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Iron isotopes trace primordial magma ocean cumulates melting in Earth’s upper mantle

Abstract.

"The differentiation of Earth ~4.5 billion years (Ga) ago is believed to have culminated in magma ocean crystallization, crystal-liquid separation, and the formation of mineralogically distinct mantle reservoirs. However, the magma ocean model remains difficult to validate because of the scarcity of geochemical tracers of lower mantle mineralogy. The Fe isotope compositions (δ57Fe) of ancient mafic rocks can be used to reconstruct the mineralogy of their mantle source regions. We present Fe isotope data for 3.7-Ga metabasalts from the Isua Supracrustal Belt (Greenland). The δ57Fe signatures[...]"

 

Source: Science Advances
Authors: Helen M. Williams et al.
DOI:10.1126/sciadv.abc7394

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A benthic oxygen oasis in the early Neoproterozoic ocean

Abstract.

"Benthic oxygen oases linked to photosynthetic mats have been reported in modern anoxic aquatic systems. Benthic macroalgal blooms were common in stratified, anoxic Neoproterozoic oceans, leading us to hypothesize the existence of benthic oxygen oases at that time. This hypothesis has significant implications regarding the bioavailability of transition metals (e.g., Cu, Zn, Ni, Mo, V) and the distribution of aerobic eukaryotes in these oceans. However, little research has been directed toward testing the benthic oxygen[...]"

 

Source: Science Direct
Authors:Haiyang Wang et al.
DOI: https://doi.org/10.1016/j.precamres.2020.106085

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Regional patterns and temporal evolution of ocean iron fertilization and CO2 drawdown during the last glacial termination

Abstract.

"The last time Earth's climate experienced geologically rapid global warming was associated with the last glacial termination, when atmospheric CO2 concentrations rose from 180 ppmv during the Last Glacial Maximum (LGM, 26-19 kaBP) to ∼260 ppmv by the early Holocene (12-8 kaBP). About one quarter of that difference is thought to be due to a stronger biological pump during glacial times, driven by increased aeolian dust deposition and hence greater iron availability in[...]"

 

Source: Science Direct
Authors: Fabrice Lambert et al.
DOI: https://doi.org/10.1016/j.epsl.2020.116675

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Seeding oceans with iron may not impact climate change

"Study finds Earth's oceans contain just the right amount of iron; adding more may not improve their ability to absorb carbon dioxide

Historically, the oceans have done much of the planet's heavy lifting when it comes to sequestering carbon dioxide from the atmosphere. Microscopic organisms known collectively as phytoplankton, which grow throughout the sunlit surface oceans and absorb carbon dioxide through photosynthesis, are a key player.

To help stem escalating carbon dioxide emissions produced by the burning of fossil fuels, some scientists have proposed seeding the oceans with iron -- an essential ingredient that can stimulate phytoplankton growth. Such "iron fertilization" would cultivate vast new fields of phytoplankton, particularly in areas normally bereft of marine life. [...]"

Source: Sciencedaily

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Distribution of iron in the Western Indian Ocean and the Eastern tropical South pacific: An inter-basin comparison

Abstract.

"The Western Indian Ocean (WIO) and Eastern Tropical South Pacific (ETSP) are distinctly different regimes, yet they share several important features. These include a strong upwelling system, a large oxygen minimum zone (OMZ) with active denitrification, a spreading center with extensive hydrothermal activity, and a vast oligotrophic upper water column. Here, we show that the distribution and geochemistry of iron shows remarkable similarities as well. [...]"

Source: Chemical Geology
Authors: James W. Moffett and Christopher R. German
DOI: 10.1016/j.chemgeo.2019.119334

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Processes affecting dissolved iron across the Subtropical North Atlantic: a model study

Abstract.

"Trace metal measurements in recent years have revealed a complex distribution of dissolved iron (dFe) in the ocean that models still struggle to reproduce. The GEOTRACES section GA03 across the subtropical North Atlantic was chosen to study the driving processes involved in the Fe cycle in the region. [...]"

Source: Ocean Dynamics
Authors: Anna Pagnone et al.
DOI: 10.1007/s10236-019-01288-w

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H2S events in the Peruvian oxygen minimum zone facilitate enhanced dissolved Fe concentrations

Abstract.

"Dissolved iron (DFe) concentrations in oxygen minimum zones (OMZs) of Eastern Boundary Upwelling Systems are enhanced as a result of high supply rates from anoxic sediments. However, pronounced variations in DFe concentrations in anoxic coastal waters of the Peruvian OMZ indicate that there are factors in addition to dissolved oxygen concentrations (O2) that control Fe cycling. [...]"

Source: Scientific Reports
Authors: Christian Schlosser et al. 
DOI: 10.1038/s41598-018-30580-w

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Iron entangled

Iron is an essential fuel for life in the oceans. The influence of this element on biogeochemistry — and nitrogen cycling in particular — varies across environments and time.

 

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