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Heat flow and basement radioactivity in Maine: First‐order results and preliminary interpretations
Author(s) -
Decker Edward R.
Publication year - 1987
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl014i003p00256
Subject(s) - radiogenic nuclide , terrane , geology , geothermal gradient , pluton , heat flux , lithosphere , borehole , mantle (geology) , paleozoic , crust , heat flow , geophysics , petrology , tectonics , geochemistry , seismology , thermal , heat transfer , paleontology , physics , meteorology , thermodynamics
New heat flow values (Q) for 70 boreholes in Maine are in the range 33‐83 mWm −2 . New radioactive heat productions (A) for 45 sites range from 0.08 to 8.74 µWm −3 . The combined data for plutonic rocks determine least‐squares lines with slopes and intercepts in the ranges 5.0‐6.5 km and 35‐39 mWm −2 , respectively. These lines provide continued support for linear relations between Q and A in continental terranes, and confirm that normal reduced flux is the characteristic geothermal parameter of all of the New York‐New England region. Gravity, seismic and thermal modeling suggest that complex distributions of pluton thicknesses and near‐surface radioactivity occur in Maine. Thus, a single Q‐A line for this region is difficult to explain with simple distributions of vertically uniform or exponentially decreasing crustal radiogenic heat in some areas. Normal reduced flux in Maine implies that the lithosphere has equilibrated since thermotectonic events in Paleozoic and Jurassic times. Moho temperature changes associated with 8‐10 km crustal thickness changes in Maine and central New Hampshire are not likely to exceed 150°C, and effects on mantle properties would be small.