Precambrian geology and mineralizatin of the upper Rociada area, San Miguel County, New Mexico
— Michael S. Fulp

The Upper Rociada area lies approximately 32 km northwest of Las Vegas, New Mexico, in the eastern foothills of the Sangre de Cristo Mountains (Fig. 1). Access to the area is provided by state highways from Las Vegas to the village of Upper Rociada. Various prospects are reached by unimproved dirt roads generally passable with two-wheeldrive vehicles.

The area lies in a region of moderately rugged hills and ridges and broad alluvial valleys. Upland areas are covered by ponderosa pine, scrub oak and mountain mahogany, and valleys support rich grasslands. Elevations range from 2300 to 2600 m. Climate is typical for northern New Mexico, with cool, wet summers and moderately cold winters. The area is commonly snow-covered from December until March.

Previous geologic work in the Rociada district has been limited to brief accounts of the mines and prospects (Lindgren et al., 1910; Harley, 1940) and reconnaissance geologic mapping (Baltz and O'Neill, 1980). In the past 10 years, the Upper Rociada area has received considerable exploration and study by major mining companies. Because this work was confidential, results have remained unpublished until now. The following paper describes the general Precambrian geology of the Upper Rociada area, locates major prospects and describes their geology and possible genesis and proposes a geologic setting and environment of deposition along with a modern-day analogue.