Geologic Map of the Central Mineral Mountains (GIS of 1980 Map), Beaver County, Utah (MP 17-2dm)

The Mineral Mountains are located in Beaver and Millard Counties,
southwestern Utah. The range is a horst located in the transition zone
between the Basin and Range and Colorado Plateau (Stokes, 1977) geologic
provinces. A multiple-phase Tertiary pluton forms most of the range, with
Paleozoic rocks exposed on the north and south and Precambrian metamorphic
rocks on the west in the Roosevelt Hot S~rings KGRA (Known Geothermal Resource
Area). Precambrian banded gneiss and Cambrian carbonate rocks have been
intruded by foliated granodioritic to monz~nitic rocks of uncertain age.
The Tertiary pluton consists of six major phases of quartz monzonitic to
leucocratic granitic rocks, two diorite stocks, and several more mafic units
that form dikes.
During uplift of the mountain block, overlying rocks and the upper part
of the pluton were partially removed by denudation faulting to the west. The
interplay of these low-angle faults and younger northerly trending Basin and
Range faults is responsible for the structural control of the Roosevelt Hot
Springs geothermal system. The structural complexity of the Roosevelt Hot
Springs KGRA is unique within the range, although the same tectonic style
continues throughout the range.
During the Quaternary, rhyolite volcanism was active in the central part
of the range and basaltic volcanism occurred in the northern portion of the
map area. The heat source for the geothermal system is probably related to
the Quaternary rhyolite volcanic activity.

This study did not document any additional evidence of recent geothermal
activity. It has, however, documented several areas of young basaltic
volcanism in the northern portion of the Mineral Mountains. In addition, a
structural framework has been developed which will be of use to geothermal
explorationists working in the area.