Rare earth element geochemistry of shallow carbonate outcropping strata in Saudi Arabia: Application for depositional environments prediction

Eltom, Hassan A.; Abdullatif, Osman; Makkawi, Mohammad; Eltoum, Isam-Eldin

doi:10.1016/j.sedgeo.2016.11.005

Cited by 28 publications

(18 citation statements)

References 26 publications

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“…Since the Ce anomaly in marine sediments is susceptible to the anomalous concentrations of La, interpretation of Ce anomaly is difficult and intricate [6,41]. The vast majority of highly negative Ce anomalies are resulted from highly positive La anomalies in marine sediments [6,25,41], and most of the analyzed samples in this study exhibit Except for two samples (ZN-9 and ZN-28, (Ce/Ce*) N = 1.00 and 1.01, respectively), all the other samples from Datang Formation show slightly negative Ce anomaly (Table 4 and Figure 6). Compared among the three lithologies, they have comparative (Ce/Ce*) N values, mirroring the weak heterogeneity during the black rock series deposition.…”

Section: Rare Earth Elementsmentioning

confidence: 99%

Elemental Geochemical Evidence for Depositional Conditions and Organic Matter Enrichment of Black Rock Series Strata in an Inter-Platform Basin: The Lower Carboniferous Datang Formation, Southern Guizhou, Southwest China

et al. 2018

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The Datang Formation black rock series deposited in an inter-platform basin are considered to be one of the main source rocks in Southwest China. However, their depositional conditions and organic matter enrichment in such a setting are not well understood. In this study, geochemical characteristics of total organic carbon (TOC), major, trace and rare earth elements (REEs) of thirty black rock series samples from a newly-cut roadside outcrop (Zhenning section) in Southern Guizhou, Southwest China are systematically investigated to examine provenance, paleoredox conditions, paleoclimate, paleoproductivity and sedimentary rate, and further to explore their influence on organic matter enrichment. Results show that TOC contents of the investigated samples range from 0.90% to 2.83%, with an average of 1.45%, with TOC variations being in accord with the stratigraphic cyclicity. These data also indicate that the target black rock series were deposited in a combination of continental island arc and active continental margin tectonic setting that exhibited moderate weathering, oxic/dysoxic oxygen levels, hot and arid to semiarid climate, and a higher sedimentary rate. Multiple paleoredox indicators (e.g., Ni/Co, V/Cr, U/Th and V/(V + Ni) ratios), together with slightly negative Ce anomalies and EF U -EF Mo covariation, totally suggest an oxic/dysoxic water environment, which is usually considered unfavorable for organic matter preservation. Average (La/Yb) N ratios (1.41) reflect a higher sedimentary rate, resulting in shortening the exposure time of organic matter in the degradation region of aerobic bacteria under oxic/dysoxic conditions. Of the three factors that could affect organic matter enrichment, including paleoproductivity, paleoredox conditions and sedimentary rate, the relatively high paleoproductivity indicated by the relatively high TOC contents appears to be the dominant factor. In contrast, the other two factors, i.e., paleoredox conditions and the rate of sedimentation play relatively less significant roles. Based on these factors, an enrichment model of organic matter for the black rock series in Southern Guizhou Depression is established. These findings also contribute to constraining the sedimentary environment in such a setting and further deepen our understanding of the potential shale gas resources of the Southern Guizhou Province.

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Section: Rare Earth Elementsmentioning

confidence: 99%

Elemental Geochemical Evidence for Depositional Conditions and Organic Matter Enrichment of Black Rock Series Strata in an Inter-Platform Basin: The Lower Carboniferous Datang Formation, Southern Guizhou, Southwest China

et al. 2018

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“…Detrital contamination of chemical marine sediments may result in such deviation from the typical seawater REE distribution (Nothdurft et al, ). The low concentration of the Al 2 O 3 contents (0.04–0.12), which are considered as a proxy for detrital contamination (e.g., Eltom, Abdullatif, Makkawi, & Eltoum, ), in the examined Abu Roash carbonates and their inverse relationship with the REE contents preclude the contamination potentiality. Moreover, the Zr contents of the Abu Roash carbonate range from 2 to 4 ppm (Table ).…”

Section: Discussionmentioning

confidence: 99%

Origin of chert within the Turonian carbonates of Abu Roash Formation, Abu Roash area, Egypt: Field, petrographic, and geochemical perspectives

