Petrology of Proterozoic to Tertiary Rocks in the Southern Burro Mountains, NM: Insights into Mazatzal to Basin and Range Magmatism and Tectonics

Petrology of Proterozoic to Tertiary Rocks in the Southern Burro Mountains, NM: Insights into Mazatzal to Basin and Range Magmatism and Tectonics

Stephen F Austin State University, Baker Patillo Student Center, Twilight and Grand Ballrooms

Analysis of thin sections from the Wind Mountain quadrangle, Burro Mountains, NM, near the Tyrone copper mine, reveals a complex geologic history. Rock samples collected in the study area were cut using a rock saw and thin sections were prepared and analyzed to determine mineral content and fabric patterns. The oldest rocks in the study area are strongly metamorphosed and locally mylonitized Proterozoic quartzofeldspathic gneisses and amphibolites of Mazatzal affinity. Mineralogical indications of shearing correlate with shear zones observed during field mapping in the area. Another set of samples are of younger Proterozoic granites and metagranites that intruded the country rock. This suite of granites is probably part of the 1.5 byo Burro Mountain granite. In addition to the ductile rocks, several thin sections were of mineralized fault breccia with abundant hydrothermal calcite and, in some samples, gozzan zone iron. Another group of thin sections were of unmetamorphosed mafic dikes rocks composed mostly of pyroxene (augite) and plagioclase. The youngest rocks studied were thin sections of Tertiary tuffs and flows. This study helps with understanding the magmatic, deformational and hydrothermal alteration history of an economically important area.