Overprinting (geology)

Overprinting is a geological process that superimposes a set of characteristics on rock that partially obscure earlier characteristics. Examples include metamorphic overprinting (superimposed metamorphism^[1]), in which new structure,^[2] texture, or mineral composition is imposed on existing rock.^[3][4] For example, the Tauern window of Alps contains beds that were originally metamorphosed to eclogite but have since been overprinted to the blueschist and then the greenschist facies.^[5] Likewise, deformation associated with the Mazatzal orogeny in Arizona and New Mexico, US, was subsequently overprinted by deformation associated with the Picuris orogeny.^[6]

In this orthogneiss from the Czech Republic the original igneous rock texture has been overprinted by foliation associated with metamorphism.

Geochemical signatures can also be overprinted when the geochemistry of a geological body is changed by eliminating or modifying the earlier geochemical signature.^[7][8]