Page 17 - Volcanic Textures A Guide To The Interpretation of Textures In Volcanic Rocks

sistently, regardless of the absolute accuracy of the coherent textures, genetic interpretation will seek to ;
terms. If necessary, the composition subdivisions shown discriminate between lavas, syn-volcanic intrusions,
in Table 1 can be made more precise by adding post-volcanic intrusions and very densely welded
percentage limits for the phenocryst abundances. pyroclastic deposits, and will depend on additional
Adjustments can be made to how terms are used, if and detailed information on textures in thin-section, contact
when accurate modal or chemical analyses become relationships and geometry.
available. For deposits with coherent and apparent

Fig. 3 Characteristics of deposits from explosive eruptions (primary pyroclastic deposits) (Part 4).

5