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Characteristics of rare earth elements of lacustrine exhalative rock in the Xiagou Formation of Lower Cretaceous in Qingxi sag, Jiuxi basin |
| WEN Huaguo1, ZHENG Rongcai1, GENG Wei1, FAN Mingtao2, WANG Manfu2 |
| 1.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu 610059, China; 2.Yumen Oilfield, PetroChina, Yumen 735200, China; |
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Abstract The exhalative rock occurring in the Xiagou Formation of Lower Cretaceous in Qingxi sag, Jiuxi basin is a sort of a rare lacustrine white smoke type, rich in ferrodolomites and albites. This paper introduces the geological background, mineral association, and lithology of the exhalative rock, and discusses its REE geochemical characteristics and connection with hydrothermal environment. It is shown that the exhalative rock has basal characteristics of hydrothermal depositional formation of LREE⟩HREE, with positive &deltaCe and negative &deltaEu, which is different from the characteristics of marine exhalative rock. Since the REE pattern and exceptional distribution of &deltaEu and &deltaCe are highly similar to the characteristics of alkalescent tholeiitic basalt in the same layer, the exhalative rock of Xiagou Formation is considered to be closely related to the origin of basalt in the same horizon. The fact that the amount of REE of exhalative rock decreases outwards indicates that exhalative rock in the Xiagou Formation may be connected with lacustrine hydrothermal convection circulation.
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Issue Date: 05 September 2007
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