- © The Mineralogical Society Of America
Investigations of mineral textures and zoning as evidence for open system processes during magmatic evolution have always been a centerpiece of petrological studies and have provided some of the best evidence for magma mixing and crustal contamination for many decades (e.g., Milch 1905; Kuno 1936; Eichelberger 1975; Sato 1975; Anderson 1976). In fact, evidence from mineral studies was instrumental in the acceptance of magma mixing as important petrological process ever since it was initially proposed by Bunsen (1851). In recent years, mineral studies are invigorated by the development of high-precision, high-resolution analytical instruments and techniques through which textural information and compositional data are combined (e.g., Jerram and Davidson 2007). As minerals respond texturally and compositionally to changing magmatic environments, they preserve in their crystal growth stratigraphy a wealth of information regarding their past history of magmatic processes and compositions (cf. Ginibre et al. 2007). On the other hand, magmatic liquids (melts) are snapshots of current magmatic states, and provide less direct evidence of the processes responsible for their evolution. In addition, liquids may crystallize thereby destroying the direct evidence they provide. With an appropriate set of observations and measurements, we can correlate textures with mineral compositions and thus produce a richer composite picture of magmatic evolution than compositional data of minerals alone. This contribution reviews the zoning and textures of minerals frequently encountered in volcanic rocks (many of which apply equally to plutonic rocks) and the interpretations ascribed to these features in terms of open system magmatic processes.
First, I will address the analytical tools that are used to acquire textural and compositional data, followed by a brief review of open system processes and a summary of the relevant textures. From that point on, I will address some mineral specific aspects followed by a discussion …