Date of Award:

5-2014

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Geology

Advisor/Chair:

James P. Evans

Co-Advisor/Chair:

James P. Evans

Abstract

This study area provides a unique opportunity to study the intersection of the Elsinore and West Salton detachment faults in southern California, effusing warm springs, and alteration products in the midst of the fault intersection. Structural mapping and compiling previous maps supply an interpretation of the fault zone geometries within the Tierra Blanca Mountains. Geochemical analysis of the crystalline basement and altered protolith help determine the effects of faulting and fluid flow in the study area. In the Tierra Blanca Mountains, the Elsinore strike-slip fault system transitions from the double-stranded Julian segment and Earthquake Valley fault in the northwest, to the single-stranded Coyote Mountain segment in the southeast. A network of cross faults striking northeast connects the fault segments. The Coyote Mountain segment encounters the inactive West Salton detachment fault in the study area. The detachment fault is a barrier to fluid flow and exhibits primarily brittle deformation, while the Coyote Mountain segment is a conduit for fluid flow along the northeastern flank of the Tierra Blanca Mountains. The damage zone of the Coyote Mountain segment reaches widths up to 500 m and contains intense fracturing and subsidiary faults striking parallel to the main trace. The tonalite protolith is bleached, stained, and altered from water-rock interactions. The most intense bleaching is at a county park, where the protolith is altered to clays and zeolites while the mineralogy of the stained regions contains iron oxides and clinochlore in addition to quartz, Ca-rich albite, and biotite preserved from the protolith. The water chemistry at Agua Caliente hot springs shows the fluid is partially equilibrated. Groundwater temperatures likely reached 75-85°C at depths up to 2.14 km before rising to the surface. Frequent seismicity in the study region is related to the spring characteristics including water level, conductivity, and temperatures. Spring temperature and conductivity displayed three behaviors during the summer 2011 logging period, attributed to seasonal changes and most likely local seismicity as well. Conductivity seems to be the property most influenced by earthquake activity in the area. Changes in fluid chemistry between sampling periods may indicate mixture with other fluid sources.

AppendixB.xlsx (1644 kB)
AppendixC.xlsx (93 kB)
AppendixD.pdf (1123 kB)
Map.pdf (57510 kB)

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