Why would CaO be more finely spread than K2O in Granodiorite?
I would suggest that there is a combination of effects here: 

Potassium(K) compounds are usually more soluble than their Calcium(Ca) equivalents, and often at much lower temperatures. For example $CaCO_3$ is in considered insoluble in even boiling water, while $K_2CO_3$ is fully soluble at room temperature. Potassium can therefore migrate more easily during weathering involving water infiltration than can Calcium leading to a finer distribution. The "clumps" of $CaO$ represent more closely it's original crystal positions while the finely divided $K_2O$ has migrated farther dispersing it through the samples.

The clumping in less weathered samples could be purely an artifact of the nature of the parent rock Granodiorite is relatively enriched in Calcium over Potassium so Calcium shows up as large concentrations while Potassium is more thinly spread through the samples.