CRITICAL MINERAL DEPOSITS OF NEW ENGLAND

New England contains a wide variety of mineral deposits owing to diverse rock types and settings and a complex geological history. Among 50 metals and minerals listed as critical by the U.S. Geological Survey in 2023, New England has past production (1658-1977) or defined resources of Li, Mn, Ti, Zn, Ni, Co, W, Sn, Sb, graphite, barite, and fluorspar. A significant Li resource occurs in a spodumene-rich pegmatite in western ME. Low-grade Mn deposits in northeastern Maine constitute the largest known U.S. resource of that metal. A large troctolite-hosted Ti ± V deposit is in northeastern Rhode Island. Small to large volcanogenic massive sulfide (VMS) deposits having minor to abundant Zn occur in coastal, northern, and western ME, northern and western NH, and western MA; a small Zn-rich sediment-hosted deposit is in northern VT. Sulfide deposits in mafic intrusions contain abundant Ni and minor Co in southern ME, northeastern MA, and western CT. Vein deposits in northern and southern CT produced minor Cu and W, respectively. Very minor production of Sn and Sb came from small mines in coastal and central ME; minor Bi was produced in coastal ME and southern CT. Minor amounts of graphite came from small mines in western ME, southern NH, northern CT, eastern RI, and MA. Barite was produced, locally with base metals, from small vein deposits in western MA and central CT. In southwestern NH, small vein deposits were mined for fluorspar.

Based on favorable geology, mineral occurrences, and geochemical anomalies in stream sediments, potential exists for undiscovered deposits of (1) Li in spodumene pegmatites (ME, NH, MA, CT); (2) Zn in VMS deposits (ME, NH, MA) and sediment-hosted deposits (VT); (3) Ni, Co, and platinum-group elements (Pt, Pd, Rh) in mafic-ultramafic intrusions (ME, MA, CT); (4) W in granite-related skarns (ME, VT); (5) V in black shales (ME); (6) rare earth elements, Nb, and Ta in alkaline intrusions (ME, NH, VT); (7) Cr in an ophiolite complex (ME); (8) Sb in stratabound replacements (ME); (9) graphite in black shales (ME); and (10) barite in vein and stratabound deposits (MA, VT). Exploration for new resources of critical metals and minerals should include areas having favorable geological settings for unconventional deposit types in New England such as W in skarns, Sb in stratabound replacements, and V and graphite in black shales.