Boron Isotopes Reveal Multiple Metasomatic Events in the Mantle Beneath the Eastern North China Craton

Hong-Yan Li; Zhou Zhou; Jeffrey G. Ryan; Gang-Jian Wei; Yi-Gang Xu

doi:10.1016/j.gca.2016.08.027

Boron Isotopes Reveal Multiple Metasomatic Events in the Mantle Beneath the Eastern North China Craton

Hong-Yan Li, Zhou Zhou, Jeffrey G. Ryan, Gang-Jian Wei, Yi-Gang Xu

School of Geosciences

Research output: Contribution to journal › Article › peer-review

Abstract

<p> <p id="x-x-sp0005"> Linkages inferred between the geochemical heterogeneity of the mantle beneath eastern Eurasia and the stagnant Pacific <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/slab" title="Learn more about Slab"> slab </a> documented geophysically in its mantle <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/transition-zone" title="Learn more about Transition Zone"> transition zone </a> are as yet not clearly characterized. In this paper we report new elemental and isotopic data for <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/boron" title="Learn more about Boron"> boron </a> (B) on a suite of well-characterized <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/cenozoic" title="Learn more about Cenozoic"> Cenozoic </a> <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/basalt" title="Learn more about Basalt"> basalts </a> (alkali basalts, <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/basanite" title="Learn more about Basanite"> basanites </a> and nephelinites), with <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ocean-island-basalt" title="Learn more about Ocean Island Basalt"> ocean island basalt </a> (OIB)-like <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/trace-element" title="Learn more about Trace Element"> trace element </a> signatures from western Shandong of the eastern North China <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/craton" title="Learn more about Craton"> Craton </a> (NCC). Correlations between major elements (e.g., FeOTversus SiO2), trace elements (e.g., CeN/PbN versus BaN/ThN) and <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/radiogenic-isotopes" title="Learn more about Radiogenic Isotopes"> radiogenic isotopes </a> (e.g., 206Pb/204Pb versus 87Sr/86Sr) suggest these basalts are derived via the mixing of melts from two mantle components: a fluid mobile element (FME; such as Ba, K, Pb and Sr) enriched component, which is most evident in the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/alkali-basalt" title="Learn more about Alkali Basalt"> alkali basalts </a> , and a FME depleted mantle component that is more evident in the basanites and <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/nephelinite" title="Learn more about Nephelinite"> nephelinites </a> . The alkali basalts in this study have lower B concentrations (1.4–2.2 μg/g) but higher δ11B (−4.9 to −1.4) values than the basanites and nephelinites (B = 2.1–5.0 μg/g; δ11B = −6.9 to −3.9), and all the samples have nearly constant B/Nb ratios between 0.03 and 0.07, similar to the observed range in B/Nb for intraplate lavas. Our high-SiO2 samples have higher δ11B than that of our low SiO2 samples, indicating that the B isotopic differences among our samples do not result from the addition of a continental crustal component in the <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/mantle-source" title="Learn more about Mantle Source"> mantle source </a> , or direct crustal assimilation during the eruption process. The positive B versus Nb correlation suggests the B <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/isotopic-composition" title="Learn more about Isotopic Composition"> isotopic compositions </a> of the western Shandong basalts primarily reflect the pre-eruptive compositions of their mantle sources. Correlations among B, Nd and Sr isotope signatures of the western Shandong basalts differ from those among basalts from <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/plume" title="Learn more about Plume"> plume </a> settings (e.g., Azores and Hawaii), and are inconsistent with models suggesting single-step metasomatic additions to the mantle. We thus call upon multiple metasomatic events in the mantle beneath the eastern NCC in order to interpret its observed radiogenic and boron isotopic variability. The heavier δ11B, FME-enriched mantle source developed during an older event, while <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/metasomatism" title="Learn more about Metasomatism"> metasomatism </a> by melts from the stagnant <a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/pacific-plate" title="Learn more about Pacific Plate"> Pacific plate </a> in the MTZ led to the development of a FME-depleted mantle source at greater depths with a lower δ11B. </p></p>

Original language	American English
Journal	Geochimica et Cosmochimica Acta
Volume	194
DOIs	https://doi.org/10.1016/j.gca.2016.08.027
State	Published - Dec 1 2016

