Cosmogenic 3 He in alluvial metal and alloy grains: Assessing the potential for quantifying sediment transport times

Olga V. Yakubovich, Finlay M. Stuart, Aleksandr V. Nesterenok, Ana Carracedo

Research output

Abstract

We have measured the He isotope composition in detrital native gold, copper, silver, Pt 3 Fe and OsIr alloy grains from placer deposits in order to assess the extent to which cosmogenic He can be quantified and used to determine the exposure history of grains in sedimentary systems. 3 He/ 4 He ratios (0.1–273 R a ) exceed values typical of radiogenic He. 4 He is dominantly the result of the decay of U and Th, or 190 Pt in the case of Pt-rich alloys. 3 He concentrations in grains from alluvial deposits range from 0.05 to 2 × 10 8 at g −1 and appears to be dominantly cosmogenic in origin. The absence of significant nucleogenic or mantle-derived 3 He in metals is tentatively confirmed by the analysis of grains from underground mine workings. The implantation of cosmogenic He is not the main source of 3 He in alluvial metals but can be relatively important for small grains. New GEANT4-based calculations predict the production rate of 3 He (including in precursor 3 H) from Au and Pt to be approximately 25 at g −1 yr. Using this we determine that cosmogenic 3 He concentrations in the detrital grains record minimum exposure times of between 0.5 and 7 million years that generally increase with distance from the putative source. Paired fragments from three large grains show that there is considerable heterogeneity in cosmogenic He concentrations that may reflect the complex origin of detrital metal grains. This work suggests that cosmogenic He in detrital metals and minerals may find use for providing the chronology of sedimentary processes.

Original languageEnglish
Pages (from-to)22-33
Number of pages12
JournalChemical Geology
Volume517
DOIs
Publication statusPublished - 5 Jul 2019

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Sediment transport
sediment transport
Metals
metal
placer deposit
alluvial deposit
Deposits
chronology
silver
Placers
gold
isotope
copper
mantle
Silver
Isotopes
Gold
mineral
history
Minerals

Scopus subject areas

  • Geology
  • Geochemistry and Petrology

Cite this

Yakubovich, Olga V. ; Stuart, Finlay M. ; Nesterenok, Aleksandr V. ; Carracedo, Ana. / Cosmogenic 3 He in alluvial metal and alloy grains : Assessing the potential for quantifying sediment transport times. In: Chemical Geology. 2019 ; Vol. 517. pp. 22-33.
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abstract = "We have measured the He isotope composition in detrital native gold, copper, silver, Pt 3 Fe and OsIr alloy grains from placer deposits in order to assess the extent to which cosmogenic He can be quantified and used to determine the exposure history of grains in sedimentary systems. 3 He/ 4 He ratios (0.1–273 R a ) exceed values typical of radiogenic He. 4 He is dominantly the result of the decay of U and Th, or 190 Pt in the case of Pt-rich alloys. 3 He concentrations in grains from alluvial deposits range from 0.05 to 2 × 10 8 at g −1 and appears to be dominantly cosmogenic in origin. The absence of significant nucleogenic or mantle-derived 3 He in metals is tentatively confirmed by the analysis of grains from underground mine workings. The implantation of cosmogenic He is not the main source of 3 He in alluvial metals but can be relatively important for small grains. New GEANT4-based calculations predict the production rate of 3 He (including in precursor 3 H) from Au and Pt to be approximately 25 at g −1 yr. Using this we determine that cosmogenic 3 He concentrations in the detrital grains record minimum exposure times of between 0.5 and 7 million years that generally increase with distance from the putative source. Paired fragments from three large grains show that there is considerable heterogeneity in cosmogenic He concentrations that may reflect the complex origin of detrital metal grains. This work suggests that cosmogenic He in detrital metals and minerals may find use for providing the chronology of sedimentary processes.",
keywords = "He/ He, Cosmogenic helium, Gold, Native metals, Placers, Platinum",
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Cosmogenic 3 He in alluvial metal and alloy grains : Assessing the potential for quantifying sediment transport times. / Yakubovich, Olga V.; Stuart, Finlay M.; Nesterenok, Aleksandr V.; Carracedo, Ana.

