ALKALI-RICH ALTERATION, PICACHO MOUNTAINS, ARIZONA AND A GLOBAL COMPARISON

Abstract

Alkali-rich alteration is a characteristic process of many extensional environments in southwestern North America. The Picacho system of southern Arizona is a prime example due to the presence of potassic and calcic metasomatism that occurs within a detachment system. K-Feldspar and plagioclase staining of hand samples indicate potassic enrichment in the upper and middle plate of the Picacho Mountains as well as calcic enrichment in the middle plate. XRF data of hand samples and rock in the field suggest potassic enrichment in the upper plate of the Picacho Mountains, calcic enrichment of the middle plate of the Picacho Mountains, and potassic enrichment near the normal faults of Picacho Peak. A geologic reconstruction of the Picacho Peak area helps to better characterize the timing relationship between the alteration with respect to volcanism and faulting. The Picacho system shares many similarities with other extensional environments in Arizona, specifically its potassic metasomatism and its Cumineralization