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Banded iron formations
(feochimicaet Cosmochimica Aota, 1973,Vol. 97. p. 1389. PergamonPress. Printed in Northern Ireland
CRITICAL COMMENTS Banded iron formations (Received 26 July 1972; accepted in revised form 13 September 1972) a. misconception about banded iron formations which seems to have crept into the literature and is repeated by Professor Holland in his recent presidential address (Geochinaica et Cosnaoc&mi~aActa 1972, Vol. 36, pp. 637-651. There (pp. 64&649) it is stated that, “The extensive bedded cherts of the Precambrian, and the frequently associated banded iron formations, seem to have no Phanerozoic analogs” and “For some time now the Precambrian banded iron formations have served as delightful sources of controversy. Proponents of a volcanic origin have been bafiled by the lack of equivalent iron formations in association with Phanerozoic volcanism”. In our experience these statements are not true. Banded iron formations with all of the varied facios-chert, magnetite, hematite, silicate and sulphide-are ~despread in the Ordovician rocks of the Bathurst-Newcastle, New Brunswick, sedimentary-volcanic complex. These have been described by a number of investigators (SMITHand SKINNER, 1958; BOYLE and DAVIES, 1964; GROWS,1967). In all of their details they represent analogues of the Algoma type iron formations of the Canadian Shield described by GROSS(1965). Having seen a number of the Algoma type and those at Bathurst we would say that they are essentially identical as regards their volcanic setting, their physical appearance and their chemistry. We are told by Dr. Gross that similar iron formations are to be found in other parts of the world in Phanerozoic volcanic belts marked by ignimbrites, extensive tuffaceous deposits, undersea hot springs, etc. Some of the best examples are to be found in the Soviet Union (No~o~~ATs~Y, 1970). We think that theories of the history of the ocean-atmosphere system should take these facts into consideration.
WE WISH to correct
R. W. BOYLE New Brunswick
Mineral Development Bathu~st, New Brunsw~~k~ manta
Branch
J. L.
DAVIES
REFERENCES and DAVIES J. L. (1964) Geology of the Austin Brook and Brunswick So. 6 sulphide deposits, Gloucester County, New Brunswick. cfeol. SWL~. Cnn. Paper 68.24. SMITH C. H. and SKINNER R. (1958) Geology of the B&thu~t-~e~~c~stle mineral district, Xew Brunswick. Bull. Gun. Inst. Min. Met. 51, (551), 150-155. GROSS G. A. (1965) Geology of iron deposits in Canada, Vol. 1. General geology and evallmtion of iron deposits. Geol. Szlra. Can. Econ. Geol. Rep. No. 22. GROSS G. A. (1967) Geology of iron deposits in Canada, Vol. 2. Iron deposits in the Appalachian and Grenville regions of Canada. GeoE.Swrv. CUS. Ecm.. Geol. Rep. No. 22. NOVOKHATSKY, I. P. (1970) Ferruginous-siliceous formations of Palaeozoic age in Kazakhstan; International Symposium on the Geology and Genesis of Precambrian Iron/_Mangnncse Formations and Ore Deposits, Kiev. Sponsored by and to be published by USESCO. Summary reprint. BOYLE
R. W.
l%Q
CRITICAL COMMENTS Banded iron formations (Received 26 July 1972; accepted in revised form 13 September 1972) a. misconception about banded iron formations which seems to have crept into the literature and is repeated by Professor Holland in his recent presidential address (Geochinaica et Cosnaoc&mi~aActa 1972, Vol. 36, pp. 637-651. There (pp. 64&649) it is stated that, “The extensive bedded cherts of the Precambrian, and the frequently associated banded iron formations, seem to have no Phanerozoic analogs” and “For some time now the Precambrian banded iron formations have served as delightful sources of controversy. Proponents of a volcanic origin have been bafiled by the lack of equivalent iron formations in association with Phanerozoic volcanism”. In our experience these statements are not true. Banded iron formations with all of the varied facios-chert, magnetite, hematite, silicate and sulphide-are ~despread in the Ordovician rocks of the Bathurst-Newcastle, New Brunswick, sedimentary-volcanic complex. These have been described by a number of investigators (SMITHand SKINNER, 1958; BOYLE and DAVIES, 1964; GROWS,1967). In all of their details they represent analogues of the Algoma type iron formations of the Canadian Shield described by GROSS(1965). Having seen a number of the Algoma type and those at Bathurst we would say that they are essentially identical as regards their volcanic setting, their physical appearance and their chemistry. We are told by Dr. Gross that similar iron formations are to be found in other parts of the world in Phanerozoic volcanic belts marked by ignimbrites, extensive tuffaceous deposits, undersea hot springs, etc. Some of the best examples are to be found in the Soviet Union (No~o~~ATs~Y, 1970). We think that theories of the history of the ocean-atmosphere system should take these facts into consideration.
WE WISH to correct
R. W. BOYLE New Brunswick
Mineral Development Bathu~st, New Brunsw~~k~ manta
Branch
J. L.
DAVIES
REFERENCES and DAVIES J. L. (1964) Geology of the Austin Brook and Brunswick So. 6 sulphide deposits, Gloucester County, New Brunswick. cfeol. SWL~. Cnn. Paper 68.24. SMITH C. H. and SKINNER R. (1958) Geology of the B&thu~t-~e~~c~stle mineral district, Xew Brunswick. Bull. Gun. Inst. Min. Met. 51, (551), 150-155. GROSS G. A. (1965) Geology of iron deposits in Canada, Vol. 1. General geology and evallmtion of iron deposits. Geol. Szlra. Can. Econ. Geol. Rep. No. 22. GROSS G. A. (1967) Geology of iron deposits in Canada, Vol. 2. Iron deposits in the Appalachian and Grenville regions of Canada. GeoE.Swrv. CUS. Ecm.. Geol. Rep. No. 22. NOVOKHATSKY, I. P. (1970) Ferruginous-siliceous formations of Palaeozoic age in Kazakhstan; International Symposium on the Geology and Genesis of Precambrian Iron/_Mangnncse Formations and Ore Deposits, Kiev. Sponsored by and to be published by USESCO. Summary reprint. BOYLE
R. W.
l%Q