11-3 ULTRAMAFIC LAMPROPHYRE DIKES IN THE WESTERN KENTUCKY FLUORSPAR DISTRICT: A REVIEW

Session: Applications of Igneous Petrology, Geochemistry, and Geochronology to Understanding Earth and Other Planetary Systems (Posters)

Poster Booth No.: 77

Presenting Author:

Thomas Anderson

Authors:

Anderson, Thomas¹, Walton, Zach², Lukoczki, Georgina³, Dietsch, Craig⁴

(1) Department of Geosciences, University of Cincinnati, Cincinnati, Ohio, USA, (2) Kentucky Geological Survey, University of Kentucky, Lexington, KY, USA, (3) Kentucky Geological Survey, University of Kentucky, Lexington, KY, USA, (4) Department of Geosciences, University of Cincinnati, Cincinnati, OH, USA,

Abstract:

Lamprophyres are rare, volatile-rich, silica-undersaturated magmas that provide direct insight into melting of metasomatized lithospheric mantle and the evolution of carbonatite magmas within broader aspects of mantle metasomatism, volatile cycling, and continental alkaline magmatism. Interpretations of the origin of lamprophyres remain hindered by inconsistent classification schemes, uneven analytical treatment, and uncertainty over the relative roles of mantle source heterogeneity, volatile fluxing, magma immiscibility, and crustal modification. Significant uncertainties also remain regarding parental melt compositions, magma evolution during ascent, and the extent to which lamprophyres record primary mantle signatures versus secondary modifications. We identify areas of growing consensus regarding ultramafic lamprophyre (UML) dikes from the Western Kentucky Fluorspar District (WKFD) and review constraints from petrography and mineral chemistry, whole-rock major and trace element systematics, radiogenic isotope compositions, and mineral- and melt-inclusion–hosted volatile measurements. UML dikes from the WKFD record evidence of multistage mantle metasomatism, multiple carbonation events, and serpentinization; various cross-cutting veins are dominantly composed of calcite and serpentine, and small veins of carbonatite are also present. Limited Nd and Sr isotopic data indicate initial derivation from an enriched mantle source. The chondrite-normalized rare earth element (REE) distribution in the dikes shows uniform light REE enrichment, but the total REE concentrations are variable, with maximum total REE concentrations of only a few hundred parts per million. UMLs commonly form dike swarms associated with tectonic reorganization, lithospheric thinning, or post-collisional relaxation. In the WKFD, the UML dike swarm cuts normal faults of the Late Neoproterozoic Rough Creek Graben at a high angle. Based on geochronological data, the formation of the UMLs is linked to the end of the Alleghenian orogenic cycle. Unresolved questions persist, and we propose priorities for future work, including integrated mineral–whole-rock datasets, new geochronologic constraints, and source-to-emplacement geochemical modeling.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

doi: 10.1130/abs/2026SE-12981

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