Chemistry:Granofels
Granofels is a term referring to medium- to coarse-grained metamorphic rocks which have a granoblastic texture (having poorly formed, equi-granular crystal grains visible to the naked eye) and lack distinct foliation or lineation.[1] The granofels term encompasses rocks which are known under more specific names, such as marble or hornfels.[2]
Formation
Granofels forms under medium- to high-grade metamorphic conditions, typically involving elevated temperatures and pressures that promote recrystallization of minerals without inducing directional stress. This process results in a granoblastic texture, characterized by equigranular, interlocking mineral grains lacking foliation.[2]
Examples
Granofels is a general term that includes several more specific rock types:
- Marble – formed from the metamorphism of limestone, composed primarily of recrystallized calcite or dolomite
- Hornfels – produced by contact metamorphism of shale or other fine-grained sedimentary rocks, often containing quartz, feldspar, and mica
- Quartzite – derived from sandstone, sometimes classified as granofels when texture is granoblastic and non-directional
These examples illustrate the diversity of protoliths and mineral compositions that can result in granofelsic textures.
References
- ↑ Goldsmith, Richard (1959). "Granofels, a New Metamorphic Rock Name". The Journal of Geology 67 (1): 109–110. doi:10.1086/626561. Bibcode: 1959JG.....67..109G.
- ↑ 2.0 2.1 Schmi, Rolf; Fettes, Douglas; Harte, Ben; Davis, Eleutheria; Desmons, Jacqueline (2007). "How to name a metamorphic rock". British Geological Survey. https://www.bgs.ac.uk/downloads/start.cfm?id=3185.
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