The timescales of magmatic processes prior to a caldera-forming eruption of Santorini
My Ph.D. was on the >10 km3 , 22-ka Cape Riva eruption of Santorini, Greece. I looked at a series of lavas and minor pyroclastic deposits that erupted prior to the Cape Riva. This eruptive sequence had previously been described as “precursory leaks” from a slowly growing magma reservoir that went on to feed the Cape Riva eruption itself. However, I found that these “precursory leaks” are enriched in incompatible trace elements relative to the Cape Riva, showing that they must have evolved separately. 39 Ar/40 Ar dates and diffusion chronometry shows that the assembly of the Cape Riva reservoir was rapid, and much of the magma arrived in the shallow system a few decades before eruption.
VIDEO
Further reading:
How Long Does it Take to Build a Caldera-Sized Magma Reservoir? Earth Observatory of Singapore Blog, 03 May 2018
17172
{17172:3PEQFNXZ},{17172:PC7GQ6IX},{17172:WD3H7CTI}
elsevier-harvard
50
1
16
https://garethfabbro.rocks/wp-content/plugins/zotpress/
%7B%22status%22%3A%22success%22%2C%22updateneeded%22%3Afalse%2C%22instance%22%3A%22zotpress-0d9d4e02d5831787bd3b84d57990919b%22%2C%22meta%22%3A%7B%22request_last%22%3A0%2C%22request_next%22%3A0%2C%22used_cache%22%3Atrue%7D%2C%22data%22%3A%5B%7B%22key%22%3A%22PC7GQ6IX%22%2C%22library%22%3A%7B%22id%22%3A17172%7D%2C%22meta%22%3A%7B%22creatorSummary%22%3A%22Fabbro%20et%20al.%22%2C%22parsedDate%22%3A%222017-12-01%22%2C%22numChildren%22%3A1%7D%2C%22bib%22%3A%22%3Cdiv%20class%3D%5C%22csl-bib-body%5C%22%20style%3D%5C%22line-height%3A%201.35%3B%20padding-left%3A%201em%3B%20text-indent%3A-1em%3B%5C%22%3E%5Cn%20%20%3Cdiv%20class%3D%5C%22csl-entry%5C%22%3EFabbro%2C%20G.N.%2C%20Druitt%2C%20T.H.%2C%20Costa%2C%20F.%2C%202017.%20Storage%20and%20eruption%20of%20silicic%20magma%20across%20the%20transition%20from%20dominantly%20effusive%20to%20caldera-forming%20states%20at%20an%20arc%20volcano%20%28Santorini%2C%20Greece%29.%20Journal%20of%20Petrology%2058%2C%202429%26%23x2013%3B2464.%20%3Ca%20href%3D%27https%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1093%5C%2Fpetrology%5C%2Fegy013%27%3Ehttps%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1093%5C%2Fpetrology%5C%2Fegy013%3C%5C%2Fa%3E%20%3Ca%20title%3D%27Download%27%20class%3D%27zp-DownloadURL%27%20href%3D%27https%3A%5C%2F%5C%2Fgarethfabbro.rocks%5C%2Fwp-content%5C%2Fplugins%5C%2Fzotpress%5C%2Flib%5C%2Frequest%5C%2Frequest.dl.php%3Fapi_user_id%3D17172%26amp%3Bdlkey%3D3AQQD34H%26amp%3Bcontent_type%3Dapplication%5C%2Fpdf%27%3EDownload%3C%5C%2Fa%3E%3C%5C%2Fdiv%3E%5Cn%3C%5C%2Fdiv%3E%22%2C%22data%22%3A%7B%22itemType%22%3A%22journalArticle%22%2C%22title%22%3A%22Storage%20and%20eruption%20of%20silicic%20magma%20across%20the%20transition%20from%20dominantly%20effusive%20to%20caldera-forming%20states%20at%20an%20arc%20volcano%20%28Santorini%2C%20Greece%29%22%2C%22creators%22%3A%5B%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Gareth%20N.%22%2C%22lastName%22%3A%22Fabbro%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Timothy%20H.%22%2C%22lastName%22%3A%22Druitt%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Fidel%22%2C%22lastName%22%3A%22Costa%22%7D%5D%2C%22abstractNote%22%3A%22Caldera-forming%20eruptions%20at%20Santorini%20discharge%20large%20volumes%20of%20silicic%20magma%20from%20upper%20crustal%20reservoirs.%20Sequences%20of%20smaller%20eruptions%20preceding%20the%20main%20explosive%20eruptions%20can%20provide%20insight%20into%20the%20conditions%20of%20the%20plumbing%20system%20that%20lead%20to%20caldera-forming%20events%2C%20which%20is%20important%20for%20interpreting%20monitoring%20data.%20We%20analysed%20textures%2C%20zoning%20patterns%2C%20trace%20element%20compositions%2C%20and%20crystal%20residence%20timescales%20calculated%20at%20pre-eruptive%20conditions%20%28NLRT%3B%20near-liquidus%20residence%20timescales%29%20of%20plagioclase%20and%20orthopyroxene%20phenocrysts%20from%20two%20eruptive%20units%20on%20Santorini%3A%20a%20%5Cu223c2%5Cu2009km3%20sequence%20of%20dacitic%20lavas%20erupted%20between%2039%20and%2025%5Cu2009ka%20%28the%20Therasia%20dome%20complex%29%2C%20and%20a%20caldera-forming%20dacitic%20eruption%20that%20occurred%20no%20more%20than%202%2C800%20%5Cu00b1%201%2C400%20y%20after%20the%20last%20Therasia%20lava%20%28the%2021.8-ka%2C%20%26gt%3B10%5Cu2009km3%20Cape%20Riva%20eruption%29.