Origin of chalcedony nodules in rhyolite from the Peloncillo Mountains, Hidalgo County, New Mexico

Abstract

A particularly intriguing occurrence of chalcedony nodules has recently been recognized in mid-Tertiary silicic volcanic rocks near the Arizona-New Mexico border in southwestern Hidalgo County, New Mexico. The occurrence is in the vicinity of Clanton Draw and Geronimo Pass, in the Coronado National Forest. The nodules formed within a late Oligocene, high-silica rhyolite lava flow (Rhyolite of Clanton Draw) along the north margin of the Geronimo Trail cauldron (McIntyre, 1988; Erb, 1979; and Charles Bryan, personal communication, 1995).