BORATE DEPOSITS OF THE FURNACE CREEK FORMATION, DEATH VALLEY

The late Tertiary borate deposits that occur within the Furnace Creek Formation, Death Valley, CA, have been mined and studied for over 100 years. These deposits, which occur within the lower half of the formation, are found along the southern edge of a NW trending structural basin that extends from Death Valley Junction near the Nevada State line to the edge of Death Valley itself.

Descriptions will be given of four of the deposits. They occur at different stratigraphic levels within the Furnace Creek sequence as measured from the underlying Artist Drive contact and from local, interformational marker beds.

The individual deposits are located adjacent to fractures that provided conduits for volcanic material and borate enriched fluids to reach the surface. Borate spring discharge, driven by the regional volcanic activity appears to account for the deposits. Subsequent tectonic activity accompanied by ground waters has modified the mineralogical character, altering the original ulexite in-situ to include a core of probertite with a significant rim of colemanite.