scholarly journals A Mesoproterozoic iron formation

2018 ◽  
Vol 115 (17) ◽  
pp. E3895-E3904 ◽  
Author(s):  
Donald E. Canfield ◽  
Shuichang Zhang ◽  
Huajian Wang ◽  
Xiaomei Wang ◽  
Wenzhi Zhao ◽  
...  
Keyword(s):  
Organic Matter ◽  
Time Window ◽  
Iron Formation ◽  
The North ◽  
Fe Oxidation ◽  
Organic Biomarkers ◽  
Rock Eval ◽  
Fe Reduction ◽  
Rule Out ◽  
Xiamaling Formation

We describe a 1,400 million-year old (Ma) iron formation (IF) from the Xiamaling Formation of the North China Craton. We estimate this IF to have contained at least 520 gigatons of authigenic Fe, comparable in size to many IFs of the Paleoproterozoic Era (2,500–1,600 Ma). Therefore, substantial IFs formed in the time window between 1,800 and 800 Ma, where they are generally believed to have been absent. The Xiamaling IF is of exceptionally low thermal maturity, allowing the preservation of organic biomarkers and an unprecedented view of iron-cycle dynamics during IF emplacement. We identify tetramethyl aryl isoprenoid (TMAI) biomarkers linked to anoxygenic photosynthetic bacteria and thus phototrophic Fe oxidation. Although we cannot rule out other pathways of Fe oxidation, iron and organic matter likely deposited to the sediment in a ratio similar to that expected for anoxygenic photosynthesis. Fe reduction was likely a dominant and efficient pathway of organic matter mineralization, as indicated by organic matter maturation by Rock Eval pyrolysis combined with carbon isotope analyses: Indeed, Fe reduction was seemingly as efficient as oxic respiration. Overall, this Mesoproterozoic-aged IF shows many similarities to Archean-aged (>2,500 Ma) banded IFs (BIFs), but with an exceptional state of preservation, allowing an unprecedented exploration of Fe-cycle dynamics in IF deposition.

GEOCHEMICAL CHARACTERISTIC OF THE SILURIAN ROCKS FROM THE EASTERN PART OF MOLDAVIAN PLATFORM (ROMANIA)

2021 ◽  
Vol 16 (1) ◽  
pp. 17-30
Author(s):  
Octavian COLŢOI ◽  
◽  
Flori CULESCU ◽  
Gilles NICOLAS
Keyword(s):  
Organic Matter ◽  
Geochemical Characteristic ◽  
Petroleum Potential ◽  
The North ◽  
North Eastern ◽  
High Maturity ◽  
Cap Rock ◽  
Rock Eval ◽  
Part Thickness ◽  
North Eastern Part

The scope of this paper is to assess the hydrocarbon potential of Silurian, respectively, the maturity of this stratigraphical interval, based, especially, of the geological and geophysical data derived from eight boreholes located in the north-eastern part of Moldavian Platform - Romania. The main conclusion is that the organic matter contents measured in the core and cutting samples of the different wells are low with the Organic Carbon (TOC) (residual) mainly clearly lower than 1%. Due to the poorness of the sample and the high maturity the petroleum potential and organic matter cannot be assessed. Estimation of the initial TOC allows to differentiate a richer interval at 24 – 27m thick below the top of Silurian. It shows higher TOC with estimated initial TOC reaching 3.6 % weight at the most. The maturity is high and shows a rapid increase with depth between around 2% at 200m and 4% eq. VRr at 1100m. An estimation of the eroded cap-rock is of around 3000m. Mineral carbon content obtained from Rock Eval permits to separate two lithological intervals: carbonated in the upper part (thickness of 250-300m), argillaceous in the lower part.

scholarly journals Study of the lithological characteristics of Domanic deposits of the Pervomayskoe field

Georesursy ◽  
2018 ◽  
Vol 20 (4) ◽  
pp. 324-330
Author(s):  
A. Takhauov ◽  
A. Titov
Keyword(s):  
Organic Matter ◽  
Microscopic Analysis ◽  
Oil Field ◽  
Core Material ◽  
Sharp Change ◽  
Reservoir Properties ◽  
The Core ◽  
The North ◽  
Lithological Composition ◽  
Rock Eval

The paper presents the results of studying rocks of the domanic horizon of the Pervomayskoe oil field represented by core material of the well 467D. In tectonic terms, this well, like the entire Pervomayskoe field, is confined to the axial part of the Kama-Kinel deflection system on the territory of the North-Tatar arch. Administratively, the Pervomayskoe deposit is located on the territories of the Elabuga, Mendeleevsky and Tukaevsky districts of the Republic of Tatarstan. To study the core material presented, different studies were conducted, including a macroscopic description of the core; comparison of the studied rocks with well logging data; optical microscopic analysis; X-ray analysis; determination of reservoir properties of rocks; study of organic matter by the Rock-Eval pyrolysis method. Based on the analysis, it was found that the domanic horizon is composed of rocks containing carbonate and siliceous minerals to varying degrees, occasionally including minor mixtures of other minerals. The section of rocks is characterized by a sharp change in the lithological composition with a thickness of interlayers of several centimeters. According to Rock-Eval data, carbonate-siliceous interlayers have a high content of organic matter. Organic matter in Domanic deposits is characterized as immature and is found in rocks in the form of kerogen.

