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M.A. Chaffee

Publications and source records attributed to M.A. Chaffee.

77 records · Page 5Linked to original sources

The zonal distribution of selected elements above the Kalamazoo porphyry copper deposit, San Manuel district, Pinal County, Arizona

There may be many as-yet-undiscovered porphyry copper deposits that exist as blind deposits deep within exposed rock bodies. The Kalamazoo porphyry copper-molybdenum deposit is a blind deposit present at depths up to at least 1,000 m (about 3,200 ft) that contains zoning features common to many of the known porphyry copper deposits found in western North and South America. As the preliminary phase in a geochemical study of the Kalamazoo deposit, whole-rock samples of core and cuttings from two drill holes have been analyzed for 60 different elements. Each hole represents a different major rock unit and each has penetrated completely through all the existing alteration zones and the ore zone. Plots of concentration vs. depth for 17 selected elements show distinct high- or low-concentration zones that are spatially related to the ore zone. For most of the ore-related elements no significant correlation with the two lithologies is apparent. The spatial distribution and abundance of elements such as Co, Cu, S, Se, Mn, Tl, Rb, Zn, B, and Li may be useful in determining the direction for exploration to proceed to locate a blind deposit. Trace element studies should be valuable in evaluating areas containing extensive outcrops of rocks with disseminated pyrite. Elemental zoning should be at least as useful as alteration-mineralization zoning for evaluating rock bodies thought to contain blind deposits similar to the Kalamazoo deposit.

Journal of Geochemical Exploration↗

Stratigraphic relations of the Bolsa Quartzite, Vekol Mountains, Pinal County, Arizona

A quartzite unit occurring between the rocks of the Precambrian Apache Group and those of the Cambrian Abrigo Formation in the Vekol Mountains, Final County, Ariz., has been called both Troy Quartzite (Precambrian) and Bolsa(?) Quartzite (Cambrian). Regional and local geologic relationships indicate that this intervening unit is definitely the Bolsa Quartzite. The Bolsa ranges in thickness from at least 200 ft at several localities in the Vekol Mountains to 0 ft over a positive area underlain by Precambrian diabase which has intruded the Apache Group. Previous observations that the diabase intruded the quartzite unit (thereby making this quartzite unit the Troy Quartzite) have been reinterpreted; all nonfaulted exposures of the basal contact of the quartzite unit show sedimentary relationships. No evidence was found to suggest that the Troy Quartzite was ever deposited in the Vekol Mountains.

Arizona↗