In March 1982, as part of the mineral resource investigations of the area, the U.S. Geological Survey conducted a reconnaissance geochemical survey of the Chuckwalla Mountains Wilderness Study Area (WSA), Riverside County, California. The survey involved collecting 196 heavy-mineral (panned) concentrates from stream sediment (the basis for these maps and the chief basis for the interpretations), the same number of sieved stream-sediment samples, and 25 samples of fresh, altered, or mineralized rocks. A broad regional geochemical framework for mineral resource evaluation was established by sampling a few miles beyond the boundaries of the WSA to include all of the Chuckwalla and Little Chuckwalla Mountains. These geochemical maps are therefore regional maps but of sufficient detail to allow valid conclusions about geochemical anomalies in the WSA.

The geochemical data were evaluated in three phases: (1) determining enrichment above background amounts for ore-forming and pathfinder (ore-associated) elements; (2) determining the dispersion patterns of the anomalous elements; and (3) relating the dispersion patterns to geologic environments favorable to ore deposition.

This report discusses and interprets geochemical results as they are seen at the reconnaissance stage. Analytical results for all samples collected are released in a U.S. Geological Survey Open-File Report (Adrian and others, 1985). A statistical summary of the data from heavy-mineral concentrates and sieved stream sediments is shown in table 1. The analytical results for selected elements in rock samples are shown in table 2.