REE In Sediments Research Articles

Redox-driven geochemical partitioning of metal(loid)s in the iron-rich anoxic sediments of a recently flooded lignite mine pit: Lake Medard, NW Czechia

We evaluated the geochemical partitioning of Fe, Mn, As, V, and REE in sediments of a recently flooded open-cast lignite mine to interpret their response to recently established anoxia, and minor variations in the redox potential of its ferruginous bottom water column. Results from a sequential extraction scheme targeting reactive Fe mineral phases are combined with an assessment of sediment enrichment factors and REE systematics. Across the sediment pile metal(loid)s are being released from pre-existing authigenic phases as minor shifts in redox potential induce elemental immobilisation through co-precipitation with Fe into mineral phases of diverse reactivity. REE systematics confirms that minor oscillations in the water column's redox state can trigger swift changes in the speciation of the redox-sensitive elements. The observed metal(loid)s enrichment in the sediments can either be considered an ecological risk, if a management scenario involving solely recreational purposes is conceived, but it can also be seen as a feasible source of critical metals (e.g., REE and V) that are amenable to sustainable, secondary metal recovery endeavours. By anticipating the fate of redox-sensitive metal(loid)s in our study site, we provide parameters useful to delineate management programmes of this and similar post-mining lakes.

Dynamics of REE accumulation and fractionation in the subcolloidal fraction of bottom sediments in the Razdol’naya River–Amur Bay section, Sea of Japan

The REE contents (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) are determined by atomic emission spectroscopy in the subcolloidal fraction of bottom sediments in the Razdol’naya River–Amur Bay section. The mean contents of lanthanides in soils and river bottom sediments (before the mixing zone) are calculated. The increase in REE content and the fractioning in the series from light to middle and heavy REE in sediments of different estuary zones (river, water mixing, and marine), with the latter related to flocculation, sorption on iron and manganese hydroxides, clay minerals (hydromica, smectites), and lifetime accumulation of marine plankton, are dtermined. Via extraction of 0.5 N sodium hydroxide solution, the content of lanthanides associated with humic substances of subcolloidal fraction from the Amur Bay sediments are determined: 1.3 to 8.2% of La; 1.1 to 11% of Ce; and 0.3 to 1.5 of Gd.

Tectonic setting and provenance of the Paleoproterozoic Willyama Supergroup, Curnamona Province, Australia: Geochemical and Nd isotopic constraints on contrasting source terrain components

The Curnamona Province Paleoproterozoic Willyama Supergroup was deposited in one of a series of basins developed along the eastern margin of the Proterozoic Australian continent. Linked tectonic evolutionary paths have previously been drawn between the northern and southern Australian cratons, based in part on similar depositional ages and stratigraphy, and tectonic evolutions of the sedimentary basins of this region. Detailed geochemical and Nd isotopic analyses from the Paleoproterozoic Willyama Supergroup suggest an intracratonic source for the lower parts of the sequence, with introduction of a significantly more juvenile source region for the ca. ≤1650 Ma uppermost part, marking a significant change in tectonic regime. The geochemical and Nd isotopic signature of both mature quartz-rich and pelitic sedimentary rocks of the lower part of the Willyama Supergroup support a dominant intracratonic central and northern Australian provenance, marked by a recycled and felsic upper crustal composition unusually enriched in REE and incompatible elements. Sedimentary REE abundance patterns double those of the Post-Archean Australian Shale average. Initial ɛ Nd values between −7 and −4 suggest old upper crustal recycled source basement. In contrast, the uppermost part of the Willyama sedimentary section has REE patterns much more like Post-Archean upper crustal shale average, and is characterised by more primitive initial ɛ Nd values of around −3 to 0. Significant ca. 1650 Ma felsic source terranes with such a juvenile Nd isotope signature are unknown in Australia. The data suggest proximity of a relatively juvenile as yet unidentified source to the present-day east of the basin. Some pre-Rodinian reconstruction models place eastern Australia proximal to southwestern Laurentia, which contains rocks of appropriate geochemical and isotopic signatures and could have delivered juvenile felsic sediment into the Willyama basin.

