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Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust
Thesis (MSc)--Stellenbosch University, 2023.
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| Format: | Thesis |
| Language: | en_ZA |
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Stellenbosch : Stellenbosch University
2023
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| _version_ | 1867613870427734016 |
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| access_status_str | Open Access |
| author | Hoffman, Sean |
| author2 | Mayne, Matthew Jason |
| author_browse | Hoffman, Sean Mayne, Matthew Jason |
| author_facet | Mayne, Matthew Jason Hoffman, Sean |
| author_sort | Hoffman, Sean |
| collection | Thesis |
| dc_rights_str_mv | Stellenbosch University |
| description | Thesis (MSc)--Stellenbosch University, 2023. |
| format | Thesis |
| id | oai:scholar.sun.ac.za:10019.1/126967 |
| institution | Stellenbosch University (South Africa) |
| language | en_ZA |
| last_indexed | 2026-06-10T12:43:00.621Z |
| license_str | Other — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from SUNScholar — Stellenbosch University Repository |
| publishDate | 2023 |
| publishDateRange | 2023 |
| publishDateSort | 2023 |
| publisher | Stellenbosch : Stellenbosch University |
| publisherStr | Stellenbosch : Stellenbosch University |
| record_format | dspace |
| source_str | SUNScholar — Stellenbosch University Repository |
| spelling | oai:scholar.sun.ac.za:10019.1/126967 Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust Hoffman, Sean Mayne, Matthew Jason Stevens, Gary Stellenbosch University. Faculty of Science. Dept. of Earth Sciences. Igneous rocks -- Petrology Rocks -- Trace element content Thermodynamic equilibrium -- Mathematical models Mineralogical chemistry Trace elements UCTD Thesis (MSc)--Stellenbosch University, 2023. ENGLISH ABSTRACT: Phase equilibria modelling techniques can constrain the equilibrium conditions of major rock forming minerals, however current thermodynamic databases and activity-composition models cannot accommodate minor and trace elements as chemical components in modelled systems. This thesis presents the integration of trace element partitioning routines between melt and solid phases in the thermodynamic modelling tool Rcrust in order to effectively estimate the trace element composition of stable phases when melt is present. Additionally, trace elements occur in large abundances in certain accessory phases, for which we do not currently have activity-composition models. These trace element-rich accessory phases may have significant influence on the trace element chemistry of a magmatic system. For this constraint, accessory phase saturation routines for apatite and monazite, two commonly occurring accessory phases in granitic rocks, are newly integrated in this thesis to the existing Rcrust modelling tool. This provides a novel methodology for approximating trace element distribution among thermodynamically constrained phases with thermodynamically unconstrained accessory phases, apatite and monazite. The results highlight the importance of major element components that also contribute to accessory phase formation, such as calcium in apatite (which can accommodate a non-trivial quantity of the available calcium) and the resultant effect on phase equilibria of major phases. Saturating apatite can alter phase equilibria, mainly for calcium-bearing phases, that is equivalent to up to 20 °C change in temperature. A case study of the Peninsula Pluton granodiorite, South Africa, is used to validate the use of accessory phase saturation and trace element partitioning with phase equilibria modelling. The model predicts LREE concentrations of apatite and monazite that match the natural sample at temperatures below 725 °C, corroborating previous findings for emplacement P-T constraints. However, phase assemblages predicted through phase equilibria modelling show that the rock equilibrated to P-T below the emplacement estimates of previous studies. By modelling both major and accessory phases, constraints are provided on the formation and crystallisation of crustal magmas which has important implications on geothermobarometry and thermochronology in the crust. AFRIKAANSE OPSOMMING: Fase-ewewig-modelleringstegnieke kan die ewewigstoestande van belangrike rotsvormende minerale beperk, maar huidige termodinamiese databasisse en aktiwiteit-samestellingmodelle kan egter nie klein- en spoorelemente as chemiese komponente in gemodelleerde stelsels akkommodeer nie. Hierdie tesis bied die integrasie van spoorelement-verdelingsroetines tussen smelt- en vaste fases in die termodinamiese modelleringsinstrument Rcrust voor om die spoorelementsamestelling van stabiele fases effektief te skat wanneer smelt teenwoordig is. Boonop kom spoorelemente in groot oorvloede voor in sekere bykomstige fases, waarvoor ons tans nie aktiwiteit-samestelling modelle het nie. Hierdie spoorelementryke bykomstige fases kan beduidende invloed hê op die spoorelementchemie van 'n magmatiese sisteem. Vir hierdie beperking is bykomstige faseversadigingsroetines vir apatiet en monasiet, twee algemeen voorkomende bykomstige fases in granitiese gesteentes, nuut geïntegreer in hierdie tesis met die bestaande Rcrust-modelleringsinstrument. Dit bied 'n nuwe metodologie vir die benadering van spoorelementverspreiding tussen termodinamies-beperkte fases met termodinamies onbeperkte bykomstige fases, apatiet en monasiet. Die resultate beklemtoon die belangrikheid van hoofelementkomponente wat ook bydra tot bykomende fase-vorming, soos kalsium in apatiet (wat 'n nie-onbeduidende hoeveelheid van die beskikbare kalsium kan akkommodeer) en die gevolglike effek op fase-ewewigte van hooffases. Versadigende apatiet kan fase-ewewigte verander, hoofsaaklik vir kalsiumdraende fases, wat gelykstaande is aan tot 20 °C verandering in temperatuur. 'n Gevallestudie van die Peninsula Pluton-granodioriet, Suid-Afrika, word gebruik om die gebruik van bykomende faseversadiging en spoorelementpartisionering met fase-ewewigmodellering te valideer. Die model voorspel LREE-konsentrasies van apatiet en monasiet wat ooreenstem met die natuurlike monster by temperature onder 725 °C, wat vorige bevindinge vir plasing P-T-beperkings bevestig. Fasesamestellings wat deur fase-ewewigmodellering voorspel is, toon egter dat die rots tot P-T onder die plasingsskattings van vorige studies geëkwilibreer het. Deur beide hoof- en bykomstige fases te modelleer, word beperkings op die vorming en kristallisasie van korsmagmas voorsien wat belangrike implikasies op geotermobarometrie en termochronologie in die kors het. Masters 2023-02-08T07:40:24Z 2023-05-18T06:57:59Z 2023-02-08T07:40:24Z 2023-05-18T06:57:59Z 2023-03 Thesis http://hdl.handle.net/10019.1/126967 en_ZA Stellenbosch University xii, 67 pages : illustrations, maps application/pdf Stellenbosch : Stellenbosch University |
| spellingShingle | Igneous rocks -- Petrology Rocks -- Trace element content Thermodynamic equilibrium -- Mathematical models Mineralogical chemistry Trace elements UCTD Hoffman, Sean Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust |
| title | Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust |
| title_full | Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust |
| title_fullStr | Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust |
| title_full_unstemmed | Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust |
| title_short | Applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in Rcrust |
| title_sort | applying phase equilibria modelling to igneous systems by coupling trace element partitioning and accessory phase saturation to compositionally variable thermodynamic modelling in rcrust |
| topic | Igneous rocks -- Petrology Rocks -- Trace element content Thermodynamic equilibrium -- Mathematical models Mineralogical chemistry Trace elements UCTD |
| url | http://hdl.handle.net/10019.1/126967 |
| work_keys_str_mv | AT hoffmansean applyingphaseequilibriamodellingtoigneoussystemsbycouplingtraceelementpartitioningandaccessoryphasesaturationtocompositionallyvariablethermodynamicmodellinginrcrust |