A review of the economic geology of the U.S. was edited by Gluskoter et al. [1991] as part of the Geology of North America Series of the Geological Society of America. Chapters on the geology of specific mineral commodities, mostly written by USGS experts, covered the major metals and industrial minerals. Three large maps showed the locations of all the deposits and districts discussed in the text.
Discovery of South Australia's giant Olympic Dam deposit, comprised
of 2 billion metric tons of hydrothermal Cu-U-Au-REE
(rare-earth-element) ore within
[4]
hematitic, granitic breccias, led to a
realization that that similar mineralization may be associated with K-rich
granites in the Precambrian basement of the U. S. midcontinent. The
strategic and critical mineral resources of the midcontinental U.S. were
therefore evaluated by a group of USGS, state and industry geologists
and the results reported in a series of papers edited by Pratt and
Sims [1990] and Day and Lane [1992]. In particular, the middle
Proterozoic Pea Ridge deposit of southeast Missouri was recognized to
be an Olympic Dam type deposit. The authors summarized the available
data and developed exploration strategies for locating other Olympic
Dam type deposits in the U. S. midcontinent. Other examples of the
development of geologic frameworks and exploration strategies for
mineral deposits can be found in a series of papers edited by Scott
et al. [1993].
The USGS continued its efforts to develop concise descriptive and grade-tonnage models of mineral deposits for use in exploration, as described in a series of papers edited by Bliss [1992]. New and revised models were developed, mainly for various types of gold deposits. Worksheet templates were provided for ranking the potential of specific occurrences or prospects using the framework of models developed so far. It will be interesting to learn from the minerals industry how useful and successful the models are in conducting exploration and mining.