Crustal thickening prior to 38Ma in southern Tibet: Evidence from lower crust-derived adakitic magmatism in the Gangdese Batholith

2012 ◽  
Vol 21 (1) ◽  
pp. 88-99 ◽  
Author(s):  
Qi Guan ◽  
Di-Cheng Zhu ◽  
Zhi-Dan Zhao ◽  
Guo-Chen Dong ◽  
Liang-Liang Zhang ◽  
...  
Keyword(s):  
Lower Crust ◽  
Crustal Thickening ◽  
Southern Tibet

scholarly journals Post-collisional crustal thickening and plateau uplift of southern Tibet: Insights from Cenozoic magmatism in the Wuyu area of the eastern Lhasa block

2020 ◽  
Author(s):  
Lu-Lu Hao ◽  
Qiang Wang ◽  
Andrew C. Kerr ◽  
Jin-Hui Yang ◽  
Lin Ma ◽  
...  
Keyword(s):  
Lower Crust ◽  
Temporal Distribution ◽  
Crustal Thickening ◽  
Indian Plate ◽  
Hf Isotopes ◽  
Southern Tibet ◽  
Tectonic Model ◽  
Surface Uplift ◽  
Thin Crust ◽  
Cenozoic Magmatism

The nature and timing of post-collisional crustal thickening and its link to surface uplift in the eastern Lhasa block of the southern Tibetan plateau remain controversial. Here we report on Cenozoic magmatism in the Wuyu area of the eastern Lhasa block. The Eocene (ca. 46 Ma) trachyandesites and trachydacites show slight fractionation of rare earth elements (REE), slightly negative Eu and Sr anomalies, and relatively homogeneous Sr-Nd and zircon Hf isotopes (87Sr/86Sr(i) = 0.7050−0.7063, εNd(t) = −0.92 to −0.03, εHf(t) = +2.6 to +4.8). Previous studies have suggested Neo-Tethys oceanic slab break-off at 50−45 Ma; thus, the Wuyu Eocene magmatism could represent a magmatic response to this slab break-off and originate from relatively juvenile Lhasa crust. The Miocene (ca. 15−12 Ma) dacites and rhyolites have adakitic affinities, e.g., high Sr (average 588 ppm), Sr/Y (29−136), and La/Yb (30−76) values, low Y (4−12 ppm) and Yb (0.4−0.9 ppm) contents, and variable Sr-Nd and zircon Hf isotopes (87Sr/86Sr(i) = 0.7064−0.7142, εNd(t) = −11.7 to −3.7, εHf(t) = −3.2 to +4.5). Their more enriched Sr-Nd-Hf isotopes relative to the Eocene lavas indicate that they should be derived from mixed Lhasa lower crust comprising juvenile crust, ultrapotassic rocks, and probably Indian lower crust-derived rocks. This study has also revealed the transformation from Eocene juvenile and thin crust with a thickness of <40 km to Miocene mixed and thickened crust with a thickness of >50 km. Combined with published tectonic data, we suggest that both lithospheric shortening and magma underplating contributed to eastern Lhasa block post-collisional crustal thickening. Given the spatial-temporal distribution of eastern Lhasa block magmatism and regional geology, we invoke a post-collisional tectonic model of steep subduction of the Indian plate and subsequent westward-propagating plate break-off beneath the eastern Lhasa block, which caused the surface uplift.

scholarly journals Petrogenesis and Geodynamic Implications of Miocene Felsic Magmatic Rocks in the Wuyu Basin, Southern Gangdese Belt, Qinghai-Tibet Plateau

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 655
Author(s):  
Hanzhi Chen ◽  
Mingcai Hou ◽  
Fuhao Xiong ◽  
Hongwei Tang ◽  
Gangqiang Shao
Keyword(s):  
Lower Crust ◽  
Volcanic Rocks ◽  
Tibet Plateau ◽  
Southern Tibet ◽  
Mixed Product ◽  
Good Opportunity ◽  
Magmatic Rocks ◽  
Adakitic Rocks ◽  
Felsic Volcanic ◽  
Qinghai Tibet Plateau

