Environmental analysis of paleoceanographic systems based on molybdenum–uranium covariation

Algeo, Thomas J.; Tribovillard, Nicolas

doi:10.1016/j.chemgeo.2009.09.001

Cited by 1,181 publications

(727 citation statements)

References 106 publications

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“…The overall Mo/U ratio decreases in the iron reduction zone. Molybdenum content in all but two carbonate concretions (Cal-C and Cal-N) is consistently greater than the crustal average (1e2 ppm; Taylor and McLennan, 1985) and much higher than that expected for pure carbonate rocks (0.02 ppm; Neubert et al, 2008 (Algeo and Tribovillard, 2009). Anomalously high Mo concentrations are believed to reflect the formation of iron sulfides after the production of hydrogen sulfide during AOM (Sato et al, 2012;Hu et al, 2014).…”

Section: Redox Conditions During Sedimentationmentioning

confidence: 91%

“…This implies that hydrogen sulfide is maintained at a low level for Mo enrichment and Fe-sulfides formation. Whilst calcite/aragonite shows average (Mo/U) EF of 2.88, reflecting precipitation from sulfidic pore water, dolomite crusts show (Mo/U) EF values as low as 0.31 reflecting a much lower sulfide concentration (Algeo and Tribovillard, 2009;Hu et al, 2014) likely related to a lower methane flux. Siderite, on the other hand, yields higher (Mo/U) EF values (average 32.2), which are evidence of precipitation under strong anoxic conditions.…”

Section: Redox Conditions During Sedimentationmentioning

confidence: 99%

“…In well-oxygenated water Mo behaves conservatively, whereas it normally enriches within organic matter and iron sulfides under anoxic conditions (Helz et al, 1996;Neubert et al, 2008;Algeo and Tribovillard, 2009). In anoxic conditions Mo is completely removed from seawater and accumulates in surface sediments (Neubert et al, 2008).…”

Section: Redox Conditions During Sedimentationmentioning

confidence: 99%

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Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

Franchi

Rovere

Gamberi

et al. 2017

Marine and Petroleum Geology

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a b s t r a c tPaola Ridge, along the NW Calabrian margin (southern Tyrrhenian Sea), is one of the few reported deep sea sites of precipitation of authigenic carbonates in the Tyrrhenian Sea. Here, the changing composition of the seeping fluids and the dynamic nature of the seepage induced the precipitation of pyrite, siderite and other carbonate phases. The occurrence of this array of authigenic precipitates is thought to be related to fluctuation of the sulfate-methane transition zone (SMTZ).Concretions of authigenic minerals formed in the near sub-bottom sediments of the Paola Ridge were investigated for their geochemical and isotopic composition. These concretions were collected in an area characterized by the presence of two alleged mud volcanoes and three mud diapirs. The mud diapirs are dotted by pockmarks and dissected by normal faults, and are known for having been a site of fluid seepage for at least the past 40 kyrs. Present-day venting activity occurs alongside the two alleged mud volcanoes and is dominated by CO 2 -rich discharging fluids. This discover led us to question the hypothesis of the mud volcanoes and investigate the origin of the fluids in each different domed structure of the study area.In this study, we used stable isotopes (carbon and oxygen) of carbonates coupled with rare earth element (REE) composition of different carbonate and non-carbonate phases for tracing fluid composition and early diagenesis of authigenic precipitates. The analyses on authigenic precipitates were coupled with chemical investigation of venting gas and sea-water.Authigenic calcite/aragonite concretions, from surficial sediments on diapiric structures, have depleted values. The siderite REE pattern shows consistent LREE (light REE) fractionation, MREE (medium REE) enrichment and positive Gd and La anomalies. As shown by the REE distribution, the 13 C-depleted composition and their association with chemosymbiotic fauna, calcite/aragonite precipitated at time of moderate to high methane flux close to the seafloor, under the influence of bottom seawater. Authigenic siderite, on the other hand, formed in the subseafloor, during periods of lower gas discharges under prolonged anoxic conditions within sediments in equilibrium with 13 C-rich dissolved inorganic carbon (DIC) and 18 O-rich water, likely related to methanogenesis and intermittent venting of deep-sourced CO 2 .

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Section: Redox Conditions During Sedimentationmentioning

confidence: 91%

Section: Redox Conditions During Sedimentationmentioning

confidence: 99%

Section: Redox Conditions During Sedimentationmentioning

confidence: 99%

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Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

Franchi

Rovere

Gamberi

et al. 2017

Marine and Petroleum Geology

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“…On the other hand, in fer ences re gard ing palaeoenvironmental con di tions based on trace el e ment con cen tra tions are com monly un re liable if sin gle el e ment dis tri bu tions are used, be cause their con cen tra tions are in flu enced by many fac tors and mech anisms (Tribovillard et al, 2006). Many au thors con sider not only the con cen tra tion of el e ments but also the de gree of enrich ment or de ple tion of a trace el e ment to re con struct palaeoenviron mental con di tions (e.g., Wedepohl, 1991;Rimmer, 2004;Brum sack, 2006;Tribovillard et al, 2006;Kombrink, 2008;Algeo and Tribovillard, 2009). The method of geo chem ical nor mal iza tion and cal cu la tion of en rich ment fac tors (EFs) is as fol lows: where: El s -el e ment con cen tra tion in the sam ple, Al s -Al con centra tion in the sam ple, El av -el e ment con cen tra tion in av er age crustal rocks or av er age shale, and Al av -Al con cen tra tion in av er age crustal rocks or av er age shale.…”

