ReNTRs and ReERs
What are ReNTRs and ReERs?
- ReNTRs are retrograde net transfer reactions
- ReERs are retrograde exchange reactions
- These reactions operate to change the composition
of minerals from those at the metamorphic peak. This makes it
a challenge to the petrologist to decipher peak metamorphic P-T
conditions using thermobarometry.
- ReNTRs can easily shift compositions so that
temperatures calculated from thermobarometry are higher than
the metamorphic peak
- ReERs typically shift compositions so that
temperatures calculated from thermobarometry are lower than the
- Operating together, ReNTRs and ReERS can,
in some instances, result in compositions that, when used for
thermometry, yield precisely the peak temperature, but the compositions
are in no way representative of the metamorphic peak compositions.
Program Gibbs and ReNTRs and ReERs
Program Gibbs can be used to calculate the
effect of ReNTRs and ReERs and thus examine the extent to which
these retrograde reactions have affected peak thermobarometry.
Gibbs can also be used to construct P-T contour diagrams so that
the P-T paths over which a particular ReNTR will operate can be
The following links are to pages that discuss
specific examples of ReNTRs and ReERs
- Florence, F. P. and Spear, F. S. (1993) Influences of reaction
history and chemical diffusion on P-T calculations for staurolite
schists from the Littleton Formation, northwestern New Hampshire.
American Mineralogist, 78, 345-359.
- Kohn, M. J. and Spear, F. S. (2000) Retrograde Net Transfer
Reaction Insurance for P-T Estimates. Geology, 28, 1127-1130.
- Robinson, P. (1991) The eye of the petrographer, the mind
of the petrologist. American Mineralogist, 76, 1781-1810.
- Robinson, P. R., Hollocher, K. T., Tracy, R. J. and Dietsch,
C. W. (1982) High grade Acadian regional metamorphism in south-central
Massachusetts. In Joesten, R. and Quarrier, S., Ed., NEIGC 74th
Annual Meeting, p. 289-340. 5, State Geological and Natural History
Survey of Connecticut, Storrs, Connecticut.
- Spear, F. S. (1991) On the interpretation of peak metamorphic
temperatures in light of garnet diffusion during cooling. Journal
of Metamorphic Geology, 9, 379-388.
- Spear, F. S. (1992) Thermobarometry and P-T paths from granulite
facies rocks: an introduction. Journal of Precambrian Research,
- Spear, F. S. and Florence, F. P. (1992) Thermobarometry in
granulites: Pitfalls and new approaches. Journal of Precambrian
Research, 55, 209-241.
- Spear, F. S. and Parrish, R. (1996) Petrology and petrologic
cooling rates of the Valhalla Complex, British Columbia, Canada.
Journal of Petrology, 37, 733-765.
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