Skip to Main Content
Book Chapter

Jurassic intraplate magmatism in southern Hunan–eastern Guangxi: 40Ar/39Ar dating, geochemistry, Sr–Nd isotopes and implications for the tectonic evolution of SE China

By
Xian-Hua Li
Xian-Hua Li
1
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences Guangzhou 510640, Guangdong, China lixh@gig.ac.cn
Search for other works by this author on:
Sun-Lin Chung
Sun-Lin Chung
2
Department of Geosciences, National Taiwan University Taipei, Taiwan
Search for other works by this author on:
Hanwen Zhou
Hanwen Zhou
1
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences Guangzhou 510640, Guangdong, China lixh@gig.ac.cn
3
Faculty of Earth Sciences, China University of Geosciences
,
Wuhan 430074, Hubei
Search for other works by this author on:
Ching-Hua Lo
Ching-Hua Lo
2
Department of Geosciences, National Taiwan University Taipei, Taiwan
Search for other works by this author on:
Ying Liu
Ying Liu
1
Guangzhou Institute of Geochemistry, Chinese Academy of Sciences Guangzhou 510640, Guangdong, China lixh@gig.ac.cn
Search for other works by this author on:
Chang-Hwa Chen
Chang-Hwa Chen
4
Institute of Earth Sciences, Academia Sinica
,
Taipei, Taiwan
Search for other works by this author on:
Published:
January 01, 2004

Abstract

The Mesozoic geology of SE China is characterized by intensive and widespread magmatism. However, the tectonic regime that accounted for the Mesozoic magmatism has been an issue with little consensus. A comprehensive study of 40Ar–39Ar dating, geochemistry and Sr–Nd isotopes has been conducted on basalts from southern Hunan and syenite intrusions from eastern Guangxi. Three episodes of Jurassic magmatism, i.e. alkaline basalts of c.175 Ma in age, syenitic intrusions of c.160 Ma and high-Mg basalts of c.150 Ma, are identified. The older, c.175 Ma alkaline basalts are characterized by low Sr (ISr = 0.7035–0.7040) and high Nd (εNd(T) = 5 to 6) isotopic compositions and OIB-like trace-element patterns (e.g. Nb/La > 1). In contrast, the younger, c.150 Ma high-Mg basalts have high Sr (ISr c.0.7054) and low Nd (εNd(T) c.−2) isotopic compositions and incompatible trace-element patterns of arc affinity. The c.160 Ma syenitic intrusions display a relatively large range of Sr and Nd isotopic compositions (ISr = 0.7032–0.7082, εNd(T) = 5.5 to −4.1), with the Qinghu syenites having the lowest ISr, highest εNd(T) and OIB-type incompatible trace-element patterns analogous to the c.175 Ma alkaline basalts. Such a secular variation in rock types and geochemical and isotopic characteristics reveals changes in melt segregation depth and mantle sources, which are inferred to have resulted from the post-Indosinian orogenic lithosphere extension and thinning. The c.175 Ma alkaline basalts are suggested to have formed by small degrees of decompression melting of the asthenosphere or an enriched lithospheric mantle source accreted by asthenosphere-derived melts during the initial extension. The c.160 Ma syenitic and c.150 Ma high-Mg basaltic rocks mainly originated from the enriched lithospheric mantle that melted owing to a raised geotherm caused by lithosphere thinning. This interpretation is at odds with the active continental margin related to the subduction of palaeo-Pacific plate, but consistent with continental rifting and extension for the Mesozoic of SE China.

You do not currently have access to this article.

Figures & Tables

Contents

Geological Society, London, Special Publications

Aspects of the Tectonic Evolution of China

J. Malpas
J. Malpas
The University of Hong Kong, Hong Kong
Search for other works by this author on:
C. J. N. Fletcher
C. J. N. Fletcher
The University of Hong Kong, Hong Kong
Search for other works by this author on:
J. R. Ali
J. R. Ali
The University of Hong Kong, Hong Kong
Search for other works by this author on:
J. C. Aitchison
J. C. Aitchison
The University of Hong Kong, Hong Kong
Search for other works by this author on:
Geological Society of London
Volume
226
ISBN electronic:
9781862394742
Publication date:
January 01, 2004

GeoRef

References

Related

Citing Books via

Close Modal
This Feature Is Available To Subscribers Only

Sign In or Create an Account

Close Modal
Close Modal