For abstraction as fundamental structure there is Richard van der Aa at the Kunst Gallery, where he has contexts or constellations of basic shapes, not as one might anticpate from runic stones but from the Middle East and, in particular, Petra. The simplicity is deceptive, especially if you let works in each cluster "speak" to one another. The anti-indulgence and spartan restrictions are admirable. The aesthetic life is rich indeed, but then some abstraction has always been close to Quaker restraint.