%20The%20study%20builds%20on%20the%20work%20of%20Fabbro%20et%20al.%20%282013%29%2C%20who%20showed%20that%20the%20Therasia%20and%20Cape%20Riva%20dacites%2C%20although%20similar%20in%20most%20major%20elements%2C%20differ%20in%20some%20trace%20element%20contents%20and%20were%20derived%20from%20different%20source%20magmas%20and%20crystal%20mushes.%20Contents%20of%20K%20and%20La%20in%20plagioclase%20phenocrysts%20mirror%20those%20in%20the%20respective%20host%20magmas%20%28higher%20in%20Therasia%2C%20lower%20in%20Cape%20Riva%29%2C%20showing%20that%20plagioclase%20provenance%20can%20be%20determined%20using%20these%20elements.%20Very%20few%20plagioclase%20cores%20from%20the%20Cape%20Riva%20dacite%20were%20recycled%20from%20Therasia%20magmas%3B%20the%20majority%20were%20derived%20from%20lower-K%2C%20lower-La%20magmas%20and%20mushes%20related%20to%20the%20Cape%20Riva%20eruption%20itself.%20Despite%20the%20very%20different%20magma%20volumes%20and%20eruptive%20fluxes%2C%20plagioclase%20and%20orthopyroxene%20crystals%20from%20the%20two%20dacite%20series%20have%20remarkably%20similar%20textures%20and%20major%20element%20compositions.%20Furthermore%2C%20Mg%20diffusion%20profiles%20in%20plagioclase%20and%20Mg-Fe%20diffusion%20profiles%20in%20orthopyroxene%20yield%20similar%20ranges%20of%20NLRT%2C%20most%20ranging%20from%20years%20to%20centuries.%20Some%20orthopyroxene%20crystals%20in%20both%20eruptive%20units%20exhibit%20Al%20sector%20zoning%20indicative%20of%20rapid%20growth.%20Processes%20driving%20crystallisation%20appear%20to%20have%20been%20similar%20in%20the%20two%20systems%2C%20despite%20the%20differences%20of%20scale.%20Based%20on%20previously%20published%20phase%20diagrams%20and%20melt%20inclusion%20volatile%20barometry%20for%20the%20Cape%20Riva%20dacite%2C%20we%20infer%20that%20in%20each%20case%20crystallisation%20of%20plagioclase%20rims%20and%20orthopyroxene%20took%20place%20centuries%20to%20years%20prior%20to%20eruption%20due%20to%20volatile-saturated%20decompression%20as%20the%20dacitic%20melts%20%28plus%20entrained%20plagioclase%20antecrystic%20cores%29%20ascended%20from%20the%20middle%20crust%20%2810-16%5Cu2009km%29%20into%20the%20upper%20crust%20%284-6%5Cu2009km%29%2C%20where%20they%20resided%20until%20eruption%20a%20few%20years%20to%20decades%20later.%20Between%2039%20and%2025%5Cu2009ka%2C%20multiple%20small%20volumes%20of%20Therasia-type%20dacitic%20magma%20were%20emplaced%20in%20the%20upper%20crust%2C%20where%20they%20either%20froze%20or%20were%20subsequently%20erupted.%20From%20about%2025%5Cu2009ka%20onwards%2C%20large%20volumes%20of%20Cape%20Riva-type%20dacitic%20magma%2C%20sourced%20from%20a%20different%20mid-crustal%20reservoir%2C%20began%20to%20ascend%20into%20the%20upper%20crust.%20Runaway%20drainage%20of%20this%20magma%20source%2C%20peaking%20during%20the%20centuries%20to%20decades%20prior%20to%20the%20Cape%20Riva%20eruption%2C%20led%20to%20establishment%20of%20a%20well-mixed%20magma%20chamber%20in%20the%20upper%20crust%20that%20was%20discharged%20during%20the%20caldera-forming%20Cape%20Riva%20event.%22%2C%22date%22%3A%222017-12-01%22%2C%22language%22%3A%22en%22%2C%22DOI%22%3A%2210.1093%5C%2Fpetrology%5C%2Fegy013%22%2C%22ISSN%22%3A%22%22%2C%22url%22%3A%22https%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1093%5C%2Fpetrology%5C%2Fegy013%22%2C%22collections%22%3A%5B%222K9JHKVR%22%2C%22LA9GP8XJ%22%5D%2C%22dateModified%22%3A%222024-11-21T20%3A03%3A37Z%22%7D%7D%2C%7B%22key%22%3A%22WD3H7CTI%22%2C%22library%22%3A%7B%22id%22%3A17172%7D%2C%22meta%22%3A%7B%22creatorSummary%22%3A%22Fabbro%20et%20al.%22%2C%22parsedDate%22%3A%222013-12-01%22%2C%22numChildren%22%3A1%7D%2C%22bib%22%3A%22%3Cdiv%20class%3D%5C%22csl-bib-body%5C%22%20style%3D%5C%22line-height%3A%201.35%3B%20padding-left%3A%201em%3B%20text-indent%3A-1em%3B%5C%22%3E%5Cn%20%20%3Cdiv%20class%3D%5C%22csl-entry%5C%22%3EFabbro%2C%20G.N.%2C%20Druitt%2C%20T.H.%2C%20Scaillet%2C%20S.%2C%202013.%20Evolution%20of%20the%20crustal%20magma%20plumbing%20system%20during%20the%20build-up%20to%20the%2022-ka%20caldera-forming%20eruption%20of%20Santorini%20%28Greece%29.%20Bulletin%20of%20Volcanology%2075%2C%201%26%23x2013%3B22.