ISSN:
1432-1866
Source:
Springer Online Journal Archives 1860-2000
Topics:
Geosciences
Notes:
Abstract Fifty wolframite crystals from San Cristobal (Peru) were analysed with the electron microprobe for Fe, Mn, and W. Detailed studies of several samples reveal complex compositional zoning within individual crystals. One sample contains two crystals with contrasting zoning: one crystal has a high-Fe core and an Fe-poor rim, whereas the other has an Fe-poor core and a high-Fe rim. This suggests that these two crystals formed at different moments and that the wolframite composition did not change monotonically with time. The full range of wolframite compositions measured is from 28 to 97 mol% ferberite (FeWO4). Although a range of 59 mol% was determined for one sample, the average range for all fifty samples is 10 mol%. Samples with average compositions in the range of 84–92 mol% ferberite have relatively small compositional variations, whereas those with average compositions in the range of 61–84 mol% are quite variable. On a vertical longitudinal section of the Main Vein of San Cristobal it appears that the low ferberite values correspond spatially with high tungsten grades. The iron content of the wolframite goes through a minimum across its depositional interval. This may be due to a change in the Fe/Mn ratio of the mineralizing solution with either distance or time.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00206662