Global Environmental Catastrophe at About 2300 Ma

It was found that the sedimentary REE patterns had changed at 2300 Ma at the southern margin of North China Craton (Chen and Zhao, 1997), resulting from the variation in oxygen fugacity of the hydrosphere and atmosphere. Since this discovery, we have studied comprehensively the changes in surficial environment at this time, and obtained a series of inspiring achievements which encourages us to exchange our research works and ideas with colleagues. Therefore, this paper attempts to display the evidence for a catastrophe at about 2300 Ma. Data shown in Table 1 support the suggestion that the geological environment (including sedimentary sphere, biosphere, hydrosphere and atmosphere) underwent a global catastrophe caused by extraterrestrial factors at about 2300 Ma. The catastrophe resulted in an obvious weakening of volcanism, the formation of an O2-rich atmosphere, a leap in palaeontological evolution, a sharp decrease in climatic temperature, and some other subsequent changes in rocks, ore deposits and element distributions. Our summary of these changes supports the points of view of Frakes (1979), Kasting (1993) and Schidlowski (1983). They had also argued that the atmosphere became oxidic from anoxic during the Palaeoproterozoic, especially around 2300 Ma. Now the time for environmental change is tentatively determined at 2300 Ma, the proof is as follows: (1) the strata over the boundary have not yet acquired convincing isotopic ages more than 2300 Ma; (2) the upper age limit of deposition for the Witwatersrand supergroup before the catastrophe is 2340 Ma (Rb-Sr isochron dating) (Frakes, 1979), and the Rb-Sr isochron age of the tuff interbeds in the Elliot Lake Group in the bottom of Huronian supergroup is 2330 Ma, they both abound with Rand-type Au-U deposits, so the catastrophe probably took place after 2330 Ma. The Cobalt Group, the topmost strata of the Huronian Supergroup, containing red beds, evaporates and carbonate rocks, showing clear negative sedimentary Eu-anomalies, was obviously formed after the catastrophe and dated at 2288+77 Ma (Rb-Sr isochron age for whole rocks) (Mossman and Harron, 1983), which indicates that the catastrophe took place before 2288 Ma. Hence, the catastrophe might occur between 2330 Ma and 2288 Ma, i.e. 2300_+ 30 Ma.

Contrasting REE Geochemical Features Between Archaean and Proterozoic Khondalite Series of North China Craton

Taylor and Mclennan (1985) have thoroughly described the sedimentary REE geochemical transition from Archaean to Proterozoic, i.e. from positive or slight Eu-anomaly to clear Eu-depletion. Gibbs et al. (1986), Condie (1993) and other researchers have proved wrong the views of Taylor and Mclennan. They argue that the transitions have been deduced from an incorrect comparison of Proterozoic platform-type sediments with those from Archaean greenstone, as if comparing an orange with an apple. To verify their views, we have studied the REE geochemical characteristics of khondalite series of the Archaean and Proterozoic of the North China Craton (NCC) and found great differences between them.

Errors involved in the taylor’s model for the crustal composition and evolution—an analysis of their causers

It is suggested in this paper that the famous Taylor’s model for the composition and evolution of the continental crust consists of three closely related key links. These links include an assumption that the surficial environment has no effect on the sedimentary REE patterns and the REE patterns in shales can reflect the composition of their provenance, a discovery about the discrepancy of sedimentary REE patterns between Archean and Proterozoic, and a deduction that there was a global scale K-granitoid event at the end of the Archean. Based on a detailed discussion, this paper substantially negates the rationality of the Taylor’s model and argues that its three critical links be three great errors indeed. Moreover, some other deficiencies or problems it confronts are described in this paper. The authors suggest that what led to the errors involved in the Taylor’s model is its wrongly neglecting the effect of the sedimentary environment on the chemical composition of sediments, and that the environment should be an important factor affecting the distribution patterns of trace elements in the sediments.

REE geochemical evolution and its significance of early precambrian metamorphic terrain, Wuyang, Henan

The supracrustal rocks of the Wuyang metamorphic terrain are divided into the Zhao ’anzhuang, Tieshanmiao and Yangshuwan Formations. These three Formations were dated at 3000–2550 Ma, 2550–2300 Ma and 2300–2200 Ma, respectively. ΣREE and La/Yb)n of the Zhao ’anzhuang Formation volcanic rocks are obviously higher than those of the Tieshanmiao Formation equivalents, suggesting a sedimentary gap (2550 Ma boundary) between these two formations. The Zhao ’anzhuang Formation is older than the Tieshanmiao Formation. The sediments of these two Formations show no obvious differences in REE and are generally characterized by low ΣREE and positive Eu anomalies. On the contrary, the sediments of the Yangshuwan Formation are characterized by high ΣREE and negative Eu anomalies. Detailed discussions demonstrate that the Yangshuwan Formation was deposited in an oxidizing environment whereas the other two formations were formed in a reducing environment. At the end of the evolution of the Tieshanmiao Formation about 2300 Ma ago, the sedimentary environment was transformed from reducing to oxidizing. On the basis of the SHAB (soft/hard acid and base) theory, an oxidation-reduction model for sedimentary REE evolution has been established. It is proposed that the mantle tends to become gradually depleted in REE, especially in LREE, and the indices ΣREE and La/Yb)n of mantle-derived volcanic rocks also tend to become lower and lower.