%20%3Ca%20href%3D%27https%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1007%5C%2Fs00445-013-0767-5%27%3Ehttps%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1007%5C%2Fs00445-013-0767-5%3C%5C%2Fa%3E%20%3Ca%20title%3D%27Download%27%20class%3D%27zp-DownloadURL%27%20href%3D%27https%3A%5C%2F%5C%2Fgarethfabbro.rocks%5C%2Fwp-content%5C%2Fplugins%5C%2Fzotpress%5C%2Flib%5C%2Frequest%5C%2Frequest.dl.php%3Fapi_user_id%3D17172%26amp%3Bdlkey%3DCANDTS35%26amp%3Bcontent_type%3Dapplication%5C%2Fpdf%27%3EDownload%3C%5C%2Fa%3E%3C%5C%2Fdiv%3E%5Cn%3C%5C%2Fdiv%3E%22%2C%22data%22%3A%7B%22itemType%22%3A%22journalArticle%22%2C%22title%22%3A%22Evolution%20of%20the%20crustal%20magma%20plumbing%20system%20during%20the%20build-up%20to%20the%2022-ka%20caldera-forming%20eruption%20of%20Santorini%20%28Greece%29%22%2C%22creators%22%3A%5B%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Gareth%20N.%22%2C%22lastName%22%3A%22Fabbro%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22T.%20H.%22%2C%22lastName%22%3A%22Druitt%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22S.%22%2C%22lastName%22%3A%22Scaillet%22%7D%5D%2C%22abstractNote%22%3A%22The%20formation%20of%20shallow%2C%20caldera-sized%20reservoirs%20of%20crystal-poor%20silicic%20magma%20requires%20the%20generation%20of%20large%20volumes%20of%20silicic%20melt%2C%20followed%20by%20the%20segregation%20of%20that%20melt%20and%20its%20accumulation%20in%20the%20upper%20crust.%20The%2021.8%20%5Cu00b1%200.4-ka%20Cape%20Riva%20eruption%20of%20Santorini%20discharged%20%3E10%20km3%20of%20crystal-poor%20dacitic%20magma%2C%20along%20with%20%3C%3C1%20km3%20of%20hybrid%20andesite%2C%20and%20collapsed%20a%20pre-existing%20lava%20shield.%20We%20have%20carried%20out%20a%20field%2C%20petrological%2C%20chemical%2C%20and%20high-resolution%2040Ar%5C%2F39Ar%20chronological%20study%20of%20a%20sequence%20of%20lavas%20discharged%20prior%20to%20the%20Cape%20Riva%20eruption%20to%20constrain%20the%20crustal%20residence%20time%20of%20the%20Cape%20Riva%20magma%20reservoir.%20The%20lavas%20were%20erupted%20between%2039%20and%2025%20ka%2C%20forming%20a%20%5Cu223c2-km3%20complex%20of%20dacitic%20flows%2C%20coul%5Cu00e9es%20and%20domes%20up%20to%20200%20m%20thick%20%28Therasia%20dome%20complex%29.%20The%20Therasia%20dacites%20show%20little%20chemical%20variation%20with%20time%2C%20suggesting%20derivation%20from%20one%20or%20more%20thermally%20buffered%20reservoirs.%20Minor%20pyroclastic%20layers%20occur%20intercalated%20within%20the%20lava%20succession%2C%20particularly%20near%20the%20top.%20A%20prominent%20pumice%20fall%20deposit%20correlates%20with%20the%2026-ka%20Y-4%20ash%20layer%20found%20in%20deep-sea%20sediments%20SE%20of%20Santorini.%20One%20of%20the%20last%20Therasia%20lavas%20to%20be%20discharged%20was%20a%20hybrid%20andesite%20formed%20by%20the%20mixing%20of%20dacite%20and%20basalt.%20The%20Cape%20Riva%20eruption%20occurred%20no%20more%20than%202%2C800%20%5Cu00b1%201%2C400%20years%20after%20the%20final%20Therasia%20activity.%20The%20Cape%20Riva%20dacite%20is%20similar%20in%20major%20element%20composition%20to%20the%20Therasia%20dacites%2C%20but%20is%20poorer%20in%20K%20and%20most%20incompatible%20trace%20elements%20%28e.g.%20Rb%2C%20Zr%20and%20LREE%29.%20The%20same%20chemical%20differences%20are%20observed%20between%20the%20Cape%20Riva%20and%20Therasia%20hybrid%20andesites%2C%20and%20between%20the%20calculated%20basaltic%20mixing%20end-members%20of%20each%20series.%20The%20Therasia%20and%20Cape%20Riva%20dacites%20are%20distinct%20silicic%20magma%20batches%20and%20are%20not%20related%20by%20shallow%20processes%20of%20crystal%20fractionation%20or%20assimilation.%20The%20Therasia%20lavas%20were%20therefore%20not%20simply%20precursory%20leaks%20from%20the%20growing%20Cape%20Riva%20magma%20reservoir.%20The%20change%2021.8%20ky%20ago%20from%20a%20magma%20series%20richer%20in%20incompatible%20elements%20to%20one%20poorer%20in%20those%20elements%20is%20one%20step%20in%20the%20well%20documented%20decrease%20with%20time%20of%20incompatibles%20in%20Santorini%20magmas%20over%20the%20last%20530%20ky.%20The%20two%20dacitic%20magma%20batches%20are%20interpreted%20to%20have%20been%20emplaced%20sequentially%20into%20the%20upper%20crust%20beneath%20the%20summit%20of%20the%20volcano%2C%20the%20first%20%28Therasia%29%20then%20being%20partially%2C%20or%20wholly%2C%20flushed%20out%20by%20the%20arrival%20of%20the%20second%20%28Cape%20Riva%29.%20This%20constrains%20the%20upper-crustal%20residence%20time%20of%20the%20Cape%20Riva%20reservoir%20to%20less%20than%202%2C800%20%5Cu00b1%201%2C400%20years%2C%20and%20the%20associated%20time-averaged%20magma%20accumulation%20rate%20to%20%3E0.004%20km3%20year-1.