UCL Discovery
UCL home » Library Services » Electronic resources » UCL Discovery

Evaluating the formation pressure of diamond-hosted majoritic garnets; A machine-learning barometer

Thomson, A; Kohn, SC; Prabhu, A; Walter, MJ; (2021) Evaluating the formation pressure of diamond-hosted majoritic garnets; A machine-learning barometer. Journal of Geophysical Research: Solid Earth , 126 (3) , Article e2020JB020604. 10.1029/2020JB020604. Green open access

[img]
Preview
Text
Thomson_Evaluating the formation pressure of diamond-hosted majoritic garnets; A machine-learning barometer_VoR.pdf - Published version

Download (4MB) | Preview

Abstract

Diamond‐hosted majoritic garnet inclusions provide unique insights into the Earth's deep, and otherwise inaccessible, mantle. Compared with other types of mineral inclusions found in sub‐lithospheric diamonds, majoritic garnets can provide the most accurate estimates of diamond formation pressures because laboratory experiments have shown that garnet chemistry varies strongly as a function of pressure. However, evaluation using a compilation of experimental data demonstrates that none of the available empirical barometers are reliable for predicting the formation pressure of many experimental majoritic garnets and cannot be applied with confidence to diamond‐hosted garnet inclusions. On the basis of the full experimental data set, we develop a novel type of majorite barometer using machine learning algorithms. Cross validation demonstrates that Random Forest Regression allows accurate prediction of the formation pressure across the full range of experimental majoritic garnet compositions found in the literature. Applying this new barometer to the global database of diamond‐hosted inclusions reveals that their formation occurs in specific pressure modes. However, exsolved clinopyroxene components that are often observed within garnet inclusions are not included in this analysis. Reconstruction of inclusions, in the 8 cases where this is currently possible, reveals that ignoring small exsolved components can lead to underestimating inclusion pressures by up to 7 GPa (∼210 km). The predicted formation pressures of majoritic garnet inclusions are consistent with crystallization of carbon‐rich slab‐derived melts in Earth's deep upper mantle and transition zone.

Type: Article
Title: Evaluating the formation pressure of diamond-hosted majoritic garnets; A machine-learning barometer
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2020JB020604
Publisher version: https://doi.org/10.1029/2020JB020604
Language: English
Additional information: © 2021 The Authors. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/).
Keywords: barometer, machine learning, majoritic garnet, sub‐lithospheric diamonds
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences
URI: https://discovery.ucl.ac.uk/id/eprint/10121197
Downloads since deposit
2Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item