Sm-Nd Residence Time Grid (felsic igneous rocks) July 2024

This is an interpolated grid of Nd residence time values, based on whole-rock Nd isotopic analyses from felsic magmatic rocks, particularly focusing on I- and A-type granites and volcanic rocks. The data provides an estimate of the duration for material residing in the crust prior to its last melting event. 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 nine-class interval binning and colour scheme applied to the source point data in the Sm-Nd Isotope Data layer (classification 2).

本数据集为钕（Nd）停留时间插值网格，基于长英质岩浆岩的全岩钕同位素分析数据构建，尤其聚焦I型、A型花岗岩及其火山岩。该数据可用于估算物质在最终熔融事件前在地壳中停留的时长。本次插值所用的点位数据，为2024年7月时收录于《同位素图谱（Isotopic Atlas）》中的钐-钕（Sm-Nd）数据的“长英质火成岩”子集。2024年7月后新增至《同位素图谱》的点位数据未被纳入本插值网格。本网格采用自然邻域插值法（Natural Neighbours）构建，单元格分辨率为0.01度，所用代码为发布于https://github.com/sakov/nn-c的nn C语言代码库。本网格提供两种分类方案：其一为遵循Champion（2013）提出的10类詹克自然断点分类法（Jenks natural breaks）（分类方案1），参考数据源为http://pid.geoscience.gov.au/dataset/ga/77772；其二为与Sm-Nd同位素数据图层中源点位数据一致的9类区间分箱配色方案（分类方案2）。