| Major Element Compositions and Rare—earth Element Abundaces of Cenozoic Basalts in Eastern China：Implications for a Pressure Control over LREE／HREE Fractionation in Continental Basalt |
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| 引用本文： | 刘丛强 AKIMASAMASUDA 等.Major Element Compositions and Rare—earth Element Abundaces of Cenozoic Basalts in Eastern China：Implications for a Pressure Control over LREE／HREE Fractionation in Continental Basalt[J].中国地球化学学报,1992,11(4):289-313. |
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| 作者姓名： | 刘丛强 AKIMASAMASUDA |
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| 作者单位： | [1]InstituteofPhysicalandChemicalResearch,Hirosawa2－1,Wako－shi,Saitama,351－01,Japan [2]DepartmentofChemistr,Hirosawa2－1,Wako－shi,Saitama,351－01,Japan |
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| 摘 要： | Major element compositions and rare-earth element (REE) and transition element(Ni,Cr and V) abundances have been determined on 44 basalt samples from eastern China.These basalts have SiO2 contents ranging from 38.63 to 55.24(wt.%),and Na2O K2O from 3.1 to 9.4(wt.%).Ni and Cr abundances are largely variable,respectively falling in ranges 60-605 and 78-1150 ppm.REE abundances,especially light rare-earth elements(LREE), are highly variable.La/Sm and La/Yb ratios vary 2.8 to 7.6 and 1.8 to 8.1. Although the segregation mainly of olivine and clinopyroxene is requested to account for the vari-able and low MgO,CaO/Al2O3,Cr and Ni characteristic of these basalts studied here,the differ-ences in REE composition of the basalts are still related mainly to the partial melting process.Obvious varations in REE abundances could be principally attributed to the partial melting process.Obvious variations in REE abundances could be principally attributed to the partial melting processes that took place at different depths,in spite of some variations caused by the fractional crystallization processes.REE abundances and La/Sm and La/Yb ratios systematically decrease with increasing SiO2,which probably indicated that the basaltic magma derived from a deeper level has higher LREE and LREE/HREE ratios than that from a shallower level.As viewed from the fact that the D^Yb/D^La ratios of clinopyroxenes in the basaltic system increase with increasing pressure,the increase of LREE/HUEE ratios with increasing melting depth can be interpreted as the pressure dependence of bulk D^HREE/D^LREE ratios of silicate minerals,in addition to the pressure control over the melting degree.
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| 关 键 词： | 新生代 稀土元素 玄武岩 华东地区 分布规律 橄榄石 斜辉石 |
Major element compositions and rare-earth element abundances of Cenozoic basalts in eastern China: Implications for a pressure control over LREE/HREE fractionation in continental basalt |
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| Congqiang Liu,Akimasa Masuda,Guanghong Xie.Major element compositions and rare-earth element abundances of Cenozoic basalts in eastern China: Implications for a pressure control over LREE/HREE fractionation in continental basalt[J].Chinese Journal of Geochemistry,1992,11(4):289-313. |
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| Authors: | Congqiang Liu Akimasa Masuda Guanghong Xie |
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| Institution: | (1) Institute of Physical and Chemical Research, Hirosawa 2-1, Wako-shi, 351-01 Saitama, Japan;(2) Department of Chemistry, Faculty of Science, The University of Tokyo, Hongo 113, Tokyo, Japan;(3) Institute of Geochemistry, Academia Sinica, 510640 Guangzhou |
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| Abstract: | Major element compositions and rare-earth element (REE) and transition element (Ni, Cr and V) abundances have been determined
on 44 basalt samples from eastern China. These basalts have SiO2 contents ranging from 38.63 to 55.24 (wt. %), and Na2O+K2O from 3.1 to 9.4 (wt. %). Ni and Cr abundances are largely variable, respectively falling in ranges 60–605 and 78–1150 ppm.
REE abundances, especially light rare-earth elements (LREE), are highly variable. La/Sm and La/Yb ratios vary from 2.8 to
7.6 and 1.8 to 8.1.
Although the segregation mainly of olivine and clinopyroxene is requested to account for the variable and low MgO, CaO/Al2O3, Cr and Ni characteristic of these basalts studied here, the differences in REE composition of the basalts are still related
mainly to the partial melting process. Obvious variations in REE abundances could be principally attributed to the partial
melting processes that took place at different depths, in spite of some variations caused by the fractional crystallization
processes. REE abundances and La/Sm and La/Yb ratios systematically decrease with increasing SiO2, which probably indicates that the basaltic magma derived from a deeper level has higher LREE and LREE/HREE ratios than that
from a shallower level. As viewed from the fact that the DYb/DLa ratios of clinopyroxenes in the basaltic system increase with increasing pressure, the increase of LREE/HREE ratios with
increasing melting depth can be interpreted as the pressure dependence of bulk DHREE/DLREE ratios of silicate minerals, in addition to the pressure control over the melting degree.
Visiting scholar from the Institute of Geochemistry, Academia Sinica. |
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