The two-dimensional pattern of metamorphic fluid flow at Mary Kathleen, Australia: fluid focusing, transverse dispersion, and implications for modeling fluid flow

The pattern of resetting of δ¹⁸O values in layered Corella calc-silicate rocks adjacent to a scapolitized metadolerite dike at Timberu in the Mary Kathleen fold belt illustrates some of the complexities of two-dimensional metamorphic fluid flow. Fluids flowing from the dike (δ¹⁸O = 9-10‰) into the calc-silicate rocks lowered calcite δ¹⁸O values from 19-20‰ to as low as 10.2‰. Time-integrated advective fluid fluxes varied from 0.72 to >8.1 m³/m² over a 4.5-m lateral distance, and there are two distinct channels of higher fluid flux. Fluid flow was largely focused across lithological layering, with rare excursions parallel to layering, suggesting that flow was probably hosted within microfractures and that the variable permeabilities resulted from variations in microfracture density. Transverse dispersion during channeled fluid flow will potentially reset O-isotope ratios adjacent to the channels and cause decoupling of geochemical parameters during advective and dispersive transport. -from Author