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distinguish between higher grade samples and lower grade samples. For Au, the second

most important variable was bladed/platy calcite (Fig. 15a), and for Ag coexisting liquid-

rich and vapor-rich fluid inclusions showed the second highest importance (Fig. 15b).

Application in Exploration for Epithermal Precious Metal Deposits

The results of the is study may be used in exploration for epithermal precious

metals deposits, both at the “grass roots” or early exploration stage to find new deposits,

and during mine development and exploration in existing deposits. The applications

described here are based on the assumption that precious metal mineralization and boiling

are genetically related. Moreover, it must be emphasized that not all hydrothermal fluids

in the epithermal environment contain Au and/or Ag – thus some systems may show

significant boiling textures but contain no Au or Ag mineralization.

The feature that is most closely related to higher Au and Ag grades in the Veta

Madre is colloform texture silica. This texture is often easily recognizable in outcrop and

hand sample, as well as during normal petrography. Lattice bladed or platy calcite and

plumose texture silica are also closely associated with high grade samples in the Veta

Madre. While lattice bladed calcite is recognizable in hand sample, it may be necessary to

examine samples in crossed polars under the microscope to reveal the plumose texture.

Fluid inclusions show only a poor correlation with higher Au and Ag grades at

Guanajuato. This lack of correlation reflects the fact that inclusions are not trapped

during precipitation of the amorphous silica phases and inclusions that are trapped during

precipitation of lattice bladed calcite are often destroyed when the calcite is replaced by



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