Proposed research will address fundamental questions about chemical process during metamorphism: (1) What is the scale, geometry, and structural control on the channelization of reactive metamorphic fluid flow? (2) How much mass is transported into or out of the flow channels by diffusion and dispersion? (3) What is the amount and scale of major element mass transport by flow? (4) How can episodes of metamorphic fluid flow be dated? The questions will be addressed by new field studies of carbonate rocks in 3 contact metamorphic terrains in California, Italy, and Scotland as well as by laboratory study of 3 rock sample suites from New England at hand. Channels for fluid flow will be mapped in the field from the distribution of mineral reaction products and correlated with structural features. The geometry amd mechanisms of mass transfer will be evaluated by quantitatively interpreting reaction progress and O-isotope data with transport theory. The amount and scale of Si-transport will be assessed from chemical analyses of rocks. The age of flow events will be determined by defining the metamorphic conditions at which monazite and allanite form and measurement of the minerals' Pb-Th-U ages by mass spectrometry.
