Estimating Temperature and Pressure in Metamorphic Rocks

Metamorphosed Limestone Layer (Marble)

Temperature: The presence of calcite in the marble suggests that it formed at relatively low temperatures, typically ranging from 200-400°C.

Pressure: The low-grade metamorphism indicated by the presence of calcite suggests pressures of less than 4 kilobar (kb).

The presence of minor quartz and wollastonite in the marble indicates some degree of regional metamorphism. Wollastonite forms at higher temperatures than calcite, around 500-700°C, suggesting that the marble may have experienced temperatures in this range.

Nearby Metapelite Layer

Temperature: The presence of garnet and kyanite suggests much higher temperatures for the metapelite, likely ranging from 550-750°C.

Pressure: Garnet forms at pressures greater than 4 kb, while kyanite forms at even higher pressures of around 8-12 kb, indicating high-grade metamorphism.

These minerals in the metapelite layer suggest pressures of at least 8 kb.

In summary, the marble likely formed at temperatures ranging from 200-700°C and pressures of less than 4 kb, while the metapelite formed at temperatures of 550-750°C and pressures of at least 8 kb. These estimates were determined by examining the mineral assemblages in each rock layer.