Reimagining Niggli Numbers for modern data applications in petrology and exploration geochemistry

McDonald, Iain ORCID: https://orcid.org/0000-0001-9066-7244 2024. Reimagining Niggli Numbers for modern data applications in petrology and exploration geochemistry. Chemical Geology 650 , 121915. 10.1016/j.chemgeo.2023.121915

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Abstract

This study seeks to refamiliarize the geochemical community with Niggli Numbers and explore how Paul Niggli's largely forgotten scheme for representing major elements as equivalent molecular numbers that are combined as groups, sums and ratios. This scheme provides simple and effective tools for tackling many modern geochemical problems – particularly to reduce complexity and degrees of freedom where there are requirements to handle large volumes of data. Niggli Numbers provide an alternative to ratio-based methods for the long-recognised problem of the constant sum and data closure in geochemistry and offer a means to represent minerals and their relationships in a straightforward and consistent chemical framework. The Niggli calculation scheme follows simple rules that are easily automated, is flexible enough to accommodate missing elements or partial analyses, and is appropriate for all rock types. Following a short review of the most useful Niggli binary diagrams and where common minerals plot in Niggli space, a series of case studies are presented to illustrate potential applications of the scheme in modern petrology and resource exploration. These cover the following: magmatic evolution of a layered intrusion such as the Bushveld Complex; contamination of magmas by country rocks; tracing hydrothermal alteration in volcanogenic massive sulfide and porphyry Cusingle bondMo deposits; and chemostratigraphy of sedimentary sequences.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Earth and Environmental Sciences
Publisher:	Elsevier
ISSN:	0009-2541
Date of First Compliant Deposit:	5 January 2024
Date of Acceptance:	26 December 2023
Last Modified:	07 Mar 2024 12:28
URI:	https://orca.cardiff.ac.uk/id/eprint/165277

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