The discovery of the Early Triassic gabbro rocks of the Duolong accretionary complexes in southern Qiangtang terrane of Tibet and its geological significance

DUAN Yaoyao; LI Yalin; DUAN Zhiming

2016 Vol. 35, No. 6

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DUAN Yaoyao, LI Yalin, DUAN Zhiming. The discovery of the Early Triassic gabbro rocks of the Duolong accretionary complexes in southern Qiangtang terrane of Tibet and its geological significance[J]. Geological Bulletin of China, 2016, 35(6): 887-893.

Citation:

DUAN Yaoyao, LI Yalin, DUAN Zhiming. The discovery of the Early Triassic gabbro rocks of the Duolong accretionary complexes in southern Qiangtang terrane of Tibet and its geological significance[J]. Geological Bulletin of China, 2016, 35(6): 887-893.

The discovery of the Early Triassic gabbro rocks of the Duolong accretionary complexes in southern Qiangtang terrane of Tibet and its geological significance

1. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;
2. Chengdu Center, China Geological Survey, Chengdu 610082, Sichuan, China

Received Date: 31 December 2015

Revised Date: 08 March 2016

Publish Date: 15 June 2016

Abstract

Abstract

The outcropped Late Triassic-Jurassic accretionary complexes are located along northern Bangong Co-Nujiang suture zone where a large subduction-type Duolong porphyry copper-gold ore concentration area is developed. Bulk-rock major and trace elements, Sr-Nd isotope and LA-ICP-MS zircon U-Pb data are reported for gabbro rocks sampled from the Duolong accretionary complexes. The ²⁰⁶Pb/²³⁸U age of zircon in the gabbro analyzed by LA-ICP-MS is 246.0±1.4Ma, which represents the crystallization age of the magma. Na, Mg, LREE and large ion lithophile elements (Ba, U, La and Sr) are concentrated whereas Ti, K and highfield strength elements (Nb and Ta) are deficient. These characteristics suggest that the geochemistry of the gabbro is similar to that of the island arc type basalt. The isotopic compositions of the Sr and Nd ((⁸⁷Sr/⁸⁶Sr)_i=0.707605~0.709778, (¹⁴³Nd/¹⁴⁴Nd)_i=0.512515~0.512678, and T_DM2=0.54~0.99Ga) suggest that gabbro is developed on the arc in an intraplate environment. It is considered that the end of early Triassic igneous activity probably resulted from the northward subduction of the Bangong Co-Nujiang Ocean crust which interacted with the lithospheric mantle material. The discovery and understanding provide the northward subduction of the Bangong Co-Nujiang ocean crust in early Triassic with important evidence of magmatism.
- LA-ICP-MS zircon U-Pb ages /
- geochemical characteristics /
- island arc gabbro /
- Bangong Co-Nujiang suture zone

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References

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