Major element mobility during serpentinization, oxidation and weathering of mantle peridotite at low temperatures

2020 ◽  
Vol 378 (2165) ◽  
pp. 20180433 ◽  
Author(s):  
Juan Carlos de Obeso ◽  
Peter B. Kelemen
Keyword(s):  
Low Temperatures ◽  
Major Element ◽  
Mantle Peridotite ◽  
Magnesium Content ◽  
Earth System ◽  
Element Mobility ◽  
Mantle Minerals ◽  
Alteration Zones ◽  
The Earth ◽  
Reaction Zones

Mantle peridotite in Wadi Fins in eastern Oman exhibits three concentric alteration zones with oxide and sulfide mineralogy recording gradients in f O 2 and f S 2 (fugacity) of more than 20 orders of magnitude over 15–20 cm. The black cores of samples (approx. 5 cm in diameter) exhibit incomplete, nearly isochemical serpentinization, with relict primary mantle minerals (olivine, orthopyroxene and clinopyroxene) along with sulfide assemblages (pentlandite/heazlewoodite/bornite) recording low f O 2 and moderate f S 2 . In addition to the black cores, two alteration zones are evident from their colouration in outcrop and hand samples: green and red. These zones exhibit non-isochemical alteration characterized by intergrowths of stevensite/lizardite. All three reaction zones are cut by calcite ± serpentine veins, which are most abundant in the outer, red zones, sometimes are flanked by narrow red and/or green zones where they cut the black zones, and thus may be approximately coeval with all three alteration zones. The alteration zones record progressively higher  f O 2 recorded by Ni-rich sulfides and iron oxides/hydroxides. These alteration zones lost 20–30% of their initial magnesium content, together with mobilization of iron over short distances from inner green zones into outer red zones, where iron is reprecipitated in goethite intermixed with silicates due to higher f O 2 . Thermodynamic modelling at 60°C and 50 MPa (estimated alteration conditions) reproduces sulfide assemblages, f O 2 changes and Mg and Fe mobility. This article is part of a discussion meeting issue ‘Serpentinite in the Earth system’.

scholarly journals Formation and loss of metastable brucite: does Fe(II)-bearing brucite support microbial activity in serpentinizing ecosystems?

2020 ◽  
Vol 378 (2165) ◽  
pp. 20180423 ◽  
Author(s):  
A. S. Templeton ◽  
E. T. Ellison
Keyword(s):  
Ultramafic Rocks ◽  
Earth System ◽  
Aqueous Alteration ◽  
Rock Interaction ◽  
Secondary Minerals ◽  
Dissolved Carbon ◽  
The Earth ◽  
Reaction Zones ◽  
Water Rock Interaction

Ultramafic rocks undergo successive stages of hydration and oxidation during water/rock interaction, giving rise to secondary minerals such as brucite, serpentine, magnetite and the production of H 2(g) . Ferroan brucite ( M g x Fe ( 1 − x ) 2 + ( OH ) 2 ) often forms under low water/rock ratios early during the ‘serpentinization’ process. The formation of ferroan brucite sequesters Fe(II) and suppresses the production of H 2 , thereby limiting the flux of reductants suitable for sustaining microbial metabolism. Yet ferroan brucite is a relatively soluble mineral ‘reservoir’ for reactive Fe(II). Brucite is often metastable and can be lost at later stages of peridotite hydration when there is a significant increase in the water/rock ratio or the activity of SiO 2 or CO 2 . The Fe(OH) 2 component of brucite has the thermodynamic potential to reduce most aqueous oxidants. Therefore, ferroan brucite may reduce water and/or dissolved carbon, nitrogen and sulfur species, while the Fe(II) is converted into more stable secondary minerals such as Fe(II/III)-oxides and hydroxides (e.g. green-rust, magnetite, iowaite and pyroaurite) and ferric serpentine. The reactivity of ferroan brucite, and the associated rate of Fe solubilization and oxidation in subsurface fluids, could be a key regulator on the rate of electron transfer from serpentinites to the rock-hosted biosphere. Aqueous alteration of ferroan brucite may significantly modulate the H 2 activity in fluids circulating within partially serpentinized rocks, and buffer H 2 as it is lost by advection or in situ consumption by a hydrogenotrophic microbial community. Moreover, there may be microbial organisms that specifically colonize and use ferroan brucite as an electron donor for their metabolism. The energy fluxes sustained by localized brucite oxidation may often be sufficiently large to sustain abundant microbial communities; water/rock reaction zones where brucite is consumed could serve as environments to search for extant or fossil serpentinite-hosted life. This article is part of a discussion meeting issue ‘Serpentinite in the Earth System’.

