Dave Maher says we can find new porphyry copper systems in southeast Arizona by exploring for the roots of Laramide igneous systems (island arcs) and working our way up the geologic section. Dave presented the results of his recent PhD dissertation (UA, Dec 2007) at the Arizona Geological Society monthly dinner meeting last night. The current method he says, focuses on identifying silicic-sericite alteration at the top of a deposit and drilling down in hopes of finding mineralization.
His research led him to conclude that "multiple deposits, prospects, and other hydrothermal features in the Globe-Miami, Superior and Ray districts are dissected portions of originally fewer, larger hydrothermal centers" that have been rotated along large listric normal faults so that the geologic cross sections of the igneous complexes are now laid out in map view on the surface. By reconstructing the Laramide and Tertiary structural offsets, he thinks he can identify missing pieces of the original system that have been faulted out and project where they should be.
We here at the Survey are talking with Dave about publishing parts of his work so it gets wider circulation.
[right: Dave records paleo-up direction in Hackberry Wash, central Tortilla Mountains, AZ]
Rhyolite Porphyry from Majuba Hill II
2 hours ago