Hussein

El‐Rahman

2019

Geological Journal

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This paper tries to elucidate the origin of the siliceous rocks (cherts) within the Turonian flint‐bearing chalky limestone member of Abu Roash Formation, Abu Roash area, north Western Desert, Egypt. Understanding the formation mechanism of the studied chert was gained through field and petrographic investigations, supplemented by geochemical analyses of both cherts and host Turonian carbonates. The field observations reveal that the chert is found in two forms: banded and nodular. The microscopic investigation determined that the cherts exhibit two types of silica: replacive silica (cryptocrystalline and microcrystalline quartz) and silica cement (length‐fast chalcedony and megaquartz). The chert texture corroborates that the examined authigenic silica was formed diagenetically by the replacement and void‐filling of the host carbonate rocks. The silica was most likely derived from the biogenic opal‐A of the siliceous radiolarian tests. The silica‐phase transformation started with the dissolution of the biogenic opal‐A and precipitation of opal‐CT. Subsequently, opal‐CT was recrystallized into crypto‐ and microquartz at low pH and high temperature. The length‐fast chalcedony and megaquartz occur later as infill to the cavities and pore spaces. The formation of chert is interpreted to be a result of mixing marine–meteoric waters. The effect of the freshwater diagenesis on carbonates is manifested by the dissolution of the allochems, precipitation of granular, drusy, and blocky calcite (meteoric cements), aggrading neomorphism of matrix, and calcitization of the skeletal particles. Geochemical analyses of the host carbonates indicate nearly flat REE patterns and absence of a negative Ce anomaly. This confirms the deviation from the typical seawater and supports the effect of phreatic meteoric water in the chert formation. The paragenetic relationships reveal that the chertification process was performed after dolomitization and before the carbonate meteoric cementation.

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“…Elements, such as Co, Cr, Cu, V, Fe, U, Zn, and Mo, are redox-sensitive (Algeo and Maynard, 2004;Eltom, et al, 2017). Accordingly, the correlation coefficients between redox-sensitive trace elements and ΣREYs of the NYG reef were computed to test whether changes in redox conditions have altered REY distributions ( Table 6).…”

Section: Redox Conditionsmentioning

confidence: 99%

“…Elements, such as Zr, Th, and Al, have been demonstrated to be useful indictors for evaluating the extent of contamination from terrestrial detritus (Nothdurft et al, 2004;Frimmel, 2009;Eltom et al, 2017). These elements have high concentrations in detrital minerals but very low abundances in seawater.…”

Section: Terrestrial Inputmentioning

confidence: 99%

“…REE compositions in carbonate are relatively stable and remain unaltered as long as the carbonate rocks have not undergone dissolution and recrystallization processes (Webb and Kamber, 2000;Shields and Webb, 2004;Azmy et al, 2011). Hence, the REE signatures in carbonates are regarded as proxies for paleoenvironment reconstructions in both Precambrian (Kamber and Webb, 2001;Allwood et al, 2007;Allwood et al, 2010) and Phanerozoic strata (Webb and Kamber, 2000;Nothdurft et al, 2004;Olivier and Boyet, 2006;Eltom et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

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Rare Earth Elements and Yttrium (REY) Geochemistry of Reefal Limestones in the Ordovician, Tarim Basin, NW China and their Paleoenvironment Implications

Meng

Liu

Tang

et al. 2019

Acta Geologica Sinica (Eng)

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This study examines the rare earth elements and yttrium (REY) concentrations of twenty-five samples from the reef outcrop exposed along the Lianglitage Mountain in the Ordovician, Tarim Basin in China. The concentration analysis provides constraints on the paleoenvironment during reef deposition. Based on the detailed sedimentology and petrographic work, we divide the reef facies into four sub-facies: the base facies, reef-core facies, reef-flank facies, and sealing facies. The geochemical data (such as major and trace elements, carbon and oxygen isotopes, and REYs) are further used to study the coeval seawater characteristics as well as potential diagenesis overprints. The result indicated that the diagenesis has little effect on the REY patterns of the reefal limestones. The REY concentrations of the reefal limestones are overall low (ranging from 3.69 to 19.60 ppm, arithmetic mean=10.22 ppm, SD=5.4). The PAAS-normalized REY patterns are consistently flat compared to the typical well-oxidized, shallow marine water patterns. However, the light REE (LREE) depletions, positive La anomalies, negative Ce anomalies and positive Y anomalies, suggest that these reefal limestones are likely an indicative of contemporaneous seawater REY signals. The seawater-like Y/Ho ratios (average at 37.51) further support that REY signals in these limestones are likely a reflection of seawater with little diagenetic modifications. The low Y/Ho ratios presented only in the reef-flank facies and sealing facies are likely a suggestion of detrital contamination. Hence, this study confirms that REY patterns of the limestones at the base facies and reef-core facies can record ancient seawater information, and reefs can be used as a potential geochemical proxy for paleoenvironment studies throughout the Earth's history.

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Rare earth element geochemistry of shallow carbonate outcropping strata in Saudi Arabia: Application for depositional environments prediction

Cited by 28 publications

References 26 publications

Elemental Geochemical Evidence for Depositional Conditions and Organic Matter Enrichment of Black Rock Series Strata in an Inter-Platform Basin: The Lower Carboniferous Datang Formation, Southern Guizhou, Southwest China

Elemental Geochemical Evidence for Depositional Conditions and Organic Matter Enrichment of Black Rock Series Strata in an Inter-Platform Basin: The Lower Carboniferous Datang Formation, Southern Guizhou, Southwest China

Origin of chert within the Turonian carbonates of Abu Roash Formation, Abu Roash area, Egypt: Field, petrographic, and geochemical perspectives

Rare Earth Elements and Yttrium (REY) Geochemistry of Reefal Limestones in the Ordovician, Tarim Basin, NW China and their Paleoenvironment Implications

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