Co-workers and I have a new paper at Contributions to Mineralogy and Petrology looking in detail at the petrology of the Bear Valley Intrusive Suite. We find lots of evidence for multiple discrete mafic magmas in the lower crust, and suggest that mixing of these magmas might be a critical step in generating the homogeneous tonalites at middle and shallow crustal levels. You can read the paper here.
Post-Doctoral Researcher, University of Lausanne