An interpretation of the 1996 aeromagnetic data for the Santa Cruz basin, Tumacacori Mountains, Santa Rita Mountains, and Patagonia Mountains, south-central Arizona

Abstract

High resolution aeromagnetic survey data flown at 250 m above the terrain and 250 m line spacing over the Santa Cruz Valley and the surrounding Tumacacori, Patagonia, and Santa Rita Mountains has been interpreted by correlation of the magnetic anomaly field and various derivative maps with geologic maps. Measurements of in-situ magnetic properties of several of the map units determined whether or not mapped lithologies were responsible for observed anomalies. Correlation of the magnetic anomaly field with mapped geology shows that numerous map units of volcanic and intrusive rocks from Jurassic Middle Tertiary in age are reversely polarized, some of which have not been previously reported. Trends derived from the magnetic anomaly data correlate closely with structures from major tectonic events in the geologic history of the area including Triassic-Jurassic crustal accretion and magmatism, Laramide magmatism and tectonism, northeast-southwest Mid-Tertiary extension, and east-west Basin and Range extension. Application of two textural measures to the magnetic anomaly data, number of peaks and troughs per km (a measure of roughness) and Euclidean length per km (a measure of amplitude), delineated areas of consistent magnetic anomaly texture. These measures were successful at the delineation of areas of consistent magnetic lithology both on the surface and in the subsurface beneath basin fill. Several areas of basement prospective for mineral resources beneath basin fill were identified.

Bedrock morphology and structure, upper Santa Cruz Basin, south-central Arizona, with transient electromagnetic survey data

“…It should be noted that there are no exposed relationships between the Grosvenor Hills volcanics and map unit Jb, but that does not preclude this relationship from occurring. Gettings, 2002, indicates that flows of the Salero Formation can have both normal and reversed remanent magnetism. To the west of the Mt.…”

Detailed interpretation of aeromagnetic data from the Patagonia Mountains area, southeastern Arizona

“…Caution must be used when modeling geologic anomalies in the Earth's magnetic field in areas that include rocks with a natural remanent magnetism with a field direction different from the direction of the Earth's current magnetic field. Interpretations based on transformations often performed on aeromagnetic survey data, including reduction to the pole, various forms of filtering, and some depth-to-source estimation techniques are not valid for magnetic fields with natural remanent magnetization directions other than that of the inducing field (Gettings, 2002). Additionally, Saltus and Blakely (2011) argued that geophysical interpretations become more constrained when information such as geological mapping, rock physical property measurements, and results from other geophysical methods are included in a geophysical interpretation.…”

“…1) is a geologically diverse region with intrusive, extrusive, and sedimentary rocks and a complicated geologic history. In 1996, the USGS contracted to acquire an aeromagnetic map over this region and the adjacent Santa Cruz Valley and Santa Rita Mountains (U.S. Geological Survey, 2000;Gettings, 2002). These aeromagnetic data have been used by several studies to make interpretations of the Patagonia Mountains and surrounding areas including Gettings (2002), Phillips (2002), Rystrom and others (2002), and Berger and others (2003).…”

Structure of the Tucson Basin, Arizona from gravity and aeromagnetic data

“…Susceptibility measurements of dozens of igneous rocks (Gettings, 2002) suggest a range within which to restrict the modeling. Table 1 shows susceptibilities of some of the rocks in the study area.…”