ProjectTitle ThebehaviouroftheeconomicallyimportantelementsduringcrustalprocessesandvolcanicdegassingatPopocatépetlvolcano,Mexico.

HostUniversity TheOpenUniversity

Theme DynamicEarthKeywords Economicgeology,metals,volcaniceruptionsSupervisoryteam(includinginstitution&emailaddress

PI:FrancesJenner,OpenUniversity(frances.jenner@open.ac.uk)Co-I:ChiaraMariaPetrone,TheNaturalHistoryMuseum(C.Petrone@nhm.ac.uk)TomArgles,OpenUniversity(tom.argles@open.ac.uk)SamHammond,OpenUniversity(sam.hammond@open.ac.uk)

IsthePhDsuitableforparttimestudy?

Yes

ProjectHighlights:

• Explorethekeyfactorscontrollingthedistributionofeconomicallyimportantmetalsinthecrust.

• Useelectronmicroprobeandstate-of-the-artlaserablation(LA)ICP-MSimagingofigneousmineralstounderstandtheprocessestakingplaceinmagmachamberspriortovolcaniceruptions.

• Calculatethetotallossofsulphurtotheatmosphereduringdifferentstylesofvolcaniceruptions.

Overview:

There isaglobalassociationbetween theoccurrenceofmagmatichydrothermaloredepositsandsubduction zones. This association indicates that subduction zonemagmas contain the necessary‘ingredients’ required to fuel the formation of copper-sulfide-rich ore deposits. However, thedistribution of ore deposits in the crust above subduction zones is sporadic. Recent studies haveshownthatthemajorityofmagmasthateruptthoughthecontinentalcrustabovesubductionzonesaretypicallydepletedineconomicallyimportantmetalssuchascopperandgold1.Itremainsunclearwhichcrustaland/ormantleprocessespredisposesomesubduction-zonemagmatic systems tobeassociated with ore deposits compared to others. In addition to the sporadic formation of oredeposits,italsoremainsunclearwhysomesubductionzonemagmasreleasevoluminouspoisonoussulphur-richgasesduringeruption,whereasothersdonot.

Popocatépetlvolcano (5426m) isoneof themostdangerousandactivevolcanoes inMexico. It islocatedonly70kmfromMexicoCity,withmorethan30millionpeople living inaradiusof70kmfromthecrater.It ischaracterisedbyextremelyhighSO2emissionrates2,awiderangeoferuptionstyles includinghighlyexplosivePlinianevents,alternatingwithpersistentactivitycharacterisedbylavadomegrowthandmoderatelyexplosivevulcanianactivity3.OneofthelargestPlinianeruptions,thePumicewithAndesitePlinianEruption(PwA)4,occurred14,000yearsago.It iswellknownthatmagmamixing is onepossible trigger of an eruption. Recent studies5 are questioning the existingparadigm that there is a direct relationship between frequency and magnitude of eruption andmagmainjection.

Figure1:PopocatépetlvolcanoisoneofthemostdangerousandactiveinMexico(photobyPetrone).

This projectwill investigatewhether there is a link betweenmagma source composition,magmamixing,sulfidecrystallisation,eruptionstyle(e.g.,volumeofsulphurdegassing)andprocessesthatcontribute to the formationof economically important oredeposits. In particular, theprojectwillexplore whether the partitioning behaviour of economically important sulfide-hosted elementsduring sulfide fractionation limits the proportion of sulphur that is lost to the atmosphere duringvolcaniceruptions.

Methodology:

TheNaturalHistoryMuseumholdsacollectionofover200specimensofthelast40kyrsofactivityof Popocatépetl volcano,Mexico. Recently-developed laser ablation (LA) ICP-MS protocolswill beemployed for in situanalysisof critical traceelement concentrations inkeymineralsandmineral-hostedmeltinclusions,includingbothspotandlasermappingtechniques.Alongsideelectronprobemicro-analysis(EPMA)formajorandvolatileelementcontents,thisdatawillbeusedtoreconstructthe behaviour of the economically important elements (e.g., S, Cu, Se, Ag and Au) during crustalprocesses(e.g.,fractionation).Elementaldiffusionbetweenmeltinclusionsandhostingmineralswillbe used to investigate the timescales ofmobility of the economically important elements. Theseconstraints will be used to calculate the total loss of sulphur to the atmosphere during differentstylesofvolcaniceruptions.

