Quartz Vein Investigation, McDowell Sonoran Preserve, Scottsdale, Maricopa County, Arizona

Milky quartz veins are visible throughout all parts of Scottsdale's McDowell Sonoran Preserve (the Preserve) (see locator map below) and at many scales. Prospectors searching for heavy metal and mineral deposits have historically been attracted to milky quartz and represent the earliest researchers. Pits and tailings are occasionally found with milky quartz, however written records of mining activity are usually not found. Quartz veins and large milky quartz deposits are commonly found in Proterozoic rocks throughout Arizona. Research targeted at milky quartz has not been done in the greater Phoenix area, and as such, little is known about their formation and emplacement history. Thus, previous works in the region and by topic were researched during our study. Karlstrom and others (1991) provided valuable context to the Fraesfield site. Jahns (1953) provided great insight into pegmatites in the White Picacho District, as they relate to pegmatites at Paraiso. Several other topical references, cited throughout this report, were used to help characterize both sites. Early geologic mapping in the Fraesfield and Paraiso areas have generally noted the presence of milky quartz in association with its host rock and identified larger milky quartz bodies. Detailed geologic mapping in the area and region have provided important context and geologic setting crucial for studying quartz veins. Christensen and others (1978) conducted the first detailed map of the southern half of the McDowell Mountains. Péwé and others later mapped portions of northern Scottsdale and the Ft. McDowell area in 1983 (published 2012). Skotnicki and others mapped most portions of the Preserve area (Skotnicki, 1996; Skotnicki and others, 1997). Vance (2012) conducted detailed structural analysis and mapping of the McDowell Mountains as part of his MS thesis at Arizona State University. And most recently Steve Skotnicki has completed the most detailed and comprehensive mapping of the McDowell Mountains and its foothills (Skotnicki, 2014, unpublished).On 10 July 2015, two high resolution 3-D models of the Paraiso and Fraesfield areas were uploaded as resources to accompany the formal report.Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact azgs-info@email.arizona.edu