3D SEISMIC CHARACTERIZATION OF THE BORAX LAKE HYDROTHERMAL SYSTEM IN THE ALVORD DESERT, SOUTHEASTERN OREGON

As part of an interdisciplinary project aiming to study the link between the physical characteristics of hydrothermal systems and biota that occupy those systems, we are conducting a detailed geophysical characterization of an active hydrothermal system. The Borax Lake Hydrothermal System (BLHS), consisting of Borax Lake and the surrounding hot springs, is located near the center of the Alvord Basin in southeastern Oregon. As a result of Basin and Range extension, the Alvord Basin is a north-south trending graben bounded by the Steens Mountains to the west and the Trout Creek Mountains to the east. We are using several geophysical techniques to generate both basin-wide and high-resolution local characterizations of the Alvord Basin and the BLHS. In particular, we have completed a high-resolution 3D seismic reflection survey (~10 – 300 m depth) of the BLHS. We acquired the 3D survey using a 7.62x39 mm SKS rifle and 240 channel recording system. The 3D patch covers approximately 90,000 sq. m with a maximum inline offset aperture of 225 m, crossline aperture of 75 m, and 360 degree azimuthal coverage. We designed the survey to span several active hydrothermal vents, including an approximately 100 m stepover in the trend of the hot springs.

After preliminary processing, brute stacks of the 3D seismic data show good reflections up to 300 ms. The initial interpretation of features seen in the stack include: a mid-basin basement high bounded by normal faults dipping to the east and west, a near-surface disturbance aligned with the hot springs, and significant near surface velocity anomalies throughout the survey area. After more extensive processing, we hope to find a structural connection between the subsurface geology and the geometry of the hot springs.