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room temperature. However, if the inclusions are trapped in a boiling or immiscible fluid

system, some inclusions will trap the liquid phase, some will trap the vapor, and some

will trap mixtures of the two phases (Bodnar et al., 1985). In each FIA identified as

described above, the phase relations of individual inclusions were examined to determine

if all the inclusions had the same liquid-to-vapor ratio, or if the inclusions in the FIA

showed variable ratios (Fig. 6). Variable liquid-to-vapor ratios may also be produced by

necking down of the inclusions after a vapor bubble has nucleated in the inclusions. In

most cases, it is not possible to distinguish between those FIAs with variable liquid-to-

vapor ratios produced by boiling and those produced by necking down. However, we

have assumed that if the FIA includes vapor-rich inclusions and liquid-rich inclusions

with variable liquid-to-vapor ratios, as well as all-liquid inclusions, that the inclusion

phase ratios are the result of necking down or possibly recrystallization of amorphous

silica or chalcedony (Sander and Black, 1988), and not the result of boiling (see

Goldstein and Reynolds, 1994).

As noted previously, microthermometric analysis was not included in this study.

However, because samples were collected over a significant vertical as well as horizontal

distance, it was deemed worthwhile to determine if any large gradients in

homogenization temperatures are obvious within the study area. Thus, the temperature of

homogenization of the inclusions was estimated based on the room temperature phase

ratios of the liquid-rich inclusions in the FIAs (Bodnar, 2003c). No obvious

homogenization temperature gradients were suggested by the fluid inclusion phase

relations, and this is consistent with previous studies by Buchanan (1979) and Mango



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