Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone

Lormand C; Zellmer GF; Sakamoto N; Ubide T; Kilgour G; Yurimoto H; Palmer A; Németh K; Iizuka Y; Moebis A

Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone

dc.citation.issue	11
dc.citation.volume	176
dc.contributor.author	Lormand C
dc.contributor.author	Zellmer GF
dc.contributor.author	Sakamoto N
dc.contributor.author	Ubide T
dc.contributor.author	Kilgour G
dc.contributor.author	Yurimoto H
dc.contributor.author	Palmer A
dc.contributor.author	Németh K
dc.contributor.author	Iizuka Y
dc.contributor.author	Moebis A
dc.date.accessioned	2024-11-12T19:41:01Z
dc.date.available	2024-11-12T19:41:01Z
dc.date.issued	2021-11-05
dc.description.abstract	Arc magmas typically contain phenocrysts with complex zoning and diverse growth histories. Microlites highlight the same level of intracrystalline variations but require nanoscale resolution which is globally less available. The southern Taupo Volcanic Zone (TVZ), New Zealand, has produced a wide range of explosive eruptions yielding glassy microlite-bearing tephras. Major oxide analyses and textural information reveal that microlite rims are commonly out of equilibrium with the surrounding glass. We mapped microlites and microcrysts at submicron resolution for major and trace element distributions and observed three plagioclase textural patterns: (1) resorption and overgrowth, (2) oscillatory zoning, and (3) normal (sharp) zoning. Pyroxene textures are diverse: (1) resorption and overgrowth, (2) calcium-rich bands, (3) hollow textures, (4) oscillatory zoning, (5) sector zoning, (6) normal zoning and (7) reverse zoning. Microlite chemistry and textures inform processes operating during pre-eruptive magma ascent. They indicate a plumbing system periodically intruded by short-lived sub-aphyric dykes that entrain microantecrysts grown under diverse physico-chemical conditions and stored in rapidly cooled, previously intruded dykes. Changes in temperature gradients between the intrusion and the host rock throughout ascent and repeated magma injections lead to fluctuations in cooling rates and generate local heterogeneities illustrated by the microlite textures and rim compositions. Late-stage degassing occurs at water saturation, forming thin calcic microcryst rims through local partitioning effects. This detailed investigation of textures cryptic to conventional imaging shows that a significant proportion of the micrometre-sized crystal cargo of the TVZ is of antecrystic origin and may not be attributed to late-stage nucleation and growth at the onset of volcanic eruptions, as typically presumed.
dc.description.confidential	false
dc.edition.edition	November 2021
dc.identifier.author-url	http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000714931400001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=c5bb3b2499afac691c2e3c1a83ef6fef
dc.identifier.citation	Lormand C, Zellmer GF, Sakamoto N, Ubide T, Kilgour G, Yurimoto H, Palmer A, Németh K, Iizuka Y, Moebis A. (2021). Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone. Contributions to Mineralogy and Petrology. 176. 11.
dc.identifier.doi	10.1007/s00410-021-01857-7
dc.identifier.eissn	1432-0967
dc.identifier.elements-type	journal-article
dc.identifier.issn	0010-7999
dc.identifier.number	ARTN 97
dc.identifier.uri	https://mro.massey.ac.nz/handle/10179/71980
dc.language	English
dc.publisher	Springer Nature
dc.publisher.uri	https://link.springer.com/article/10.1007/s00410-021-01857-7
dc.relation.isPartOf	Contributions to Mineralogy and Petrology
dc.rights	© Crown 2021
dc.rights	CC BY 4.0
dc.rights.uri	https://creativecommons.org/licenses/by/4.0/
dc.subject	Microcrysts
dc.subject	Tongariro volcanic centre
dc.subject	Chemical zoning
dc.subject	Intermediate magmas
dc.subject	Magma ascent
dc.title	Shallow magmatic processes revealed by cryptic microantecrysts: a case study from the Taupo Volcanic Zone
dc.type	Journal article
pubs.elements-id	449573
pubs.organisational-group	College of Health