Elemental Data
The relative abundances of seventeen elements were determined using a Cameca SX-51 electron microprobe, with a typical analytical accuracy of 1 - 5 % for major and minor elements. The elements under consideration in this study are the transition metals Cu, Co, Cr, Fe, Mn, Mo, Ni, Ti, Zn, as well as Al, Ba, Ca, Mg, Na, O, S, and Si. Only major elements and elements of direct importance to mass spectrometry are reported herein.
Results suggest major element variation in sphalerites between the inner conduit and outer interface. Sphalerites measured from the inner conduit to the outer interface range in Fe composition from 1.1 to 13.4%, over 1001 separate point analyses. Zinc in these same sphalerites varies between 48.5 and 65.5% while sulfur exhibits a much narrower range between 30.7 and 36.3%. This variation in Fe is interesting in light of the fact that Fe in sphalerite has been used to ascertain temperature of precipitation [Hannington et al. (1995)]. A plot of % Fe in sphalerites across the cross-section generally indicates that temperatures of precipitation are not simply distributed from a hot inner conduit to a cool outer wall but that the section includes reworked sections and fractures that carried relatively hot fluid into cool portions of the chimney.
Diffusion of iron into sphalerites does not appear to be an issue in the majority of grains analyzed. A plot of relative % iron in sphalerites of different sizes shows that edge processes that remove iron, such as reworking and weathering, are dominant.
In contrast, chalcopyrite throughout the sample is fairly homogeneous, exhibiting average Fe and Cu compositions of 30.53 ± 0.02% and 33.4 ± 0.1%, respectively. Those elements which interfere isobarically with Fe (Ni, Cr) were not found in any appreciable amounts (<100 ppm) with this technique.
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