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.