CSIRO VNIR spectral library - Evaluation and status report 2016

[摘要] The visible near infrared (VNIR; 350 to 1100 nm) spectral reference library (SRL) is an important component of interpreting reflectance spectra derived from hyperspectral drill core sensors, such as the HyLogger. It is therefore critical to ensure that the currently used VNIR-SRL is fully representative of minerals that are being discovered in the growing holdings of the National Virtual Core Library (NVCL). To strengthen the confidence of the NVCL nodes and other users of the NVCL data in the current VNIR-SRL, it became necessary to undertake a review of the current spectral library and to identify additional essential or fit for purpose samples.This report summarises the current status of the VNIR-SRL, by 1) attempting to clarify the provenance and composition of the minerals contained within the VNIR-SRL, 2) assessing the extensiveness of the current set of samples in the VNIR-SRL, and 3) identifying potential minerals for replacement and addition to the current VNIR-SRL.During this evaluation it became clear that the provenance and composition of mineral groups and species present in the current VNIR-SRL is largely imprecise. Based solely on the VNIR spectral signatures, the naming of the samples appears to be correct overall. However, there are considerable overlaps between the spectral signatures of, for example, iron oxides and sulphides in the VNIR-SRL, which imply that validation using, for example, QXRD or EPMA, would be required before treating these as reference spectra. As the samples are not accessible, new sample material would have to be required, eventually replacing the existing reference spectra.This evaluation also suggests that the current VNIR-SRL is incomplete and not fully representative of the mineral groups and species found across Australia. The collection of iron oxides and sulphides is incomplete and other increasingly important mineral species, such as the REE-bearing carbonates and phosphates, are completely missing. Sample candidates for replacement or addition have been identified in the frame of this project.Recommendations:1) Reconstruction of a new VNIR-SRL, comprising a larger suite of iron oxides, sulphides, sulphates, REE-bearing phosphates and carbonates as well as silicates.2) Using validated samples that are part of the TIR-SRL and/or available from other projects to kick-start the resetting of the VNIR-SRL3) Creation of a test dataset to enable an evaluation of the performance of TSAV4) Collection of continuous (UV)-VNIR-SWIR-MIR-TIR-FIR spectra of all new samples to create a single SRLA single SRL would remove the complications associated with curation of three separate SRLs and could considerably improve our understanding of spectral signatures of rock forming minerals across the visible and infrared wavelengths of the electromagnetic spectrum. This could, in turn feed into future, improved unmixing methods across the various wavelength ranges and prepare the NVCL community for the interpretation and application of the currently not used UV, MIR and FIR wavelength ranges, which may create opportunities for exploration across a variety of geological settings.

[发布日期] 2016-09-02 [发布机构] CSIRO

[学科分类] 地球科学(综合)