or

that copper deposition was only possible in the higher temperature lower zones of zeolitisation, at the base of the lava pile, as defined by Walker.

42 Strathmore Park, Belfast 15.

Acknowledgements

My most sincere thanks to Dr J. Preston of Queen's University Geology Department for his criticisms, use of equipment and specimens, and his guidance throughout the preparation of this account. I also thank Mr Harry Foy, for information concerning various localities, and use of specimens, and Mr Harold Wilson

(Geological Survey) for his remarks, interest and help in the publication.

REFERENCES: Heddle, M. T. (1901). The Mineralogy of Scotland.

Walker, F. P. L. (1959). The Amygdale Minerals in the Tertiary Lavas of Ireland. II The Distribution of Gmelinite. Min. Mag., 32: 202-217.

NOTES ON THE OCCURRENCE OF THE ISOPOD PARASITE BOPYRUS SQVILLARUM LATREILLE

Padraic de Bhaldraithe

While carrying out a study on aspects of the biology of the prawn Palaemon serratus (Pennant) off the Galway coast between 1969 and 1971, it was noted that many of the prawns examined were infested by the epicaridean isopod Bopyrus squillarum Latreille. This is the only species of Bopyrus occurring in northern European waters,

and other species of Bopyrus which have appeared in past literature are regarded as

synonyms of Bopyrus squillarum (Bourdon, 1968). The parasite infects the gill

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