The provenance of Archean clastic metasediments in the Narryer Gneiss Complex, Western Australia: Trace element geochemistry, Nd isotopes, and U-Pb ages for detrital zircons

Clastic metasedimentary rocks of mid-Archean age from the Mt. Narryer and Jack Hills metasedimentary belts have REE patterns resembling those of mid- to late-Archean pelitic-quartzitic cratonic sequences elsewhere, and post-Archean continental rocks in general. Detrital zircons in the metasediments range in age from ca. 3000 to 3700 Ma. This indicates a provenance from mature cratonic sources controlled by K-rich granitic rocks. Additional minor sediment sources were identified as older, mainly chemical sedimentary sequences, ultramafic rocks, and felsic rocks characterized by low HREE contents, perhaps of tonalitic affinity. The association of the near-shore/fluviatile clastic association studied here with extensive turbiditic and chemical sedimentary sequences indicates these sources formed part of a (rifted ?) cratonic margin ca. 3 Ga ago. Differences between sedimentary REE patterns and those in the surrounding 3.73-3.0 Ga orthogneiss terrain, and between detrital zircon ages and the age distribution in the gneisses, suggest that the present association of the metasedimentary belts with the orthogneiss terrain is of tectonic origin. The occurrence of detrital zircons with U-Pb ages > 4 Ga in certain quartzites and conglomerates of the Jack Hills and Mt. Narryer metasedimentary sequences indicates a further, most likely granitic, source. ϵ Nd ( T Dep ) values in Jack Hills metasediments vary widely (+5 to −12) but have a smaller range in the Mt. Narryer belt (−5 to −9). The lowest ϵ Nd values of both sequences are interpreted to reflect the presence of detritus derived from 4.1–4.2 Ga old LREE-enriched continental crust in proportions considerably larger (≥ 10%) than estimated previously from the abundance of pre-4 Ga detrital zircons (≈3%). This would imply the former existence of significant volumes of pre-4 Ga continental crust in the provenance of the Mt. Narryer and Jack Hills metasediments.

Rare-earth element behaviour associated with strata-bound scheelite mineralisation (Broken Hill, Australia)

Strata-bound scheelite mineralisation occurs within calc-silicates of a metamorphosed Proterozoic volcano-sedimentary sequence and is spatially related to lenticular bodies of basaltic volcanics, tourmalinites and quartz-gahnite rocks. A pre-metamorphic alteration halo has been detected within the enclosing basalts in the form of elevated Fe, As and Eu contents which were formed by reducing and/or high-temperature hydrothermal fluids. Changing Eh conditions during alteration gave rise to Ce-enriched basalts and sediments proximal and distal to the mineralisation. The calc-silicate horizon represents a hydrothermally altered and metamorphosed carbonate-rich sediment, as indicated by calc-silicate pods containing primary sedimentary REE patterns. The calc-silicate horizon displays a lateral zonation from an unmineralised, hydrothermally altered LREE-depleted core, to mineralised LREE-depleted, HREE-and Eu-enriched margins. The wide range of REE patterns, and the distinctive variation in REE spectra from the centre to the margins is due to the progressive dissolution of carbonates, and the deposition of scheelite with decreasing temperature from the W-Fe-As-Eu-enriched ore fluids.

The chemical composition of the Archaean crust

Summary Three separate observations, from sedimentary rock compositions, subduction zone igneous rocks and heat flow constraints combine to suggest that the composition of the Archaean crust was distinct from that of the present-day continental crust. The sedimentary REE patterns are consistent with derivation of the upper crust from a 1:1 mixture of the Archaean bimodal basic-felsic suite. The andesite model, while adequate to account for present-day continental growth does not provide enough Cr and Ni for the Archaean crust. Average crustal component heat flow values of 14 mW m −2 for Archaean terrains are significantly lower than the post-Archaean average of 23 mW m −2 for crustally produced heat. Correlations from the sedimentary trace element data provide Archaean upper crustal values of 1.5% K, 5.7 ppm Th and 1.5 ppm U. Heat flow constraints restrict such compositions to the upper layers. The total crustal values are consistent with a 2:1 basic/felsic composition, and give values for the total crust of 0.75% K, 2.9 ppm Th and 0.75 ppm U, which provide crustal heat flow components of 14 mW m −2 for a 30 km thick crust and 19 mW m −2 for a 40 km crust.

Geochemistry of the Archean Yellowknife Supergroup

The Archean Yellowknife Supergroup (Slave Structural Province. Canada) is composed of a thick sequence of supracrustal rocks, which differs from most Archean greenstone belts in that it contains a large proportion ( ~ 80%) of sedimentary rocks. Felsic volcanics of the Banting Formation are characterized by HREE depletion without Eu-anomalies, indicating an origin by small degrees of partial melting of a mafic source, with minor garnet in the residua. Granitic rocks include synkinematic granites [HREE-depleted; low ( 87Sr 86Sr ) I], post-kinematic granites [negative Eu-anomalies, high ( 87Sr 86Sr ) I] and granitic gneisses with REE patterns similar to the post-kinematic granites. Sedimentary rocks (turbidites) of the Burwash and Walsh Formations have similar chemical compositions and were derived from 20% mafic-intermediate volcanics, 55% felsic volcanics and 25% granitic rocks. Jackson Lake Formation lithic wackes can be divided into two groups with Group A derived from 50% mafic-intermediate volcanics and 50% felsic volcanics and Group B, characterized by HREE depletion, derived almost exclusively from felsic volcanics. REE patterns of Yellowknife sedimentary rocks are similar to other Archean sedimentary REE patterns, although they have higher La N Yb N . These patterns differ significantly from typical post-Archean sedimentary REE patterns, supporting the idea that Archean exposed crust had a different composition than the present day exposed crust.