In: Chemical Geology, Vol. 517, 05.07.2019, p. 22-33.

Research output

TY - JOUR

T1 - Cosmogenic 3 He in alluvial metal and alloy grains

T2 - Assessing the potential for quantifying sediment transport times

AU - Yakubovich, Olga V.

AU - Stuart, Finlay M.

AU - Nesterenok, Aleksandr V.

AU - Carracedo, Ana

PY - 2019/7/5

Y1 - 2019/7/5

N2 - We have measured the He isotope composition in detrital native gold, copper, silver, Pt 3 Fe and OsIr alloy grains from placer deposits in order to assess the extent to which cosmogenic He can be quantified and used to determine the exposure history of grains in sedimentary systems. 3 He/ 4 He ratios (0.1–273 R a ) exceed values typical of radiogenic He. 4 He is dominantly the result of the decay of U and Th, or 190 Pt in the case of Pt-rich alloys. 3 He concentrations in grains from alluvial deposits range from 0.05 to 2 × 10 8 at g −1 and appears to be dominantly cosmogenic in origin. The absence of significant nucleogenic or mantle-derived 3 He in metals is tentatively confirmed by the analysis of grains from underground mine workings. The implantation of cosmogenic He is not the main source of 3 He in alluvial metals but can be relatively important for small grains. New GEANT4-based calculations predict the production rate of 3 He (including in precursor 3 H) from Au and Pt to be approximately 25 at g −1 yr. Using this we determine that cosmogenic 3 He concentrations in the detrital grains record minimum exposure times of between 0.5 and 7 million years that generally increase with distance from the putative source. Paired fragments from three large grains show that there is considerable heterogeneity in cosmogenic He concentrations that may reflect the complex origin of detrital metal grains. This work suggests that cosmogenic He in detrital metals and minerals may find use for providing the chronology of sedimentary processes.

AB - We have measured the He isotope composition in detrital native gold, copper, silver, Pt 3 Fe and OsIr alloy grains from placer deposits in order to assess the extent to which cosmogenic He can be quantified and used to determine the exposure history of grains in sedimentary systems. 3 He/ 4 He ratios (0.1–273 R a ) exceed values typical of radiogenic He. 4 He is dominantly the result of the decay of U and Th, or 190 Pt in the case of Pt-rich alloys. 3 He concentrations in grains from alluvial deposits range from 0.05 to 2 × 10 8 at g −1 and appears to be dominantly cosmogenic in origin. The absence of significant nucleogenic or mantle-derived 3 He in metals is tentatively confirmed by the analysis of grains from underground mine workings. The implantation of cosmogenic He is not the main source of 3 He in alluvial metals but can be relatively important for small grains. New GEANT4-based calculations predict the production rate of 3 He (including in precursor 3 H) from Au and Pt to be approximately 25 at g −1 yr. Using this we determine that cosmogenic 3 He concentrations in the detrital grains record minimum exposure times of between 0.5 and 7 million years that generally increase with distance from the putative source. Paired fragments from three large grains show that there is considerable heterogeneity in cosmogenic He concentrations that may reflect the complex origin of detrital metal grains. This work suggests that cosmogenic He in detrital metals and minerals may find use for providing the chronology of sedimentary processes.

KW - He/ He

KW - Cosmogenic helium

KW - Gold

KW - Native metals

KW - Placers

KW - Platinum

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U2 - 10.1016/j.chemgeo.2019.04.010

DO - 10.1016/j.chemgeo.2019.04.010

M3 - Article

AN - SCOPUS:85064635497

VL - 517

SP - 22

EP - 33

JO - Chemical Geology

JF - Chemical Geology

SN - 0009-2541

ER -