Keywords

Boron isotope
North China Craton
Intracontinental basalts
Recycled oceanic crust

Access to Document

10.1016/j.gca.2016.08.027License: CC BY

https://doi.org/10.1016/j.gca.2016.08.027

Cite this

@article{15352838a3f74a23b8913caccb60374f,

title = "Boron Isotopes Reveal Multiple Metasomatic Events in the Mantle Beneath the Eastern North China Craton",

abstract = " Linkages inferred between the geochemical heterogeneity of the mantle beneath eastern Eurasia and the stagnant Pacific slab documented geophysically in its mantle transition zone are as yet not clearly characterized. In this paper we report new elemental and isotopic data for boron (B) on a suite of well-characterized Cenozoic basalts (alkali basalts, basanites and nephelinites), with ocean island basalt (OIB)-like trace element signatures from western Shandong of the eastern North China Craton (NCC). Correlations between major elements (e.g., FeOTversus SiO2), trace elements (e.g., CeN/PbN versus BaN/ThN) and radiogenic isotopes (e.g., 206Pb/204Pb versus 87Sr/86Sr) suggest these basalts are derived via the mixing of melts from two mantle components: a fluid mobile element (FME; such as Ba, K, Pb and Sr) enriched component, which is most evident in the alkali basalts , and a FME depleted mantle component that is more evident in the basanites and nephelinites . The alkali basalts in this study have lower B concentrations (1.4–2.2 μg/g) but higher δ11B (−4.9 to −1.4) values than the basanites and nephelinites (B = 2.1–5.0 μg/g; δ11B = −6.9 to −3.9), and all the samples have nearly constant B/Nb ratios between 0.03 and 0.07, similar to the observed range in B/Nb for intraplate lavas. Our high-SiO2 samples have higher δ11B than that of our low SiO2 samples, indicating that the B isotopic differences among our samples do not result from the addition of a continental crustal component in the mantle source , or direct crustal assimilation during the eruption process. The positive B versus Nb correlation suggests the B isotopic compositions of the western Shandong basalts primarily reflect the pre-eruptive compositions of their mantle sources. Correlations among B, Nd and Sr isotope signatures of the western Shandong basalts differ from those among basalts from plume settings (e.g., Azores and Hawaii), and are inconsistent with models suggesting single-step metasomatic additions to the mantle. We thus call upon multiple metasomatic events in the mantle beneath the eastern NCC in order to interpret its observed radiogenic and boron isotopic variability. The heavier δ11B, FME-enriched mantle source developed during an older event, while metasomatism by melts from the stagnant Pacific plate in the MTZ led to the development of a FME-depleted mantle source at greater depths with a lower δ11B. ",

keywords = "Boron isotope, North China Craton, Intracontinental basalts, Recycled oceanic crust",

author = "Hong-Yan Li and Zhou Zhou and Ryan, {Jeffrey G.} and Gang-Jian Wei and Yi-Gang Xu",

year = "2016",

month = dec,

day = "1",

doi = "10.1016/j.gca.2016.08.027",

language = "American English",

volume = "194",

journal = "Geochimica et Cosmochimica Acta",

}

TY - JOUR

T1 - Boron Isotopes Reveal Multiple Metasomatic Events in the Mantle Beneath the Eastern North China Craton

AU - Li, Hong-Yan

AU - Zhou, Zhou

AU - Ryan, Jeffrey G.

