O'Neill, J. Michael

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Precambrian basement geologic map of Montana--An interpretation of aeromagnetic anomalies

Geologic map showing the structure and history of the basement rocks of Montana. Most of the state is covered by Phanerozoic bedrock units; the underlying basement structure must be inferred from magnetic anomaly data combined with geologic observations.

Geologic map of the Big Delta B-1 quadrangle, east-central Alaska

Geologic mapping and U-Pb age dating of the Big Delta B-1 quadrangle provides insights into the geology and gold mineralization of the headwater region of the Goodpaster River.

Geologic field notes, geochemical analyses, and field photographs of outcrops and rock samples from the Big Delta B-1 quadrangle, east-central Alaska

Major element oxide and trace element geochemical analyses, including those for gold, silver, and base metals, for representative rock units and for grab samples from quartz veins and mineralized zones within the quadrangle

Geologic map of the Kechumstuk fault zone in the Mount Veta area, Fortymile mining district, east-central Alaska

This map depicts the fundamental geologic features for the western part of the Fortymile mining district and delineates the location of known bedrock mineral prospects and their relationship to rock types and structural features.

Effect of ultramafic intrusions and associated mineralized rocks on the aqueous geochemistry of the Tangle Lakes Area, Alaska

Stream water was collected at 30 sites within the Tangle Lakes area of the Delta mineral belt in Alaska. Sampling focused on streams near the ultramafic rocks of the Fish Lake intrusive complex south of Eureka Creek and the Tangle Complex area east of Fou