%20Rapid%20ascent%20and%20accumulation%20of%20the%20Cape%20Riva%20dacite%20may%20have%20been%20caused%20by%20an%20increased%20flux%20of%20mantle-derived%20basalt%20into%20the%20crust%2C%20explaining%20the%20occurrence%20of%20hybrid%20andesites%20%28formed%20by%20the%20mixing%20of%20olivine%20basalt%20and%20dacite%20in%20approximately%20equal%20proportions%29%20in%20the%20Cape%20Riva%20and%20late%20Therasia%20products.%20Pressurisation%20of%20the%20upper%20crustal%20plumbing%20system%20by%20sustained%2C%20high-flux%20injection%20of%20dacite%20and%20basalt%20may%20have%20triggered%20the%20transition%20from%20prolonged%2C%20largely%20effusive%20activity%20to%20explosive%20eruption%20and%20caldera%20collapse.%22%2C%22date%22%3A%222013%5C%2F12%5C%2F01%22%2C%22language%22%3A%22en%22%2C%22DOI%22%3A%2210.1007%5C%2Fs00445-013-0767-5%22%2C%22ISSN%22%3A%220258-8900%2C%201432-0819%22%2C%22url%22%3A%22http%3A%5C%2F%5C%2Frdcu.be%5C%2Fv5Pw%22%2C%22collections%22%3A%5B%22LA9GP8XJ%22%5D%2C%22dateModified%22%3A%222024-11-21T20%3A03%3A37Z%22%7D%7D%2C%7B%22key%22%3A%223PEQFNXZ%22%2C%22library%22%3A%7B%22id%22%3A17172%7D%2C%22meta%22%3A%7B%22creatorSummary%22%3A%22Fabbro%22%2C%22parsedDate%22%3A%222014-04-24%22%2C%22numChildren%22%3A1%7D%2C%22bib%22%3A%22%3Cdiv%20class%3D%5C%22csl-bib-body%5C%22%20style%3D%5C%22line-height%3A%201.35%3B%20padding-left%3A%201em%3B%20text-indent%3A-1em%3B%5C%22%3E%5Cn%20%20%3Cdiv%20class%3D%5C%22csl-entry%5C%22%3EFabbro%2C%20G.N.%2C%202014.%20The%20timescales%20of%20magmatic%20processes%20prior%20to%20a%20caldera-forming%20eruption%20%28Ph.D.%29.%20Universit%26%23xE9%3B%20Blaise%20Pascal%2C%20Clermont-Ferrand.%20%3Ca%20title%3D%27Download%27%20class%3D%27zp-DownloadURL%27%20href%3D%27https%3A%5C%2F%5C%2Fgarethfabbro.rocks%5C%2Fwp-content%5C%2Fplugins%5C%2Fzotpress%5C%2Flib%5C%2Frequest%5C%2Frequest.dl.php%3Fapi_user_id%3D17172%26amp%3Bdlkey%3DGKUQF7P9%26amp%3Bcontent_type%3Dapplication%5C%2Fpdf%27%3EDownload%3C%5C%2Fa%3E%3C%5C%2Fdiv%3E%5Cn%3C%5C%2Fdiv%3E%22%2C%22data%22%3A%7B%22itemType%22%3A%22thesis%22%2C%22title%22%3A%22The%20timescales%20of%20magmatic%20processes%20prior%20to%20a%20caldera-forming%20eruption%22%2C%22creators%22%3A%5B%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Gareth%20N.%22%2C%22lastName%22%3A%22Fabbro%22%7D%5D%2C%22abstractNote%22%3A%22Large%2C%20explosive%2C%20caldera-forming%20eruptions%20are%20amongst%20the%20most%20destructive%20phenomena%20on%20the%20planet%2C%20but%20the%20processes%20that%20allow%20the%20large%20bodies%20of%20crystal-poor%20silicic%20magma%20that%20feed%20them%20to%20assemble%20in%20the%20shallow%20crust%20are%20still%20poorly%20understood.%20Of%20particular%20interest%20is%20the%20timescales%20over%20which%20these%20reservoirs%20exist%20prior%20to%20eruption.%20Long%20storage%20times%5Cu2014up%20to%20105%20y%5Cu2014have%20previously%20been%20estimated%20using%20the%20repose%20times%20between%20eruptions%20and%20radiometric%20dating%20of%20crystals%20found%20within%20the%20eruptive%20products.%20However%2C%20more%20recent%20work%20modelling%20diffusion%20within%20single%20crystals%20has%20been%20used%20to%20argue%20that%20the%20reservoirs%20that%20feed%20even%20the%20largest%20eruptions%20are%20assembled%20over%20much%20shorter%20periods%5Cu2014101%5Cu2013102%5Cu00a0y.%5Cn%5CnIn%20order%20to%20address%20this%20question%2C%20I%20studied%20the%20%3E10%5Cu00a0km3%2C%2022-ka%2C%20dacitic%20Cape%20Riva%20eruption%20of%20Santorini%2C%20Greece.%20Over%20the%20~18%5Cu00a0ky%20preceding%20the%20Cape%20Riva%20eruption%20a%20series%20of%20dacitic%20lava%20dome%20and%20coul%5Cu00e9es%20were%20erupted%2C%20and%20these%20lavas%20are%20interspersed%20with%20occasional%20dacitic%20pumice%20fall%20deposits%20%28the%20Therasia%20dome%20complex%29.%20These%20dacites%20have%20similar%20major%20element%20contents%20to%20the%20dacite%20that%20was%20erupted%20during%20the%20Cape%20Riva%20eruption%2C%20and%20have%20previously%20been%20described%20as%20%5Cu201cprecursory%20leaks%5Cu201d%20from%20the%20growing%20Cape%20Riva%20magma%20reservoir.%20However%2C%20the%20Cape%20Riva%20magma%20is%20depleted%20in%20incompatible%20elements%20%28such%20as%20K%2C%20Zr%2C%20La%2C%20Ce%29%20relative%20to%20the%20Therasia%20magma%2C%20as%20are%20the%20plagioclase%20crystals%20in%20the%20respective%20magmas.