AU - Wei, Gang-Jian

AU - Xu, Yi-Gang

PY - 2016/12/1

Y1 - 2016/12/1

N2 - Linkages inferred between the geochemical heterogeneity of the mantle beneath eastern Eurasia and the stagnant Pacific slab documented geophysically in its mantle transition zone are as yet not clearly characterized. In this paper we report new elemental and isotopic data for boron (B) on a suite of well-characterized Cenozoic basalts (alkali basalts, basanites and nephelinites), with ocean island basalt (OIB)-like trace element signatures from western Shandong of the eastern North China Craton (NCC). Correlations between major elements (e.g., FeOTversus SiO2), trace elements (e.g., CeN/PbN versus BaN/ThN) and radiogenic isotopes (e.g., 206Pb/204Pb versus 87Sr/86Sr) suggest these basalts are derived via the mixing of melts from two mantle components: a fluid mobile element (FME; such as Ba, K, Pb and Sr) enriched component, which is most evident in the alkali basalts , and a FME depleted mantle component that is more evident in the basanites and nephelinites . The alkali basalts in this study have lower B concentrations (1.4–2.2 μg/g) but higher δ11B (−4.9 to −1.4) values than the basanites and nephelinites (B = 2.1–5.0 μg/g; δ11B = −6.9 to −3.9), and all the samples have nearly constant B/Nb ratios between 0.03 and 0.07, similar to the observed range in B/Nb for intraplate lavas. Our high-SiO2 samples have higher δ11B than that of our low SiO2 samples, indicating that the B isotopic differences among our samples do not result from the addition of a continental crustal component in the mantle source , or direct crustal assimilation during the eruption process. The positive B versus Nb correlation suggests the B isotopic compositions of the western Shandong basalts primarily reflect the pre-eruptive compositions of their mantle sources. Correlations among B, Nd and Sr isotope signatures of the western Shandong basalts differ from those among basalts from plume settings (e.g., Azores and Hawaii), and are inconsistent with models suggesting single-step metasomatic additions to the mantle. We thus call upon multiple metasomatic events in the mantle beneath the eastern NCC in order to interpret its observed radiogenic and boron isotopic variability. The heavier δ11B, FME-enriched mantle source developed during an older event, while metasomatism by melts from the stagnant Pacific plate in the MTZ led to the development of a FME-depleted mantle source at greater depths with a lower δ11B.

AB - Linkages inferred between the geochemical heterogeneity of the mantle beneath eastern Eurasia and the stagnant Pacific slab documented geophysically in its mantle transition zone are as yet not clearly characterized. In this paper we report new elemental and isotopic data for boron (B) on a suite of well-characterized Cenozoic basalts (alkali basalts, basanites and nephelinites), with ocean island basalt (OIB)-like trace element signatures from western Shandong of the eastern North China Craton (NCC). Correlations between major elements (e.g., FeOTversus SiO2), trace elements (e.g., CeN/PbN versus BaN/ThN) and radiogenic isotopes (e.g., 206Pb/204Pb versus 87Sr/86Sr) suggest these basalts are derived via the mixing of melts from two mantle components: a fluid mobile element (FME; such as Ba, K, Pb and Sr) enriched component, which is most evident in the alkali basalts , and a FME depleted mantle component that is more evident in the basanites and nephelinites . The alkali basalts in this study have lower B concentrations (1.4–2.2 μg/g) but higher δ11B (−4.9 to −1.4) values than the basanites and nephelinites (B = 2.1–5.0 μg/g; δ11B = −6.9 to −3.9), and all the samples have nearly constant B/Nb ratios between 0.03 and 0.07, similar to the observed range in B/Nb for intraplate lavas. Our high-SiO2 samples have higher δ11B than that of our low SiO2 samples, indicating that the B isotopic differences among our samples do not result from the addition of a continental crustal component in the mantle source , or direct crustal assimilation during the eruption process. The positive B versus Nb correlation suggests the B isotopic compositions of the western Shandong basalts primarily reflect the pre-eruptive compositions of their mantle sources. Correlations among B, Nd and Sr isotope signatures of the western Shandong basalts differ from those among basalts from plume settings (e.g., Azores and Hawaii), and are inconsistent with models suggesting single-step metasomatic additions to the mantle. We thus call upon multiple metasomatic events in the mantle beneath the eastern NCC in order to interpret its observed radiogenic and boron isotopic variability. The heavier δ11B, FME-enriched mantle source developed during an older event, while metasomatism by melts from the stagnant Pacific plate in the MTZ led to the development of a FME-depleted mantle source at greater depths with a lower δ11B.

KW - Boron isotope

KW - North China Craton

KW - Intracontinental basalts

KW - Recycled oceanic crust

UR - https://digitalcommons.usf.edu/geo_facpub/1136

UR - https://doi.org/10.1016/j.gca.2016.08.027

U2 - 10.1016/j.gca.2016.08.027

DO - 10.1016/j.gca.2016.08.027

M3 - Article

VL - 194

JO - Geochimica et Cosmochimica Acta

JF - Geochimica et Cosmochimica Acta

ER -

Boron Isotopes Reveal Multiple Metasomatic Events in the Mantle Beneath the Eastern North China Craton

Abstract

Keywords

Access to Document

Other files and links

Cite this