National mineral assessment tract NA17 (Sediment-hosted Au)

Tract NA17
Geographic region Northern Appalachian Mountains
Tract area 3,600sq km
Deposit type Sediment-hosted Au
Deposit age Ordovician

Deposit model

Model code 26a
Model type descriptive
Title Descriptive model of carbonate-hosted Au-Ag
Authors Byron R. Berger
URL https://pubs.usgs.gov/bul/b1693/html/bull7m7b.htm
Source https://pubs.er.usgs.gov/publication/b1693

Rationale

Explained by J.F. Slack
On the choice of deposit models
No sediment-hosted gold deposits are known in the northern United States Appalachians. However, one part of the Taconic allochthons of southwestern Vermont and eastern New York has potential for this deposit type. Such deposits, which may form by uncertain processes, typically consist of disseminations of very fine-grained gold and minor silver-bearing minerals within (or associated with) altered carbonate rocks, siliceous shale, and silicified limestone (Bagby and Berger, 1985; Ruggieri and others, 1993).
On the delineation of permissive tracts
Geologic and geochemical studies under the auspices of the Glens Falls CUSMAP project identified significant gold and silver anomalies in heavy-mineral concentrates of stream sediments in parts of the Taconic allochthon (Watts, 1990). One anomaly is considered particularly significant, because it occurs on the northeastern side of the allochthon in the area of a known Mesozoic extensional fault. Slack (1990) interpreted this setting as having potential for gold and (or) silver mineralization in or near this fault, especially within carbonate-rich rocks of the allochthon or within those of the underlying lower Paleozoic shelf sequence. No undiscovered deposits are assigned to this tract, however.
References
Bagby, W.C., and Berger, B.R., 1985, Geologic characteristics of sediment-hosted, disseminated precious-metal deposits in the western United States, in Berger, B.R., and Bethke, P.M., eds., Geology and geochemistry of epithermal systems: Reviews in Economic Geology, v. 2, p. 169-202.
Ruggieri, G., Lattanzai, P., and Tanelli, G., 1993, Carbonate-hosted epithermal gold mineralization in southern Tuscany (Italy): The examples of Frassine and La Campigliola, in Fenoll Hach-Ali, P., Torres-Ruiz, J., and Gervilla, F., eds., Current research in geology applied to ore deposits: Granada, Spain, University of Granada, Proceedings of the Second Annual Biennial SGA Meeting, Granada, Spain, September 9-11, 1993, p. 551-554.
Slack, J.F., 1990, Preliminary assessment of metallic mineral resources in the Glens Falls 1° x 2° quadrangle, New York, Vermont, and New Hampshire, in Slack, J.F., ed., Summary results of the Glens Falls CUSMAP project, New York, Vermont, and New Hampshire: U.S. Geological Survey Bulletin 1887-R, 26 p.
Watts, K.C., Jr., 1990, Regional exploration geochemistry of the Glens Falls 1° x 2° quadrangle, New York, Vermont, and New Hampshire, in Slack, J.F., ed., Summary results of the Glens Falls CUSMAP project, New York, Vermont, and New Hampshire: U.S. Geological Survey Bulletin 1887-F, 70 p.

Geographic coverage

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