%20This%20difference%20cannot%20be%20explained%20using%20shallow%20processes%20such%20as%20fractional%20crystallisation%20or%20crustal%20assimilation%2C%20which%20suggests%20that%20the%20Cape%20Riva%20and%20Therasia%20magmas%20are%20separate%20batches.%20Furthermore%2C%20there%20is%20evidence%20that%20the%20Therasia%20dacites%20were%20not%20fed%20from%20a%20long-lived%2C%20melt-dominated%20reservoir.%20There%20are%20non-systematic%20variations%20in%20melt%20composition%2C%20plagioclase%20rim%20compositions%2C%20and%20plagioclase%20textures%20throughout%20the%20sequence.%20In%20addition%2C%20high-temperature%20residence%20times%20of%20plagioclase%20and%20orthopyroxene%20crystals%20from%20the%20Therasia%20dacites%20estimated%20using%20diffusion%20chronometry%20are%20101%5Cu2013102%5Cu00a0y.%20This%20is%20short%20compared%20to%20the%20average%20time%20between%20eruptions%20%28~1%2C500%5Cu00a0y%29%2C%20which%20suggests%20the%20crystals%20in%20each%20lava%20grew%20only%20shortly%20before%20eruption.%20The%20different%20incompatible%20element%20contents%20of%20the%20Cape%20Riva%20and%20Therasia%20magmas%20and%20plagioclase%20crystals%20suggest%20that%20a%20new%20batch%20of%20incompatible-depleted%20silicic%20magma%20arrived%20in%20the%20shallow%20volcanic%20plumbing%20system%20shortly%20before%20the%20Cape%20Riva%20eruption.%20This%20influx%20must%20have%20taken%20place%20after%20the%20last%20Therasia%20eruption%2C%20which%2040Ar%5C%2F39Ar%20dates%20show%20occurred%20less%20than%202%2C800%5Cu00a0%5Cu00b1%5Cu00a01%2C400%20years%20before%20the%20Cape%20Riva%20eruption.%5Cn%5CnThe%20rims%20of%20the%20plagioclase%20crystals%20found%20in%20the%20Cape%20Riva%20dacite%20are%20in%20equilibrium%20with%20a%20rhyodacite%2C%20with%20a%20similar%20composition%20to%20the%20Cape%20Riva%20glass.%20However%2C%20the%20major%20and%20trace%20element%20zoning%20patterns%20of%20the%20crystals%20record%20variations%20in%20the%20melt%20composition%20during%20their%20growth.%20The%20compositions%20at%20the%20centre%20of%20most%20crystals%20are%20the%20same%20as%20the%20rims%3B%20however%2C%20these%20crystals%20are%20often%20partially%20resorbed%20and%20overgrown%20by%20more%20calcic%20plagioclase.%20The%20plagioclase%20then%20grades%20normally%20back%20to%20rim%20compositions.%20This%20cycle%20is%20repeated%20up%20to%20three%20times.%20The%20tight%20relationships%20between%20the%20anorthite%2C%20Sr%20and%20Ti%20contents%20of%20the%20different%20zones%20suggests%20that%20the%20composition%20of%20the%20plagioclase%20crystals%20correlates%20with%20the%20composition%20of%20the%20melt%20from%20which%20they%20grew.%20The%20different%20plagioclase%20compositions%20correspond%20to%20dacitic%20and%20rhyodacitic%20melt%20compositions.%20The%20orthopyroxene%20crystals%20reveal%20a%20similar%20sequence%2C%20although%20they%20only%20record%20one%20cycle.%20These%20zoning%20patterns%20are%20interpreted%20to%20document%20the%20assembly%20of%20the%20Cape%20Riva%20reservoir%20in%20the%20shallow%20crust%20through%20the%20amalgamation%20of%20multiple%20batches%20of%20compositionally%20diverse%20magma.%20Models%20of%20magnesium%20diffusion%20in%20plagioclase%20and%20Fe%5Cu2013Mg%20interdiffusion%20in%20orthopyroxene%20suggest%20that%20this%20amalgamation%20took%20place%20within%20101%5Cu2013102%5Cu00a0y%20of%20the%20Cape%20Riva%20eruption.%22%2C%22thesisType%22%3A%22Ph.D.%22%2C%22university%22%3A%22Universit%5Cu00e9%20Blaise%20Pascal%22%2C%22date%22%3A%2224%20April%202014%22%2C%22language%22%3A%22%22%2C%22url%22%3A%22http%3A%5C%2F%5C%2Fwww.theses.fr%5C%2F2014CLF22452%22%2C%22collections%22%3A%5B%5D%2C%22dateModified%22%3A%222018-07-06T16%3A09%3A56Z%22%7D%7D%5D%7D
Fabbro, G.N., Druitt, T.H., Costa, F., 2017. Storage and eruption of silicic magma across the transition from dominantly effusive to caldera-forming states at an arc volcano (Santorini, Greece). Journal of Petrology 58, 2429–2464.
https://doi.org/10.1093/petrology/egy013 Download
Fabbro, G.N., Druitt, T.H., Scaillet, S., 2013. Evolution of the crustal magma plumbing system during the build-up to the 22-ka caldera-forming eruption of Santorini (Greece). Bulletin of Volcanology 75, 1–22.
https://doi.org/10.1007/s00445-013-0767-5 Download
Fabbro, G.N., 2014. The timescales of magmatic processes prior to a caldera-forming eruption (Ph.D.). Université Blaise Pascal, Clermont-Ferrand.
