Gravity and aeromagnetic gradients within the Yukon-Tanana upland, Big Delta quadrangle, east-central Alaska: Geological Society of America Abstracts with Programs, v

• Main Authors: R. W. Saltus, W. C. Day
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2005
• Subjects: Quadrangle; Quadrangle The; Yukon; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.386.3666; http://pubs.usgs.gov/of/2006/1391/pdf/OF06-1391.pdf

R.W. Saltus making a gravity measurement during the smoky 2004 field season The Yukon-Tanana Upland is a complex composite assemblage of variably metamorphosed crystalline rocks with strong North American affinities. At the broadest scale, the Upland has a relatively neutral magnetic character. More detailed examination, however, reveals a fundamental northeast-southwesttrending magnetic gradient, representing a 20-nT step (as measured at a flight height of 300 m) with higher values to the northwest, that extends from the Denali fault to the Tintina fault and bisects the Upland. This newly recognized geophysical gradient is parallel to, but about 100 km east of, the Shaw Creek fault. The Shaw Creek fault is mapped as a major left-lateral, strike-slip fault, but does not coincide with a geophysical boundary. A gravity gradient coincides loosely with the southwestern half of the magnetic gradient. This gravity gradient is the eastern boundary of a 30-mGal residual gravity high that occupies much of the western and central portions of the Big Delta quadrangle. The adjacent lower gravity values to the east correlate, at least in part, with mapped post-metamorphic granitic rocks. Ground-based gravity and physical property measurements were made in the southeastern-most section of the Big Delta quadrangle in 2004 to investigate these geophysical features. Preliminary geophysical models suggest that the magnetic boundary is deeper and more fundamental than the gravity boundary. The two geophysical boundaries coincide in and around the Tibbs Creek region, an area of interest to mineral exploration. A newly mapped tectonic zone (the Black Mountain tectonic zone of O’Neill and others, 2005) correlates with the coincident geophysical boundaries. Delta Junction quadrangle