“The Southeast Missouri Iron Metallogenic Province in the Midwestern USA contains seven major and several minor IOA/IOCG-type deposits, all of which are spatially associated with the early Mesoproterozoic (1.50-1.44 Ga) magmatism in the St. Francois Mountains terrane. This Ph.D. project focuses on the Pilot Knob deposits, i.e., the deeper largely massive Pilot Knob Magnetite (PKM) and the shallower Pilot Knob Hematite (PKH) deposits, and the Shepherd Mountain deposit that are located less than 2.1 km distance from one another. The first precise age for the formation of the PKM ore is constrained at 1438±5.8 Ma using apatite U-Pb method. Petrographic observations and whole-rock compositions of the PKH ore, and the mineral chemistry of hematite, suggest that the PKH deposit formed from acidic and hypersaline hydrothermal fluids at temperatures 200-250°C. Also, petrographic observations, whole-rock data, and the trace element and Fe isotope composition of magnetite and hematite show that the Shepherd Mountain deposit formed from at least five pulses of magmatic-hydrothermal fluids with different compositions and physicochemical parameters. Integration of the data for the individual deposits (i.e., PKM, PKH, and Shepherd Mountain) with published data from PKM shows that the three deposits are genetically linked through two local faults. The Ironton and Pilot Knob faults provided fluid pathways to connect the PKM deposit to the shallower Shepherd Mountain and PKH deposits. Consequently, the Shepherd Mountain and PKH deposits are near-surface extensions of the same magmatic to hydrothermal plumbing system that formed the PKM deposit at depth”--Abstract, page iv.
Borrok, David M.
Wronkiewicz, David J.
Seeger, Cheryl M.
Awuah-Offei, Kwame, 1975-
Geosciences and Geological and Petroleum Engineering
Ph. D. in Geology and Geophysics
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- The Pilot Knob Iron Ore Deposits in Southeast Missouri, USA: A High-To-Low Temperature Magmatic-Hydrothermal Continuum
- The Shepherd Mountain Iron Ore Deposit in Southeast Missouri, USA -- An Extension of the Pilot Knob Magmatic-Hydrothermal Ore System: Evidence from Iron Oxide Chemistry
xiv, 244 pages
© 2021 Bolorchimeg Nanzad, All rights reserved.
Dissertation - Open Access
Tunnell, Bolorchimeg N., "The Pilot Knob Magnetite, Pilot Knob Hematite, and Shepherd Mountain iron oxide deposits in Southeast Missouri -- Local expressions of a magmatic-hydrothermal plumbing system?" (2021). Doctoral Dissertations. 3020.