X hits on this document





32 / 63

noted and used to infer whether boiling occurred at the sample location at some time

during or after deposition of the original material. The number of samples containing

each of the textures described here is summarized in Figure 9. A compilation of all data

from this study, including sample numbers and locations, assay values for Au, Ag, As,

Sb, Cu, Pb and Zn, and which textures were present in each sample is included in

Appendix 1.

Fluid inclusions

Petrographic examination of Fluid Inclusion Assemblages (FIAs) can provide

evidence concerning the chemical and physical environment of formation of epithermal

precious metals deposits (Bodnar et al., 1985; Bodnar, 2003c). As noted by previous

workers (Bodnar et al., 1985; Sander and Black, 1988; Dong et al., 1995), some types of

silica from the epithermal environment contain no useful fluid inclusions. Thus, primary-

appearing fluid inclusions in colloform banded plumose, colloform banded jigsaw, jigsaw

and plumose texture silica do not record the conditions of formation because these phases

were originally precipitated as amorphous silica or fine-grained chalcedony and have

subsequently recrystallized. On the other hand, secondary fluid inclusions trapped along

healed fractures in quartz that has recrystallized from amorphous silica or fine-grained

chalcedony do record the conditions of this later fracture healing event. In each sample

containing these textures, secondary FIAs were monitored to determine if the inclusions

showed evidence of boiling.

When fluid inclusions are trapped in a single-phase fluid system, all of the

inclusions will show the same phase behavior when observed under the microscope at


Document info
Document views79
Page views79
Page last viewedFri Oct 21 15:07:08 UTC 2016