Metamorphic rocks, thermal history

Harrison T. M. and McDougall I. (1981). Excess " °Ar in metamorphic rocks from Broken Hill, New South Wales Implications for " °Ar/ Ar age spectra and the thermal history of the region. Earth Planet. Sci Letters, 55 123-149. 

The most often encountered thermal history by geologists is continuous cooling from a high temperature to room temperature (such as cooling of volcanic rocks, plutonic rocks, and metamorphic rocks). One of the many ways to approximate the cooling history is as follows ... 

Because D increases with increasing temperature (the Arrhenius equation 1-73), time-dependent D is often encountered in geology because an igneous rock may have cooled down from a high temperature, or metamorphic rock may have experienced a complicated thermal history. If the initial and boundary conditions are simple and if D depends only on time, the diffusion problem is easy to deal with. Because D is independent of x. Equation 3-9 can be written as... 

Ruppel C., Royden L., and Hodges K. V. (1988) Thermal modeling of extensional tectonics application to pressure— temperature-time histories of metamorphic rocks. Tectonics 7, 947-957. 

Chondrites are the oldest and most primitive rocks in the solar system. They are hosts for interstellar grains that predate solar system formation. Most chondrites have experienced a complex history, which includes primary formation processes and secondary processes that inclnde thermal metamorphism and aqneons alteration. It is generally very difficult to distinguish between the effects of primary and secondary processes on the basis of isotope composition. Chondrites display a wide diversity of isotopic compositions including large variations in oxygen isotopes. 

---