scholarly journals Geochemical features of the organic matter from Jurassic sediments of the Nadym‑Taz interfluve

Georesursy ◽  
2020 ◽  
Vol 22 (3) ◽  
pp. 21-27
Author(s):  
Lyubov S. Borisova ◽  
Alexander N. Fomin ◽  
Ekaterina S. Yaroslavtseva
Keyword(s):  
Organic Matter ◽  
Sedimentary Cover ◽  
Lower Jurassic ◽  
Geochemical Data ◽  
The North ◽  
Deep Wells ◽  
Geochemical Parameters ◽  
Insoluble Organic Matter ◽  
Bazhenov Horizon ◽  
Rock Eval

This paper deals with the evaluation of oil-generation potential derived from the geochemical data on deep-buried Jurassic sedimentary rocks of the Nadym-Taz interfluve being part of the West Siberian petroleum basin (PB). The study provides analysis of samples from ultra-deep and deep wells that penetrated the Mesozoic-Cenozoic sedimentary cover in the north of the central part of PB (En-Yakhinsky, Evo-Yakhinsky, Yarudeysky, Tyumensky areas, etc.). The research focuses on the insoluble organic matter (OM) from Upper, Middle and Lower Jurassic sediments (54 samples). A comprehensive study of the kerogen by elemental, isotope analyses and pyrolysis Rock-Eval allowed obtaining the data critical for determining the genetic type of OM, its thermal maturity and residual petroleum generating potential. Using the Surfer and Corel Draw software, schematic maps and diagrams of variations in the most informative (i.e. area-specific and depth-dependent) geochemical parameters of the kerogen on the studied area and also down the section (from the Upper to the Lower Jurassic) were constructed and analyzed. The obtained geochemical data indicate that in the Jurassic sediments of the Nadym-Tazovsky interfluve, the highest OM generation potential is found in the Bazhenov horizon, as well as in individual members of the Malyshevsky, Leontievsky, Sharapovsky and Kiterbyutsky horizons. Based upon the level of OM maturity in the Upper and Middle Jurassic sediments, deposits of mainly oil and fat gases could be preserved, and in the Lower Jurassic – deposits of fat and dry gases.

Earth’s Middle Ages: What Came after the GOE

2017 ◽  
Author(s):  
Donald Eugene Canfield
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Middle Ages ◽  
Atmospheric Oxygen ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Dissolved Iron ◽  
Great Oxidation Event ◽  
Low Levels ◽  
Substantial Rise

This chapter considers the aftermath of the great oxidation event (GOE). It suggests that there was a substantial rise in oxygen defining the GOE, which may, in turn have led to the Lomagundi isotope excursion, which was associated with high rates of organic matter burial and perhaps even higher concentrations of oxygen. This excursion was soon followed by a crash in oxygen to very low levels and a return to banded iron formation deposition. When the massive amounts of organic carbon buried during the excursion were brought into the weathering environment, they would have represented a huge oxygen sink, drawing down levels of atmospheric oxygen. There appeared to be a veritable seesaw in oxygen concentrations, apparently triggered initially by the GOE. The GOE did not produce enough oxygen to oxygenate the oceans. Dissolved iron was removed from the oceans not by reaction with oxygen but rather by reaction with sulfide. Thus, the deep oceans remained anoxic and became rich in sulfide, instead of becoming well oxygenated.

A new volcanic province: evidence from glacial erratics in western North Greenland

2000 ◽  
pp. 35-41 ◽  
Author(s):  
Peter R. Dawes ◽  
Bjørn Thomassen ◽  
T.I. Hauge Andersson
Keyword(s):  
Volcanic Rocks ◽  
Iron Formation ◽  
Banded Iron Formation ◽  
Common Component ◽  
Volcanic Province ◽  
North West ◽  
North East ◽  
The North ◽  
Surficial Deposits ◽  
North Greenland

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Dawes, P. R., Thomassen, B., & Andersson, T. H. (2000). A new volcanic province: evidence from glacial erratics in western North Greenland. Geology of Greenland Survey Bulletin, 186, 35-41. https://doi.org/10.34194/ggub.v186.5213 _______________ Mapping and regional geological studies in northern Greenland were carried out during the project Kane Basin 1999 (see Dawes et al. 2000, this volume). During ore geological studies in Washington Land by one of us (B.T.), finds of erratics of banded iron formation (BIF) directed special attention to the till, glaciofluvial and fluvial sediments. This led to the discovery that in certain parts of Daugaard-Jensen Land and Washington Land volcanic rocks form a common component of the surficial deposits, with particularly colourful, red porphyries catching the eye. The presence of BIF is interesting but not altogether unexpected since BIF erratics have been reported from southern Hall Land just to the north-east (Kelly & Bennike 1992) and such rocks crop out in the Precambrian shield of North-West Greenland to the south (Fig. 1; Dawes 1991). On the other hand, the presence of volcanic erratics was unexpected and stimulated the work reported on here.

