Mid-Silurian back-arc spreading at the northeastern margin of Gondwana: The Dapingzhang dacite-hosted massive sulfide deposit, Lancangjiang zone, southwestern Yunnan, China

2013 ◽  
Vol 24 (2) ◽  
pp. 648-663 ◽  
Author(s):  
Bernd Lehmann ◽  
Xinfu Zhao ◽  
Meifu Zhou ◽  
Andao Du ◽  
Jingwen Mao ◽  
...  
1998 ◽  
Vol 35 (6) ◽  
pp. 620-636 ◽  
Author(s):  
Pierre Doucet ◽  
Wulf Mueller ◽  
Francis Chartrand

The Coniagas Mine in the northeastern Abitibi greenstone belt is a small, isolated Archean, volcanic-hosted, massive sulfide deposit rich in Zn-Pb-Ag. The Main lens, which is part of four massive sulfide lenses, is restricted to a 40 m thick massive felsic lapilli tuff unit of the 280 m thick sequence. The massive sulfides, a product of subsurface replacement, have features common to both Mattabi- and Noranda-type deposits. The Coniagas Mine sequence represents part of a small subaqueous volcanic edifice that probably evolved close to an arc or back-arc spreading ridge. A distinct alteration halo of chlorite + sericite ± epidote ± spessartine garnet in the immediate footwall and a hanging wall alteration assemblage of quartz + sericite ± epidote ± chlorite characterize the deposit. The sphalerite + pyrite + galena ± chalcopyrite sulfide mineral assemblage in the Main lens differs significantly from the pyrite + chalcopyrite + sphalerite + pyrrhotite ± galena assemblage in the stringer zone. Chlorite compositions are Fe rich close to the mineralized zone, with an Fe/(Fe + Mg) ratio of 0.38-0.48 in the hanging wall and 0.65-0.70 below the ore. Delicate sulfide textures including colloform pyrite and concentric sphalerite are consistent with a low temperature of formation, whereas higher temperatures are inferred for the stockwork zone. Electron probe microanalysis of sphalerite supports inferred hydrothermal fluid temperatures. The low Fe contents (6.7-10.8 mol% FeS) in sphalerite associated with colloform pyrite of the Main lens contrast with the elevated Fe content (12.7-14.1 mol% FeS) in sphalerite from the stockwork.


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.


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

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