GEOLOGICAL ANALYSIS OF APLITE DIKES, TEXAS CANYON STOCK, ARIZONA

Abstract

An area of the Texas Canyon stock near Dragoon, Arizona, containing exposures of aplite dikes (thin, resistant, fine crystalline intrusions) (Wells and Bishop, 1954), was scouted and geologically mapped in order to find the extent and character of a dike swarm located in that area. A sample of the aplite material was collected to be studied with geochronology techniques to determine its age, to serve as a guide to interpret the timing of the development of the fracture pattern in the granite, with the orientations of the aplite dikes studied in mind. The dikes in the swarm were found to dip steeply (70⁰ to 90⁰); the overwhelming majority had strikes roughly east-northeast, which is the same direction the swarm itself is aligned. The swarm was found to be approximately 580 meters in north-south length and 76 meters in east-west width, with an average dike thickness of 5-15 centimeters. The results of geochronology on the aplite revealed that the date of its intrusion (as well as the fracture pattern in the granite filled by aplite) is approximately 56.3 million years ago. This knowledge will be useful in the understanding of other plutons in the region that show the same patterns.