3D Subsurface Characterization of Banded Iron Formation Mineralization using Large-Scale Gravity Data: A Case Study in Parts of Bharatpur, Dausa and Karauli Districts of Rajasthan, India

2021 ◽  
Author(s):  
Saudamini Sahoo ◽  
Anand Singh ◽  
Santu Biswas ◽  
S. P. Sharma
Keyword(s):  
Large Scale ◽  
Gravity Data ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Subsurface Characterization

scholarly journals Photoferrotrophy, deposition of banded iron formations, and methane production in Archean oceans

2019 ◽  
Vol 5 (11) ◽  
pp. eaav2869 ◽  
Author(s):  
Katharine J. Thompson ◽  
Paul A. Kenward ◽  
Kohen W. Bauer ◽  
Tyler Warchola ◽  
Tina Gauger ◽  
...  
Keyword(s):  
Large Scale ◽  
Iron Oxidation ◽  
Coastal Sediments ◽  
Oxygenic Photosynthesis ◽  
Iron Formation ◽  
Banded Iron Formations ◽  
Banded Iron Formation ◽  
Earth’S Climate ◽  
Iron Formations ◽  
Scale Deposition

Banded iron formation (BIF) deposition was the likely result of oxidation of ferrous iron in seawater by either oxygenic photosynthesis or iron-dependent anoxygenic photosynthesis—photoferrotrophy. BIF deposition, however, remains enigmatic because the photosynthetic biomass produced during iron oxidation is conspicuously absent from BIFs. We have addressed this enigma through experiments with photosynthetic bacteria and modeling of biogeochemical cycling in the Archean oceans. Our experiments reveal that, in the presence of silica, photoferrotroph cell surfaces repel iron (oxyhydr)oxides. In silica-rich Precambrian seawater, this repulsion would separate biomass from ferric iron and would lead to large-scale deposition of BIFs lean in organic matter. Excess biomass not deposited with BIF would have deposited in coastal sediments, formed organic-rich shales, and fueled microbial methanogenesis. As a result, the deposition of BIFs by photoferrotrophs would have contributed fluxes of methane to the atmosphere and thus helped to stabilize Earth’s climate under a dim early Sun.

scholarly journals Sedimentary mechanisms of a modern banded iron formation on Milos Island, Greece

Solid Earth ◽  
2018 ◽  
Vol 9 (3) ◽  
pp. 573-598 ◽  
Author(s):  
Ernest Chi Fru ◽  
Stephanos Kilias ◽  
Magnus Ivarsson ◽  
Jayne E. Rattray ◽  
Katerina Gkika ◽  
...  
Keyword(s):  
Large Scale ◽  
Carbonaceous Material ◽  
Iron Formation ◽  
Geochemical Data ◽  
Formation Mechanisms ◽  
Banded Iron Formation ◽  
Crystalline Quartz ◽  
Tectonic Processes ◽  
Iron Deposits ◽  
Amorphous Si

Abstract. An early Quaternary shallow submarine hydrothermal iron formation (IF) in the Cape Vani sedimentary basin (CVSB) on Milos Island, Greece, displays banded rhythmicity similar to Precambrian banded iron formation (BIF). Field-wide stratigraphic and biogeochemical reconstructions show two temporal and spatially isolated iron deposits in the CVSB with distinct sedimentological character. Petrographic screening suggests the presence of a photoferrotrophic-like microfossil-rich IF (MFIF), accumulated on a basement consisting of andesites in a ∼ 150 m wide basin in the SW margin of the basin. A banded nonfossiliferous IF (NFIF) sits on top of the Mn-rich sandstones at the transition to the renowned Mn-rich formation, capping the NFIF unit. Geochemical data relate the origin of the NFIF to periodic submarine volcanism and water column oxidation of released Fe(II) in conditions predominated by anoxia, similar to the MFIF. Raman spectroscopy pairs hematite-rich grains in the NFIF with relics of a carbonaceous material carrying an average δ13Corg signature of ∼ −25‰. A similar δ13Corg signature in the MFIF could not be directly coupled to hematite by mineralogy. The NFIF, which postdates large-scale Mn deposition in the CVSB, is composed primarily of amorphous Si (opal-SiO2 ⋅ nH2O) while crystalline quartz (SiO2) predominates the MFIF. An intricate interaction between tectonic processes, changing redox, biological activity, and abiotic Si precipitation are proposed to have collectively formed the unmetamorphosed BIF-type deposits in a shallow submarine volcanic center. Despite the differences in Precambrian ocean–atmosphere chemistry and the present geologic time, these formation mechanisms coincide with those believed to have formed Algoma-type BIFs proximal to active seafloor volcanic centers.

scholarly journals The Effects of Explicit versus Parameterized Convection on the MJO in a Large-Domain High-Resolution Tropical Case Study. Part I: Characterization of Large-Scale Organization and Propagation*

2013 ◽  
Vol 70 (5) ◽  
pp. 1342-1369 ◽  
Author(s):  
Christopher E. Holloway ◽  
Steven J. Woolnough ◽  
Grenville M. S. Lister
Keyword(s):  
High Resolution ◽  
Large Scale ◽  
Propagation Speed ◽  
Simulation Models ◽  
Horizontal Resolution ◽  
Convective Heating ◽  
Convection Model ◽  
Boundary Layer Scheme