Miocene felsic magmatic rocks with high Sr/Y ratios are widely distributed throughout the Gangdese belt of southern Tibet. These provide a good opportunity to explore the magmatic process and deep dynamic mechanisms that occurred after collision between the Indo and the Asian plates. In this paper, felsic volcanic rocks from the Zongdangcun Formation in the Wuyu Basin in the central part of the southern Gangdese belt are used to disclose their origin. Zircon U-Pb geochronology analysis shows that the felsic magmatism occurred at ca. 10.3 ± 0.2 Ma, indicating that the Zongdangcun Formation formed during the Miocene. Most of these felsic magmatic rocks plot in the rhyolite area in the TAS diagram. The rhyolite specimens from the Zongdangcun Formation have the characteristics of high SiO2 (>64%), K2O, SiO2, and Sr contents, a low Y content and a high Sr/Y ratio, and the rocks are rich in LREE and depleted in HREE, showing geochemical affinity to adakitic rocks. The rocks have an enriched Sr-Nd isotopic composition (εNd(t) = −6.76 to −6.68, (87Sr/86Sr)i = 0.7082–0.7088), which is similar to the mixed product of the juvenile Lhasa lower continental crust and the ancient Indian crust. The Hf isotopes of zircon define a wide compositional range (εHf(t) = −4.19 to 6.72) with predominant enriched signatures. The Miocene-aged crustal thickness in southern Tibet, calculated on the basis of the Sr/Y and (La/Yb)N ratios was approximately 60–80 km, which is consistent with the thickening of the Qinghai-Tibet Plateau. The origin of Miocene felsic magmatic rocks with high Sr/Y ratios in the middle section of the Gangdese belt likely involved a partial melting of the thickened lower crust, essentially formed by the lower crust of the Lhasa block, with minor contribution from the ancient Indian crust. After comprehensively analyzing the post-collisional high Sr/Y magmatic rocks (33–8 Ma) collected from the southern margin of the Gangdese belt, we propose that the front edge tearing and segmented subduction of the Indian continental slab may be the major factor driving the east-west trending compositional changes of the Miocene adakitic rocks in southern Tibet.

Post-collisional ore-bearing adakitic porphyries from Gangdese porphyry copper belt, southern Tibet: Melting of thickened juvenile arc lower crust

Lithos ◽  
2011 ◽  
Vol 126 (3-4) ◽  
pp. 265-277 ◽  
Author(s):  
Jin-Xiang Li ◽  
Ke-Zhang Qin ◽  
Guang-Ming Li ◽  
Bo Xiao ◽  
Lei Chen ◽  
...  
Keyword(s):  
Lower Crust ◽  
Porphyry Copper ◽  
Southern Tibet

Lithium isotopic evidence for subduction of the Indian lower crust beneath southern Tibet

2020 ◽  
Vol 77 ◽  
pp. 168-183 ◽  
Author(s):  
Shihong Tian ◽  
Zengqian Hou ◽  
Xuanxue Mo ◽  
Yuheng Tian ◽  
Yue Zhao ◽  
...  
Keyword(s):  
Lower Crust ◽  
Southern Tibet ◽  
Isotopic Evidence

scholarly journals Formation and composition of the Late Cretaceous Gangdese arc lower crust in southern Tibet

2020 ◽  
Vol 175 (6) ◽  
Author(s):  
Liang Guo ◽  
Oliver Jagoutz ◽  
William J. Shinevar ◽  
Hong-Fei Zhang
Keyword(s):  
Late Cretaceous ◽  
Lower Crust ◽  
Southern Tibet

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

2017 ◽  
Vol 155 (1) ◽  
pp. 132-148 ◽  
Author(s):  
XINFANG SHUI ◽  
ZHENYU HE ◽  
REINER KLEMD ◽  
ZEMING ZHANG ◽  
TIANYU LU ◽  
...  
Keyword(s):  
Partial Melting ◽  
Lower Crust ◽  
Inductively Coupled Plasma ◽  
Early Jurassic ◽  
Oceanic Plate ◽  
Southern Tibet ◽  
Inductively Coupled ◽  
Adakitic Rocks ◽  
Plasma Mass Spectrometry ◽  
Geochemical Studies

AbstractCretaceous–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 εHf(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 εHf(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.

scholarly journals Adakites from continental collision zones: Melting of thickened lower crust beneath southern Tibet

Geology ◽  
2003 ◽  
Vol 31 (11) ◽  
pp. 1021 ◽  
Author(s):  
Sun-Lin Chung ◽  
Dunyi Liu ◽  
Jianqing Ji ◽  
Mei-Fei Chu ◽  
Hao-Yang Lee ◽  
...  
Keyword(s):  
Lower Crust ◽  
Continental Collision ◽  
Southern Tibet

Subduction of the Indian lower crust beneath southern Tibet revealed by the post-collisional potassic and ultrapotassic rocks in SW Tibet

2017 ◽  
Vol 41 ◽  
pp. 29-50 ◽  
Author(s):  
Shi-Hong Tian ◽  
Zhu-Sen Yang ◽  
Zeng-Qian Hou ◽  
Xuan-Xue Mo ◽  
Wen-Jie Hu ◽  
...  
Keyword(s):  
Lower Crust ◽  
Southern Tibet

Juxtaposition of Barrovian and migmatite domains in the Chinese Altai: a result of crustal thickening followed by doming of partially molten lower crust

2014 ◽  
Vol 33 (1) ◽  
pp. 45-70 ◽  
Author(s):  
Y. D. Jiang ◽  
P. Štípská ◽  
M. Sun ◽  
K. Schulmann ◽  
J. Zhang ◽  
...  
Keyword(s):  
Lower Crust ◽  
Crustal Thickening
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