Gravity and ground magnetic surveys of the Thermo Hot Springs KGRA region, Beaver County, Utah
During the period June to September 1976, gravity and ground magnetic surveys were made in the Thermo Hot Springs KGRA region which is located southwest of the town of Milford, Beaver County, Utah. The regional surveys comprised 273 new gravity and magnetic stations and incorporated 104 previous gravity stations over an area of approximately 620 km{sup 2}. The detailed surveys consisted of 9 east-west profiles in the immediate vicinity of the Thermo Hot Springs KGRA. The gravity data were reduced and are presented as terrain-corrected Bouguer gravity anomaly maps. Terrain corrections were made to a distance of 18.8 km. The regional gravity map shows the following features: (1) a large north-south trend with total relief of 5 mgal extending through the central portion of the study area; (2) an east-west trend with relief of about 7-8 mgal south of the Star Range and Shauntie Hills; (3) a north-south trend with 5 mgal relief east of Blue Mountain; and (4) a broad low of approximately 5 mgal closure southwest of the Shauntie Hills. The trends are probably caused by major faults and the gravity low is probably caused by the southern end of the Wah Wah Valley graben. The detailed gravity map indicates two possible east-west trending faults intersecting a major north-south trending fault in the immediate vicinity of the Thermo Hot Springs. The location of the hot springs appears to be fault controlled. To facilitate interpretation of the gravity data, the following processing and modeling techniques were used: (1) high-pass frequency filtering; (2) polynomial fitting; (3) second derivative; (4) strike filtering; (5) two-dimensional modeling; and (6) three-dimensional modeling. These techniques proved helpful as they more clearly delineated features of interest. The residual maps outlined an elongate north-south graben that extends through the survey area. The strike-filtered maps emphasize the major north-south and east-west faults of the region. Modeling provided reasonable depth estimates for bedrock in the vicinity of the hot springs and supported the structural interpretation for the hot springs area. The magnetic data are presented as total magnetic intensity anomaly maps for both the regional and detailed surveys. The regional map delineates a magnetic high with 600-gammas closure that corresponds to a Tertiary quartz monzonite intrusive in the northeast part of the survey area. An east-west trend with about 300-gammas relief is delineated south of the Shauntie Hills and Star Range and possibly corresponds to an east-west fault. The detailed magnetic map outlines an anomalous low with nearly 100-gammas closure associated with the Thermo Hot Springs. This magnetic low may reflect an alteration zone which is structurally controlled. The following processing and modeling techniques were applied to aid interpretation of the magnetic data: (1) low-pass frequency filtering; (2) strike-filtering; (3) pseudogravity; (4) two and one-half dimensional modeling; and (5) three-dimensional modeling. The low-pass filtering clearly delineates the intrusive and the east-west trend south of the Star Range. The strike-filtering outlines north-south and east-west trends which correlate with faults implied by gravity data. The pseudogravity map indicates that the magnetic and gravity anomalies are not caused by the same bodies. The two and one-half dimensional modeling in the hot springs area provides a possible model for an alteration zone which appears to be structurally controlled. The three-dimensional model of the Tertiary quartz monzonite intrusive indicates a relatively shallow, slightly elongate intrusion that continues to a depth of at least 1 km.
- Research Organization:
- Utah Univ., Salt Lake City (USA). Department of Geology and Geophysics
- Sponsoring Organization:
- National Science Foundation, Arlington, VA (USA)
- OSTI ID:
- 895548
- Report Number(s):
- UU-77-8-Z; TRN: US200703%%136
- Country of Publication:
- United States
- Language:
- English
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