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cerium anomaly and cerium thermodynamics in the sea water

Acta Oceanologica Sinica 1994年第3期13卷 389-400页

作者： Wang Yunliang and Zang Desen(The Third Department,Chengdu University of Technology, Chengdu 610059, China)

cerium anomaly in a marine carbonatite could be used as an indicator of redox condition in the paleosea- water. The bottom sea water of the Angola Basin and the Brazil Basin (SOuth Atlantic Ocean) was anoxic duringCretaceous period. At about 58×106-54×106 a BP, the sea water of the South Atlantic Ocean became oxidizedcondition which was similar to that of the modern Atlantic Ocean. This paper presents a new cerium redox thermodynamic equation which could explain the long-standing problems, such as the different characteristics of the ceriumanomalies in the sea water and river water and why there are positive cerium anomalies in the surface sea water,*** reveals that at 58×106-54×106 a BP, the plates of Africa and South America were separatedfrom each other thoroughly and the unified Atlantic Ocean took shape. We suggest that the Alpine and Himalayanmovements were in synchronism.

关键词： cerium anomaly carbonate thermodynamics

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Rare earth elements(REE)and isotope composition(δ^(13)C andδ^(18)O)of manganese ores of Chiatura deposit(Georgia):features of ore formation and genesis

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Acta Geochimica 2023年第4期42卷 779-801页

作者： Vladimir N.Kuleshov Andrey Yu.Bychkov Irina Yu.Nikolaeva Maria E.Tarnopolskaya Geological Institute Russian Academy of SciencesPyzhevskii Per.7MoscowRussia 119017 Lomonosov Moscow State University Leninskie Gory1MoscowRussia 119899

The rare earth elements(REE)geochemistry and the isotope(δ^(13)C,δ^(18)O)composition of manganese ores of the Chiatura(Georgia)deposit were *** of the major features of all types of manganese ores is negative cerium(Ce/Ce*_(PAAS))anomaly and the absence of europium(Eu/Eu*_(PAAS))*** oolitic manganese ores were formed in oxic shallow marine *** content and distribution of REEs(in particular Ce and Eu)in these ores are connected mainly with ferrous *** performed C-and O-isotope research in Mn-carbonates(oolitic and massive)has indicated that carbonate ores were formed by the participation of isotopic ally light CO_(2)which is a result of the oxidation of organic matter in the sediment strata by reducing environments of early diagenesis(and,partially,catagenesis)*** negative cerium anomalies in the studied carbonate ores reflect the specific REE patterns in pore waters of sediments of earlier isdiagenesis zone of the Oligocene Chiatura's *** deficiency of cerium in this zone remains debatable and requires further *** of manganese carbonates took place multistage by the input of incisional solutions of different chemistry into sea bottom waters and *** absence of europium anomaly indicates about lack of hydrothermal solution input.

关键词： REE cerium anomaly Carbon and oxygen isotope geochemistry Oxide and carbonate manganese ores Chiatura deposit

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Origin and geochemical characterization of the glauconites in the Upper Cretaceous Lameta Formation, Narmada Basin, central India

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Journal of Palaeogeography 2018年第2期7卷 99-116页

作者： Udita Bansal Santanu Banerjee Dhiren K.Ruidas Kanchan Pande Department of Earth Sciences Indian Institute of Technology Bombay

This study presents geochemical characteristics of glauconites in estuarine deposits within the Maastrichtian Lameta Formation in central India. Resting conformably over the Bagh Group, the Lameta Formation consists of ~4-5 m thick arenaceous, argillaceous and calcareous green sandstones underlying the Deccan Traps. The sandstone is friable, medium-to coarse-grained, well-sorted and thoroughly crossstratified, and contains marine fossils. Detailed petrography, spectroscopy and mineral chemistry indicates unique chemical composition of glauconite with high KO, MgO, AlOand moderate TFeO. Glauconite is formed by the replacement of K-feldspars, initially as stringers in the cleavages and fractures of feldspars. Incipient glauconite subsequently evolves fully, appearing as pellets. Fully-evolved glauconite pellets often leave tiny relics of K-feldspar. XRD exhibits characteristic peak of 10A from basal(001)reflection of glauconite, indicating the "evolved" character. The KO content of glauconites in the Lameta Formation varies from 5.51% to 8.29%, corroborating the "evolved" to "highly-evolved" maturation *** TFeOcontent of glauconite varies from 12.56% to 18.90%. The PASS-normalized-REE patterns of glauconite exhibit a "hat-shape" confirming the authigenic origin of glauconites. The slightly-negative to slightly-positive Ce anomaly value and the moderate TFeOcontent of glauconite agree well with a suboxic,estuarine condition. The replacement of K-feldspar by the glauconite contributes towards the high KO content. Compositional evolution of glauconites in the Lameta Formation is similar to those observed in many Precambrian sedimentary sequences.

关键词： Glauconite Estuary Mineral chemistry cerium anomaly Redox condition Lameta Formation Narmada Basin

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