scholarly journals Composition of Sedimentary Organic Matter across the Laptev Sea Shelf: Evidences from Rock-Eval Parameters and Molecular Indicators

Water ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 3511
Author(s):  
Elena Gershelis ◽  
Andrey Grinko ◽  
Irina Oberemok ◽  
Elizaveta Klevantseva ◽  
Natalina Poltavskaya ◽  
...  
Keyword(s):  
Organic Matter ◽  
Surface Sediments ◽  
Continental Margins ◽  
Laptev Sea ◽  
Lena River ◽  
Nearshore Sediments ◽  
Rock Eval ◽  
Molecular Indicators ◽  
Sedimentation Regime ◽  
The Laptev Sea

Global warming in high latitudes causes destabilization of vulnerable permafrost deposits followed by massive thaw-release of organic carbon. Permafrost-derived carbon may be buried in the nearshore sediments, transported towards the deeper basins or degraded into the greenhouse gases, potentially initiating a positive feedback to climate change. In the present study, we aim to identify the sources, distribution and degradation state of organic matter (OM) stored in the surface sediments of the Laptev Sea (LS), which receives a large input of terrestrial carbon from both Lena River discharge and intense coastal erosion. We applied a suite of geochemical indicators including the Rock Eval parameters, traditionally used for the matured OM characterization, and terrestrial lipid biomarkers. In addition, we analyzed a comprehensive grain size data in order to assess hydrodynamic sedimentation regime across the LS shelf. Rock-Eval (RE) data characterize LS sedimentary OM with generally low hydrogen index (100–200 mg HC/g TOC) and oxygen index (200 and 300 CO2/g TOC) both increasing off to the continental slope. According to Tpeak values, there is a clear regional distinction between two groups (369–401 °C for the inner and mid shelf; 451–464 °C for the outer shelf). We suggest that permafrost-derived OM is traced across the shallow and mid depths with high Tpeak and slightly elevated HI values if compared to other Arctic continental margins. Molecular-based degradation indicators show a trend to more degraded terrestrial OC with increasing distance from the coast corroborating with RE results. However, we observed much less variation of the degradation markers down to the deeper sampling horizons, which supports the notion that the most active OM degradation in LS land-shelf system takes part during the cross-shelf transport, not while getting buried deeper.

Sinking organic matter spreads the nitrogen isotope signal of pelagic denitrification in the North Pacific

2009 ◽  
Vol 36 (8) ◽  
Author(s):  
Daniel M. Sigman ◽  
Peter J. DiFiore ◽  
Mathis P. Hain ◽  
Curtis Deutsch ◽  
David M. Karl
Keyword(s):  
Organic Matter ◽  
North Pacific ◽  
Nitrogen Isotope ◽  
The North ◽  
The North Pacific

Prediction of the Sungpan-Pingwu earthquakes, August 1976

1980 ◽  
Vol 70 (4) ◽  
pp. 1199-1223
Author(s):  
Robert E. Wallace ◽  
Ta-Liang Teng
Keyword(s):  
Fracture Zone ◽  
Time Window ◽  
Substantial Reduction ◽  
Good Time ◽  
Large Space ◽  
Republic Of China ◽  
Plant Behavior ◽  
The North ◽  
Axis Parallel ◽  
Mass Evacuation

abstract On August 16, 22, and 23, 1976, a succession of three large earthquakes (M = 7.2, 6.8, 7.2) occurred in the Sungpan-Pingwu area of Szechuan Province, People's Republic of China. Their successful predictions resulted in a substantial reduction in the loss of lives. The epicenters of these events progressed from north to south along the Huya Fault, a NNW-striking fault between the NE-trending Lungmenshan fracture zone and the north-trending Mienchiang fracture zone in western Szechuan. The greatest intensity reported was IX; isoseismals were crudely elliptical with the long axis parallel to the trend of the Huya Fault. The predictions were made with a reasonably good magnitude window (less than 0.5 magnitude unit), a rather large space window (about 150 km ×150 km), and a remarkably good time window (within a day). The detailed prediction process began with field monitoring some 6 yr before the Sungpan-Pingwu events and ended with the final issuance of warning and mass evacuation. During the few weeks preceding the earthquakes, about 1,300 observations of noninstrumental anomalies and precursory phenomena were reported by scientists and lay brigades: outgassings, fireballs and other earthquake lights, abnormal animal and plant behavior, and telluric currents.

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