Relevant bibliographies by topics / Palaeo-redox

Academic literature on the topic 'Palaeo-redox'

Author: Grafiati
Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "Palaeo-redox"

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Lüning, Sebastian, Sadat Kolonic, David K. Loydell, and Jonathan Craig. "Reconstruction of the original organic richness in weathered Silurian shale outcrops (Murzuq and Kufra basins, southern Libya)." GeoArabia 8, no. 2 (April 1, 2003): 299–308. http://dx.doi.org/10.2113/geoarabia0802299.

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ABSTRACT The early Silurian in North Africa and Arabia was characterised by widespread deposition of organic-rich shales in palaeo-depressions. The unit represents an important hydrocarbon source rock in the region and can be detected easily in well logs because of strong uranium-related natural radiation. In exposures, however, organic matter is commonly heavily oxidised through weathering so that identification of the unit in the field is difficult. Uranium and pyrite framboids appear to be less vulnerable to weathering and may be used to identify intervals of originally organic-rich shales in exposures. Framboids are discrete spheroidal aggregates of pyrite microcrystallites and their size distribution is thought to be controlled by palaeo-depositional bottom-water redox-conditions. Analyses of fresh Silurian organic-rich shales from a core reveal a close correspondence, for the most part, between total organic carbon, total gamma-ray response, uranium content (as determined by spectral gamma-ray) and framboid parameters. Feasibility tests of the concept have been carried out at two exposures in southern Libya and may form the basis for improved Silurian organic-rich shale distribution maps and more precise age models for Silurian organic-rich depositional phases in northern Gondwana.
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Jin, Chengsheng, Chao Li, Thomas J. Algeo, Guochang Wang, Wei Shi, Meng Cheng, Zihu Zhang, Haiyang Wang, Na Li, and Wei Wang. "Spatial heterogeneity of redox-sensitive trace metal enrichments in upper Ediacaran anoxic black shales." Journal of the Geological Society 178, no. 5 (March 4, 2021): jgs2020–234. http://dx.doi.org/10.1144/jgs2020-234.

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The Ediacaran radiation of metazoans is widely thought to have been triggered by an increase in atmospheric and oceanic oxygen levels. Although supported by other proxies, rising oxygen levels were deduced to a significant degree from sedimentary enrichments of redox-sensitive trace elements (RSTEs). However, some organic-rich shales of this period show only minor enrichments in RSTEs, leaving the significance of RSTE data for palaeo-oxygenation interpretations in doubt. We measured and compiled proxies for marine redox conditions (Fe species, RSTEs), total organic carbon (TOC) and water mass restriction (Mo/TOC and Co × Mn v. Cd/Mo) in the intra-shelf Jiulongwan and basinal Sandu sections of the Nanhua Basin in South China. Compared with the same proxies from coeval sections in the Nanhua Basin and globally, our results document a strong spatial heterogeneity of RSTE enrichments in anoxic black shales during the late Ediacaran. We infer that RSTE enrichments were strongly influenced by local factors, such as basinal restriction, seawater RSTE concentrations, and differential elemental responses to redox conditions and other influences. The broader significance of our findings is that they highlight the difficulty of investigating global redox conditions based on an analysis of local RSTE proxies within a single depositional basin or a limited number of study sections.Thematic collection: This article is part of the Advances in the Cambrian Explosion collection available at: https://www.lyellcollection.org/cc/advances-cambrian-explosionSupplementary material: Tables S1–S3 are available at https://doi.org/10.6084/m9.figshare.c.5325047
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Mahoney, Carol, Christian März, Jim Buckman, Tom Wagner, and Vladimir-Orlando Blanco-Velandia. "Pyrite oxidation in shales: Implications for palaeo-redox proxies based on geochemical and SEM-EDX evidence." Sedimentary Geology 389 (July 2019): 186–99. http://dx.doi.org/10.1016/j.sedgeo.2019.06.006.

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Yiqing, Zhu, Wang Xingzhi, Feng Mingyou, Pu Kun, and Cai Jiacheng. "Palaeo-redox environment analysis of Longmaxi formation shale in southern Sichuan basin by XRF and ICP-MS." ScienceAsia 44, no. 2 (2018): 109. http://dx.doi.org/10.2306/scienceasia1513-1874.2018.44.109.

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Killick, A. M. "The setting and style of manganese mineralization in the Constantiaberg Massif, Cape Peninsula, South Africa." South African Journal of Geology 123, no. 4 (October 26, 2020): 493–510. http://dx.doi.org/10.25131/sajg.123.0034.

