Although the compositional trends of bulk rocks and melt inclusions largely overlap, there is a prominent contrast in the petrographic distribution and relative frequency of melt inclusions between different rocks (Fig.  8 ) and between the compositions of melt inclusions in apparently coexisting phenocryst minerals in any one rock (Fig.  9 ).

Overall, the frequency of melt inclusions with intermediate compositions (58 to 60 wt SiO ₂ ) is low compared to the great predominance of andesitic bulk rock compositions in the Farallón Negro Volcanic Complex (Fig.  8 A).

Thus, andesitic melt inclusions are completely absent from plagioclase in intrusive rocks (Fig.  8 B) and rare in plagioclase from volcanic rocks (Fig.  8 C).

Dacitic to rhyodacitic melt inclusions are frequent in plagioclase, particularly in intrusive rocks (Fig.  8 F), and quartz never contains melt inclusions with SiO ₂ below 69 wt% (Fig.  8 G).

In intrusive rocks, there is virtually no compositional overlap between basaltic or andesitic melt inclusions in mafic phenocrysts and dacitic or more silica rich melt inclusions in plagioclase and quartz (Fig.  8 B).

Other strong evidence for mixing are melt inclusions of 66 to 68 wt% SiO ₂ in plagioclase phenocrysts, themselves trapped in amphibole hosting inclusions with 50 wt% SiO ₂ (Fig.  4 B), and by the bimodal distribution of melt inclusion chemistries (Fig.  8 )..

Additional striking evidence for mixing is indicated by melt inclusions trapped in amphibole and felsic minerals from intrusive rocks that hardly ever overlap in their silica content (Fig.  8 ), despite the widespread common occurrence of these phases.

In particular, melt inclusions in intrusive rocks appear to be more silica-rich than inclusions in volcanic rocks (Fig.  8 ), suggesting a higher degree of crystallization (mainly of plagioclase) in intrusions.

Characteristic differences between intrusive and extrusive rocks (Fig.  8 ), despite a common source (Fig.  6 ), show that intrusions tapped different parts of this magma chamber than did volcanic rocks.