Rare earth element behavior in soils and salt pan sediments of a semi-arid granitic terrain in the Western Cape, South Africa

Compton, John S.; White, Richard Allen; Smith, Meris

doi:10.1016/s0009-2541(03)00239-0

Cited by 177 publications

(89 citation statements)

References 35 publications

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“…Enrichment of REE due to weathering is also apparent from our data, which demonstrate a bowl shape. This pattern is caused by light-REE-enrichment due to clay formation and heavy-REE-enrichment due to carbonate in soils (Compton et al, 2003) and paleosols (Metzger et al, 2004). Barite-bearing Kida paleosols did not have a parent material unusual for Cucaracha Formation paleosols.…”

Section: Pedogen1c Barite?mentioning

confidence: 99%

Middle Miocene Global Change and Paleogeography of Panama

Retallack¹,

Kirby²

2007

PALAIOS

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Fossil leaves in the middle Miocene Cucaracha Formation along the Panama Canal are 10-15 cm long, thick, and entire-margined; fossil pollen is also dicot dominated, as expected for wet tropical forests. Fossil woods include palms and ring-porous dicots, with smooth bark as is found in weakly seasonal tropical climates. In contrast, late Hemingfordian to early Barstovian mammals of the Cucaracha Formation are the same as those found in Nebraska, Kansas, and Florida, where climate was drier and cooler and vegetation more open. Cucaracha paleosols reconcile these differences as evidence of a mosaic of swamps to mangal (mangrove forests) preserving plants and dry uplands preserving mammals. A dozen pedotypes represent as many vegetation types, including mangrove, fresh-water and marineinfluenced swamp, early successional riparian woodland, colonizing forest, dry tropical forest, and woodland. Many paleosols have calcareous nodules, and some have pedogenic barite nodules. Depth to carbonate and paleosol thickness with carbonate indicate mean annual precipitation of 573-916 ± 147 mm and mean annual range of precipitation of 27-65 ± 22 mm. Chemical analyses of paleosol Bt horizons confirm mean annual precipitation of 296-1142 mm and mean annual temperature of 15-16 ± 4.4°C. Low precipitation and temperature estimates imply a rain shadow from a high (1400-4000 m) volcanic mountain range to the west, with continuous land connection to allow immigration of mammals from North America. Partial enclosure of the Caribbean Sea by a mountainous Panama peninsula, as well as by Antillean arcs, initiated high Caribbean marine temperature and salinity well before Pliocene isthmian closure.

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Section: Pedogen1c Barite?mentioning

confidence: 99%

Middle Miocene Global Change and Paleogeography of Panama

Retallack¹,

Kirby²

2007

PALAIOS

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“…The chemical compositions were determined from the substitution of Ce 3+ in the Ca 2+ site. More recently, in some natural apatites, the cerium was found to be tetravalent depending on the oxidizing conditions considered but not homogeneously distributed in the structure [12,13]. Although a lot of natural Th-bearing apatites were considered for the Th-U thermochronology [14][15][16], no study was published on synthetic Th-apatites except the preparation of the full-silicated apatite Ca 6 Th 4 (SiO 4 ) 6 O 2 reported by Engel [17].…”

Section: Introductionmentioning

confidence: 99%

Synthesis and characterization of thorium-bearing britholites

Terra

Audubert

Dacheux

et al. 2006

Journal of Nuclear Materials

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In the field of the immobilization of tri-and tetravalent minor actinides, apatites and especially britholites were already proposed as good candidates. In order to simulate tetravalent minor actinides, the incorporation of thorium, through dry chemical routes, was studied in britholite samples of general formula Ca 9 Nd 1-x Th x (PO 4 ) 5-x (SiO 4 ) 1+x F 2 . The study showed that the incorporation of thorium was effective whatever the thorium reagent used or the grinding conditions considered. Nevertheless, it appeared necessary to use mechanical grinding (30 Hz, 15 minutes) before heating treatment (T = 1400°C, 6 hours) to improve the reactivity of powders and the sample homogeneity. In these conditions, the incorporation of thorium in the britholite structure occurred above 1100°C. The heating treatment at 1400°C led to single phase and homogeneous compounds. This work also underlined the necessity to prefer the coupled substitution (Nd 3+ , PO 4 3-) ⇔ (Th 4+ , SiO 4 4-) instead of (Nd 3+ , F -) ⇔ (Th 4+ , O 2-), in order to prepare pure and single phase samples in all the range of composition examined.3

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“…Minor REE variations across the bauxite horizons probably reflect Eh and pH fluctuations during formation of each horizon [72]. Mobility of LREEs depends on pH variation in the bauxite profile in the weathering system.…”

Section: Discussionmentioning

confidence: 99%

Mineralogy, Geochemistry and Stable Isotope Studies of the Dopolan Bauxite Deposit, Zagros Mountain, Iran

et al. 2016

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Abstract:The Dopolan deposit is a Mediterranean-type bauxite located in the Zagros Fold-Thrust Zone, Iran. This deposit consists of five lithological members including iron-rich, clay-rich, oolitic, pisolitic and organic matter-containing bauxites. The mineralogy of the deposit includes diaspore, boehmite, and kaolinite, nacrite, with minor pyrite, anatase and rutile. Geochemical studies show that light rare earth elements (LREEs) are enriched relative to heavy rare earth elements (HREEs) in all members, supporting an authigenic origin. Mass changes based on Ti as an immobile element indicate that conventionally-immobile elements (Al, Nb, Ta, Zr, Hf) are enriched in situ in the residual units, whereas mobile elements (K, Ca, Si) were depleted during bauxitization. This study shows that the Khaneh-Kat argillitic dolomite is the likely parent rock. The δ 18 O (7.63‰to 9.35‰) and δD values (´49.91‰to´66.49‰) for kaolinite in the bauxite samples suggest equilibration with meteoric waters which supports a supergene origin. Bauxitization occurred in a warm climate with relatively constant isotopic composition suggesting climate stability during the development of bauxite horizons and remobilization of Al (with formation of secondary boehmite). The δ 13 C values of calcite (´7.3‰) in the bauxite support the idea that the Khaneh-Kat Formation has experienced post-depositional isotope exchange with meteoric waters during the karstification process.

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Rare earth element behavior in soils and salt pan sediments of a semi-arid granitic terrain in the Western Cape, South Africa

Cited by 177 publications

References 35 publications

Middle Miocene Global Change and Paleogeography of Panama

Middle Miocene Global Change and Paleogeography of Panama

Synthesis and characterization of thorium-bearing britholites

Mineralogy, Geochemistry and Stable Isotope Studies of the Dopolan Bauxite Deposit, Zagros Mountain, Iran

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