Iron and oxygen isotope signatures of the Pea Ridge and Pilot Knob magnetite-apatite deposits, southeast Missouri, USA
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Abstract
New O and Fe stable isotope ratios are reported for magnetite samples from high-grade massive magnetite of the Mesoproterozoic Pea Ridge and Pilot Knob magnetite-apatite ore deposits and these results are compared with data for other iron oxide-apatite deposits to shed light on the origin of the southeast Missouri deposits. The δ18O values of magnetite from Pea Ridge (n = 12) and Pilot Knob (n = 3) range from 1.0 to 7.0 and 3.3 to 6.7‰, respectively. The δ56Fe values of magnetite from Pea Ridge (n = 10) and Pilot Knob (n = 6) are 0.03 to 0.35 and 0.06 to 0.27‰, respectively. These δ18O and the δ56Fe values suggest that magnetite crystallized from a silicate melt (typical igneous δ56Fe ranges 0.06–0.49‰) and grew in equilibrium with a magmatic-hydrothermal aqueous fluid. We propose that the δ18O and δ56Fe data for the Pea Ridge and Pilot Knob magnetite-apatite deposits are consistent with the flotation model recently proposed by Knipping et al. (2015a), which invokes flotation of a magmatic magnetite-fluid suspension and offers a plausible explanation for the igneous (i.e., up to ~15.9 wt % TiO2 in magnetite) and hydrothermal features of the deposits.
Suggested Citation
Childress, T., Simon, A.C., Day, W.C., Lundstrom, C.C., Bindeman, I.N., 2016, Iron and oxygen isotope signatures of the Pea Ridge and Pilot Knob magnetite-apatite deposits, southeast Missouri, USA: Economic Geology, v. 111, no. 8, p. 2033-2044, https://doi.org/10.2113/econgeo.111.8.2033.
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Iron and oxygen isotope signatures of the Pea Ridge and Pilot Knob magnetite-apatite deposits, southeast Missouri, USA |
| Series title | Economic Geology |
| DOI | 10.2113/econgeo.111.8.2033 |
| Volume | 111 |
| Issue | 8 |
| Publication Date | November 16, 2016 |
| Year Published | 2016 |
| Language | English |
| Publisher | Society of Economic Geologists |
| Contributing office(s) | Central Mineral and Environmental Resources Science Center |
| Description | 12 p. |
| First page | 2033 |
| Last page | 2044 |
| Online Only (Y/N) | N |
| Additional Online Files (Y/N) | N |