Potassium isotope fractionation during magmatic differentiation of basalt to rhyolite

Tuller-Ross, Brenna; Savage, Paul S.; Chen, Heng; Wang, Kun

doi:10.1016/j.chemgeo.2019.07.017

Cited by 49 publications

(23 citation statements)

References 40 publications

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“…The basalt standard BHVO-1 derived from the 1919 Kilauea eruption is also plotted. (d) Limited range of δ 41 K in basalts measured in this study and in Hekla basalts (Tuller-Ross, Savage, et al, 2019b) as opposed to substantial variability among global oceanic basalts reported in Tuller- Ross, Marty, et al (2019). "EPR" stands for "East Pacific Rise" and "MAR" stands for "Mid-Atlantic Ridge".…”

Section: 1029/2020jb021543contrasting

confidence: 56%

Potassium Isotope Fractionation During Magmatic Differentiation and the Composition of the Mantle

Teng

Helz

et al. 2021

JGR Solid Earth

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Potassium (K) is a primary constituent of planetary crusts and studies of its stable isotope ratio (41 K/ 39 K) have been used recently to provide new insights into planetary accretion and differentiation. Experimental work shows that, as a moderately volatile element, K isotopes fractionate substantially during evaporation-condensation processes (e.g., Yu et al., 2003). Measurements of differentiated lunar and terrestrial lavas indicated that the Moon is enriched in heavy K isotopes by ∼0.4‰ relative to the Earth, which has been interpreted as evaporative loss of light K during the Moon-forming giant impact (Wang & Jacobsen, 2016a). Such inter-planetary comparison is based on a key assumption that negligible K isotope fractionation occurs during igneous differentiation; therefore, crustal rocks are assumed to be representative of their planetary bodies. This assumption is supported by less equilibrium isotope fractionation as temperature increases (∼1/T 2 , Bigeleisen & Mayer, 1947; Urey, 1947). Also, K has a strong tendency to partition into melts during mantle melting and magmatic differentiation. Hence crystal-melt fractionation is not expected to significantly influence the K budget and isotopic composition of evolving magmas. However, despite these theoretical considerations, there is sparse confirmation in natural samples. Potassium occurs in several major silicate groups that are commonly involved in magmatic differentiation. Plagioclase crystallization is widely associated with basaltic differentiation while crystallization of K-rich hornblende, biotite, and K-feldspar occurs in more evolved magmas. The sparse δ 41 K data reported for these minerals span a range of 0.6‰, with biotite being isotopically lighter than typical igneous rocks and feldspar being mostly heavier except a few outliers (Chen, Tian, et al., 2019; Morgan et al., 2018). Their contrasting preferences for K isotopes could reflect differing K coordination environments between crystallized minerals and melts, or among various K-bearing minerals. Theoretical calculations also suggest that the K-O bond strength of a mineral varies with its chemical composition, for example, feldspar with lower K/(K + Na)

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Section: 1029/2020jb021543contrasting

confidence: 56%

Potassium Isotope Fractionation During Magmatic Differentiation and the Composition of the Mantle

Teng

Helz

et al. 2021

JGR Solid Earth

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“…Therefore, shallow dehydration reactions are expected to have little effect on the K isotopic compositions of the subducting sediments, and melting of sediments is generally required to liberate appreciable amount of K ( 48 ). The sediment melts will inherit the δ 41 K signatures of their precursors because partial melting does not fractionate K isotopes ( 19 , 20 ). Altered seafloor basalts have δ 41 K close to fresh basalts [this study and ( 34 )] or substantially higher [−0.17 to 0.19‰ ( 21 , 35 )].…”

Section: Discussionmentioning

confidence: 99%

“…Markedly improved analytical precision of δ 41 K [δ 41 K (‰) = (( 41 K/ 39 K) sample /( 41 K/ 39 K) standard − 1) × 1000] allows identification of K-rich crustal materials that are recycled to the mantle. Studies of an Iceland’s basalt-to-rhyolite differentiation sequence suggest negligible K isotope fractionation (<0.1‰) during mantle partial melting and magmatic differentiation ( 19 ), which is supported by theoretically calculated fractionations between silicate melts and minerals at equilibrium ( 20 ). Hence, δ 41 K values in basalts are representative of their mantle sources.…”

Section: Introductionmentioning

confidence: 85%

“…Fresh oceanic basalts sampled globally have δ 41 K values that range from −0.66 to −0.25‰, with 90% of the samples clustering between −0.52 and −0.34‰ (fig. S1), indicating a relatively homogeneous K isotopic composition of the global ambient mantle ( 19 , 21 ). A suite of continental basalts from northeastern China displays a noticeably larger variation (−0.81 to −0.15‰), and their δ 41 K values correlate with elemental ratios and radiogenic isotopes that are indicative of crustal inputs ( 22 ).…”

Section: Introductionmentioning

confidence: 99%

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Potassium isotopic heterogeneity in subducting oceanic plates

Teng

Plank

et al. 2020

Sci. Adv.