Section: Redox-sensitive Trace Elementunclassified

“…-dem on strate con ser va tive be hav iour un der oxic con ditions and have long res i dence times in sea wa ter, -ex hibit nearly con sis tent con cen tra tions in sea wa ter glob ally, -are pres ent in low con cen tra tions in plank ton, so en richments in sed i ments gen er ally co mes from sea wa ter, espe cially un der ox y gen-de pleted con di tions (Algeo and Tribovillard, 2009). TEs com monly ex hibit con sid er able en rich ment in lam inated, or ganic-rich fa cies, es pe cially those de pos ited un der euxinic con di tions (Algeo and Maynard, 2008).…”

Section: Redox-sensitive Trace Elementmentioning

confidence: 99%

Geochemical and faunal proxies in the Westphalian A (Langsettian) marine horizon of the Lublin Coal Basin

Krzeszowska

2017

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Krzeszowska, E., 2017. Geo chem i cal and fau nal prox ies in the Westphalian A (Langsettian) ma rine ho ri zon of the Lublin Coal Ba sin. Geo log i cal Quar terly, 61 (4): 751-764, doi: 10.7306/gq.1374The up per most Westphalian ma rine ho ri zon (Dunbarella ho ri zon) is es pe cially im por tant for cor re la tion of Car bon if er ous depos its in the Lublin Coal Ba sin and in other bas ins of the North west Eu ro pean Car bon if er ous Ba sin. The Dunbarella ho ri zon is char ac ter ized by cy clic sed i men ta tion and con se quent fau nal spec trum vari abil ity, typ i cal for Westphalian ma rine ho ri zons of north west ern Eu rope. Palaeontological study of the Dunbarella ho ri zon showed the pres ence of macrofauna rep re sent ing dif fer ent palaeoenvironments, from ma rine to brack ish (non-ma rine) and fresh wa ter con di tions. The ver ti cal sea level fluc tua tions and changes in sea wa ter sa lin ity re sult ing in palaeontological re cord changes do not link with geo chem i cal prox ies. TOC, re dox-sen si tive trace el e ment con cen tra tions, and V/Cr, Ni/Co and V/(V + Ni) ra tios gen er ally sug gest that the Dunbarella ho ri zon sed i ments were de pos ited un der pre dom i nantly oxic con di tions (with lo cal ex cep tions dur ing the ini tial phase of the Dunbarella ingression; Kopina 1 bore hole).

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Re-Os age and depositional environment for black shales from the Cambrian-Ordovician boundary, Green Point, western Newfoundland

Tripathy

Hannah

Stein

et al. 2014

Geochem. Geophys. Geosyst.

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Chemical and isotopic signatures for black shales serve as potential proxies for reconstruction of paleoenvironmental conditions. Here we bring Rock-Eval, major and trace element and Re-Os isotopic data together to examine the environmental record at the Cambrian-Ordovician Global Stratotype Section and Point (GSSP) at Green Point in western Newfoundland, Canada. The Green Point shales are oil mature and contain Type II organic material of marine origin. A Re-Os isochron for the shales provides the first radiometric age for shale deposition at the GSSP at 484 6 16 Ma, with an initial 187 Os/ 188Os ratio of 0.74 6 0.05 (Model 3 age; MSWD 5 21; n 5 13; 2r uncertainties). Factor analysis of the geochemical data set shows association of most trace elements with total organic carbon (TOC) and S contents, ensuring an authigenic origin for most elements and hence, their validity for evaluating the paleo-redox state. Relatively high-enrichment factors for redox-sensitive elements (e.g., Re, U, and Mo) compared to average shale, but comparatively low enrichment compared to modern Black Sea sediments, suggest deposition in anoxic, but not euxinic waters. Comparison of Lower Ordovician shale geochemistry data sets at a global scale leads us to suggest that anoxic conditions and warm oceanic regimes were restricted to the margins of Laurentia and Baltica, whereas depositional basins with colder waters (e.g., Avalonia and Gondwana) were less reducing. These outcomes underscore the important role of paleogeography in regulating oceanic conditions and marine life.

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Environmental analysis of paleoceanographic systems based on molybdenum–uranium covariation

Cited by 1,181 publications

References 106 publications

Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

Authigenic minerals from the Paola Ridge (southern Tyrrhenian Sea): Evidences of episodic methane seepage

Geochemical and faunal proxies in the Westphalian A (Langsettian) marine horizon of the Lublin Coal Basin

Re-Os age and depositional environment for black shales from the Cambrian-Ordovician boundary, Green Point, western Newfoundland

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