Decoupling of inorganic and organic carbon during slab mantle devolatilisation

AbstractSerpentinites are an important sink for both inorganic and organic carbon, and their behavior during subduction is thought to play a fundamental role in the global cycling of carbon. Here we show that fluid-derived veins are preserved within the Zermatt-Saas ultra-high pressure serpentinites providing key evidence for carbonate mobility during serpentinite devolatilisation. We show through the O, C, and Sr isotope analyses of vein minerals and the host serpentinites that about 90% of the meta-serpentinite inorganic carbon is remobilized during slab devolatilisation. In contrast, graphite-like carbonaceous compounds remain trapped within the host rock as inclusions within metamorphic olivine while the bulk elemental and isotope composition of organic carbon remains relatively unchanged during the subduction process. This shows a decoupling behavior of carbon during serpentinite dehydration in subduction zones. This process will therefore facilitate the transfer of inorganic carbon to the mantle wedge and the preferential slab sequestration of organic carbon en route to the deep mantle.

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Up the down escalator: the exhumation of (ultra)-high pressure terranes during on-going subduction

Solid Earth Discussions ◽

10.5194/sed-4-745-2012 ◽

2012 ◽

Vol 4 (1) ◽

pp. 745-781 ◽

Cited By ~ 5

Author(s):

C. J. Warren

Keyword(s):

High Pressure ◽

Subduction Zone ◽

Continental Crust ◽

Subduction Zones ◽

Crustal Material ◽

Time And Space ◽

Ultra High Pressure ◽

Tectonic Environment ◽

Tectonic Style ◽

Weak Material

Abstract. The exhumation of high and ultra-high pressure rocks is ubiquitous in Phanerozoic orogens created during continental collisions, and is common in many ocean-ocean and ocean-continent subduction zone environments. Three different tectonic environments have previously been reported, which exhume deeply buried material by different mechanisms and at different rates. However it is becoming increasingly clear that no single mechanism dominates in any particular tectonic environment, and the mechanism may change in time and space within the same subduction zone. In order for buoyant continental crust to subduct, it must remain attached to a stronger and denser substrate, but in order to exhume, it must detach (and therefore at least locally weaken) and be initially buoyant. Denser oceanic crust subducts more readily than more buoyant continental crust but exhumation must be assisted by entrainment within more buoyant and weak material such as serpentinite or driven by the exhumation of structurally lower continental crustal material. Weakening mechanisms responsible for the detachment of crust at depth include strain, hydration, melting, grain size reduction and the development of foliation. These may act locally or may act on the bulk of the subducted material. Metamorphic reactions, metastability and the composition of the subducted crust all affect buoyancy and overall strength. Subduction zones change in style both in time and space, and exhumation mechanisms change to reflect the tectonic style and overall force regime within the subduction zone. Exhumation events may be transient and occur only once in a particular subduction zone or orogen, or may be more continuous or occur multiple times.

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A Syringe Gas-Stripping Procedure for Gas-Chromatographic Determination of Dissolved Inorganic and Organic Carbon in Fresh Water and Carbonates in Sediments

Journal of the Fisheries Research Board of Canada ◽

10.1139/f73-234 ◽

1973 ◽

Vol 30 (10) ◽

pp. 1441-1445 ◽

Cited By ~ 96

Author(s):

Michael P. Stainton

Keyword(s):

Organic Carbon ◽

Gas Phase ◽

Atmospheric Pressure ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Chromatographic Determination ◽

Canadian Shield ◽

Gas Stripping ◽

Inorganic And Organic

A simple, rapid method for determining dissolved inorganic carbon in water is described. A 20-cm3 sample of water is drawn into a 50-cm3 polypropylene syringe and acidified by injection of 1 cm3 of dilute sulphuric acid. Twenty-nine cubic centimeters of helium at atmospheric pressure is injected into the syringe followed by 10 sec of manual agitation to partition CO2 between gas and liquid phase. The gas phase containing 60% of CO2 from the sample is then analyzed by gas chromatography. This method has been used to determine dissolved inorganic and organic carbon in Canadian Shield waters and to determine total carbonates in sediments.

