Abstract

The Buffalo Mountain pluton in southern Humboldt County, Nevada, is cut by an extensive dike swarm. Dikes occur mainly within the plutonic rocks, although a few extend as much as 3.5 km into the surrounding sedimentary rocks. The dikes are composed of rhyolite porphyry and quartz latite porphyry or their altered equivalents.

Dikes vary in width from a few centimeters to several hundred meters. In plan, individual dikes are sigmoidal or curving, and they branch and intersect intricately to form a very complex pattern. A statistical analysis of dike orientations shows a strong north trend and a weaker northwest trend.

The amount of dilation produced by dike injection is approximately 1,160 m in an east-west direction. Space to accommodate dilation probably was the result of a regional east-west crustal relaxation. The dike swarm apparently formed during three overlapping stages.

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