Editorial: Fire in the Earth System

PAGES news ◽  
2010 ◽  
Vol 18 (2) ◽  
pp. 55-57 ◽  
Author(s):  
Cathy Whitlock ◽  
Willy Tinner
Keyword(s):  
Earth System ◽  
The Earth

SPIES AND BLOGGERS: NEW SYNTHETIC BIOLOGY TOOLS TO UNDERSTAND MICROBIAL PROCESSES IN THE EARTH SYSTEM

2017 ◽  
Author(s):  
Caroline A. Masiello ◽  
◽  
Jonathan J. Silberg ◽  
Hsiao-Ying Cheng ◽  
Ilenne Del Valle ◽  
...  
Keyword(s):  
Synthetic Biology ◽  
Microbial Processes ◽  
Earth System ◽  
The Earth

scholarly journals High and specific diversity of protists in the deep-sea basins dominated by diplonemids, kinetoplastids, ciliates and foraminiferans

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Alexandra Schoenle ◽  
Manon Hohlfeld ◽  
Karoline Hermanns ◽  
Frédéric Mahé ◽  
Colomban de Vargas ◽  
...  
Keyword(s):  
Carbon Cycling ◽  
Deep Sea ◽  
Trophic Levels ◽  
Earth System ◽  
Parasitic Species ◽  
Unicellular Eukaryotes ◽  
The Earth ◽  
Dna Metabarcoding ◽  
Global Carbon ◽  
Pelagic Communities

AbstractHeterotrophic protists (unicellular eukaryotes) form a major link from bacteria and algae to higher trophic levels in the sunlit ocean. Their role on the deep seafloor, however, is only fragmentarily understood, despite their potential key function for global carbon cycling. Using the approach of combined DNA metabarcoding and cultivation-based surveys of 11 deep-sea regions, we show that protist communities, mostly overlooked in current deep-sea foodweb models, are highly specific, locally diverse and have little overlap to pelagic communities. Besides traditionally considered foraminiferans, tiny protists including diplonemids, kinetoplastids and ciliates were genetically highly diverse considerably exceeding the diversity of metazoans. Deep-sea protists, including many parasitic species, represent thus one of the most diverse biodiversity compartments of the Earth system, forming an essential link to metazoans.

scholarly journals Applicability of NGGM near-real time simulations in flood detection

2019 ◽  
Vol 9 (1) ◽  
pp. 111-126
Author(s):  
A. F. Purkhauser ◽  
J. A. Koch ◽  
R. Pail
Keyword(s):  
European Space Agency ◽  
Earth System ◽  
The Earth ◽  
Future Mission ◽  
Space Agency ◽  
Flood Detection ◽  
The One ◽  
Real Time Simulations ◽  
Grace Mission ◽  
Gravity Mission

Abstract The GRACE mission has demonstrated a tremendous potential for observing mass changes in the Earth system from space for climate research and the observation of climate change. Future mission should on the one hand extend the already existing time series and also provide higher spatial and temporal resolution that is required to fulfil all needs placed on a future mission. To analyse the applicability of such a Next Generation Gravity Mission (NGGM) concept regarding hydrological applications, two GRACE-FO-type pairs in Bender formation are analysed. The numerical closed loop simulations with a realistic noise assumption are based on the short arc approach and make use of the Wiese approach, enabling a self-de-aliasing of high-frequency atmospheric and oceanic signals, and a NRT approach for a short latency. Numerical simulations for future gravity mission concepts are based on geophysical models, representing the time-variable gravity field. First tests regarding the usability of the hydrology component contained in the Earth System Model (ESM) by the European Space Agency (ESA) for the analysis regarding a possible flood monitoring and detection showed a clear signal in a third of the analysed flood cases. Our analysis of selected cases found that detection of floods was clearly possible with the reconstructed AOHIS/HIS signal in 20% of the tested examples, while in 40% of the cases a peak was visible but not clearly recognisable.

scholarly journals A potential feedback loop underlying glacial-interglacial cycles

