| A Study on the Forming Conditions of Basalts in Seamounts of the South China Sea |
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| 摘 要： |
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| 关 键 词： | 玄武岩 岩石化学 包裹体 地球气压计 南海 火山岩 |
A study on the forming conditions of basalts in seamounts of the South China Sea |
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| Authors: | Li Zhaolin Qiu Zhili Qin Shecai Pang Xuebin Liang Dehua Teng Yunye Li Yang |
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| Institution: | (1) Department of Geology, Zhongshm University, 510275 Guangzhou;(2) Guangzhou Marine Geology Survey, Ministry of Geology and Mineral Resources, 510075 Guangzhou |
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| Abstract: | Volcanic rocks in seamounts of the South China Sea consist mainly of alkali basalt, tholeiitic basalt, trachyandesitic pumice,
dacite, etc. Inclusions in the minerals of the volcanic rocks are mainly amorphous melt inclusions, which reflects that the
volcanic rocks are characterized by submarine eruption and rapid cooling on the seafloor. Furthermore, fluid-melt inclusions
have been discovered for the first time in alkali basalts and mantle-derived xenoliths. indicating a process of differentiation
between magma and fluid in the course of mantle partial melting. Alkali basalts and inclusions may have been formed in this
nonhomogeneous system.
Rock-forming temperatures of four seamounts were estimated as follows: the Zhongnan seamount alkali basalt 1155 ∼ 1185 °C;
the Xianbei seamount alkali basalt 960 ∼ 1200 °C; tholeiitic basalt 1040 ∼ 1230 °C; the Daimao seamount tholeiitic basalt
1245 ∼ 1280 °C; and the Jianfeng seamount trachyandestic pumice 880 ∼ 1140 °C. Equilibrium pressures of alkali basalts in
the Zhongnan and Xianbei seamounts are 13.57 and 8.8 × 108 Pa, respectively. Pyroxene equilibrium temperatures of mantle xenoliths from the Xianbei seamount were estimated at 1073
∼ 1121 °C, and pressures at (15.58 ∼ 22.47)×108Pa, suggesting a deep-source (e.g. the asthenosphere) for the alkali basalts.
This project was financially supported by the National Natural Science Foundation of China and Guangzhou Marine Geology Survey. |
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| Keywords: | seamount basalt petrochemistry melt inclusion geobarometer South China Sea |
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