Download
A complete caldera cycle at Rabaul, Papua New Guinea
During my postdoctoral fellowship, I studied Rabaul, Papua New Guinea. I found that there was a major change in the shallow plumbing system after the most recent caldera-forming eruption. In the post-caldera system, there is frequent basaltic intrusion, as opposed to andesitic recharge prior to the caldera-forming eruption. This suggests that a silicic reservoir large enough to block the rise of basalt existed before the caldera-forming eruption, but a similar reservoir is not present today under Rabaul. Currently, I am studying the pre-caldera eruptions to track the composition of the recharge and the evolution of the silicic reservoir.
Further reading:
Sizing Up the Next Eruption. Earth Observatory of Singapore Blog, 15 Jul 2016.
17172
{17172:RQTVWKH3},{17172:DQSGM4A8}
elsevier-harvard
50
1
16
https://garethfabbro.rocks/wp-content/plugins/zotpress/
%7B%22status%22%3A%22success%22%2C%22updateneeded%22%3Afalse%2C%22instance%22%3A%22zotpress-81b340572193d3b7dd839e14b6aa1059%22%2C%22meta%22%3A%7B%22request_last%22%3A0%2C%22request_next%22%3A0%2C%22used_cache%22%3Atrue%7D%2C%22data%22%3A%5B%7B%22key%22%3A%22RQTVWKH3%22%2C%22library%22%3A%7B%22id%22%3A17172%7D%2C%22meta%22%3A%7B%22creatorSummary%22%3A%22Fabbro%20et%20al.%22%2C%22parsedDate%22%3A%222020-03-01%22%2C%22numChildren%22%3A1%7D%2C%22bib%22%3A%22%3Cdiv%20class%3D%5C%22csl-bib-body%5C%22%20style%3D%5C%22line-height%3A%201.35%3B%20padding-left%3A%201em%3B%20text-indent%3A-1em%3B%5C%22%3E%5Cn%20%20%3Cdiv%20class%3D%5C%22csl-entry%5C%22%3EFabbro%2C%20G.N.%2C%20McKee%2C%20C.O.%2C%20Sindang%2C%20M.E.%2C%20Eggins%2C%20S.%2C%20Bouvet%20de%20Maisonneuve%2C%20C.%2C%202020.%20Variable%20mafic%20recharge%20across%20a%20caldera%20cycle%20at%20Rabaul%2C%20Papua%20New%20Guinea.%20Journal%20of%20Volcanology%20and%20Geothermal%20Research%20393%2C%20106810.%20%3Ca%20href%3D%27https%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1016%5C%2Fj.jvolgeores.2020.106810%27%3Ehttps%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1016%5C%2Fj.jvolgeores.2020.106810%3C%5C%2Fa%3E%20%3Ca%20title%3D%27Download%27%20class%3D%27zp-DownloadURL%27%20href%3D%27https%3A%5C%2F%5C%2Fgarethfabbro.rocks%5C%2Fwp-content%5C%2Fplugins%5C%2Fzotpress%5C%2Flib%5C%2Frequest%5C%2Frequest.dl.php%3Fapi_user_id%3D17172%26amp%3Bdlkey%3DMZ9BE8W6%26amp%3Bcontent_type%3Dapplication%5C%2Fpdf%27%3EDownload%3C%5C%2Fa%3E%3C%5C%2Fdiv%3E%5Cn%3C%5C%2Fdiv%3E%22%2C%22data%22%3A%7B%22itemType%22%3A%22journalArticle%22%2C%22title%22%3A%22Variable%20mafic%20recharge%20across%20a%20caldera%20cycle%20at%20Rabaul%2C%20Papua%20New%20Guinea%22%2C%22creators%22%3A%5B%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Gareth%20N.%22%2C%22lastName%22%3A%22Fabbro%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Chris%20O.%22%2C%22lastName%22%3A%22McKee%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Mikhail%20E.%22%2C%22lastName%22%3A%22Sindang%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Stephen%22%2C%22lastName%22%3A%22Eggins%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Caroline%22%2C%22lastName%22%3A%22Bouvet%20de%20Maisonneuve%22%7D%5D%2C%22abstractNote%22%3A%22The%20size%20of%20eruptions%20from%20calderas%20varies%20greatly%2C%20from%20small%20effusive%20eruptions%20that%20pose%20danger%20only%20in%20the%20immediate%20vicinity%20of%20the%20vent%2C%20to%20large%2C%20caldera-forming%20events%20with%20global%20impact.%20However%2C%20we%20currently%20have%20little%20way%20of%20knowing%20the%20size%20of%20the%20next%20eruption.%20Here%2C%20we%20focus%20on%20Rabaul%20Caldera%2C%20Papua%20New%20Guinea%2C%20to%20investigate%20differences%20between%20the%20magmatic%20processes%20that%20occurred%20prior%20to%20the%20%3E11-km3%20caldera-forming%20%5Cu201c1400%20BP%5Cu201d%20Rabaul%20Pyroclastics%20eruption%20and%20prior%20to%20subsequent%2C%20smaller%20%28%3C1%5Cu202fkm3%29%20post-caldera%20eruptions.