Thermal Consequences of Gneiss Dome Formation

Tim Allen and C Page Chamberlain (Both at: Department of Earth Sciences, Dartmouth College, Hanover, NH 03755; 603-646-2373)

Two-dimensional thermal models of mantled gneiss domes are used to constrain the velocity of emplacement and to understand the P-T-t paths of mantling metamorphic rocks. Our calculations show that: 1) observed metamorphic anomalies surrounding the gneiss domes in New England can be created by ductile emplacement of quartzo-feldspathic domes into surrounding metasediments at velocities of around 2 mm/year; and 2) that P-T-t paths around domes should be characterized by isobaric heating paths for rocks overlying the domes and decompressive cooling paths for rocks within the core of the dome.

The complex thermal histories and thermal patterns observed around gneiss domes are the result of emplacement of relatively high thermal conductivity rocks (domes) into lower thermal conductivity metasediments (mantling strata). The degree of the thermal anomaly is primarily dependent upon the conductivity contrast, but is also dependent on the velocity of emplacement. Many ofthe metamorphic features that are observed around mantled gneiss domes can be explained merely by the emplacement of high conductivity rocks into low conductivity rocks without invoking additional heat sources or post-metamorphic deformation.

1988 EOS, Transactions of the American Geophysical Unions 69(16): 509