Figure 9. Complex secondary mineral precipitate. (a-c)BSE image of a secondary mineral crust deposited on the edge of the igneous rock in sample B5 thin section. (d-g) Elemental maps of silicon, manganese, copper, and aluminum. (h) BSE image of close-up of secondary mineral crust. (i-l) Composite elemental maps of manganese and silicon (i) , phosphorus, manganese, and aluminum (j) , manganese and copper (k) , and carbon and silicon (l) . (m) EDS sum spectrum of (h) showing copper, phosphorus, and manganese enrichment. The EDS sum spectrum of (c) can be seen in Supporting Information.
These elemental maps suggest that a variety of minerals are precipitating alongside each other in the complex secondary mineral precipitate in Figure 9c, starting with an aluminum-poor copper silicate on the bottom right, followed by a copper phosphate, a manganese oxide or hydroxide, an aluminum-rich copper silicate, and topped off with a carbonate-bearing layer. The aluminum-rich copper silicate may be chrysocolla as discussed in previous sections. Pseudomalachite could be a candidate for the copper phosphate species based on the elemental distribution, and that it is similar in outward appearance and known to be associated with chrysocolla.