Potassium isotope systematics of oceanic basalts

Tuller-Ross, Brenna; Marty, Bernard; Chen, Heng; Kelley, K. A.; Lee, Heather; Wang, Kun

doi:10.1016/j.gca.2019.06.001

Cited by 60 publications

(38 citation statements)

References 60 publications

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“…The mixing calculation also lends support to previous conclusion that lithospheric mantle modified by subducted sediments is responsible for the formation of low- 41 K (−0.81 to −0.43‰) potassic basalts from northeastern China (22). The modeled results concentrate between −0.6 and −0.2‰, which is comparable to the range of −0.66 to −0.25‰ reported for global oceanic basalts (19,21), and suggest that recycled sediments may have been involved in the generation of a few oceanic basalts that have  41 K values deviated from the typical mantle range (fig. S1).…”

Section: Implications For Crustal Recycling and Mantle Heterogeneitysupporting

confidence: 88%

“…The δ 41 K values measured in altered crust vary from −0.60 to −0.05‰ and in subducting sediments from −1.3 to −0.02‰ (tables S1 and S2); these values span a range of 20 times greater than the long-term precision of our analytical methods. The δ 41 K data straddle the average mantle value of −0.43‰ ( 21 ); however, they are all lower than the seawater value of 0.12‰ (see Materials and Methods for sample details) ( 30 , 31 ).…”

Section: Resultsmentioning

confidence: 87%

“…The sediment melts will inherit the  41 K signatures of their precursors because partial melting does not fractionate K isotopes (19,20). Altered seafloor basalts have  41 K close to fresh basalts [this study and (34)] or substantially higher [−0.17 to 0.19‰ (21,35)]. On the basis of eclogite studies, dehydration of the basaltic crust is expected to release most of its K to fluids (49), with the fluids enriching in heavy K isotopes relative to dehydrated eclogites by a fractionation factor of 1.5‰ (50).…”

Section: Implications For Crustal Recycling and Mantle Heterogeneitymentioning

confidence: 87%

“…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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Section: Implications For Crustal Recycling and Mantle Heterogeneitysupporting

confidence: 88%

Section: Resultsmentioning

confidence: 87%

Section: Implications For Crustal Recycling and Mantle Heterogeneitymentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Potassium isotopic heterogeneity in subducting oceanic plates

Teng

Plank

et al. 2020

Sci. Adv.

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“…In contrast, low-temperature hydrothermal alteration of oceanic crust is likely not important in determining the K composition of seawater based on analyses of seawater-altered [12], Rudnick and Gao [13], and Berner and Berner [11], respectively. The K isotopic compositions of the mantle are constrained by oceanic basalts [14], the K isotopic composition of the continental crust is from Huang et al [7], while those of the rivers are from Li et al [9], and that of the oceans is from this study. The black vertical bars represent the average d 41 K value of upper continental crust and river waters.…”

mentioning

confidence: 95%

Homogeneous and heavy potassium isotopic composition of global oceans

Hille

Huang

et al. 2019

Science Bulletin

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Application of a “Continuous‐Acquisition‐Method” to potassium isotope measurements by multi‐collector inductively coupled plasma mass spectrometry

Sun

Huang

et al. 2021

Rapid Comm Mass Spectrometry

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Rationale The very small mass difference between 41K and 40ArH+ makes the flat, hydride interference‐free peak shoulders very narrow (0.002–0.003 m/z unit), bringing a number of analytical challenges when measuring K isotopic compositions by multi‐collector inductively coupled plasma mass spectrometry (MC‐ICP‐MS). In traditional Sequence Run mode, the parameters are loaded every line of the sequence which can introduce tiny drifts of tune parameters and mass peaks. This may occasionally lead to the failure of K isotope measurements when mass drifts exceed 0.002 m/z unit. It is thus essential to keep the tune parameters, especially the magnet current, very stable to achieve high‐precision K isotopic compositions. Method We developed a “Continuous‐Acquisition‐Method” (CAM) MC‐ICP‐MS Run mode to improve the stability when determining K isotopes. Two sets of experiments were designed: (a) Stability test: measuring a single pure K solution (viz. NIST‐999c) for ~3 h and comparing the stability of the two run modes; and (b) GSB‐K test: measuring our inhouse pure K standard solution (GSB‐K) in both run modes and comparing the accuracy and precision. Results The traditional Sequence Run mode only kept the MC‐ICP‐MS system stable for the first ~1.5 h during the ~3‐h test, with an offset of the mass peaks of ~0.003 m/z unit. The CAM Run mode yielded higher stability during the whole test (~3 h), with a peak shift <0.0004 m/z unit. Measurement of the GSB‐K standard solution in Sequence Run and CAM Run modes gives identical δ41K values when the magnet was kept stable, with the CAM Run mode offering a better precision and keeping the instrument stable for longer time. Conclusions The MC‐ICP‐MS CAM Run mode shows higher stability and better precision. It is, therefore, good for high‐precision K isotope measurements.

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Potassium isotope systematics of oceanic basalts

Cited by 60 publications

References 60 publications

Potassium isotopic heterogeneity in subducting oceanic plates

Potassium isotopic heterogeneity in subducting oceanic plates

Homogeneous and heavy potassium isotopic composition of global oceans

Application of a “Continuous‐Acquisition‐Method” to potassium isotope measurements by multi‐collector inductively coupled plasma mass spectrometry

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