Early Jurassic adakitic rocks in the southern Lhasa sub-terrane, southern Tibet: petrogenesis and geodynamic implications

Journal article


Publication Details

Author(s): Shui X, He Z, Klemd R, Zhang Z, Lu T, Yan L
Journal: Geological Magazine
Publication year: 2018
Volume: 155
Journal issue: 1
Pages range: 132-148
ISSN: 0016-7568
Language: English


Abstract

Cretaceous–Miocene adakitic rocks in the southern Lhasa sub-terrane have been intensively investigated, while possible Early Jurassic adakitic rocks in this area have been largely neglected. Petrological and geochemical studies revealed adakitic affinities of an Early Jurassic quartz diorite intrusion with mafic enclaves and three tonalite bodies from the Jiacha area in the southern Lhasa sub-terrane. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb dating suggests crystallization ages of 199–179 Ma for these rocks. Both quartz diorites and tonalites have typical adakitic geochemical characteristics such as high Al2O3 (15.14–18.22 wt.%) and Sr (363–530 ppm) contents, low Y (4.46–15.9 ppm) and Yb (0.51–1.74 ppm) contents and high Sr/Y ratios of 27–106. The adakitic quartz diorites are further characterized by high MgO (2.63–3.46 wt.%), Mg# (48–54) and ε Hf(t) (6.6–13.4) values, which were probably produced by partial melting of a subducted oceanic slab with a mantle contribution. The adakitic tonalites have very low abundances of compatible elements and relatively low ε Hf(t) values (3.5–10.3), and are interpreted to have formed by partial melting of Neoproterozoic mafic lower crust. Upwelling asthenosphere, triggered by rollback of the subducting Bangong–Nujiang (Meso-Tethys) oceanic plate, provided the necessary heat for slab and lower crust melting, resulting in the geochemical diversity of the coexisting felsic intrusive rocks. Contrary to other models, this study further demonstrates that the Bangong–Nujiang oceanic plate was subducted southward beneath the Lhasa terrane during the Early Jurassic.


FAU Authors / FAU Editors

He, Zhenyu Dr.
Geozentrum Nordbayern
Klemd, Reiner Prof. Dr.
Professur für Geochemie und Lagerstättenkunde
Lu, Tianyu
Professur für Geochemie und Lagerstättenkunde
Yan, Lili
Professur für Geochemie und Lagerstättenkunde


External institutions with authors

Chinese Academy of Geological Sciences (CAGS) / 中国地质科学院


How to cite

APA:
Shui, X., He, Z., Klemd, R., Zhang, Z., Lu, T., & Yan, L. (2018). Early Jurassic adakitic rocks in the southern Lhasa sub-terrane, southern Tibet: petrogenesis and geodynamic implications. Geological Magazine, 155(1), 132-148. https://dx.doi.org/10.1017/S0016756817000577

MLA:
Shui, Xinfang, et al. "Early Jurassic adakitic rocks in the southern Lhasa sub-terrane, southern Tibet: petrogenesis and geodynamic implications." Geological Magazine 155.1 (2018): 132-148.

BibTeX: 

Last updated on 2019-01-08 at 07:24