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Lattice preferred orientation of talc and implications for seismic anisotropy

10.5194/egusphere-egu2020-4440 ◽

2020 ◽

Author(s):

Jungjin Lee ◽

Haemyeong Jung ◽

Reiner Klemd ◽

Matthew Tarling ◽

Dmitry Konopelko

Keyword(s):

High Pressure ◽

Subduction Zones ◽

Seismic Anisotropy ◽

Preferred Orientation ◽

Azimuthal Anisotropy ◽

Hydrous Minerals ◽

Ultra High Pressure ◽

Lattice Preferred Orientation ◽

Radial Anisotropy ◽

First Time

Strong seismic anisotropy is generally observed in subduction zones. Lattice preferred orientation (LPO) of olivine and elastically anisotropic hydrous minerals has been considered to be an important factor causing anomalous seismic anisotropy. For the first time, we report on measured LPOs of polycrystalline talc. The study comprises subduction-related ultra-high-pressure metamorphic schists from the Makbal Complex in Kyrgyzstan-Kazakhstan and amphibolite-facies metasomatic schists from the Valla Field Block in Unst, Scotland. The here studied talc revealed a strong alignment of [001] axes (sub)normal to the foliation and a girdle distribution of [100] axes and (010) poles (sub)parallel to the foliation. The LPOs of polycrystalline talc produced a significant P&#8211;wave anisotropy (AVp = 72%) and a high S&#8211;wave anisotropy (AVs = 24%). The results imply that the LPO of talc influence both the strong trench-parallel azimuthal anisotropy and positive/negative radial anisotropy of P&#8211;waves, and the trench-parallel seismic anisotropy of S&#8211;waves in subduction zones.

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Metasomatic flow of metacarbonate-derived fluids carrying isotopically heavy boron in continental subduction zones: Insights from tourmaline-bearing ultra-high pressure eclogites and veins (Dabie terrane, eastern China)

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2019.03.013 ◽

2019 ◽

Vol 253 ◽

pp. 159-200 ◽

Cited By ~ 4

Author(s):

Shun Guo ◽

Kuidong Zhao ◽

Timm John ◽

Pan Tang ◽

Yi Chen ◽

...

Keyword(s):

High Pressure ◽

Subduction Zones ◽

Eastern China ◽

Ultra High Pressure ◽

Continental Subduction

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Preparation of Inorganic and Organic Carbon for 14C Analysis from a Single Marine Sample

Radiocarbon ◽

10.1017/s0033822200017847 ◽

1997 ◽

Vol 40 (1) ◽

pp. 29-34 ◽

Cited By ~ 1

Author(s):

Sheila Griffin ◽

Ellen R. M. Druffel

Keyword(s):

Pacific Ocean ◽

Organic Carbon ◽

Deep Sea ◽

Inorganic Carbon ◽

Sediment Traps ◽

Deep Sea Sediment ◽

Northeast Pacific ◽

Organic And Inorganic Carbon ◽

Northeast Pacific Ocean ◽

Inorganic And Organic

We have developed a technique using a single apparatus to recover the inorganic and organic carbon from a small (few milligrams) aliquot of dried marine material for radiocarbon analysis. The main advantages of using a single apparatus are: 1) less sample is required, 2) decreased handling reduces contamination, and 3) less time and materials are used. Blank values of ∼5 μg and 19–44 μg are obtained for the inorganic and organic carbon extractions, respectively. δ14C results from sinking particulate organic and inorganic carbon are presented for samples collected in deep-sea sediment traps deployed for 10–30 day periods at 650 and 100 m above bottom (mab) in the northeast Pacific Ocean.

