"INDUCED POLARIZATION DATA AT ... - University of Utah

CHU
pore solution. This value is thought to reflect the contribution of
clays to the IP effect. Qv can be determined independently from the
ratio of cation exchange capacity of the core sample (meq) to the pore
volume of the sample (ml). The cation exchange capacity, CEC, in meq
per 100gm of the rock sample, was measured by atomic absorption
spectrometry. A summary of the measurements is given in Table 1.
Both Qv and porosity depend upon the volume of interconnected pore
passages within the rock. For non-expanding core samples, the pore
volume was taken to be the volume of water absorbed by the rock after
the two to three month soaking period. For samples which expanded [(c)
and (f) of Table 1J, the pore volume was assumed to be the difference
between the volume of water absorbed and the change in volume of the
core sample. This latter procedure may have resulted in inflated QV
values; but if the former procedure had been followed, the QV values for
the expanded samples (c) and (f) would have been 1.34 equiv/l and 2.22
equiv/l respectively, which are still larger than the Qv values for the
non-expanded samples.
The porosity (effective porosity) was determined from the ratio of
the pore volume of the sample to the volume of the rock when wet.
Data Interpretation
Ten samples were prepared. Two of the samples were slightly
hydrothermally altered, while another two were inadequately
encapsulated. The remaining six samples were highly altered, and the
data for these are shown in Table 1 and Figures 2a-2f.
Effects of temperature. - The resistivity of the altered rocks is