A Case History of the Neves-Corvo Massive Sulfide Deposit, Portugal, and Implications for Future Discoveries

1994 ◽  
Vol 31 (10) ◽  
pp. 1569-1584 ◽  
Author(s):  
P. Doucet ◽  
W. Mueller ◽  
F. Chartrand

The mafic-dominated volcanic and related volcaniclastic sedimentary rocks, which host the Archean Coniagas Zn–Pb–Ag massive sulfide deposit, are inferred to be the result of submarine explosive and effusive eruptions at depths of approximately 1000 m, as suggested by the presence of volcaniclastic turbidites, the absence of wave-induced sedimentary structures, pillowed lava flows, the sulfide deposit itself, and the incipient arc setting. The rock assemblage includes massive, pillowed and brecciated, basaltic to andesitic flows, massive, andesitic to rhyodacitic lapilli tuffs, andesitic stratified lapilli tuffs, and bedded tuffs. Preserved fragments and delicate volcanic textures, such as angularity of clasts, chilled clast margins, and clast vesicularity, and sedimentary structures are consistent with a subaqueous hydroclastic origin for the volcaniclastic sedimentary rocks. Explosive degasification of magma and (or) lava, in conjunction with fragmentation due to the interaction of magma–water, or nonexplosive hydroclastic fragmentation can account for the observed characteristics in the volcaniclastic deposits.The 280 m thick Coniagas volcano-sedimentary succession, used to reconstruct the volcanic history of the deposit, records two explosive–effusive volcanic cycles. The initial stage of each cycle is envisaged to have commenced with a small fire fountain or boiling-over eruption. Transport and deposition of the fragmented debris along the flanks of the volcanic edifice is attributed to high-concentration particulate gravity flows. The massive lapilli tuffs are interpreted as laminar debris flows, whereas the stratified lapilli tuffs may reflect turbulent flow deposits. The bedded tuffs were produced during the waning eruptive stages or elutriated from high-concentration syneruption flows. Ingestion of water, causing hydroclastic fragmentation, occurred during the eruptive and (or) the transport process. Calm, effusive mafic volcanism, characterized by massive, pillowed and brecciated flows and reworked counterparts, terminates each volcanic cycle. The massive, felsic lapilli tuffs, which host the mineralization, are inferred to represent locally reworked hydroclastic products of explosive or nonexplosive origin. The Coniagas mine deposit may serve as a guide for future exploration of small Archean volcanic-hosted massive sulfide deposits with a restricted alteration halo.


1984 ◽  
Vol 79 (5) ◽  
pp. 933-946 ◽  
Author(s):  
Bruce E. Nesbitt ◽  
Fred J. Longstaffe ◽  
David R. Shaw ◽  
Karlis Muehlenbachs

2018 ◽  
Vol 82 (S1) ◽  
pp. S5-S41 ◽  
Author(s):  
J. R. S. Carvalho ◽  
J. M. R. S. Relvas ◽  
A. M. M. Pinto ◽  
M. Frenzel ◽  
J. Krause ◽  
...  

ABSTRACTHigh concentrations of indium (In) and selenium (Se) have been reported in the Neves-Corvo volcanic-hosted massive sulfide deposit, Portugal. The distribution of these ore metals in the deposit is complex as a result of the combined effects of early ore-forming processes and late tectonometamorphic remobilization. The In and Se contents are higher in Cu-rich ore types, and lower in Zn-rich ore types. At the deposit scale, both In and Se correlate positively with Cu, whereas their correlations with Zn are close to zero. This argues for a genetic connection between Cu, In and Se in terms of metal sourcing and precipitation. However, re-distribution and re-concentration of In and Se associated with tectonometamorphic deformation are also processes of major importance for the actual distribution of these metals throughout the whole deposit. Although minor roquesite and other In-bearing phases were recognized, it is clear that most In within the deposit is found incorporated within sphalerite and chalcopyrite. When chalcopyrite and sphalerite coexist, the In content in sphalerite (avg. 1400 ppm) is, on average, 2–3 times higher than in chalcopyrite (avg. 660 ppm). The In content in stannite (avg. 1.3 wt.%) is even higher than in sphalerite, but the overall abundance of stannite is subordinate to either sphalerite or chalcopyrite. Selenium is dispersed widely between many different ore minerals, but galena is the main Se-carrier. On average, the Se content in galena is ~50 times greater than in either chalcopyrite (avg. 610 ppm) or sphalerite (avg. 590 ppm). The copper concentrate produced at Neves-Corvo contains very significant In (+Se) content, well above economic values if the copper smelters recovered it. Moreover, the high In content of sphalerite from some Cu-Zn ores, or associated with shear structures, could possibly justify, in the future, a selective exploitation strategy for the production of an In-rich zinc concentrate.


Island Arc ◽  
2017 ◽  
Vol 26 (2) ◽  
pp. e12177 ◽  
Author(s):  
Mohd Basril Iswadi Basori ◽  
Khin Zaw ◽  
Sebastien Meffre ◽  
Ross Raymond Large ◽  
Wan Fuad Wan Hassan

2020 ◽  
Author(s):  
Melissa. O Anderson ◽  
Mark Hannington ◽  
Timothy McConachy ◽  
John Jamieson ◽  
Thor Hansteen ◽  
...  

Sign in / Sign up

Export Citation Format

Share Document