METALLIC MINERAL DEPOSITS OF NEW ENGLAND: HISTORICAL OVERVIEW, KNOWN DEPOSITS, AND POTENTIAL UNDISCOVERED RESOURCES

Diverse types of metallic mineral deposits have been mined in New England for over 400 years. In 1605, the first smelting of iron ore in the U.S. was at Saugus, MA. Early mining of copper in veins occurred in 1707 at Newgate, CT. In 1738, vein-hosted gold was mined in RI. Copperas (iron sulfate) was mined in 1793 at the Elizabeth (VT) volcanogenic massive sulfide (VMS) deposit; the nearby Ely VMS deposit was a major source of copper in the U.S. in the mid-1800s. The Jackson tin mine (NH), discovered in 1840, was the first tin mine in the U.S. In the late 1960s to late 1970s, metal mines in ME developed Zn-rich VMS deposits at the Harborside and Black Hawk mines. The Katahdin (ME) massive pyrrhotite deposit, mined for iron from 1840 to 1890, is a large (>200 Mt) magmatic sulfide accumulation in gabbro. Small VMS and vein deposits have been mined throughout New England.

Important known metal deposits (all in ME) as yet unmined are: (1) Maple-Hovey Mountain, a 325 Mt sedimentary Mn-Fe deposit that represents the largest Mn resource in the U.S.; (2) Bald Mountain, a 30 Mt Cu-Zn-Ag-Au VMS deposit, and other smaller (~3-5 Mt) VMS deposits including Pickett Mountain (Mt. Chase), Ledge Ridge, and Alder Pond; (3) Warren, a gabbro-hosted Ni-Cu-Co deposit; (4) Catheart Mountain, a porphyry Cu-Mo deposit; and (5) Pembroke (Barrett-Big Hill), a group of epithermal Zn-Pb-Ag-Au deposits.

Mineral occurrences and geochemical anomalies, together with favorable geological settings, suggest that New England is prospective for a variety of undiscovered metal deposits. In addition to VMS deposits in ME, NH, VT, and MA, and porphyry Cu-Mo deposits in ME, potential exists for the following deposit types: (1) granite-related W skarns ± veins in eastern/northeastern VT, northern NH, and western ME; (2) sediment-hosted (Carlin-type) Au in western VT; (3) intrusion-related Au in central/western VT, and in southern/eastern ME; (4) REE-Nb-Ta in alkaline/peralkaline intrusions in central NH and western/southern ME; (5) U-Th or Sn in felsic plutons in central NH and ME; (6) Li-Cs-Ta-Be in pegmatites in western ME and NH; (7) sediment-hosted Zn-Pb-Ag in carbonate rocks in northern VT; (8) Ni-Cu-Co-PGE in mafic plutons in central/eastern ME; (9) PGE in ultramafic-hosted chromitite in western ME; and (10) epithermal Zn-Pb-Ag-Cu-Au in volcanic rocks in eastern ME.