Spatio-temporal variations of Late Triassic granitic magmatism in the Lincang batholith and implications for post-collisional process along the Paleo-Tethys suture in SW China

ABSTRACT

The most striking Lincang granitic batholith widely distributed in the Sanjiang Paleo-Tethys Orogen provides us a crucial window to understand the subduction, consumption, and associated geodynamic mechanism of the Paleo-Tethys Ocean during the late Paleozoic to early Mesozoic. In this study, we carry out an integrated study of petrology, zircon U-Pb geochronology, whole-rock major and trace elements, and in situ zircon Hf isotope of the Late Triassic granitic rocks from the Lincang granitic batholith, with the aim of investigating their geochronological framework, spatio-temporal variations, genetic mechanism, and tectonic significance. The granitic rocks presented in this study consist of granodiorite and monzogranite, with minor syenogranite. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating of these granitic rocks yield crystallization ages of 237.6–209.0 Ma, indicating multi-stage granitic magmatic activities during the Late Triassic. Geochemical analyses show that these granitic rocks belong to medium-K calc-alkaline and shoshonite series, and have metaluminous to peraluminous characteristics and low whole-rock zircon saturation temperature (726–834°C). The Late Triassic granitic rocks show transitional characteristics and originate from different magma sources, indicative of transitional I-type and S-type granite affinities. The 237.6 Ma gneissic granodiorites belong to I-type granite and have typical continental arc granites of enrichments in large ion lithophile elements (Rb, K, Pb, and Th) and light rare earth elements (LREEs), and depletion in high field strength elements (Nb, Ta, Ba, Ti, and P) and heavy rare earth elements (HREEs), with parental magma derived from garnet amphibolite facies lower crust. Whereas the 222.7–209.0 Ma granitic rocks have S-type granite affinities with psammitic source. The transitional geochemical characteristics led us to favour that syn-collisional stage in response to final closure of the Paleo-Tethys Ocean in Southwestern Yunnan lasted at least until 237.6 Ma. Subsequent extensional mechanism and associated asthenosphere upwelling after final closure of the Paleo-Tethys Ocean induce large-scale partial melting of the middle-lower crust, resulting in voluminous generation of S-type and A-type granitic rocks and associated volcanic rocks in Southwestern Yunnan.

GRAPHICAL ABSTRACT

KEYWORDS:

• Sanjiang Paleo-Tethys Orogen
• Lincang granitic batholith
• Late Triassic
• compositional variations
• I/S-type granites
• Paleo-Tethys Ocean

Acknowledgments

We gratefully acknowledge the staff of the ALS Chemex (Guangzhou) Co Ltd, Guangzhou and the Key Laboratory of Mineral Resources Evaluation in Northeast Asia, China, for their advice and assistance during the whole-rock major and trace elements and zircon U-Pb dating analyses. We also appreciate the Wuhan SampleSolution Analytical Technology Co., Ltd., Wuhan, China, for their aid and suggestions in the analyses of in situ zircon Hf isotope. This study was financially supported by the National Natural Science Foundation of China (91955205).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2024.2318738

Additional information

Funding

The work was supported by the National Natural Science Foundation of China [91955205].