Scientific References

This page lists the bibliographic foundations for the analytical methods, matching algorithms, fractionation models, and standard databases implemented in IsoFind. Each reference is linked to the specific software functionality it supports.

Entries are organized by functional domain. Color-coded tags indicate the type of reference: Algorithm calculation and matching methods, Standard reference materials and values, Application traceability and forensics, Fractionation isotopic models, ML machine learning contextualization.

International Isotopic Standards

IsoFind integrates certified reference values from the primary international standards used in isotope geochemistry. The numerical values stored in the isotope_standards table are sourced from the following primary literature.

NIST Standards (National Institute of Standards and Technology)

Catanzaro, E.J. et al. : Absolute isotopic abundance ratios and atomic weight of terrestrial rubidium. Journal of Research of the National Bureau of Standards, 73A, 511–516 (1969). Standard
Rb reference values. Used for 87Sr/86Sr normalization via instrumental mass fractionation corrections.

Wieser, M.E. & Coplen, T.B. : Atomic weights of the elements 2009 (IUPAC Technical Report). Pure and Applied Chemistry, 83(2), 359–396 (2011). Standard
10.1351/PAC-REP-10-09-14 IUPAC standard atomic weights. Used in the molecular weight calculator and mass spectra simulations.

Wasserburg, G.J., Jacobsen, S.B., DePaolo, D.J., McCulloch, M.T. & Wen, T. : Precise determinations of Sm/Nd ratios, Sm and Nd isotopic abundances in standard solutions. Geochimica et Cosmochimica Acta, 45(12), 2311–2323 (1981). Standard
10.1016/0016-7037(81)90085-5 CHUR (Chondritic Uniform Reservoir) values: 143Nd/144Nd = 0.512638, 147Sm/144Nd = 0.1967. Reference for epsilon-Nd calculations.

Tanaka, T. et al. : JNdi-1: a neodymium isotopic reference in consistency with LaJolla neodymium. Chemical Geology, 168(3–4), 279–281 (2000). Standard
10.1016/S0009-2541(00)00198-4 JNdi-1 standard for neodymium normalization. 143Nd/144Nd = 0.512115 ± 0.000007. Primary IsoFind reference for the Sm-Nd system.

Thirlwall, M.F. : Long-term reproducibility of multicollector Sr and Nd isotope ratio analysis. Chemical Geology (Isotope Geoscience Section), 94(1–2), 85–104 (1991). Standard
10.1016/S0168-9622(11)80006-X NIST SRM 987 standard for strontium: 87Sr/86Sr = 0.710248 ± 0.000015. Primary IsoFind reference for Sr normalization.

IAEA Standards (International Atomic Energy Agency)

Coplen, T.B. : Normalization of oxygen and hydrogen isotope data. Chemical Geology (Isotope Geoscience Section), 72(4), 293–297 (1988). Standard
10.1016/0168-9622(88)90042-5 Formalization of VSMOW (Vienna Standard Mean Ocean Water) and VSMOW2 for the normalization of light stable isotopes O and H. Reference for delta18O and deltaD.

Coplen, T.B. : New guidelines for reporting stable hydrogen, carbon, and oxygen isotope-ratio data. Geochimica et Cosmochimica Acta, 60(17), 3359–3360 (1996). Standard
10.1016/0016-7037(96)00263-3 VPDB (Vienna Pee Dee Belemnite) for carbon. Defines delta-value sign conventions and reporting relative to VPDB-CO2. Reference for delta13C in IsoFind.

Robinson, B.W. & Kusakabe, M. : Quantitative preparation of sulfur dioxide, for ³⁴S/³²S analyses, from sulfides by combustion with cuprous oxide. Analytical Chemistry, 47(7), 1179–1181 (1975). Standard
10.1021/ac60357a026 VCDT (Vienna Canyon Diablo Troilite) standard for sulfur. Reference for delta34S.

Mariotti, A. : Atmospheric nitrogen is a reliable standard for natural ¹⁵N abundance measurements. Nature, 303, 685–687 (1983). Standard
10.1038/303685a0 AIR-N2 standard for atmospheric nitrogen. Reference for delta15N and enriched fraction calculations.

