Related Experiment Video
Updated: Sep 19, 2025
11:19
Measuring Carbon-based Contaminant Mineralization Using Combined CO2 Flux and Radiocarbon Analyses
Published on: October 21, 2016
12.0K
Enigmatic carbon isotopic variability in the oceanic upper mantle
Yves Moussallam1, Estelle F Rose-Koga2, Cyril Aubaud3
1Lamont-Doherty Earth Observatory, Columbia University, New York, NY 10964.
Summary
Earth's mantle carbon isotopes reveal significant upper mantle heterogeneity, challenging previous assumptions about its origin and suggesting a revision of the bulk silicate Earth's carbon value.
Area of Science:
- Geochemistry
- Isotope Geochemistry
- Planetary Science
Background:
- The origin of Earth's carbon and the isotopic composition of deep carbon reservoirs are poorly understood.
- Multiple isotopic fractionation events during planet formation complicate tracing carbon's history.
Purpose of the Study:
- To investigate the carbon isotopic signature (δ13C) of Earth's present-day upper mantle.
- To assess mantle heterogeneity and its implications for carbon cycling and Earth's formation.
Main Methods:
- Carbon isotopic measurements (δ13C) were performed on rare, undegassed mid-ocean ridge basalts.
- Samples were collected from the Pacific, Atlantic, and Arctic Oceans to represent diverse mantle sources.
Main Results:
- The convecting upper mantle exhibits variable δ13C values ranging from -10‰ to -4‰.
- These values differ significantly from peridotitic diamonds, with the highest values concentrated in the Atlantic.
- Observed mantle heterogeneity is uncorrelated with known geochemical markers of subduction or lower mantle contributions.
Conclusions:
- Earth's upper mantle is more heterogeneous in its carbon isotopic composition than previously assumed.
- The origin of this heterogeneity is puzzling and may involve primordial mantle composition.
- The δ13C value of the bulk silicate Earth may require revision based on these findings.
Related Concept Videos
01:21Isothermal Processes
4.0K
A thermodynamic process that occurs at constant temperature is called an isothermal process. Heat slowly flows into the system or out of the system to maintain thermal equilibrium. Processes involving phase changes like water evaporation into steam or freezing water into ice at a constant temperature are examples of Isothermal Processes.
An ideal gas can also undergo isothermal expansion or compression.
For example, consider 1 mole of an ideal gas inside an isolated cylinder at initial volume V...
An ideal gas can also undergo isothermal expansion or compression.
For example, consider 1 mole of an ideal gas inside an isolated cylinder at initial volume V...
4.0K
01:04¹³C NMR: ¹H–¹³C Decoupling
1.2K
The probability of having two carbon-13 atoms next to each other is negligible because of the low natural abundance of carbon-13. Consequently, peak splitting due to carbon-carbon spin-spin coupling is not observed in spectra. However, protons up to three sigma bonds away split the carbon signal according to the n+1 rule, resulting in complicated spectra.
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
A broadband decoupling technique is used to simplify these complex, sometimes overlapping, signals. Broadband decoupling relies on a...
1.2K
01:10Carbon-13 (¹³C) NMR: Overview
6.1K
Carbon-13 is a naturally occurring NMR-active isotope of carbon with a low natural abundance of 1.1%. In contrast, carbon-12 is the most abundant isotope of carbon with zero nuclear spin. Therefore, it is NMR inactive. The gyromagnetic ratio of carbon-13 is smaller than that of protons. As a result, carbon-13 resonance is about 6000 times weaker than proton resonance. For a given magnetic field strength, the resonance frequency of carbon-13 is about one-fourth of the resonance frequency for...
6.1K
01:14The Carbon Cycle
40.1K
Carbon is the basis of all organic matter on Earth, and is recycled through the ecosystem in two primary processes: one in which carbon is exchanged among living organisms, and one in which carbon is cycled over long periods of time through fossilized organic remains, weathering of rocks, and volcanic activity. Human activities, including increased agricultural practices and the burning of fossil fuels, has greatly affected the balance of the natural carbon cycle.
40.1K
01:31Magnetic Susceptibility and Permeability
1.4K
In linear magnetic materials, like paramagnets and diamagnets, magnetization is proportional to the magnetic field intensity. The constant of proportionality, a dimensionless number, is called magnetic susceptibility. The value of the susceptibility depends on the type of material.
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
1.4K
01:13Mass Spectrometry: Isotope Effect
2.5K
Most elements exist in nature as a mixture of isotopes. The isotopes differ in weight due to their respective number of neutrons. The molecular weight of a molecule is different depending on the specific isotope of its elements involved. As a result, the mass spectrum of the molecule exhibits peaks from the same fragment at multiple positions. The positions of these mass signals depend on the difference between the molecular mass. Furthermore, the intensity of these signals is dependent on the...
2.5K