Primary Sediment Production from Granitic Rocks in Southeastern Arizona

• Main Author: Acaba, Joseph Michael
• Other Authors: Schreiber, Joseph F., Jr.
• Language: en_US
• Published: The University of Arizona. 1992
• Subjects: Arizona; clay mineralogy; Benson Arizona; biotite; clay minerals; Cochise County Arizona; feldspar group; framework silicates; grain size; granodiorites; igneous rocks; mica group; mineral composition; montmorillonite; plutonic rocks; quartz monzonite; sheet silicates; silicates; soil profiles; southeastern Arizona; Texas Canyon; United States; vermiculite; weathering; X-ray diffraction data
• Online Access: http://hdl.handle.net/10150/231212

Isolated granitic rock bodies (granites, granodiorites, quartz monzonites) in the vicinity of Benson in southeastern Arizona were studied to trace the behavior of rock weathering. Thin sections of fresh granites were examined to characterize the original mineralogy which consisted mainly of quartz, feldspars, and micas. The weathering products show up on the granites as grus and soil profiles as well as down slope in the basin deposits. X -ray diffraction studies of the < 2 micrometers fraction of the weathering products proved illite, smectite, illite-smectite mixed layer, and kaolinite to be the dominant clays; quartz and feldspar also persisted into this size fraction. Silt sized material produced similar results. The quartz monzonite of Texas Canyon afforded a special study of the initial weathering stages of feldspars and micas. In the < 2 micrometers fraction obtained from granitic material placed in an ultra sonic bath, the feldspars weathered to a Na-montmorillinite while biotite weathered to vermiculite.