Keywords and Phrases
Economic; Geology; Missouri; Ore; Southeastern; St. Francois
"The St. Francois Mountains in SE Missouri are an extensive terrane of granitic ring complexes and associated rhyolites. They were an important source of Ag, W, and Sn and mined intermittently from the 1800s until the 1950s. The Ag-W ores occur in the Silvermine Granite and rhyolite roof rocks. The deposits are classified as a xenothermal ore system with mineralization occurring in quartz veins and surrounding greisen (up to 2.5 m). Exploration for hydrothermal ore deposits often focuses on the identification of alteration halos in the surrounding host rocks. In the vast majority of xenothermal ore deposits, such as in the Silver Mine District, the extent of alteration halos is often very small (cm to m scale) due to the rapid cooling experienced by the ore bearing fluids. As a consequence, such alteration halos are difficult to identify in the field.
This study investigates alteration halos around Silver Mine District Ag-W-Sn veins using petrographic observations and bulk rock chemistry. The goal is to develop an empirical, field-based exploration model than can provide a basis for identifying vectors towards ore zones. Samples were collected in incremental steps of 1 m, 3 m, 5 m, 10 m, 15 m, 25 m, 50 m, 100 m, and 200 m away from the Einstein vein. Field observations show distinct color changes within the rock, most notably at the 1 m, 5-15 m, 25-50 m and 100-200 m increments. Petrographically, the samples do not show significant changes. Bulk rock analysis of the samples show that Li, Be, Sr, Ba, Zr, Tl, Sn, and Sb contents vary as a function of distance from the ore, thus providing additional vectors towards mineralized zones. Results of this project show that a combination of field-observations, mineralogy and geochemical essays can be used to guide the exploration for xenothermal ore systems.”--Abstract, page iii.
Seeger, Cheryl M.
Hogan, John Patrick
Geosciences and Geological and Petroleum Engineering
M.S. in Geology and Geophysics
Missouri University of Science and Technology
viii, 39 pages
St. Francois County, Missouri
© 2019 Daniel Joseph Warbritton, All rights reserved.
Thesis - Open Access
Warbritton, Daniel Joseph, "Exploration for alteration halos around the AG-W deposits in Southeastern Missouri, USA" (2019). Masters Theses. 8083.