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Abstract Manganese oxyhydroxide mineralization is widespread in the Constantiaberg Massif. It is largely hosted by west-northwest – east-southeast trending brittle structures in the competent Ordovician arenites of the Peninsula Formation of the Cape Supergroup. Manganese is also found impregnating more porous Peninsula Formation arenites and Quaternary scree. This study proposes that the more significant deposits at Hout Bay and Constantiaberg differ from most of the mineralization in that they are spatially associated with saprolithic dolerite dykes belonging to the 132 Ma False Bay dolerite dyke swarm. It is suggested that this deep weathering may be related to a Miocene palaeo-landsurface, yielding a maximum age for these more important Mn deposits. However, there is evidence for mineralization of different ages through the Quaternary Period. Apart from Mn-mineralization hosted by rare breccias containing hydrothermal quartz, most of the mineralization is supergene, having been leached and transported in reduced acidic groundwater and precipitated at or near a redox front in a near-surface environment.
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Guo, Yu, Wenzhe Gang, Gang Gao, Shangru Yang, Chong Jiang, Guo Chen, Chuanzhen Zhu, et al. "An integrated organic–inorganic geochemical characterization of Paleogene sediments in No.1 Structural Belt of the Nanpu Sag, Bohai Bay Basin, eastern China: implications for the origin of organic matter." Geochemistry: Exploration, Environment, Analysis 21, no. 1 (October 5, 2020): geochem2019–060. http://dx.doi.org/10.1144/geochem2019-060.

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Paleogene sediments, especially the third member of the Dongying Formation (Ed3) and the first and third members of the Shahejie Formation (Es1 and Es3), have been regarded as the most important source rocks in the Nanpu Sag. Organic and inorganic analyses, including Rock-Eval pyrolysis, gas chromatography-mass spectrometry, and element geochemistry, in 91 mudstone samples, were used to reconstruct the palaeoenvironmental conditions, such as palaeoclimate, palaeo-salinity and palaeo-redox conditions, and to recognize the origin of organic matter. The results show that Es3 has a higher TOC content than Es1 and Ed3. Hydrocarbon genetic potential (S1 + S2) of the samples indicate fair to good hydrocarbon potential. The kerogen type of Ed3 and Es1 source rocks are Type II1–II2, while Es3 source rocks are dominated by Type II2–III kerogens. Biomarkers and inorganic geochemical indicatives of source rocks, such as Pr/Ph, V/(V + Ni) and Cu/Zn, indicate a lacustrine environment with fresh to brackish water under suboxic to anoxic conditions during deposition. Ed3 source rocks are characterized by low G/C30H (gamacerane/C30hopane) (<0.1), TT/C30H (tricyclic terpane/C30hopane) and S/H (serane/hopane), high Pr/Ph (pristane/phytane) and C24TeT/C23TT (C24tetracyclic terpane/C23tricyclic terpane), indicating mixed input of both algae and terrestrial higher plants, dominated by terrestrial higher plants. Es1 source rocks display medium G/C30H, TT/C30H, S/H, Pr/Ph and C24TeT/C23TT, indicative of a mixed input of both algae and terrestrial higher plants. Es3 source rocks are characterized by high G/C30H (>0.1), TT/C30H and S/H, low Pr/Ph and C24TeT/C23TT, typical of a mixed input of algae and terrestrial higher plants, with algal dominance. Ed3, Es1 and Es3 source rocks were mostly deposited in semi-arid to humid-warm climate conditions, with an average temperature higher than 15°C. This study suggests that suitable temperatures, a fresh to brackish lacustrine environment and suboxic to anoxic conditions could result in a high organic matter concentration and preservation, thus providing prerequisites for the formation of high-quality source rocks.Supplementary material: Tables S1–S3 are available at https://doi.org/10.6084/m9.figshare.c.5227684
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Men, Yekai, Ende Wang, Jianfei Fu, Sanshi Jia, Xinwei You, and Qiangwen He. "Geology and geochemistry of the Yuanjiacun banded iron formation in Shanxi Province, China: constraints on the genesis." Geological Magazine 156, no. 11 (April 15, 2019): 1839–62. http://dx.doi.org/10.1017/s0016756819000219.