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Decoupled oscillatory and O-isotope zonation in high pressure low temperature garnet: records of heterogeneous fluid transfer processes

10.5194/egusphere-egu21-3061 ◽

2021 ◽

Author(s):

Freya R. George ◽

Daniel R. Viete ◽

Janaína Ávila ◽

Gareth G. E. Seward

Keyword(s):

High Pressure ◽

Grain Boundary ◽

Short Wavelength ◽

Subduction Zones ◽

Isotope Composition ◽

Oscillatory Zoning ◽

Garnet Growth ◽

Spatial Covariance ◽

O Isotope ◽

Fluid Transfer

High pressure garnet porpyhroblasts formed in subduction zones serve as a witness to an integrated history of fluid flow, deformation, metamorphic reaction, and exhumation processes. Seemingly ubiquitous within garnet from a heterogeneous suite of eclogite and blueschist units is primary oscillatory elemental zoning&#8212;rhythmic, short wavelength (< 10 &#181;m) concentric fluctuations concentrated near the rims of porphyroblasts&#8212;which has been documented using a combined major element X-ray mapping and trace element LA-ICP-MS mapping approach. This oscillatory zoning must reflect some fundamental petrogenetic process operating during subduction zone metamorphism. While longer length scale (> 50 &#181;m) oscillations have been interpreted to reflect rock-wide P&#8211;T changes during physical cycling through the subduction channel, these short wavelength oscillations have typically been interpreted to reflect changes in the effective grain boundary chemistry induced by fluid fluxing during mineral growth.Here, we present secondary ion mass spectrometry (SIMS) O-isotope data across the oscillatory zoning in garnet from six subduction settings. A lack of spatial covariance between the elemental and &#948;18O records is inconsistent with the interpretation that oscillatory zoning is directly linked to infiltration of chemically and isotopically distinct fluids. However, in most samples, vascillations in &#948;18O of < 2 &#8240; (over 20&#8211;50 &#181;m) in the mantle and rim, coupled with < 1 &#8240; net core-to-rim change may point to the predominance of: (a) an internally-controlled grain boundary fluid and relatively stagnant fluid conditions, with grain boundaries that may experience transient opening, heterogeneous and locally-derived fluid fluxing, and then re-sealing, or (b) a rock-buffered oxygen isotope composition during garnet growth between &#160;450 &#730;C and 550 &#730;C. However, several samples exhibit a systematic 2.5&#8211;4 &#8240; change in &#948;18O across oscillatory major and trance element zoning, accompanied by a 2&#8211;3 mol% decrease in andradite content. This change, outside that predicted via closed system crystallization and fractionation, is suggested to reflect the relatively uncommon and sudden transient passage of a reduced external fluid. While this dataset does not reveal the mystery of the oscillatory zoning, it demonstrates spatial and temporal heterogeneity of fluid transfer in subduction zones.

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Aqueous fluids and hydrous melts in high-pressure and ultra-high pressure rocks: Implications for element transfer in subduction zones

Lithos ◽

10.1016/j.lithos.2006.03.055 ◽

2006 ◽

Vol 92 (3-4) ◽

pp. 399-417 ◽

Cited By ~ 358

Author(s):

J HERMANN ◽

C SPANDLER ◽

A HACK ◽

A KORSAKOV

Keyword(s):

High Pressure ◽

Subduction Zones ◽

Ultra High Pressure ◽

Element Transfer

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14C Measurements of Dissolved Inorganic and Organic Carbon in Qinghai Lake and Inflowing Rivers (NE Tibet, Qinghai Plateau), China

Radiocarbon ◽

10.2458/56.17776 ◽

2014 ◽

Vol 56 (3) ◽

pp. 1115-1127 ◽

Cited By ~ 10

Author(s):

A J T Jull ◽

G S Burr ◽

W Zhou ◽

P Cheng ◽

S H Song ◽

...

Keyword(s):

Organic Carbon ◽

Dissolved Organic Carbon ◽

Inorganic Carbon ◽

Dissolved Inorganic Carbon ◽

Qinghai Lake ◽

Main Process ◽

The Past ◽

Atmospheric Exchange ◽

Sediment Carbon ◽

Inorganic And Organic

There have been a number of studies that have attempted to estimate the past radiocarbon reservoir effects in Qinghai Lake, China. This article reports on measurements on modern samples collected at the lake in October 2003 and October 2009, which allow us to better understand the systematics of the lake and shed new insights on the processes occurring in the lake. The results indicate that atmospheric exchange of 14C is the main process affecting surface dissolved inorganic carbon (DIC) in the lake, but dissolved organic carbon (DOC) can be explained as a combination of sources. We also conclude that sediment carbon can be explained by a model where input from the surrounding rivers and groundwater are important, in agreement with the model of Yu et al. (2007).

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