| Study on lithogeochemistry of Middle Jurassic basalts from southern China represented by the Fankeng basalts from Yongding of Fujian Province |
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| 摘 要： | There exists an E-W trending Middle Jurassic volcanic zone in southern China. The Fankeng basalts in the Yongding basin of Fujian Province are considered to be a typical example. The Fankeng basalts have TiO2 contents in the range of 1.92%-3.21%. They are classified as high-Ti basalts. They also have higher total Fe (averaging FeO* = 11.09%). The Middle Jurassic Fankeng basalts from southwestern Fujian have obvious distinctive lithogeochemical features from early Cre- taceous basalts from southeastern coast of China. They have higher HFSE, such as Th, Nb, Ta, Zr and Ti. Their element ratios related with HFSE, such as Zr/Ba, La/Nb, La/Ta ,Zr/Y, Ti/Y, Ba/Nb, K/Ti and Rb/Zr are similar to those of OIB. The most samples have ε Nd(T) of-0.70-0.24, which are near chondrite. Some samples have higher ε Nd(T) of 1.87-3.55.Therefore, these basaltic magmas might be derived from depleted asthenospheric mantle. The lithogeochemical characteristics of the Fankeng basalts may be caused by interaction between asthenosphere and lithosphere at the time. The (Early-) Middle Jurassic basalts and gabbros from southeastern Hunan, southern Jiangxi and northern Guangdong provinces show similar geochemical features to those of the Fankeng basalts from the Yongding of Fujian. Occurrence of these OIB-type basalts in the area may be regarded as the petrological mark of upwelling of asthenosphere at the time. Upwelling of asthenosphere has led to tectonic extension and the formation of rifted basin in the area.
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| 收稿时间： | 24 August 2004 |
| 修稿时间： | 21 April 2005 |
Study on lithogeochemistry of Middle Jurassic basalts from southern China represented by the Fankeng basalts from Yongding of Fujian Province |
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| Authors: | ZHOU Jincheng JIANG Shaoyong WANG Xiaolei YANG Jinghong ZHANG Mengqun |
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| Institution: | 1. State Key Laboratory of Mineral Deposit Research,Nanjing University,Nanjing 210093,China;Department of Earth Sciences,Nanjing University,Nanjing 210093,China
2. Modem Analysis Center,Nanjing University,Nanjing 210093,China |
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| Abstract: | There exists an E-W trending Middle Jurassic volcanic zone in southern China. The Fankeng basalts in the Yongding basin of
Fujian Province are considered to be a typical example. The Fankeng basalts have TiO2 contents in the range of 1.92%–3.21%. They are classified as high-Ti basalts. They also have higher total Fe (averaging FeO*
= 11.09%). The Middle Jurassic Fankeng basalts from southwestern Fujian have obvious distinctive lithogeochemical features
from early Cretaceous basalts from southeastern coast of China. They have higher HFSE, such as Th, Nb, Ta, Zr and Ti. Their
element ratios related with HFSE, such as Zr/Ba, La/Nb, La/Ta, Zr/Y, Ti/Y, Ba/Nb, K/Ti and Rb/Zr are similar to those of OIB.
The most samples have ɛ
Nd(T) of −0.7–0.24, which are near chondrite. Some samples have higher ɛ
Nd(T) of 1.87–3.55. Therefore, these basaltic magmas might be derived from depleted asthenospheric mantle. The lithogeochemical
characteristics of the Fankeng basalts may be caused by interaction between asthenosphere and lithosphere at the time. The
(Early-) Middle Jurassic basalts and gabbros from southeastern Hunan, southern Jiangxi and northern Guangdong provinces show
similar geochemical features to those of the Fankeng basalts from the Yongding of Fujian. Occurrence of these OIB-type basalts
in the area may be regarded as the petrological mark of upwelling of asthenosphere at the time. Upwelling of asthenosphere
has led to tectonic extension and the formation of rifted basin in the area. |
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| Keywords: | interaction between asthenosphere and lithosphere lithogeochemistry basalts Middle Jurassic southern China |
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