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 duringCre...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,etc.Investigation 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.展开更多
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 studied.One of the major features of all types of manganese ores is negativ...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 studied.One 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))anomaly.Oxide oolitic manganese ores were formed in oxic shallow marine environments.The content and distribution of REEs(in particular Ce and Eu)in these ores are connected mainly with ferrous oxides.The 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)zone.Obtained 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 basin.The deficiency of cerium in this zone remains debatable and requires further study.Formation of manganese carbonates took place multistage by the input of incisional solutions of different chemistry into sea bottom waters and sediments.The absence of europium anomaly indicates about lack of hydrothermal solution input.展开更多
文摘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,etc.Investigation 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.
基金accomplished in accordance with the Research Program of the Geological Institute of the Russian Academy of Sciences。
文摘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 studied.One 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))anomaly.Oxide oolitic manganese ores were formed in oxic shallow marine environments.The content and distribution of REEs(in particular Ce and Eu)in these ores are connected mainly with ferrous oxides.The 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)zone.Obtained 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 basin.The deficiency of cerium in this zone remains debatable and requires further study.Formation of manganese carbonates took place multistage by the input of incisional solutions of different chemistry into sea bottom waters and sediments.The absence of europium anomaly indicates about lack of hydrothermal solution input.
