TY - JOUR
T1 - Mantle noble gas abundance ratios inferred from oceanic basalts and model estimates
AU - Yamamoto, Junji
AU - Kurz, Mark D.
N1 - Funding Information:
We are extremely grateful to two anonymous reviewers, who provided thoughtful comments that improved the manuscript to an enormous degree. The authors also thank Hiroshi Aoyama for his useful help with Monte Carlo calculations. MK acknowledges support from the U.S. National Science Foundation and WHOI . This study was supported by Grants-in-Aid for Scientific Research (Nos. 20H0200000 and 20K2093100 ) from the Japan Society for the Promotion of Science .
Publisher Copyright:
© 2022 Elsevier B.V.
PY - 2022/6
Y1 - 2022/6
N2 - We investigated mantle noble gas abundance ratios using a global compilation of data from mid-ocean ridge basalts (MORB) and high 3He/4He ocean island basalts (OIB), coupled with calculated abundances based on closed-system evolution models. Assuming that the mantle sources of MORB and high 3He/4He OIB are derived from the same early Earth parental material, variations in their noble gas abundance ratios are useful to ascertain which source is more depleted or degassed, or if the mantle noble gases might be a hybrid of different parental materials. Therefore, noble gas compositions of mantle sources can be a key to elucidating mantle evolution and structure. We calculated the noble gas abundance patterns using a Monte Carlo approach with validated end-members, which provides new estimates for the abundance ratios and their uncertainties. The adequacy of the calculated values was confirmed by existing data. We compiled all published noble gas data extracted by total heating of glassy oceanic basalts, which enables estimation of the pristine abundance patterns of noble gases including Kr for both sources of MORB and OIB. The pristine abundance ratios of the mantle sources for oceanic basalts are estimated by correcting measured values for atmospheric influences and elemental fractionation. The corrected abundance ratios resemble mantle values calculated using the proposed end-members for MORB and high 3He/4He OIB. The estimated relative abundance ratios in the high 3He/4He OIB source are similar to those of C1 chondrites in the range of He to Kr, supporting the hypothesis that a less degassed primitive OIB source can exist in the Earth's mantle. By contrast, the MORB source shows depletion of lighter noble gases, but with high relative helium content compared to the OIB source. The contrast in He/Ne abundance ratios between MORB and OIB, is a key constraint on mantle evolution models, andis expected to reflect several stages of diffusive fractionation during Earth history, or different initial mantle sources, which would require heterogeneous Earth accretion.
AB - We investigated mantle noble gas abundance ratios using a global compilation of data from mid-ocean ridge basalts (MORB) and high 3He/4He ocean island basalts (OIB), coupled with calculated abundances based on closed-system evolution models. Assuming that the mantle sources of MORB and high 3He/4He OIB are derived from the same early Earth parental material, variations in their noble gas abundance ratios are useful to ascertain which source is more depleted or degassed, or if the mantle noble gases might be a hybrid of different parental materials. Therefore, noble gas compositions of mantle sources can be a key to elucidating mantle evolution and structure. We calculated the noble gas abundance patterns using a Monte Carlo approach with validated end-members, which provides new estimates for the abundance ratios and their uncertainties. The adequacy of the calculated values was confirmed by existing data. We compiled all published noble gas data extracted by total heating of glassy oceanic basalts, which enables estimation of the pristine abundance patterns of noble gases including Kr for both sources of MORB and OIB. The pristine abundance ratios of the mantle sources for oceanic basalts are estimated by correcting measured values for atmospheric influences and elemental fractionation. The corrected abundance ratios resemble mantle values calculated using the proposed end-members for MORB and high 3He/4He OIB. The estimated relative abundance ratios in the high 3He/4He OIB source are similar to those of C1 chondrites in the range of He to Kr, supporting the hypothesis that a less degassed primitive OIB source can exist in the Earth's mantle. By contrast, the MORB source shows depletion of lighter noble gases, but with high relative helium content compared to the OIB source. The contrast in He/Ne abundance ratios between MORB and OIB, is a key constraint on mantle evolution models, andis expected to reflect several stages of diffusive fractionation during Earth history, or different initial mantle sources, which would require heterogeneous Earth accretion.
UR - http://www.scopus.com/inward/record.url?scp=85128462174&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85128462174&partnerID=8YFLogxK
U2 - 10.1016/j.pepi.2022.106875
DO - 10.1016/j.pepi.2022.106875
M3 - Article
AN - SCOPUS:85128462174
SN - 0031-9201
VL - 327
JO - Physics of the Earth and Planetary Interiors
JF - Physics of the Earth and Planetary Interiors
M1 - 106875
ER -