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Oceanic crust and sediments are the primary K sinks for seawater, and they deliver considerable amounts of K to the mantle via subduction. Historically, these crustal components were not studied for K isotopes because of the lack of analytical precision to differentiate terrestrial variations. Here, we report a high-precision dataset that reveals substantial variability in oceanic plates and provides further insights into the oceanic K cycle. Sixty-nine sediments worldwide yield a broad δ41K range from −1.3 to −0.02‰. The unusually low values are indicative of release of heavy K during continental weathering and uptake of light K during submarine diagenetic alteration. Twenty samples of altered western Pacific crust from ODP Site 801 display δ41K from −0.60 to −0.05‰, averaging at −0.32‰. Our results indicate that submarine alteration of oceanic plates is essential for generating the high-δ41K signature of seawater. These regionally varying subducting components are heterogeneous K inputs to the mantle.

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“…Komposisi geokimia banyak bermanfaat untuk menjelaskan fenomena kebumian. Proses diferensiasi magma (magma differentiation) yang dipengaruhi oleh faktor derajat lelehan sebagian (partial melting), fraksionasi kristal (crystal fractionation), pencampuran magma (magma mixing), dan kontaminasi dapat dicirikan berdasarkan karakter geokimia [1][2][3][4]. Kondisi tektonik pembentukan batuan dapat diklasifikasikan melalui rasio beberapa konsentrasi unsur jejak, unsur tanah jarang (UTJ), maupun isotop [5][6][7].…”

Section: Pendahuluanunclassified

Komparasi Geokimia Batuan Gunung Api Kuarter dan Tersier di Tepian Selatan Lampung

Irzon

2020

EKSPLORIUM

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ABSTRAK Keterdapatan batuan gunung api di Sumatra diakibatkan oleh penunjaman Lempeng Samudra India-Australia ke bawah Lempeng West Sumatra sejak Eosen. Tanggamus adalah kabupaten di ujung selatan Lampung dengan keterdapatan beberapa unit batuan gunung api berumur Tersier maupun Kuarter. Studi ini bertujuan untuk membandingkan komposisi geokimia batuan gunung api Tersier Formasi Hulusimpang dengan batuan gunung api Kuarter Gunung Tanggamus. Perangkat XRF dan ICP-MS dimanfaatkan untuk mengetahui kadar oksida utama, unsur jejak, dan unsur tanah jarang pada penelitian ini. Berdasarkan karakter geokimia, sampel dari Formasi Hulusimpang adalah batuan gunung api kalk-alkali, metalumina hingga peralumina, dan dalam rentang trakiandesit basaltik hingga riolit. Sampel batuan gunung api berumur Kuarter berada pada rentang kadar silika yang lebih sempit dan cenderung metalumina. Studi ini membuktikan bahwa kedua kelompok batuan berasal dari magma yang sama, tetapi dengan kontaminasi kerak selama diferensiasi. Proses pembentukan yang berbeda pada kedua kelompok batuan diperjelas oleh derajat kemiringan kurva diagram laba-laba UTJ dan jenis anomali Eu.ABSTRACT The presence of volcanic rocks in Sumatra is due to the subduction of the Indian-Australian Ocean Plate under the West Sumatra Plate since the Eocene. Tanggamus Regency situated at the southern edge of Lampung with the occurrence of several Tertiary and Quaternary volcanic rock units. The aim of this study is to compare the geochemical composition of Tertiary volcanic rocks from the Hulusimpang Formation and Quaternary volcanic rocks from Mount Tanggamus in the Tanggamus Regency. XRF and ICP-MS devices were used to determine the compositions of major oxides, trace elements, and rare earth elements in this study. Based on geochemical characters, samples from the Hulusimpang Formation are calc-alkaline volcanic rocks, metaluminous to peraluminous, and in the basaltic trachyandesite to rhyolite ranges. Quaternary samples are in a narrower range of silica content and tend to be metaluminous. This study proves that the two rock groups originate from the same magma but with crustal contamination during differentiation. The two volcanic should experience through different formation processes based on the slope of the heavy-REE and the type of Eu anomaly.

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Potassium isotope fractionation during magmatic differentiation of basalt to rhyolite

Cited by 49 publications

References 40 publications

Potassium Isotope Fractionation During Magmatic Differentiation and the Composition of the Mantle

Potassium Isotope Fractionation During Magmatic Differentiation and the Composition of the Mantle

Potassium isotopic heterogeneity in subducting oceanic plates

Komparasi Geokimia Batuan Gunung Api Kuarter dan Tersier di Tepian Selatan Lampung

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