We highlight the late date of the move to gold and the variety of transition strategies. In this paper we chart the geography of the gold standard. The results of this study complement a growing body of evidence to indicate that the Re-Os chronometer in molybdenite can be an accurate and robust tool for establishing timing relations in ore systems. These age relationships indicate that the Re-Os molybdenite method records the timing of sulfide and gold mineralization, whereas much younger 40Ar/39Ar dates are affected by post-ore thermal events, slow cooling, and/or systemic analytical effects. At the Pogo deposit, Re-Os molybdenite dates are also much older than 40Ar/39Ar dates from hydrothermal mica, but dissimilar to the age of local granites. However, 40Ar/39Ar dates from hydrothermal and igneous mica are considerably. At Fort Knox, the Re-Os molybdenite date is identical to the U-Pb zircon age for the host intrusion, supporting an intrusive-related origin for the deposit. New Re-Os molybdenite dates from two lode gold deposits of the Tintina Gold Belt, Alaska, provide direct timing constraints for sulfide and gold mineralization. In other cases, several decades may be required before a balance between force and resistance is reached. Landscape stability, which depends on the relationship of the distribution of energy to the material landscape, has been reestablished in some basins in the Central City area. Threshold values of erosive force were surpassed in response to changes in general basin vegetation cover, valley floor vegetation, channel slope, width, and roughness. The spatial distribution of energy and force has been substantially altered by human activities.
before settlement to 8 dynes during the mining period. Arroyos and gullies developed on many valley floors as responses to increases in channel tractive force from 1 dyne.
Central City is typical of mountain mining towns with clearly defined periods of discovery and settlement, bonanza, investment, development, and, finally, decline. Gold and silver mining activities in the Central City District, Colorado, caused severe disruption of the landscape.
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