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AbstractThe Yuanjiacun banded iron formation (BIF) is hosted in lower Proterozoic metamorphic strata, and its structures are dominated by bands or streaks. Based on their differences in mineral compositions, the iron ores can be subdivided into haematite quartzite, magnetite quartzite, stilpnomelane magnetite quartzite and stilpnomelane haematite quartzite. The geochemical characteristics of the surrounding rocks show that the protoliths consisted of argillaceous and arenaceous sedimentary rocks. The predominant provenance was a high-maturity felsic sedimentary terrane. The absence of syn-depositional igneous rocks and the tectonic setting discrimination diagrams indicate that the Yuanjiacun BIF formed in a passive continental margin setting. Negligible terrigenous materials were involved in the precipitation of the Yuanjiacun BIF. The precipitation of the Yuanjiacun BIF was predominantly controlled by the mixing of seawater and hydrothermal fluids. Its metallogenic material originated from the leaching of mafic oceanic crust by hydrothermal fluids. The observed Ce anomaly deficiency and heavy Fe isotope enrichment indicate that the Yuanjiacun BIF formed in an anoxic marine environment. In a redox-stratified palaeo-ocean, the Yuanjiacun BIF formed in reducing seawater below the oxidation–reduction transition zone. The Si and O isotope compositions of quartz suggest that the formation of the Yuanjiacun BIF was closely related to submarine hydrothermal activity. The Si and Fe erupted from the seafloor and precipitated by supersaturation and biological oxidation under anoxic conditions, respectively.
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Zheng, Xue, Baruch Spiro, and Zuozhen Han. "Comparison of Geochemical and Mineralogical Characteristics of Palaeogene Oil Shales and Coals from the Huangxian Basin, Shandong Province, East China." Minerals 10, no. 6 (May 29, 2020): 496. http://dx.doi.org/10.3390/min10060496.

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Coal and oil shale are both organic matter-rich sedimentary rocks. However, their sources of organic matter and their depositional environments are different. The present study focuses on the Palaeogene Lijiaya Formation sequence in the Huangxian Basin, Shandong Province, East China, which has oil shales showing marine geochemical indicators overlain by coals indicating marine regression. We investigated the C1 coal seam and underlying OS2 oil shale layers, compared their geochemical and mineralogical characteristics, clarified the details of their constituents, in order to elucidate the features of their sources, their depositional environments, and the post depositional processes in the context of the geological evolution of the basin. The Al2O3/TiO2 (18.1–64.9) and TiO2/Zr ratios (28.2–66.5) in the C1 coals and OS2 oil shales, respectively, suggest a felsic to intermediate source, and the Mesozoic granite on the South of Huangxian Fault may be one of the provenances of these sediments. The low sulphur content (0.53–0.59%) and low Sr/Ba ratios (0.32–0.67) suggest a freshwater depositional environment for the C1 coals. In contrast, the higher total sulphur contents (0.60–1.44%), the higher Sr/Ba ratios (0.31–1.11%), and the occurrence of calcareous shells, indicate seawater intrusions during deposition of the oil shales. The V/Ni, V/(V + Ni), and V/Cr ratios of the OS2 oil shale suggest oxic to suboxic conditions with a distinct change in palaeo-redox between the lower and upper parts of OS2 seam. The high boron contents in C1 coals (average, 504 ppm) is related to the high content of analcime (with the correlation coefficient of 0.96), and the high concentration of boron was attributed to a secondary enrichment by epigenetic hydrothermal solutions. The occurrence of idiomorphic-authigenic albite in association with analcime and quartz in veins in the coals suggests that albite is a product of a reaction between analcime and silica, both of volcanic origin. The reaction takes place at about 190 °C, indicating that the area was affected by hydrothermal fluids.
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Zhang, Lei, Shan Chang, Maliha Zareen Khan, Qinglai Feng, Cui Luo, Michael Steiner, Marie-Béatrice Forel, Kai Liu, and Sébastien Clausen. "Influence of palaeo-redox and diagenetic conditions on the spatial distribution of Cambrian biotas: A case study from the upper Shuijingtuo Formation (Cambrian Series 2, Stage 3), Three Gorges area of South China." Palaeogeography, Palaeoclimatology, Palaeoecology 548 (June 2020): 109696. http://dx.doi.org/10.1016/j.palaeo.2020.109696.

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Bullock, Liam A., John Parnell, Joseph G. T. Armstrong, Magali Perez, and Sam Spinks. "Gold in Irish Coal: Palaeo-Concentration from Metalliferous Groundwaters." Minerals 10, no. 7 (July 17, 2020): 635. http://dx.doi.org/10.3390/min10070635.

