Textures and Chemistry of Crystal Cargo of the Pleiades Volcanic Field, Antarctica: Potential Influence of Ice Load in Modulating the Plumbing System

• Published in: Journal of Petrology
• Main Authors: Rocchi, Irene, Tomassini, Alice, Masotta, Matteo, Petrelli, Maurizio, Ágreda López, Mónica, Rocchi, Sergio
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2024
• Subjects: magmamixing; phenocryst texture; plumbingsystem; ice load; Antarc*; Antarctica
• Online Access: https://hdl.handle.net/11568/1250293; https://doi.org/10.1093/petrology/egae027

ThePleiadesVolcanicField(PVF)ofnorthernVictoriaLand(Antarctica)ismadeupofadozenscoriaconeswhoseeruptedproductspresentanunusuallycompleteevolutionarytrendfromalkali-basalttotrachyte.WiththeaimofreconstructingtheevolutionofthePVFplumbingsystem,wehaveinvestigatedthepetrographyandchemistryofmainmineralphasesusingscanningelectronmicroscopy(SEM-EDS)coupledwithmajorelementanalysesusinganelectronprobemicroanalyser(EPMA-WDS).Wefurtherfocussedonclinopyroxenephenocrystsobtainingamoredetailedcharacterizationbymeansoftracelaserablation-inductivelycoupledplasma-massspectrometry(LA-ICP-MS)elementanalysescoupledwithmachinelearningthermobarometry.Theresultsindicatethatfractionalcrystallizationandmagmamixingarethemajorprocessesdeterminingthedevelopmentofthecompleteevolutiontrend.Whilefractionalcrystallizationisapersistentlyactiveprocessinallpartsoftheplumbingsystem,mixingamongdifferentlyevolvedmagmabatchespertainingtothesameassociationisresponsiblefortheformationofintermediatecompositionsinthedifferentiationlineageataspecificpressurerange(0.4–0.5GPa).Theseprocessesarecompatiblewithsignificantresidencetimeofmagmasatdepth,resultinginmultipleepisodesofmagmamixing,astestifiedbyresorptionandovergrowthtexturesinphenocrystassemblageoccurringunderisobaricconditions.Theprolongedresidencetimelikelyincreasedtheefficiencyofthemixingprocess,leadingtotheformationofmagmaswithintermediatecomposition.Inturn,thebuild-upofvolatilesduringthemagmadifferentiationatdepthcouldhavefavouredtheeruptionofthese(variablydifferentiated)magmas.ConsideringthatthePVFissituatedinaglacialregion,aprocessforcinglongmagmaresidencetimecanbeenvisagedassociatedwithincreasediceloadingduringglacialstages.Thisstudyspecificallyconsiderstheicefluctuationsinthelast100ka,theorizingthepossibilityofaclimate-controlledvolcanoplumbingsystem.