Trace Elements and Heavy Metals Standards

Todt, W., Cliff, R.A., Hanser, A. & Hofmann, A.W. : Evaluation of a ²⁰²Pb-²⁰⁵Pb double spike for high-precision lead isotope analysis. In: Basu A. & Hart S.R. (eds), Earth Processes: Reading the Isotopic Code, Geophysical Monograph 95, 429–437 (1996). Standard NIST SRM 981 standard (Common Lead) for Pb normalization. Reference values: 206Pb/204Pb = 16.9356, 207Pb/204Pb = 15.4891, 208Pb/204Pb = 36.7006.

Rosman, K.J.R. & Taylor, P.D.P. : Isotopic compositions of the elements 1997 (IUPAC Technical Report). Pure and Applied Chemistry, 70(1), 217–235 (1998). Standard
10.1351/pac199870010217 Reference natural isotopic compositions for all elements. Used in the molecular weight calculator and isotopic distribution simulations.

Rouxel, O., Ludden, J. & Fouquet, Y. : Antimony isotope variations in natural systems and implications for their use as geochemical tracers. Chemical Geology, 200(1–2), 25–40 (2003). Standard
10.1016/S0009-2541(03)00121-9 First high-precision study on antimony isotopes by HG-MC-ICP-MS. Establishes reference isotopic compositions for the Earth's crust (delta-123Sb = 0.2 ± 0.1 epsilon), seawater, and hydrothermal sulfides. NIST SRM 3102a is recommended as the zero-delta standard. Primary IsoFind reference for the Sb system.

Kleine, T. et al. : Tungsten isotopes and the chronology of the solar system and the early Earth. Earth and Planetary Science Letters, 273(1–2), 12–20 (2008). Standard
10.1016/j.epsl.2008.06.012 Reference values for tungsten (186W/184W, 182W/184W, mu-W notation). Reference for tungsten isotope tracing in defense and critical materials contexts.

Schiller, M., Handler, M.R. & Baker, J.A. : High-precision Nd isotope measurements of geological materials by MC-ICPMS: an evaluation of on-peak and interpolated background correction. Chemical Geology, 297(1–2), 121–132 (2012). Standard
10.1016/j.chemgeo.2012.01.009

Blichert-Toft, J. & Albarède, F. : The Lu-Hf isotope geochemistry of chondrites and the evolution of the mantle-crust system. Earth and Planetary Science Letters, 148(1–2), 243–258 (1997). Standard
10.1016/S0012-821X(97)00040-X Hafnium CHUR: 176Hf/177Hf = 0.282772, 176Lu/177Hf = 0.0336. Reference for epsilon-Hf calculation in IsoFind.

Isotopic Matching Algorithms

The algorithms implemented in IsoFind's matching module are based on the following statistical approaches. The default recommended hybrid algorithm combines these three approaches with adaptive weighting.

Mahalanobis, P.C. : On the generalised distance in statistics. Proceedings of the National Institute of Sciences of India, 2(1), 49–55 (1936). Algorithm Foundation of the Mahalanobis distance algorithm implemented in IsoFind. The distance accounts for element correlations and respective analytical uncertainties, unlike simple Euclidean distance.

Bayes, T. & Price, R. : An essay towards solving a problem in the doctrine of chances. Philosophical Transactions of the Royal Society of London, 53, 370–418 (1763). Algorithm Theoretical foundation of the Bayesian algorithm. In IsoFind, likelihood is calculated assuming a normal distribution for each isotopic ratio, with a uniform prior over geographic areas.

Albarède, F., Beard, B.L. : Analytical methods for non-traditional isotopes. Reviews in Mineralogy and Geochemistry, 55(1), 113–152 (2004). Algorithm
10.2138/gsrmg.55.1.113 MC-ICP-MS isotopic data processing methodology. Foundation for instrumental mass fractionation corrections (exponential law, power law) implemented in IsoFind.