%20During%20the%20current%2C%20post-caldera%20phase%2C%20basaltic%20enclaves%20and%20mafic%20minerals%20are%20common%20among%20the%20erupted%20products%2C%20indicating%20basalt%20has%20been%20free%20to%20enter%20the%20mobile%2C%20dacite-dominated%20region%20of%20the%20sub-caldera%20plumbing%20system.%20Many%20of%20the%20post-caldera%20magmas%20are%20hybrid%20andesites%2C%20reflecting%20the%20importance%20of%20mixing%20and%20mingling%20of%20basalt%20and%20dacite%20magmas%20during%20this%20period.%20In%20contrast%2C%20before%20the%20Rabaul%20Pyroclastics%20eruption%2C%20the%20recharge%20was%20an%20andesite%20that%20was%20not%20the%20product%20of%20mixing%20basalt%20and%20dacite.%20The%20lack%20of%20basaltic%20recharge%20prior%20to%20the%20Rabaul%20Pyroclastics%20eruption%20suggests%20basalt%20was%20prevented%20from%20entering%20the%20shallow%2C%20sub-caldera%20magma%20system%20at%20that%20time%2C%20possibly%20by%20the%20presence%20of%20a%20large%2C%20silicic%2C%20melt-dominated%20body.%20That%20basalt%20can%20currently%20enter%20the%20shallow%20system%20is%20consistent%20with%20reduced%20thermal%20and%20rheological%20contrasts%20between%20the%20recharge%20and%20resident%20magma%2C%20implying%20a%20similar%20large%20silicic%20melt%20body%20currently%20does%20not%20exist%20beneath%20the%20caldera.%20If%20this%20hypothesis%20is%20correct%2C%20monitoring%20the%20petrology%20of%20eruptive%20products%20may%20be%20used%20to%20track%20the%20growth%20and%20evolution%20of%20large%20magma%20reservoirs%20that%20feed%20caldera-forming%20eruptions.%22%2C%22date%22%3A%221%20March%2C%202020%22%2C%22language%22%3A%22en%22%2C%22DOI%22%3A%2210.1016%5C%2Fj.jvolgeores.2020.106810%22%2C%22ISSN%22%3A%220377-0273%22%2C%22url%22%3A%22http%3A%5C%2F%5C%2Fwww.sciencedirect.com%5C%2Fscience%5C%2Farticle%5C%2Fpii%5C%2FS0377027318303391%22%2C%22collections%22%3A%5B%22LA9GP8XJ%22%5D%2C%22dateModified%22%3A%222024-11-21T20%3A03%3A37Z%22%7D%7D%2C%7B%22key%22%3A%22DQSGM4A8%22%2C%22library%22%3A%7B%22id%22%3A17172%7D%2C%22meta%22%3A%7B%22creatorSummary%22%3A%22McKee%20and%20Fabbro%22%2C%22parsedDate%22%3A%222018-10-27%22%2C%22numChildren%22%3A1%7D%2C%22bib%22%3A%22%3Cdiv%20class%3D%5C%22csl-bib-body%5C%22%20style%3D%5C%22line-height%3A%201.35%3B%20padding-left%3A%201em%3B%20text-indent%3A-1em%3B%5C%22%3E%5Cn%20%20%3Cdiv%20class%3D%5C%22csl-entry%5C%22%3EMcKee%2C%20C.O.%2C%20Fabbro%2C%20G.N.%2C%202018.%20The%20Talili%20Pyroclastics%20eruption%20sequence%3A%20VEI%205%20precursor%20to%20the%20seventh%20century%20CE%20caldera-forming%20event%20at%20Rabaul%2C%20Papua%20New%20Guinea.%20Bull%20Volcanol%2080%2C%2079.%20%3Ca%20href%3D%27https%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1007%5C%2Fs00445-018-1255-8%27%3Ehttps%3A%5C%2F%5C%2Fdoi.org%5C%2F10.1007%5C%2Fs00445-018-1255-8%3C%5C%2Fa%3E%20%3Ca%20title%3D%27Download%27%20class%3D%27zp-DownloadURL%27%20href%3D%27https%3A%5C%2F%5C%2Fgarethfabbro.rocks%5C%2Fwp-content%5C%2Fplugins%5C%2Fzotpress%5C%2Flib%5C%2Frequest%5C%2Frequest.dl.php%3Fapi_user_id%3D17172%26amp%3Bdlkey%3DXZFFW44W%26amp%3Bcontent_type%3Dapplication%5C%2Fpdf%27%3EDownload%3C%5C%2Fa%3E%3C%5C%2Fdiv%3E%5Cn%3C%5C%2Fdiv%3E%22%2C%22data%22%3A%7B%22itemType%22%3A%22journalArticle%22%2C%22title%22%3A%22The%20Talili%20Pyroclastics%20eruption%20sequence%3A%20VEI%205%20precursor%20to%20the%20seventh%20century%20CE%20caldera-forming%20event%20at%20Rabaul%2C%20Papua%20New%20Guinea%22%2C%22creators%22%3A%5B%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Chris%20O.%22%2C%22lastName%22%3A%22McKee%22%7D%2C%7B%22creatorType%22%3A%22author%22%2C%22firstName%22%3A%22Gareth%20N.%22%2C%22lastName%22%3A%22Fabbro%22%7D%5D%2C%22abstractNote%22%3A%22Studies%20of%20the%20products%20of%20the%20activity%20precursory%20to%20caldera-forming%20events%20are%20essential%20in%20revealing%20how%20caldera%20systems%20evolve%20in%20the%20prelude%20to%20climactic%20eruptions.