Absence of magnetite microlites, geochemistry of magnetite veins and replacements in IOA deposits, SE Missouri, USA: Relations to intermediate intrusions

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Abstract

The paragenesis, textures, and chemical compositions of magnetite in two mafic to intermediate intrusions and four IOA deposits in SE Missouri were studied to discriminate between igneous and hydrothermal sources. In this study, we found that replacement magnetite with mineral inclusion-rich cores yields erroneously high Ti, Al, Si, Mg, and Mn contents as determined by EMP and LA-ICP-MS due to rutile and silicate inclusions. Thus, identification of high-Ti microlites on the basis of inclusion-rich cores with high Ti contents is an analytical artefact. Since the high-Ti magnetite microlite flotation model is critically dependent on this type of analysis, it may be invalid. The presence of coarse-grained high-Ti vein magnetite with ilmenite lamellae enveloped by replacement magnetite with inclusion-rich cores in ore zones suggests that the veins were high-temperature conduits for low-temperature replacement ores. The trace element compositions of vein and replacement magnetite suggest that iron was sourced from mafic to intermediate intrusions. These results support a magmatic-hydrothermal origin for IOA systems in SE Missouri.

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Additional publication details

Publication type Conference Paper
Publication Subtype Conference Paper
Title Absence of magnetite microlites, geochemistry of magnetite veins and replacements in IOA deposits, SE Missouri, USA: Relations to intermediate intrusions
Volume 1
Year Published 2019
Language English
Publisher Society for Geology Applied to Mineral Deposits (SGA)
Contributing office(s) Central Mineral and Environmental Resources Science Center
Description 4 p.
Larger Work Type Book
Larger Work Subtype Conference publication
Larger Work Title Life with Ore Deposits on Earth – 15th SGA Biennial Meeting 2019
First page 396
Last page 399
Conference Title 15th SGA Biennial Meeting 2019
Conference Location Glasgow, Scotland
Conference Date August 27-30, 2019
Country United States
State Missouri
Other Geospatial St. Francois Mountains
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