Abstract High-resolution simulations over a large tropical domain (~20°S–20°N, 42°E–180°) using both explicit and parameterized convection are analyzed and compared to observations during a 10-day case study of an active Madden–Julian oscillation (MJO) event. The parameterized convection model simulations at both 40- and 12-km grid spacing have a very weak MJO signal and little eastward propagation. A 4-km explicit convection simulation using Smagorinsky subgrid mixing in the vertical and horizontal dimensions exhibits the best MJO strength and propagation speed. Explicit convection simulations at 12 km also perform much better than the 12-km parameterized convection run, suggesting that the convection scheme, rather than horizontal resolution, is key for these MJO simulations. Interestingly, a 4-km explicit convection simulation using the conventional boundary layer scheme for vertical subgrid mixing (but still using Smagorinsky horizontal mixing) completely loses the large-scale MJO organization, showing that relatively high resolution with explicit convection does not guarantee a good MJO simulation. Models with a good MJO representation have a more realistic relationship between lower-free-tropospheric moisture and precipitation, supporting the idea that the moisture–convection feedback is a key process for MJO propagation. There is also increased generation of available potential energy and conversion of that energy into kinetic energy in models with a more realistic MJO, which is related to larger zonal variance in convective heating and vertical velocity, larger zonal temperature variance around 200 hPa, and larger correlations between temperature and ascent (and between temperature and diabatic heating) between 500 and 400 hPa.

scholarly journals Sedimentary mechanisms of a modern banded iron formation on Milos Island, Greece

2017 ◽  
Author(s):  
Ernest Chi Fru ◽  
Stephanos Kilias ◽  
Magnus Ivarsson ◽  
Jayne E. Rattray ◽  
Katerina Gkika ◽  
...  
Keyword(s):  
Large Scale ◽  
Carbonaceous Material ◽  
Tectonic Activity ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Mineralogical Characterization ◽  
Tectonic Processes ◽  
Spatial Coverage ◽  
Iron Deposits ◽  
Mn Ore

Abstract. An Early Quaternary shallow submarine hydrothermal iron formation (IF) in the Cape Vani sedimentary basin (CVSB) on Milos Island, Greece, displays banded rhythmicity similar to Precambrian banded iron formation (BIF). Sedimentary, stratigraphic reconstruction, biogeochemical analysis and micro-nanoscale mineralogical characterization confirms the Milos rocks as modern Precambrian BIF analogues. Spatial coverage of the BIF-type rocks in relation to the economic grade Mn ore that brought prominence to the CVSB implicates tectonic activity and changing redox in the deposition of the BIF-type rocks. Field-wide stratigraphic and biogeochemical reconstruction demonstrates two temporal and spatially isolated iron deposits in the CVSB with distinct sedimentological character. Petrographic screening suggest the previously described photoferrotrophic-like microfossil-rich IF (MFIF), accumulated on basement andesite in a ~ 150 m wide basin, in the SW margin of the basin. A strongly banded non-fossiliferous IF (NFIF) caps the Mn-rich sandstones at the transition to the renowned Mn-rich formation. Geochemical evidence relates the origin of the NFIF to periodic submarine volcanism and water column oxidation of released Fe(II) in conditions apparently predominated by anoxia, similar to the MFIF. This is manifested in the lack of shale-normalized Ce anomalies. Raman spectroscopy pairs hematite-rich grains in the NFIF with relics of a carbonaceous material carrying an average δ13Corg signature of ~ −25 ‰. However, a similar δ13Corg signature in the MFIF is not directly coupled to hematite by mineralogy. The NFIF, which post dates large-scale Mn deposition in the CVSB, is composed primarily of amorphous Si (opal-SiO2 · nH2O) while crystalline quartz (SiO2) predominates the MFIF. An intricate interaction between tectonic processes, changing redox, biological activity and abiotic Si precipitation, formed the unmetamorphosed BIF-type deposits.

scholarly journals A Non-Stationary Heat Spell Frequency, Intensity, and Duration Model for France, Integrating Teleconnection Patterns and Climate Change

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1387
Author(s):  
Yasser Hamdi ◽  
Christian Charron ◽  
Taha B. M. J. Ouarda
Keyword(s):  
Large Scale ◽  
Value Theory ◽  
Climate Indices ◽  
Daily Maximum ◽  
Teleconnection Patterns ◽  
Duration Magnitude ◽  
Change Context ◽  
Maximum Temperatures

The warming observed over the past summers since 2000 is unprecedented in climate records in Europe and especially in France. Extreme temperatures and heat spells were often analyzed in the literature by applying extreme value theory but rarely in a non-stationary (NS) framework and duration modeling is often excluded. For a modern risk-based approach, it is important to have knowledge of the duration, magnitude, and frequency of occurrence of heat spells in a climate variability and change context. Yet, despite their obvious importance, teleconnections and associated climate indices (CIs) have often been excluded from heat spell modelling. The notion of duration is also not easily interpretable in a frequency analysis and can even be subtle, especially in a NS context. In this study, we used time-varying statistical distributions with parameters conditional on covariates representing the time and CIs. The daily maximum temperatures (DMTs) observed at the Orange and Dijon stations in France were used as a case study. This paper highlights a possible relationship between some large-scale climate patterns and the heat spells in France. Overall, the results suggest that considering the combined effect of global warming and these patterns in NS models is useful for a more appropriate characterization of the hazard heat spells in France.

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