Preliminary Studies of Geothermal Resources-Northern Great Salt Lake Region, Utah

摘要

The northeastern Basin and Range Province surrounding Great Salt Lake of northern Utah has relatively high heat flow (＞ 100 mW/m~2) and other characteristics suggesting geothermal resource potential. Deep Neogene sedimentary basins, observed in wildcat oil/gas wells and geophysical surveys, underlying the main north and south arms of Great Salt Lake are separated into two troughs that include Gunnison Bay (north basin/trough) and Gilbert Bay (south basin/trough). Gravity data also suggests similar deep Neogene basins underlying Bear River Bay and the northern Wasatch Front, although deep drilling data are lacking in these areas. Beneath Gunnison Bay, more than 3 km of low-thermal-conductivity sediments and volcaniclastic deposits overlie Paleozoic and Precambrian carbonate, silicic, and metamorphic stratigraphic sequences that are known to have primary and secondary permeability elsewhere in the Great Basin. The thick basin-fill deposits within a region of high heat flow provide conditions for high (＞ 200°C) temperatures at depths between 3 and 4 km below the basin fill and within the Paleozoic and Precambrian rocks. Young volcanic rocks in the region include basalts, ranging in age between 2.2 Ma and about 28 ka, and rhyolite dated at about 2.1 Ma. Quaternary faults within and around Great Salt Lake, currently under investigation, likely contribute to fracturing within basement rock units, helping enhance permeability. The major thermal springs of the region all issue from fractured Paleozoic carbonate or Precambrian metamorphic rocks, equivalent to units projected beneath the thick basin-fill deposits in this region. Future development of geothermal resources in deep basins beneath Great Salt Lake may be challenging from technical, economic, and environmental perspectives, however, similar geologic conditions may exist beneath Bear River Bay and the northern Wasatch Front regions where development potential may be more attractive.