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APPLICATION OF FLUID INCLUSIONS AND MINERAL TEXTURES IN EXPLORATION FOR EPITHERMAL PRECIOUS METALS DEPOSITS Daniel Moncada ABSTRACT Fluid inclusion and mineralogical features indicative of boiling have been

characterized in 855 samples from epithermal precious metals deposits along the Veta

Madre at Guanajuato, Mexico. Features associated with boiling that have been identified

at Guanajuato include colloform texture silica, plumose texture silica, moss texture

silica, ghost-sphere texture silica, lattice-bladed calcite, lattice-bladed calcite replaced by

quartz and pseudo-acicular quartz after calcite and coexisting liquid-rich and vapor-rich

fluid inclusions. Most samples were assayed for Au, Ag, Cu, Pb, Zn, As and Sb, and were

divided into high-grade and low-grade samples based on the gold and silver

concentrations. For silver, the cutoff for high grade was 100 ppm Ag, and for gold the

cutoff was 1 ppm Au. The feature that is most closely associated with high grades of both

gold and silver is colloform texture silica, and this feature also shows the largest

difference in grade between the presence or absence of that feature (178.8 ppm Ag versus

17.2 ppm Ag, and 1.1 ppm Au versus 0.2 ppm Au). For both Ag and Au, there is no

significant difference in average grade as a function of whether or not coexisting liquid-

rich and vapor-rich fluid inclusions are present.

The textural and fluid inclusion data obtained in this study were analyzed using

the binary classifier within SPSS Clementine. The models that correctly predicted high

versus low grade samples most consistently (˜70-75% of the tests) for both Ag and Au

were the neural network, the C5 decision tree and Quest decision tree models. For both

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