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Evolution of Alkalic Magma Systems: Insight from Coeval Evolution of Sodic and Potassic Fractionation Lineages at The Pleiades Volcanic Complex, Antarctica

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Cited 4 time in scopus
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Title
Evolution of Alkalic Magma Systems: Insight from Coeval Evolution of Sodic and Potassic Fractionation Lineages at The Pleiades Volcanic Complex, Antarctica
Other Titles
남극 북빅토리아랜드 플레이아데스 화산 복합체의 동시기 소듐 및 중-포타슘 마그마 분화 계열
Authors
Kim, Jihyuk
Park, Jung-Woo
Lee, Mi Jung
Lee, Jong Ik
Kyle, Philip R.
Subject
Geochemistry & Geophysics
Keywords
McMurdo volcanic group; The Pleiades volcanic complex; alkalic magmatism; crustal contamination; fractional crystallization; partial melting
Issue Date
2019-01
Citation
Kim, Jihyuk, et al. 2019. "Evolution of Alkalic Magma Systems: Insight from Coeval Evolution of Sodic and Potassic Fractionation Lineages at The Pleiades Volcanic Complex, Antarctica". JOURNAL OF PETROLOGY, 60(1): 117-150.
Abstract
The magmatic evolution of The Pleiades, a Quaternary alkalic volcanic complex in Northern Victoria Land (NVL), Antarctica, is investigated using major and trace element, and Sr, Nd and Pb isotopic data. The volcanic rocks can be subdivided into two distinct magmatic lineages based on petrography and whole-rock compositions: (1) a sodic silica-undersaturated lineage with abundant kaersutite phenocrysts and (2) a potassic and mildly-alkalic, silica-saturated to slightly undersaturated lineage containing olivine phenocrysts but no kaersutite. The pressure?temperature paths estimated by clinopyroxene?liquid thermobarometry are similar in each lineage. Massbalance calculations using whole-rock and mineral compositions show that kaersutite fractionation without olivine has played a major role in magmatic differentiation of the sodic lineage, whereas the compositional variations of the potassic lineage can be ascribed to fractionation of an assemblage of plagioclase, clinopyroxene, olivine, titanomagnetite and apatite, combined with about 10% lower crustal assimilation. The higher 87Sr/86Sr (> 07035), lower 143Nd/144Nd (< 051285), and 206Pb/204Pb (< 193) ratios of the evolved potassic lavas compared to the mafic lavas support crustal assimilation. The mafic lavas from both lineages are characterized by elevated 206Pb/204Pb (>195) ratios and narrow ranges of 87Sr/86Sr (070313?070327) and 143Nd/144Nd (051289?051290) ratios, which is consistent with a high m-like (HIMU, where m¼( 238U/204Pb)t¼0) component typical of Cenozoic volcanic rocks in Antarctica and Zealandia. This HIMU-like isotopic signature of The Pleiades volcanic rocks, together with elevated Nb concentrations and negative K anomalies in primitive mantle-normalized diagrams, suggests an amphibole-bearing metasomatized lithospheric mantle source. We suggest that the primary magmas of the two lineages were formed by partial melting of metasomatic hydrous veins in the lithospheric mantle with varying degrees of reaction with the surrounding, anhydrous peridotite. The drier potassic magma experienced greater peridotite assimilation relative to the more hydrous sodic magmas. This hypothesis is supported by lower contents of Al2O3, TiO2, K2O, Rb, and Nb in the mafic potassic lavas compared to the sodic ones. This initial difference was intensified by crustal assimilation in the potassic magma suite, resulting in a silica-saturated alkalic trend which is distinct from the trend of the sodic silica-undersaturated alkalic magmas.
URI
https://repository.kopri.re.kr/handle/201206/10890
DOI
http://dx.doi.org/10.1093/petrology/egy108
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