McLachlan, G.J. : Discriminant Analysis and Statistical Pattern Recognition. Wiley-Interscience, New York (1992). ISBN 978-0-471-69115-0. Algorithm Theoretical basis for the multivariate discriminant analysis used in IsoFind's hybrid algorithm. Treats the multi-element matching problem as a supervised classification task.

Balsam, W., Ji, J. & Chen, J. : Climatic interpretation of the Luochuan and Lingtai loess sections, China, based on changing iron oxide mineralogy and magnetic susceptibility. Earth and Planetary Science Letters, 223(3–4), 335–348 (2004). Algorithm
10.1016/j.epsl.2004.04.023 Application of multivariate analysis to the geochemical discrimination of materials. Reference methodology for the geographic zone matching approach.

Isotopic Fractionation Models (Nexus)

The fractionation models implemented in IsoFind Nexus are based on the following classical formulations. Each fractionation node within a Nexus workflow is explicitly parameterized using the corresponding equations.

Rayleigh, Lord (J.W. Strutt) : On the distillation of binary mixtures. Philosophical Magazine, 4(23), 521–537 (1902). Fractionation Original Rayleigh equation. Within IsoFind Nexus, the Rayleigh model calculates the isotopic composition of the residue (R/R0 = f^(alpha-1)), the instantaneous product, and the cumulative product as a function of the reacted fraction and the fractionation factor (alpha).

Hoefs, J. : Stable Isotope Geochemistry (8th edition). Springer International Publishing, 2018. ISBN 978-3-319-78526-4. Fractionation Comprehensive reference for equilibrium and kinetic isotopic fractionation models. Provides the basis for default fractionation parameters for light elements (C, N, O, S, H) in Nexus.

Young, E.D., Galy, A. & Nagahara, H. : Kinetic and equilibrium mass-dependent isotope fractionation laws in nature and their geochemical and cosmochemical significance. Geochimica et Cosmochimica Acta, 66(6), 1095–1104 (2002). Fractionation
10.1016/S0016-7037(01)00832-8 Distinction between equilibrium (exponential) and kinetic (power) mass-dependent fractionation laws. Foundation for the fractionation law selector in Nexus nodes.

Eiler, J.M., Farquhar, J. & Ono, S. (eds) : Frontiers of Stable Isotope Geoscience. Annual Review of Earth and Planetary Sciences, 35, 1–46 (2007). Fractionation
10.1146/annurev.earth.35.031306.140251 Review of recent developments in stable isotope geochemistry. Provides scientific context for non-traditional isotopic systems (Fe, Zn, Cu, Mo) implemented in IsoFind.

Zeebe, R.E. & Wolf-Gladrow, D.A. : CO2 in Seawater: Equilibrium, Kinetics, Isotopes. Elsevier Oceanography Series, vol. 65, Amsterdam (2001). ISBN 978-0-444-50579-9. Fractionation Isotopic fractionation factors for oxygen and carbon in carbonate systems. Reference for sedimentary and diagenetic process nodes in Nexus.

Criss, R.E. : Principles of Stable Isotope Distribution. Oxford University Press, New York (1999). ISBN 978-0-19-511743-5. Fractionation Rigorous mathematical formulation of isotopic mass balance equations. Reference for verifying mass balances in multi-step Nexus workflows.

Traceability, Provenance, and Forensics

IsoFind's analytical applications in the fields of provenance and geochemical forensics are based on the following works.

Multi-Elemental Isotopic Systems

Faure, G. & Mensing, T.M. : Isotopes: Principles and Applications (3rd edition). Wiley, New Jersey (2005). ISBN 978-0-471-38437-3. Application Foundational reference on radiogenic systems (Rb-Sr, Sm-Nd, U-Pb, Lu-Hf, Re-Os). Conceptual basis for IsoFind’s multi-system matching modules.

Bentley, R.A. : Strontium isotopes from the earth to the archaeological skeleton: a review. Journal of Archaeological Method and Theory, 13(3), 135–187 (2006). Application
10.1007/s10816-006-9009-x Methodology for provenance tracing using strontium isotopes. Reference for archaeometric and forensic applications using IsoFind.

