The Neotethyan subduction and collision with the Asian, Indian, and Australian plates is evidenced by a giant Andean-type arc system and a remarkable Neotethyan igneous belt along the southwestern Eurasian margin. However, the southward extent, and cause, of Neotethyan subduction is poorly understood. Here, a zircon U-Pb dating and whole-rock geochemical study of two groups of Eocene (50−48 Ma) mafic intrusions from Tangse, North Sumatra, helps to unravel the Neotethyan subduction story. Group 1 consists of diabase samples, which have mid-oceanic-ridge− and arc-like geochemical affinities, with low chondrite-normalized La/Yb(cn) (∼0.6) ratios and a high measured εNd(t) value of +8.7. Such geochemical signatures indicate that the magmatic rocks were derived from a refractory depleted mantle source that was metasomatized by slab melts. Group 2 consists of gabbro-diorites, which are enriched in the large-ion lithophile elements and depleted in some high field strength elements. These samples have high La/Yb(cn) (2.9−6.6), low Nb/La(cn) (0.2−0.3), εNd(t) values of +1.1 to +5.0, and εHf(t) values of +8.8 to +15.3. Group 2 samples were produced by the melting of a depleted mantle wedge metasomatized by slab fluids. The magmatism provides evidence for the southern continuation of the Neotethyan igneous belt and tectonic system, whereby slab rollback triggered melting and upwelling in an arc−back-arc geodynamic system from South Tibet to SE Asia.
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Research Article|
March 10, 2023
Southward continuation and slab rollback of the Neotethyan arc−back-arc system: Insights from Eocene mafic intrusions from North Sumatra, SE Asia
Xiaoqing Yu;
Xiaoqing Yu
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
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Yuzhi Zhang;
Yuzhi Zhang
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China2
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
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Xin Qian;
Xin Qian
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China2
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
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Azman A. Ghani;
Azman A. Ghani
3
Department of Geology, University of Malaya, Kuala Lumpur, Malaysia
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Thomas C. Sheldrick;
Thomas C. Sheldrick
4
School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH, UK
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Chang Xu;
Chang Xu
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
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Yuejun Wang
Yuejun Wang
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China2
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
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Xiaoqing Yu
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
Yuzhi Zhang
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China2
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
Xin Qian
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China2
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
Azman A. Ghani
3
Department of Geology, University of Malaya, Kuala Lumpur, Malaysia
Thomas C. Sheldrick
4
School of Geography, Geology and the Environment, University of Leicester, University Road, Leicester, LE1 7RH, UK
Chang Xu
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China
Yuejun Wang
1
Guangdong Provincial Key Lab of Geodynamics and Geohazards, School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou 510275, China2
Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Zhuhai 519082, China
Publisher: Geological Society of America
Received:
23 Jun 2022
Revision Received:
28 Nov 2022
Accepted:
17 Dec 2022
First Online:
10 Mar 2023
Online ISSN: 1943-2674
Print ISSN: 0016-7606
© 2023 Geological Society of America
GSA Bulletin (2023)
Article history
Received:
23 Jun 2022
Revision Received:
28 Nov 2022
Accepted:
17 Dec 2022
First Online:
10 Mar 2023
Citation
Xiaoqing Yu, Yuzhi Zhang, Xin Qian, Azman A. Ghani, Thomas C. Sheldrick, Chang Xu, Yuejun Wang; Southward continuation and slab rollback of the Neotethyan arc−back-arc system: Insights from Eocene mafic intrusions from North Sumatra, SE Asia. GSA Bulletin 2023; doi: https://doi.org/10.1130/B36651.1
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