Sm-Nd Epsilon Grid (felsic igneous rocks) July 2024

This is an interpolated grid of Sm-Nd epsilon values, based on whole-rock Nd isotopic analyses from felsic magmatic rocks, particularly focusing on I- and A-type granites and volcanic rocks. The point data used for the interpolation is the “felsic igneous rock” subset of the Sm-Nd data held in the Isotopic Atlas as of July 2024. Point data added to the Isotopic Atlas after July 2024 is not represented in this grid. The grid is a Natural Neighbours interpolation with a cell size of 0.01 degrees, generated using the nn C code library published at https://github.com/sakov/nn-c. Two classifications are provided for this grid; a Jenks natural breaks classification with ten classes (classification 1) as per Champion (2013) http://pid.geoscience.gov.au/dataset/ga/77772, and; the same seven-class interval binning and colour scheme applied to the source point data in the Sm-Nd Isotope Data layer (classification 2).