HYDRO26604 - Laserfiche WebLink

Home Browse Search

Many of the samples aze either poorly located in the stratigraphic section, or are not located at all. Also, the mineralogical composition of the stratigraphic section, which is critical to any geochemical interpretation that requires mixing or mineral dissolution, is not provided. The temperature information, which is abstracted in Dr. Mayo's February 20 memo, lacks detail on the B-East Mains fault -- the fault from which the hot waters appear to have been recorded. Such records are important as they might very well negate the conclusions of the memo. Without the above information, which is fundamental to an open evaluation of the results, conclusions by both the Division and the Operator must rely on potentially credulous assumptions. One must assume that they data are of high quality; adequate collection procedures must be presumed; and some sample locations must be assumed or interpreted. Obviously, in the absence of fundamental documentation, conclusions in the present report should be regarded as very preliminary. If the fault waters are to be shown to be the seep water sources, there should be a clear explanation of chemical processes that caused the waters to have or to develop different compositions. Interaction with certain minerals, precipitation of certain minerals, and/or mixing with meteoric or other unsampled waters are required to explain the compositional differences. However, given the absence of fundamental background information described above and some incomplete analyses, it should not be surprising if multiple interpretations appear, or if unique conclusions are not drawn. Even in cases where samples have been collected and analyzed tinder ideal conditions, such as some USGS studies of basin brines or regional formation waters, unique solutions with chemically balanced equations to water/rock interaction problems seem difficult to attain. That is, there nearly always seems to be some residual error, some excess concentration or not enough of some element to totally explain the geochemistry. INTERPRETATIONS In the present case, there appears to be a relatively simple, straightforward solution that relates a generalized view of the geochemistry of the fault waters closely with the seep water. Moreover, there is a close geochemical similarity between the Edwards Portal seep water and the Lone Pine Seal water that was not examined well in the West Elk reports. The Lone Pine seal water -ies more or less on a trajectory, in Piper diagram space, between the fault waters and the seep water, with very minor deviation being explained by higher Na and K in the Lone Pine Seal and higher sulfate in the seep, a trajectory that is compatible with a mixing trend between the two end-members. Together, these suggest that the Lone Pine seal waters describe an intermediate composition between the faults and the seep, with minor deviations to be explained. The following sections describe a plausible, simple interpretation of the data for the West Elk situation and shows how each set of geochemical infotmation supports this interpretation.