**8. Summary**

Subduction-related magmas transport and release large quantities of water into the crust. Water released by crystallizing magma probably escapes along multiple paths through previously crystallized plutonic rock. It is difficult to quantify how much of the water follows each path, but it is likely that a large fraction is channeled along fractures and pipes. However, pervasive infiltration of aqueous fluid along grain boundaries and microfractures commonly has significantly modified primary mineral compositions and textures. We sugges<sup>t</sup> that the infiltrating fluid was derived from crystallization of younger, deeper magmatic increments added to the growing pluton. This suggestion is clearly speculative; more evidence is needed to test whether the grain-boundary fluid was derived from cogenetic magma.

Fluid release from crystallizing magma does not a ffect the temperature of the magma but the fluid advects a large fraction of the magma's energy into adjacent already-solidified granite. This implies that the sawtooth postsolidus thermal histories predicted for early intrusive increments by conductive incremental-growth thermal models (e.g., [15]) substantially underestimate the actual amplitude of the thermal fluctuations. In some instances, infiltration of magmatic fluid may produce not only mineral reactions and textural modification but also remelting of previously solidified portions of the pluton. Remelting of already solidified granite by this mechanism would be di fficult to conclusively demonstrate because the result will be a granitic pore melt in a matrix of granite; therefore, cooling will merely redeposit quartz and feldspars on crystals that survived remelting. The result is likely to be textural modifications that would be di fficult to distinguish from subsolidus textural modifications.

The sparseness of mappable internal contacts in plutons is a major reason that the incremental growth of plutons over million-year time scales was not recognized until the development of high-precision geochronology. We sugges<sup>t</sup> that an important reason that increment contacts are rarely observable in the field is extensive postemplacement textural modification. Modification is a practically inevitable consequence of incremental growth because much, if not all, of the modification is caused by pulses of water and heat released by magmatic crystallization entering already-crystallized portions of the pluton.

**Author Contributions:** Conceptualization, J.M.B., A.F.G., M.A.S., D.S.C.; methodology, J.M.B., A.F.G., M.A.S., D.S.C.; formal analysis, A.F.G., M.A.S.; investigation, J.M.B., A.F.G., M.A.S.; resources, J.M.B., A.F.G., M.A.S.; data curation, A.F.G., M.A.S.; writing—original draft preparation, J.M.B.; writing—review and editing, A.F.G., M.A.S., D.S.C.; visualization, J.M.B., A.F.G., M.A.S.; project administration, J.M.B., A.F.G., M.A.S., D.S.C.; funding acquisition, J.M.B., A.F.G., M.A.S., D.S.C. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the U.S. National Science Foundation through gran<sup>t</sup> numbers EAR-0538094 and EAR-1853496 to J.B.; gran<sup>t</sup> number EAR-1250505 to A.G.; gran<sup>t</sup> number EAR-0538129 to A.G. and D.C.; and gran<sup>t</sup> number EAR-1853496 to M.S. A.G. also gratefully acknowledges support from the Mary Lily Kenan Flagler Bingham Professorship.

**Acknowledgments:** Discussions with Ryan D. Mills and John R. Bowman contributed to development of the ideas presented in this paper. Input from two anonymous reviewers helped us to improve the clarity of the paper. U.S. National Park Service personnel, especially Greg Stock, Jan van Wagtendonk, and Peggy Moore, have been supportive and helpful to our field studies in Yosemite. John Bowman provided the CL image from the Alta Granodiorite in Figure 4d.

**Conflicts of Interest:** The authors declare no conflict of interest.
