pyroxene-hornfels facies
Quick Summary
The pyroxene-hornfels facies is a classification in geology that describes a set of metamorphic rocks formed under specific temperature and pressure conditions, typically near large igneous intrusions like granite or gabbro. These rocks form at relatively low pressures, a few hundred bars, and lower temperatures compared to other facies.1
Key characteristics of the pyroxene-hornfels facies include:
* Mineral Assemblages: Rocks in this facies are often anhydrous (lacking water) but reflect lower temperatures. Pelitic rocks (derived from clay-rich sediments) may contain minerals like quartz, feldspar, andalusite, sillimanite, cordierite, orthopyroxene, and plagioclase. Calcareous rocks (derived from limestone) can include plagioclase, diopside, grossularite, and wollastonite.1
* Formation Environment: They are commonly found in contact aureoles surrounding large bodies of magma, where the heat from the magma alters the surrounding rock. Unlike rocks formed under regional metamorphism, those in the pyroxene-hornfels facies often lack schistosity or foliation.1
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