New Mexico Mineral Symposium — Abstracts

The Kilbourne Hole maar is a young volcanic feature found 42 km southwest of Las Cruces, New Mexico, or 53 km west of El Paso, Texas. It is one of five Pleistocene maar volcanoes found near the Potrillo volcanic field. It is a well-known collecting locality for mantle and crustal xenocrystic and xenolithic material. Investigations and reports on the rocks found at Kilbourne Hole have provided detailed information about mantle and deep crustal processes that have operated under southern New Mexico.

Collecting xenoliths at Kilbourne Hole has been a popular activity for many years. Peridot is abundant, usually small in size, and easily found in a variety of mantle xenoliths. Kilbourne Hole also provides geologists with the opportunity to examine a diverse suite of crustal rocks. This suite includes representatives of lower, middle, and upper crustal lithologies plus a variety of volcanic rocks.

A Hardin—Simmons University geology field project, conducted in 1996, surveyed the distribution of crustal xenoliths. The purpose of the project was to determine if any distribution bias could be detected statistically. Several teams established sites to collect, describe, and count the xenoliths. Although no statistical difference in distribution was noted, a comprehensive description of the types of crustal rocks was obtained. An extended list of crustal xenoliths would include: alkalic basalt, granite, felsic porphyry, fossiliferous limestone, sandstone, arkose, various conglomerates and breccias, granodioritic gneiss, mafic granuloblastite, sillimanite-quartz granuloblastite, granulite, and pelitic granulite. Many of the crustal rocks were sectioned and photographed. Photomicrographs will show the variety of textures, minerals, and lithologies found at the Kilbourne Hole xenolith collecting locality.