Abstract
The Greens Creek polymetallic massive sulphide deposit is hosted in a typical polyphase deformed lower greenschist facies orogenic setting. The structure of the host rocks is well constrained, exhibiting a series of three superimposed ductile deformations followed by two brittle episodes. The ore is found both in fold hinges where early-formed depositional features are preserved and in fold limbs where primary features are typically strongly modified or obliterated. Samples from both settings have been investigated using electron backscatter diffraction (EBSD) coupled with forescatter orientation contrast (OC) imaging in order to observe the effects of deformation and lower greenschist facies metamorphism on pyrite. Results suggest that colloform pyrite may preserve information relevant to palaeoenvironment, that apparently simple textures are generally more complex, and that pyrite can deform plastically by dislocation glide and creep processes at lower temperatures and/or strain rates than generally accepted. This analysis indicates that EBSD and OC imaging provide powerful tools for observing textural relationships in pyrite that are not shown by more traditional methods. They should become routine tools for pyrite texture analysis.
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Acknowledgements
We thank Kees Veldtkamp for assistance with SEM work, and Dave Prior for assistance with Channel+ and its related software programs at Liverpool University. We would like to thank Kennecott Greens Creek Mining Company for letting us study the samples and publish the results and Colorado School of Mines for the travel grant that enabled Katja Freitag to visit Liverpool. Finally, the manuscript has benefited from careful reviews by Prof. Heinrich Siemes and Dr. Karen Kelley.
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Freitag, K., Boyle, A.P., Nelson, E. et al. The use of electron backscatter diffraction and orientation contrast imaging as tools for sulphide textural studies: example from the Greens Creek deposit (Alaska). Miner Deposita 39, 103–113 (2004). https://doi.org/10.1007/s00126-003-0386-8
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DOI: https://doi.org/10.1007/s00126-003-0386-8