2021 ◽  
Author(s):  
Els Weinans ◽  
Anne Willem Omta ◽  
George A. K. van Voorn ◽  
Egbert H. van Nes
Keyword(s):  
Ocean Circulation ◽  
Feedback Loop ◽  
Atmospheric Temperature ◽  
Earth System ◽  
Biological Productivity ◽  
Ocean Ventilation ◽  
The Earth ◽  
Main Driver ◽  
Underlying Mechanisms ◽  
Convergent Cross Mapping

AbstractThe sawtooth-patterned glacial-interglacial cycles in the Earth’s atmospheric temperature are a well-known, though poorly understood phenomenon. Pinpointing the relevant mechanisms behind these cycles will not only provide insights into past climate dynamics, but also help predict possible future responses of the Earth system to changing CO$$_2$$ 2 levels. Previous work on this phenomenon suggests that the most important underlying mechanisms are interactions between marine biological production, ocean circulation, temperature and dust. So far, interaction directions (i.e., what causes what) have remained elusive. In this paper, we apply Convergent Cross-Mapping (CCM) to analyze paleoclimatic and paleoceanographic records to elucidate which mechanisms proposed in the literature play an important role in glacial-interglacial cycles, and to test the directionality of interactions. We find causal links between ocean ventilation, biological productivity, benthic $$\delta ^{18}$$ δ 18 O and dust, consistent with some but not all of the mechanisms proposed in the literature. Most importantly, we find evidence for a potential feedback loop from ocean ventilation to biological productivity to climate back to ocean ventilation. Here, we propose the hypothesis that this feedback loop of connected mechanisms could be the main driver for the glacial-interglacial cycles.

scholarly journals A Clear Past and a Murky Future: Life in the Anthropocene on the Pampana River, Sierra Leone

Land ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 72 ◽  
Author(s):  
Richard Marcantonio ◽  
Agustin Fuentes
Keyword(s):  
Environmental Change ◽  
Sierra Leone ◽  
Complex Adaptive Systems ◽  
Human Activities ◽  
Adaptive Systems ◽  
Participant Observation ◽  
Earth System ◽  
Sierra Leonean ◽  
The Earth ◽  
Complex Adaptive

The impacts of human activities on ecosystems are significantly increasing the rate of environmental change in the earth system, reshaping the global landscape. The rapid rate of environmental change is disrupting the ability of millions of people around the globe to live their everyday lives and maintain their human niche. Evidence suggests that we have entered (or created) a new epoch, the Anthropocene, which is defined as the period in which humans and human activities are the primary drivers of planetary change. The Anthropocene denotes a global shift, but it is the collective of local processes. This is our frame for investigating local accounts of human-caused disruptive environmental change in the Pampana River in Tonkolili District, Northern Province, Sierra Leone. Since the end of the Sierra Leonean civil war in 2002, the country has experienced a rapid increase in extractive industries, namely mining. We explored the effects of this development by working with communities along the Pampana River in Tonkolili, with a specific focus given to engaging local fishermen through ethnographic interviews (N = 21 fishermen and 33 non-fishermen), focus group discussions (N = 21 fishermen), and participant observation. We deployed theoretical and methodological frameworks from human niche construction theory, complex adaptive systems, and ethnography to track disruptive environmental change in and on the Pampana from upstream activities and the concomitant shifts in the local human niche. We highlight the value of integrating ethnographic methods with human evolutionary theory, produce important insights about local human coping processes with disruptive environmental change, and help to further account for and understand the ongoing global process of human modification of the earth system in the Anthropocene.

Dryland Degradation and Expansion: Implications for Mexican Policies from the Earth System Perspective

2020 ◽  
pp. 1-4
Author(s):  
Gabriel Lopez Porras
Keyword(s):  
Climate Change ◽  
Ecosystem Services ◽  
Science Policy ◽  
Land Degradation ◽  
Water Scarcity ◽  
Large Scale ◽  
Earth System ◽  
Sustainable Land Management ◽  
System Perspective ◽  
The Earth

Despite international efforts to stop dryland degradation and expansion, current dryland pathways are predicted to result in large-scale migration, growing poverty and famine, and increasing climate change, land degradation, conflicts and water scarcity. Earth system science has played a key role in analysing dryland problems, and has been even incorporated in global assessments such as the ones made by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services. However, policies addressing dryland degradation, like the ‘Mexican programme for the promotion of sustainable land management’, do not embrace an Earth system perspective, so they do not consider the complexity and non-linearity that underlie dryland problems. By exploring how this Mexican programme could integrate the Earth system perspective, this paper discusses how ’Earth system’ policies could better address dryland degradation and expansion in the Anthropocene.

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