Beard, B.L. & Johnson, C.M. : High precision iron isotope measurements of terrestrial and lunar materials. Geochimica et Cosmochimica Acta, 63(11–12), 1653–1660 (1999). Application
10.1016/S0016-7037(99)00083-3 First demonstration of iron isotope variability in terrestrial materials and its significance for provenance tracing. Foundation for the iron isotopic tracing module in IsoFind.

Moynier, F., Vance, D., Fujii, T. & Savage, P. : The isotope geochemistry of zinc and copper. Reviews in Mineralogy and Geochemistry, 82(1), 543–600 (2017). Application
10.2138/rmg.2017.82.13 Review of Zn and Cu isotopic systems. Basis for default parameters in mining and pollution tracing applications within IsoFind.

Critical Materials Traceability

Mathur, R. et al. : Exploring copper isotope systematics during metallurgical smelting. Archaeometry, 58(5), 749–773 (2016). Application
10.1111/arcm.12173 Alteration of copper isotopic signatures during metallurgical smelting. Reference for source/product distinction in IsoFind's classification module applied to processed metals.

Resongles, E., Freydier, R., Casiot, C., Viers, J., Chmeleff, J. & Elbaz-Poulichet, F. : Antimony isotopic composition in river waters affected by ancient mining activity. Talanta, 144, 851–861 (2015). Application
10.1016/j.talanta.2015.07.013 First application of Sb isotopes for tracing mining pollution in hydrological contexts. Development of a preconcentration method using thiol-cellulose powder. Direct reference for antimony use cases in IsoFind (mining traceability, CRM Act compliance). This study originated from the HydroSciences Montpellier laboratory, the same institution as IsoFind's PhD roots.

Polat, A. et al. : Tungsten isotope constraints on the origin and early evolution of the Eoarchean Saglek–Hebron gneiss complex of Labrador, Canada. Earth and Planetary Science Letters, 489, 94–104 (2018). Application
10.1016/j.epsl.2018.06.026 Application of tungsten isotopes to geochemical tracing. Reference for tungsten traceability use cases in defense and tooling industries (CRM Act).

European Commission : Critical Raw Materials Act (Regulation EU 2024/1252). Official Journal of the European Union, L series (2024). Application Regulatory framework for the traceability of critical raw materials in Europe. IsoFind is positioned as a compliance tool for isotopic traceability within the CRM Act context (antimony, tungsten, rare earth elements, lithium).

Reference Geochemical Databases

Jochum, K.P. et al. : GeoReM: a new geochemical database for reference materials and isotopic standards. Geostandards and Geoanalytical Research, 29(3), 333–338 (2005). Standard
10.1111/j.1751-908X.2005.tb00904.x GeoReM database (Max-Planck-Institut für Chemie) for geochemical reference materials. Integrated into IsoFind via the GET /api/crm/georem endpoint for updating CRM certified values.

Lehnert, K. et al. : A global geochemical database structure for rocks. Geochemistry, Geophysics, Geosystems, 1(5) (2000). Standard
10.1029/1999GC000026 PetDB/EarthChem: global geochemical data infrastructure. Partial source of regional geochemical background data in IsoFind's reference_data table.

Rudnick, R.L. & Gao, S. : Composition of the continental crust. Treatise on Geochemistry, vol. 3, 1–64 (2003). Elsevier. Standard
10.1016/B0-08-043751-6/03016-4 Isotopic composition of the upper and lower continental crust. Provides reference geochemical background values for multiple elements within IsoFind's geographic zones.

Analytical Methods and Instrumentation

Rehkämper, M. & Halliday, A.N. : Accuracy and long-term reproducibility of lead isotopic measurements by multiple-collector inductively coupled plasma mass spectrometry using an external method for correction of mass discrimination. International Journal of Mass Spectrometry and Ion Processes, 181(1–3), 123–133 (1998). Standard
10.1016/S0168-1176(98)00258-5 Correction of instrumental mass fractionation using external standards (SSB, standard-sample bracketing). Basis for normalization methods implemented in IsoFind for MC-ICP-MS measurements.

