Mantle helium in ground waters of eastern North America; time and space constraints on sources
Mantle helium in ground waters of eastern North America; time and space constraints on sources
Geology (Boulder) (August 1995) 23 (8): 675-678
- Canada
- Carroll County New Hampshire
- Eastern Canada
- Eastern U.S.
- gases
- geochemistry
- ground water
- helium
- hot spots
- hydrochemistry
- magmas
- Maine
- mantle
- Mirror Lake
- Monteregian Hills
- New England
- New Hampshire
- noble gases
- North America
- plate tectonics
- Quebec
- United States
- Vermont
- volatiles
- White Mountains
Mantle helium in continental environments is generally considered to be the result of active volcanism and/or active extension. The latest episodes of volcanism in northeastern North America are the track of the New England hotspot (95-190 Ma) and the closure of the Iapetus sea (before 300 Ma). Thus, the identification of mantle helium in young ground waters of central New England is counter to the conventional wisdom. On the basis of evaluation of helium evolution in emplaced magmas, we postulate an "aged" mantle source for the excess helium component in ground waters of central New England that is either (1) a local, near-surface-emplaced, gas-rich magma that has retained significant volatiles (e.g., in fluid inclusions) or (2) a deeply emplaced gas-rich magma with high initial (super 3) He/ (super 4) He (10 (super -5) ) and helium transport (with dispersion) through the crust over time. This gas-rich initial condition may support the concept of a volatile-enriched mantle wedge and thus explain the increased buoyancy flux of the New England hotspot as it traversed eastern North America, as has been suggested by others.