Trainingandskills:

Thesuccessfulstudentwillbetrainedinadvancedpetrologicalandgeochemicalanalysisofigneousrocks. In situ analysis and laser mapping will be central to the project. Training in modellingtechniques, including thebehaviour of trace elements duringmeltingof themantle, fractionationanddiffusionwillbeprovided.TheSchoolofEnvironment,EarthandEcosystemScienceshasathrivingpostgraduatecommunity.Online teaching opportunities via theOpenUniversity Virtual Learning Environment are available,including on the newMassive OpenOnline Courses (MOOCs). Our current graduate students areveryactive inscienceoutreachondigitalplatforms(e.g.http://www.fieldworkdiaries.com/)andatlocal primary schools. The student will also benefit from constant interaction with the NaturalHistoryMuseum,whichhostscuttingedgefacilitiesandaworld-leadingcollectionofsamplesfromPopocatépetlvolcano.StudentswillbeawardedCENTA2TrainingCredits(CTCs)forparticipationinCENTA2-providedand‘free choice’ external training.OneCTCequates to1⁄2day sessionand studentsmust accrue100CTCsacrossthethreeyearsoftheirPhD.

Partnersandcollaboration(includingCASE):

ThePhDprojectwillberunincollaborationwithaNERCfundedconsortium(FromArcMagmastoOre Systems, FAMOS) of international researchers. The project aims to develop new explorationtools tohelp locatemetal resources in volcanic arcsbyunderstanding the fundamental processesinvolvedincyclingmagmas,fluidsadmetalsinthesezones(http://www.nhm.ac.uk/our-science/our-work/sustainability/from-arc-magmas-to-ores.html).Possibletimeline:

Year 1: Learning from the previous literature the potential controls on the behaviour of theeconomically important elements duringmagmatic processes. Sample preparation and initial datacollection.Year2:Furtherdatacollection,modellingofigneousprocesses,initialsynthesisoffindings(paperorconference).Year3:Finaldatacollectionandsynthesisofresults.Preparationofpublicationsandthesischapters.Presentationofresultsataninternationalconference.

Furtherreading:

[1] Jenner, F. (2017) 'Cumulate causes for the low contents of sulfide-loving elements in thecontinentalcrust',NatureGeoscience,10,pp.524-529.[2] Delgado-Granados, H., L. Cárdenas González, and N. Piedad Sánchez (2001), 'Sulfur dioxideemissions from Popocatépetl volcano (Mexico): case study of a high-emission rate, passivelydegassingeruptingvolcano',JournalofVolcanologyandGeothermalResearch,108,pp.107-120.

[3] Straub and Martin del Pozzo (2001), 'The significance of phenocryst diversity in tephra fromrecenteruptionsatPopocatépetlvolcano(centralMexico)',Contrib.Mineral.Petrol.,140,pp.487-510.

[4] Sosa-CeballosG., et al. (2012) 'A caldera-forming eruption ~14,100 14C yr BP at Popocatépetlvolcano,Mexico: insights fromeruptiondynamicsandmagmamixing', J.VolcanolGeotherm.Res.,213-214,pp.27-40.

[5]Petrone,C.M.andMangler,M.(2017)'TheinterplinianactivityofPopocatepelvolcano(Mexico):months-scalemagmamixingeventsatasteady-statevolcano'IAVCEIConference2017.

Furtherdetails:

Studentsshouldhaveastrongbackground ingeochemistryandenthusiasmfor igneouspetrology.Experience of geochemical modelling is desirable. The student will join a well-established teamresearchinggeochemicalprocessesattheOpenUniversity.

PleasecontactFrancesJenner[frances.jenner@open.ac.uk]orChiaraPetrone,[C.Petrone@nhm.ac.uk]forfurtherinformation.

Applicationsmustinclude:• acoverletteroutliningwhytheprojectisofinterestandhowyourskillsarewellsuitedto

theproject• anacademicCVcontainingcontactdetailsofthreeacademicreferences• aCENTAapplicationform,downloadablefrom:

http://www.centa.org.uk/media/1202/centa-studentship-application-form.docx• andanOpenUniversityapplicationform,downloadablefrom:https://tinyurl.com/y73hrfou

ApplicationsshouldbesenttoSTEM-EEES-PhD-Student-Recruitment@open.ac.ukby12pm(noon)on21stJanuary2019