41-15 Chert and Algal Mats as Controls on Mississippi Valley-Type Mineralization in The Knox Dolomite Within the Kentucky-Tennessee Mineral District

Session: Paleontology, Stratigraphy, Sediments, and Soils (Posters)

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Abstract:

Mississippi Valley-type (MVT) mineralization within the Lower Ordovician Knox Dolomite of the Kentucky-Tennessee Mineral District represents a potential source of critical minerals. While the association of these deposits with paleokarst is established, the sedimentological, stratigraphic, and diagenetic controls on mineralization remain poorly understood. This research tests the hypothesis that chert bodies and algal mats served as controls on MVT mineralization in Upper Knox carbonates. 

Field observations and drill cores show a spatial relationship between mineralization and these features. Fractured or brecciated algal-mat dolomites commonly host MVT mineralization. Nonporous blue-gray chert nodules and beds typically form competent layers that bound mineralized zones, suggesting they acted as impermeable barriers, focusing fluid flow. In contrast, tan-white tripolitic chert is porous, occurs as fracture fill and breccia clast cement, and is spatially associated with mineralization, indicating it may have functioned as a permeable conduit. Ore minerals are concentrated within breccia bodies, fractures, and vugs, with paragenetic relationships indicating multiple fluid pulses. 

Detailed logging of cores provides the macroscopic framework linking mineralization to brecciated algal-mat dolomite and localized fractures and vugs while distinguishing barrier-forming blue-gray chert from conduit-like tripolitic chert. Thin-section petrography confirms these contrasts: blue-gray nodular chert preserves pre-chertification fabrics and shows dense, fibrous, nonporous textures, whereas tripolitic chert is fabric-destructive, porous, contains dolomite rhombs, and locally hosts minor sulfides. Oxygen isotope analysis of carbonates and cherts will discriminate between early marine and hydrothermal diagenetic phases, constrain fluid sources, and estimate formation temperatures. Raman spectroscopy will provide isotopic data for carbonates and, through the analysis of carbonaceous material within cherts, deliver constraints on the peak thermal conditions experienced by the chert. 

This study aims to clarify the mechanisms by which chertification physically influenced fluid flow and algal-mat dolomite localized mineralization through sulfur availability. This will refine genetic models for MVT mineralization in the Knox Dolomite, contributing to geological exploration criteria. This work has broader implications for understanding critical mineral deposits in carbonate rocks in Appalachia and globally.

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

doi: 10.1130/abs/2026SE-11987

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