This project compares trends in the abundance of trace elements from the lanthanide series of rare earth elements (REE) from five garnets from the ultrahigh-pressure metamorphic Tso Morari Complex (TMC), Ladakh Province, NW India. Raw trace element abundance data were obtained by McElroy in 2013, using laser ablated-inductively coupled plasma mass spectrometry, and plotted in counts per second against length of laser ablation. These data were corrected using the known abundance of the isotope 29silicon in garnet as an internal standard, following the procedure of Lin (2006). Changing trends of trace element abundance indicate changes in the rate at which trace elements are transported between garnet grains, commonly influenced by changes in metamorphic conditions. By correlating the sections of the element abundance profiles from the five garnets that represent periods of simultaneous growth, this study observed trends in the shape of the profiles that indicate changes in the rate at which trace elements were incorporated into the growing garnets as the trace elements diffuse through the parent rock. In the TMC garnets, the light REE form bell-shaped profiles, associated with rapid diffusion of trace elements in an unchanging assemblage of matrix minerals, or oscillating profiles, associated with rapid diffusion during the breakdown of matrix minerals (Moore et al., 2013). M-shaped profiles in the medium and heavy REE is interpreted to mean that the limiting factor in the rate of trace element uptake by the garnets was the rate at which the trace elements were transported through the intergranular medium (Moore et al., 2013).
Anne Zegers, ’16
Sponsor: Emily Walsh