Maréchal, C.N., Télouk, P. & Albarède, F. : Precise analysis of copper and zinc isotopic compositions by plasma-source mass spectrometry. Chemical Geology, 156(1–4), 251–273 (1999). Standard
10.1016/S0009-2541(98)00191-0 Double spike and internal standard correction methods for Cu and Zn. Reference for the analytical protocols of these elements in IsoFind's method library.

Weyer, S. & Schwieters, J.B. : High precision Fe isotope measurements with high mass resolution MC-ICPMS. International Journal of Mass Spectrometry, 226(3), 355–368 (2003). Standard
10.1016/S1387-3806(03)00078-2 High-resolution measurement protocol for iron isotopes. Basis for instrumental parameters for Fe methods in IsoFind.

Machine Learning Models (Contextualization)

IsoFind integrates contextualization models trained on 1.7 million geochemical data points. These models do not replace deterministic matching algorithms; rather, they provide statistical and geochemical context, while final decisions always rely on explicit physico-chemical models.

Breiman, L. : Random forests. Machine Learning, 45(1), 5–32 (2001). ML
10.1023/A:1010933404324 Random Forest algorithm used in IsoFind's geochemical contextualization module. Provides confidence scores for material classification and the geochemical plausibility of signatures.

Pedregosa, F. et al. : Scikit-learn: Machine Learning in Python. Journal of Machine Learning Research, 12, 2825–2830 (2011). ML Machine learning framework used for training and deploying contextualization models. Models exported in ONNX format are loaded via onnxruntime within IsoFind.

Kohn, M.J., Mering, J.A., Lackey, J.S. & Valley, J.W. : Modeling oxygen isotope compositions of meteoric water and crustal rocks from stable isotopic systematics. American Journal of Science, 302(3), 151–174 (2002). ML
10.2475/ajs.302.3.151 Geostatistical modeling of regional isotopic signatures. Reference approach for constructing the regional predictive models used in IsoFind contextualization.

Inter-laboratory Normalization and Reproducibility

Carignan, J. et al. : Routine analyses of trace elements in geological samples using flow injection and low pressure on-line liquid chromatography coupled to ICP-MS: a study of geochemical reference materials BR, DR-N, UB-N, AN-G and GH. Geostandards Newsletter, 25(2–3), 187–198 (2001). Standard
10.1111/j.1751-908X.2001.tb00595.x Reference protocols for the analysis of French geological CRMs (BR, DR-N, UB-N, AN-G, GH). Basis for the certified values of these materials in IsoFind.

Jochum, K.P. et al. : Determination of reference values for NIST SRM 610–617 glasses following ISO guidelines. Geostandards and Geoanalytical Research, 35(4), 397–429 (2011). Standard
10.1111/j.1751-908X.2011.00120.x ISO reference values for NIST SRM 610–617 glasses. Used as secondary CRMs in IsoFind for validating LA-ICP-MS analytical sessions.

Isogeochem (International Community) : EARTHTIME initiative for inter-laboratory calibration of U-Pb geochronology. earthtime.org (2003–ongoing). Standard Reference for inter-laboratory harmonization protocols. Methodological basis for IsoFind's inter-laboratory normalization module (isotopic_shifts, data standardization on common calibrants).

ISOF Format and Data Exchange

Ferrari, C. : ISOF: Isotopic Open Format: v1.0 specification. IsoFind SAS, 2025. Available at isofind.tech/isof-spec. Application Official specification of the ISOF format for isotopic data exchange. Open JSON format with optional cryptographic signatures (Level 1 SHA-256, Level 2 ECDSA P-256). See the ISOF Standard section of this documentation.

Ferrari, C. : isof: Python reader and verifier for the ISOF v1.0 geochemical data exchange format. PyPI package v0.1.0, 2025. github.com/isofind/isof-parser, MIT license. Application Open-source Python package for reading and verifying ISOF files. Can be used independently of IsoFind. See the Open-source code integration page.

To report a missing reference, an incorrect standard value, or to propose the addition of a new isotopic system, please contact colin.ferrari@isofind.tech . Validated corrections are integrated into the next update.