The significance of Schnitteffekt in petrofabric diagrams

Abstract

Peripheral girdles in petrofabric diagrams can be due entirely to the weak preferred orientation and inequidimensional shape of the minerals measured. This is termed Schnitteffekt (cut effect). A fabric analysis of a tectonite containing albite porphyroblasts with quartz inclusions shows that without thorough fabric analysis and the exercise of necessary controls, serious mistakes in interpretation can arise. Diagrams of the quartz inclusions showed similar patterns regardless of the direction in which the thin section was cut. Several controls by which mistakes due to Schnitteffekt can be avoided are suggested.