Li, Cheng, Ma, Lin, Kerr, Andrew C.  ORCID: https://orcid.org/0000-0001-5569-4730, Dan, Wei, Wang, Qiang, Yu, Zhiwei, Qiao, Wei, Pu, Rui and Yang, Fan
2026.
Petrogenesis of Late Triassic adakitic rocks and basalts from the southern Lhasa: Insights into subduction initiation of Neo-Tethys.
Lithos: Journal of Petrology, Mineralogy and Geochemistry
530-31
, 108498.
10.1016/j.lithos.2026.108498
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Abstract
Although a critical part of reconstructing the dynamic evolution of the Neo-Tethyan ocean, the timing and mechanism of subduction initiation remains highly controversial. In this contribution, we report petrological and geochemical data for newly identified Late Triassic Aza biotite granodiorites and Chango basalts in southern Tibet. The Aza biotite granodiorites (ca. 236 Ma) display adakitic affinities. These granodiorites are characterized by high SiO₂ (62.8–68.6 wt%), moderate MgO (1.3–3.1 wt%), high Sr (444–546 ppm) and low Y (8.4–14.0 ppm) and Yb (0.87–1.48 ppm) contents, along with high Na₂O/K₂O (0.9–2.1), Sr/Y (35.3–59.0) and La/Yb (7.4–24.4) ratios and positive εNd(t) values of +6.1 to +6.7, similar to melts of subducting oceanic slab. The Chango basalts (ca. 219 Ma) have typical arc basalt features, such as enriched large ion lithophile elements (LILE) and depleted high field strength elements (HFSE) with εNd(t) of +6.4 to +7.2, suggesting derivation from a metasomatized asthenospheric mantle wedge source. The presence of these two suites of magmatic rocks provides solid evidence for the early subduction of the Neo-Tethys Ocean during the Late Triassic. Moreover, numerical modeling indicates that the closure of the Sumdo Ocean (ca. 240 Ma) is the most likely potential candidate as the driving force for the subduction initiation of the Neo-Tethys Ocean. The closure of the Sumdo Ocean and the earliest magmatic rocks related to subduction in southern Lhasa jointly constrain the onset of Neo-Tethys subduction to around 240 Ma.
| Item Type: | Article |
|---|---|
| Date Type: | Publication |
| Status: | Published |
| Schools: | Schools > Earth and Environmental Sciences |
| Additional Information: | RRS policy applied |
| Publisher: | Elsevier |
| ISSN: | 0024-4937 |
| Date of First Compliant Deposit: | 24 March 2026 |
| Date of Acceptance: | 12 March 2026 |
| Last Modified: | 24 Mar 2026 12:15 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/185970 |
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