Paper No. 157-3
Presentation Time: 9:00 AM-6:00 PM
PETROLOGICAL AND GEOCHEMICAL ANALYSIS: MAPPING OF MITER FLOWS IN ICE SPRINGS VOLCANIC FIELD, BLACK ROCK DESERT, UTAH
The Ice Springs Volcanic Field is the easternmost of the seven areas mapped by Condie and Barsky (1972) in the Black Rock Desert, Utah. The Black Rock Desert has undergone volcanism that dominated the Great Basin during the Paleogene, which primarily produced basaltic and rhyolitic magma suites, including calc-alkali basalts that grade eastward into an alkali basalt suite (Christiansen and Lipman, 1972). Ice Springs eruptions are post-Lake Bonneville in age; based on a radiocarbon date of roots from under the most recent lava flow, the last eruption occurred approximately 660 +/- 170 years ago (Valestero et al. 1972). Within the area are four intact cinder cones: Crescent, Miter, Pocket, and Terrace. Previous studies, including Gilbert (1890), have concluded that at least nine craters populated the area but have been eroded with time. Flow boundaries from the multiple cinder cones and lava flows are unclear and current maps do not distinguish between individual flows. This study is focused on the distribution of the Miter flows to determine how the rheology dictated emplacement. A flow boundary was determined based on characteristics of extent of vegetative cover, morphology, and vesicularity. The Miter flow represents the second oldest eruption in the area extends approximately .70 miles northwest and 1 mile west of the Miter cone. Gilbert (1890) and Hoover (1974) suggested that the Miter flows began from a northern breach in the crater and created a channel that was directed to the north and northwest. A shift of direction of the flow to the west and southwest was created by a second breach in the crater’s western edge. Observations by Hoover (1974) and Gilbert (1890) detail that a channel west of Miter was formed by the western breach in the rim and overlays the lava flow emplaced primarily from earlier episodes of activity. Based on Hoover (1974), the southern wall of the channel marks the boundary between the Miter and Terrace Flows. Preliminary mapping generally agrees with previous workers, however, some of the flow boundaries remain unclear. A total of 18 samples were collected from the Miter and surrounding flows. Patterns in bulk rock major and trace element chemistry obtained by X-ray fluorescence spectrometry (XRF) may provide some clarification of the flow boundaries from different parts of the study area.