Location 1: Rio Puerco volcanic field

Field Trip Date:  Sunday, August 5, 2018
Field Trip Leader: Dr. Jin Zhang
Field Trip cost: $55 includes breakfast, lunch with beverage and transportation
Deadline to register: July 13, 2018

Field trip limited to 30 participants.

Description: The first location is the Rio Puerco Volcanic field. It is located within the Jemez Lineament, an NE-trending zone of the later Tertiary-Quaternary volcanic centers that extend from SW Arizona to NW New Mexico. It corresponds to the tectono-physiographic transition zone that separates the thick lithosphere of Colorado Plateau from the thin west margin of the Rio Grande rift. The Rio Puerco Volcanic field are small-volume, mafic plugs composed of alkaline basalts with xenoliths. including pyroxenite, harzburgite, and spinel lherzolite.
The second location is the Grants Ridge Rhyolite. The lithology is dominated by light gray, sparsely porphyritic lava containing phenocrysts of K-feldspar, plagioclase and very rare quartz. Miarolitic cavities with mm-size garnet and topaz are commonly found. Other accessory minerals include quartz, K-feldspar, and hematite.