%20%20Here%2C%20we%20investigate%20the%20deposits%20formed%20by%20the%20Talili%20Pyroclastics%20eruption%20sequence%2C%20which%20preceded%20the%20youngest%20major%20eruptive%20event%2C%20the%207th%20century%20CE%20%281400%20BP%29%20Rabaul%20Pyroclastics%20VEI%206%20caldera-forming%20eruption%2C%20at%20Rabaul%20in%20northeastern%20Papua%20New%20Guinea.%5Cn%5CnThe%20Talili%20Pyroclastics%20deposits%20are%20essentially%20a%20bimodal%20%28dacite-basalt%29%20tephra%20sequence%20that%20was%20emplaced%20during%20the%202.8%20ky%20leading%20to%20the%20Rabaul%20Pyroclastics%20eruption.%20%20The%20dominant%20activity%20during%20the%20Talili%20period%2C%20starting%20at%204200%20BP%2C%20involved%20strong%20%28up%20to%20VEI%205%29%2C%20water-modified%20explosive%20eruptions%20of%20dacite%20from%20intra-caldera%20vents.%20%20This%20activity%20generated%20%3E4.4%20km3%20of%20unstratified%2C%20bedded%20and%20laminated%20fine-grained%20fall%20deposits%2C%20pyroclastic%20surges%20and%20a%20small%20ignimbrite.%20%20In%20addition%2C%20all%20three%20of%20the%20young%20stratovolcanoes%20on%20the%20eastern%20and%20northeastern%20fringes%20of%20Rabaul%20Caldera%20were%20active%20during%20the%20Talili%20era%2C%20producing%20%3E0.7%20km3%20of%20basaltic%20scoria%20fall%20and%20flow%20deposits.%20%20The%20main%20phase%20of%20Talili%20era%20basalt%20production%20occurred%20at%204100%20BP%20and%20involved%20sequential%20eruptions%20from%20two%20of%20the%20stratovolcanoes%2C%20Palangiangia%20and%20Kabiu.%5Cn%5CnThe%20sequence%20of%20dacitic%20Talili%20eruptives%20shows%20a%20progressive%20decline%20then%20late-stage%20increase%20in%20SiO2%20contents%2C%20with%20corresponding%20changes%20in%20Fe2O3%2C%20MgO%20and%20CaO.%20%20Early%20and%20late%20products%20have%20compositions%20similar%20to%20those%20of%20the%20most-evolved%20products%20of%20the%20major%20eruptions%20at%20Rabaul%20%28intermediate%20to%20high-SiO2%20dacites%29%2C%20while%20middle-stage%20products%20are%20similar%20to%20those%20of%20the%20historical%20eruptions%20%28lower-SiO2%20dacites%20and%20andesites%29.%20%20The%20basaltic%20eruptives%20have%20three%20different%20compositions%2C%20attributed%20to%20three%20different%20%28stratovolcano%29%20sources.%20%20There%20is%20no%20evidence%20of%20mixing%20or%20mingling%20of%20basalt%20and%20dacite.%20%20However%2C%20andesitic%20scoria%20inclusions%20in%20the%20early-erupted%20dacitic%20ignimbrite%20represent%20mingling%20of%20andesitic%20and%20dacitic%20magmas.%5Cn%5CnAs%20with%20the%20Talili%20Pyroclastics%2C%20at%20least%20two%20other%20earlier%20tephra%20sequences%20at%20Rabaul%20probably%20resulted%20from%20phases%20of%20VEI%205%20volcanism%20and%20directly%20underlie%20the%20deposits%20of%20major%20eruptions.%20%20This%20leads%20to%20the%20inference%20that%20cycles%20of%20escalating%20eruptive%20activity%20have%20prevailed%20prior%20to%20some%20of%20the%20major%20eruptions%2C%20and%20suggests%20that%20the%20strength%20of%20volcanism%20at%20Rabaul%20may%20rise%20from%20the%20lower%20levels%20%28maximum%20of%20VEI%204%29%20evident%20since%20the%20Rabaul%20Pyroclastics%20event%20as%20the%20system%20moves%20towards%20the%20next%20major%20eruption.%22%2C%22date%22%3A%222018-10-27%22%2C%22language%22%3A%22en%22%2C%22DOI%22%3A%2210.1007%5C%2Fs00445-018-1255-8%22%2C%22ISSN%22%3A%221432-0819%22%2C%22url%22%3A%22https%3A%5C%2F%5C%2Frdcu.be%5C%2Fbax58%22%2C%22collections%22%3A%5B%22LA9GP8XJ%22%5D%2C%22dateModified%22%3A%222018-11-02T00%3A31%3A07Z%22%7D%7D%5D%7D
Fabbro, G.N., McKee, C.O., Sindang, M.E., Eggins, S., Bouvet de Maisonneuve, C., 2020. Variable mafic recharge across a caldera cycle at Rabaul, Papua New Guinea. Journal of Volcanology and Geothermal Research 393, 106810.
https://doi.org/10.1016/j.jvolgeores.2020.106810 Download
McKee, C.O., Fabbro, G.N., 2018. The Talili Pyroclastics eruption sequence: VEI 5 precursor to the seventh century CE caldera-forming event at Rabaul, Papua New Guinea. Bull Volcanol 80, 79.
https://doi.org/10.1007/s00445-018-1255-8 Download