THE GUANAJUATO MINING DISTRICT, MEXICO: HALF ZANTOP'S CONTRIBUTIONS AND GUIDANCE

The Guanajuato silver deposit is one of Mexico's oldest and most important mining districts. Since the 1980s, Half Zantop and his students have been studying the physical and chemical characteristics of Guanajuato's silver and base-metal veins and host rocks.

Research in Guanajuato by Dartmouth students began with Paul Taylor (PhD, 1972), under the supervision of Richard Stoiber. Later, Dr. Stoiber focused his talents on the study of volcanoes, and Half joined the Dartmouth Earth Sciences faculty as its economic geologist, where he continued his research on the mining districts of Mexico.

Half supervised nine theses concerning the geology and geochemistry of Guanajuato, beginning with a study of the central Las Rayas mine, with its unusual high-grade and base-metal-rich "deep" ore, by Helen Mango (MS, 1988) and Eben Frankenberg (Honors, 1988). Phillip Resor (Honors, 1989) analyzed the mineral composition of veins in the Peregrina and El Cubo mines. Jill Blumberg (Honors, 1992) looked into the possible environmental impact of the tailings pond of the Torres mine. Helen Mango (PhD, 1992) studied the fluid inclusion and isotope geochemistry of the mines along the central Veta Madre vein system. Riki Girnius (Honors, 1993) used fluid inclusions to study the upper ore of the El Cubo mine. Kristin Lester (Honors, 1994) and Phil Gutry (Honors, 1995) attempted to correlate two igneous units in the district. Phillip Larson (MS, 1996) studied the relationship between Cenozoic igneous activity and precious metal mineralization.

I continued my research in Guanajuato in collaboration with Half (GSA 1993 and 1994), and as recently as last year sought his help on a project I am conducting in Guanajuato with a Mexican colleague. I greatly miss Half's guidance and friendship.