Hostname: page-component-78c5997874-4rdpn Total loading time: 0 Render date: 2024-11-14T19:17:04.675Z Has data issue: false hasContentIssue false
  • English
  • Français

The ore textures of the Neves-Corvo volcanogenic massive sulphides and their implications for ore beneficiation

Published online by Cambridge University Press:  05 July 2018

O. Gaspar  and
A. Pinto
O. Gaspar
Affiliation:
Laboratório da Direcçāo-Geral de Geologia e Minas, 4465 S. Mamede de Infesta, Portugal
A. Pinto
Affiliation:
SOMINCOR, S.A.-7780 Castro Verde, Portugal
Get access Rights & Permissions [Opens in a new window]

Abstract

The Neves-Corvo mine opened officially in December 1988 and it is already the biggest producer of copper in the Iberian Pyrite Belt (IPB). Tin production started in 1990. The ore deposits of the IPB are related to felsic submarine volcanism which developed during the lower Tournaisian to the middle Visean. At the end of the first phase of Hercynian deformation in the middle Westphalian, the ore deposits were affected by low-pressure metamorphism producing schistosity and prehenite-pumpellyite greenschist facies assemblages in the volcanogenic sediments of the IPB.

The unique nature of the mineralogy of the Neves-Corvo deposit compared with other IPB deposits is mainly a result of the introduction of later Cu-rich hydrothermal solutions to the primitive ore pile and the presence of tin mineralisation. The cupriferous ores are rich in tetrahedrite-tennantite, stannite, kesterite, stannoidite and mawsonite.

Cassiterite occurs in Neves-Corvo: (a) as thin layers of euhedral crystals in cupriferous ores, partially replaced by chalcopyrite; (b) in the schistosity of a banded black shale chalcopyrite hanging wall formation; (c) as metre-sized lenses of massive cassiterite overlying the cupriferous ores.

The ore textures at Neves-Corvo are complex, due to intergrowths of fine colloform pyrite with the base metal minerals. Because of the low grade of metamorphism, colloform, geopetal and soft-sediment diagenetic features are preserved in the ‘complex ores’. These ‘complex ores’ have contents of 0.5% Cu, 1% Pb and 5.5% Zn. In copper-rich ores (7.9% Cu and 1.4% Zn), replacement of the primary ore by chalcopyrite has obliterated most of these textures and produced fine chalcopyrite-tetrahedrite-pyrite intergrowths. The textures clearly indicate the genesis of these ores but they impose a practical problem in recovery of the metals. There is no clear correlation between these textures and the ore classification used at the mine, but an understanding of the textures is vital since the ‘complex ores’ require fine grinding to achieve liberation and the fine grinding adversely affects the froth flotation processing of the ore.

The implications of the complex sulphide textures for ore beneficiation have been studied using reflected light microscopy, with determination of modal analyses and grain-size distributions of free particles and middlings from concentrates and tailings.

The outcome of a one-year intensive study is that the ore microscopy laboratory at the mine now produces daily information about the textures of the feed ores so that metallurgical engineers can optimise the performance of the ore dressing plant.

Keywords

ore texturessulphidesIberian pyrite belt
Type
Research Article
Information
Mineralogical Magazine , Volume 55 , Issue 380 , September 1991 , pp. 417 - 422
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Barton, P. B. Jr., (1973) Some ore textures involving sphalerite from the Furutobe mine, Akita Perfecture, Japan. Mining Geology, 28, 293–300.Google Scholar
Carvalho, P. (1986) An introduction to Neves-Corvo copper mine. S.G.A. Iberian Field Conference, Portuguese Section, Lab. Geol. I.S.T., 83–99.Google Scholar
Chadwick, J. (1989) Neves Corvo's riches. Int. Minin, May 11–27.Google Scholar
Eldridge, C. S., Barton, P. B. Jr., , and Ohmoto, H. (1983) Mineral textures and their bearing on formation of the Kuroko orebodies. Econ. Geol, Monograph 5, 241-81.Google Scholar
Gaspar, O. (1984) Microscopy applied to beneficiation of the Afjustrel ores. Est. Not. Trab. S. F.M., 26, fasc. 1-4, 49–61.Google Scholar
Gaspar, O. (1990) Mineralogy of the complex sulphide ores from Neves-Corvo. 15th General Meeting of I.M.A., Beijing, Abstracts, vol. 1, 250-1.Google Scholar
Gaspar, O. and Conde, L. (1978) A caracterizacão dos sulfure-tos de Aljustrel com vista ao seu aproveitamento integral. Congresso 78, Ordem dos Eng., Tema 3, Comunicacao 12.Google Scholar
Graham, U. M., Bluth, G. J., and Ohmoto, H. (1988) Sulfide-sulfate chimneys on the East Pacific Rise, 11° and 13°N latitudes. Part I: mineralogy and para-genesis. Can. Mineral., 26, 487–504.Google Scholar
Leca, X., Albouy, L., Aye, F., and Picot, P. (1985) Caractéristiques principales du gisement de Neves-Corvo (Portugal). Chron. rech. geol. min., no. 481, 53-8.Google Scholar
Marchig, V., Rosch, H., Lalou, C., Brichet, E., and Oudin, E. (1988) Mineralogical zonation and radio-chronological relations in a large sulfide chimney from the East Pacific Rise at 18° 25′S. Can. Mineral., 26, 541-54.Google Scholar
Munhá, J. (1983) Low grade regional metamorphism in the Iberian Pyrite Belt. Comun. Serv. Geolog. Portugal, 69, fasc. 1, 3–35.Google Scholar
Ohmoto, H., Mizukami, N., Drummond, S. E., Eldridge, C. S., Pisutha-Arnond, V., and Lenagh, T. C. (1983) Chemical Processes of Kuroko Formation. Econ. Geol., Monograph 5, 570–604.Google Scholar
Paradis, S., Jonasson, I. R., Le Cheminent, G. M., and Watkinson, D. H. (1988) Two zinc rich chimneys from the Plume Site, Southern Juan de Fuca Ridge. Can. Mineral., 26, 637-54.Google Scholar
Watanabe, M. (1974) On the textures of ores from the Daikoku Ore Deposit, Ainai Mine, Akita Perfecture, Northeast of Japan, and their implications in the ore genesis. Mining Geol. Special Issue, 6, 337-48.Google Scholar