Isocon diagrams for metasomatic alteration of Grant (2005), showing samples from CS (A) and AS-GS (B). These diagrams allow to determine the alteration degree of all samples by plotting an altered composition against an original composition. A) Samples from CS plotted against the least altered sample from CS (SA2026); B) Samples from AS-GS plotted against the least altered sample from AS (AL2088), both synclines present the same stratigraphic succession and are found in the same region reason why GS samples where plotted against an AS sample.