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Gold grains, up to 40 μm in size and containing variable percentages of admixed platinum, have been identified in coals from the Leinster Coalfield, Castlecomer, SE Ireland, for the first time. Gold mineralisation occurs in sideritic nodules in coals and in association with pyrite and anomalous selenium content. Mineralisation here may have reflected very high heat flow in foreland basins north of the emerging Variscan orogenic front, responsible for gold occurrence in the South Wales Coalfield. At Castlecomer, gold (–platinum) is attributed to precipitation with replacive pyrite and selenium from groundwaters at redox interfaces, such as siderite nodules. Pyrite in the cores of the nodules indicates fluid ingress. The underlying Caledonian basement bedrock is mineralised by gold, and thus likely provided a source for gold. The combination of the gold occurrences in coal in Castlecomer and in South Wales, proximal to the Variscan orogenic front, suggests that these coals along the front could comprise an exploration target for low-temperature concentrations of precious metals.
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Dissertations / Theses on the topic "Palaeo-redox"

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Liebelt, S. R. "Testing the redox coupling between chromium and nitrogen isotopes in modern and ancient redox-stratified depositional systems: the Coorong Lagoon and the Greater McArthur Basin." Thesis, 2019. https://hdl.handle.net/2440/136963.

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The history of Earth’s atmospheric oxidation following the Great Oxidation Event (GOE) is widely debated and currently poorly constrained. This uncertainty is largely because the use of different geochemical proxies provides a broad range of possible palaeo-redox conditions during the mid-Proterozoic. Such proxies include nitrogen (δ15N) and chromium (δ53Cr) isotopes, which are the focus of this study. These redox-sensitive proxies have recently demonstrated coupled behaviour in both modern seawaters and recent marine sediments, suggesting isotopic fractionation of Cr could result from biologically mediated redox cycling of N. This concept is opposed to Cr isotope fractionation being purely representative of oxidative weathering on continents, thus challenging the reliability of the δ53Cr proxy as a direct tracer for past atmospheric O2 levels. The aim of this study is to test the purported redox coupling of the δ53Cr and δ15N proxies in two redox-stratified depositional systems, specifically investigating (i) modern waters and organic matter from the Coorong Lagoon of South Australia, and (ii) organic-rich shales from the greater McArthur Basin in the Northern Territory (including the Velkerri, Mainoru, Barney Creek and Fraynes Formations). These marine settings display notable redox gradients, allowing insight into the isotopic behaviour of N and Cr through a variety of conditions. Contrary to published data, this study revealed no positive co-variance between δ53Cr and δ15N records. Rather, δ15N changes in both waters and shales are interpreted to largely result from pH-driven volatilisation of NH3, while δ53Cr variations in shales exhibit a systematic temporal increase. This increase likely reflects progressive basin oxygenation, linked to gradually increasing atmospheric O2 during the mid-Proterozoic (i.e. from 1.64 to 1.31 Ga). Thus, the validity of δ53Cr values in marine archives as a palaeo-redox proxy are supported in this instance, with no direct evidence for biologically driven redox cycling of Cr coupled to local N cycling.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2019
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McFadzean, G. J. "Geochemical analysis of the McArthur and Tawallah Groups, McArthur Basin: chemostratigraphy & palaeo-redox proxies using shales and carbonates." Thesis, 2019. https://hdl.handle.net/2440/136976.

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The lower portion of the McArthur Basin includes the Palaeoproterozoic to Mesoproterozoic McArthur and Tawallah Groups. During this time, Earth had comparatively less oxygen following the beginning of ‘The Great Oxygenation Event’ (GOE, Palaeoproterozoic ca. 2.34 Ga) and organisms were simple. In conjunction, the ‘Boring Billion’ (1800 to 800 Ma) is an acknowledged period following the GOE due to reported flat carbon and oxygen isotope trends which is evidence for a relatively stable climate and delayed organism evolution. The aim of this thesis is to gather a coupled dataset using conventional geochemistry and organic geochemistry through the use of carbon/oxygen isotopes, redox sensitive trace elements (Mo, V and U), rare earth elements and organic carbon content in order to understand the oxygen conditions (through palaeo-redox techniques) within the lower portions of the Palaeoproterozoic McArthur Basin. Shale units of the McArthur and Tawallah groups (Mallapunyah, Wollogorang and Wuraliwuntya Formations) are shown to be deposited in a stratified oxygenation and sulfidic environment. These episodes of anoxia or euxinia are shown by elevated concentrations of rare earth elements (REE) and trace elements at specific drill core depth. Subtle and fluctuating cerium and europium anomalies along with trace and major elemental data were coupled by total organic carbon (TOC) to show a relationship with the organic matter within the Wollogorang Formation specifically. The trace elements seemingly concentrated within the regions of high organic content, which resulted in euxinia events causing elevated levels of trace metals. Potential trace metal elevations within the Wollogorang and Mallapunyah Formations specifically are compared against the reported evidence for sedimentary exhalative deposits (SedEX deposits). The Amelia Dolostone recorded carbon isotope values of 0 to -2‰ and oxygen isotope values of -5 to -9‰ - expected carbon and oxygen isotopic concentrations for the Palaeoproterozoic to Mesoproterozoic Era.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2019
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