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

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

Early Cenozoic partial melting of meta-sedimentary rocks of the eastern Gangdese arc, southern Tibet, and its contribution to syn-collisional magmatism

2021 ◽  
Author(s):  
Yuan-Yuan Jiang ◽  
Ze-Ming Zhang ◽  
Richard M. Palin ◽  
Hui-Xia Ding ◽  
Xuan-Xue Mo
Keyword(s):  
Partial Melting ◽  
Lower Crust ◽  
Sedimentary Rocks ◽  
Late Carboniferous ◽  
Southern Tibet ◽  
Magmatic Arc ◽  
Magmatic Rocks ◽  
Deep Crust ◽  
Juvenile Crust ◽  
Early Cenozoic

Continental magmatic arcs are characterized by the accretion of voluminous mantle-derived magmatic rocks and the growth of juvenile crust. However, significant volumes of meta-sedimentary rocks occur in the middle and lower arc crust, and the contributions of these rocks to the evolution of arc crust remain unclear. In this paper, we conduct a systematic study of petrology, geochronology, and geochemistry of migmatitic paragneisses from the eastern Gangdese magmatic arc, southern Tibet. The results show that the paragneisses were derived from late Carboniferous greywacke, and underwent an early Cenozoic (69−41 Ma) upper amphibolite-facies metamorphism and partial melting at pressure-temperature conditions of ∼11 kbar and ∼740 °C, and generated granitic melts with enriched Hf isotopic compositions (anatectic zircon εHf(t) = −10.57 to +0.78). Combined with the existing results, we conclude that the widely distributed meta-sedimentary rocks in the eastern Gangdese arc deep crust have the same protolith ages of late Carboniferous, and record northwestward-decreasing metamorphic conditions. We consider that the deeply buried sedimentary rocks resulted in the compositional change of juvenile lower crust from mafic to felsic and the formation of syn-collisional S-type granitoids. The mixing of melts derived from mantle, juvenile lower crust, and ancient crustal materials resulted in the isotopic enrichment of the syn-collisional arc-type magmatic rocks of the Gangdese arc. We suggest that crustal shortening and underthrusting, and the accretion of mantle-derived magma during the Indo-Asian collision transported the supracrustal rocks to the deep crust of the Gangdese arc.

scholarly journals Seismic velocities in Southern Tibet lower crust: a receiver function approach for eclogite detection

2009 ◽  
Vol 177 (3) ◽  
pp. 1037-1049 ◽  
Author(s):  
Gérard Wittlinger ◽  
Véronique Farra ◽  
György Hetényi ◽  
Jérôme Vergne ◽  
John Nábělek
Keyword(s):  
Lower Crust ◽  
Receiver Function ◽  
Function Approach ◽  
Seismic Velocities ◽  
Southern Tibet

Isotopic spatial-temporal evolution of magmatic rocks in the Gangdese belt: Implications for the origin of Miocene post-collisional giant porphyry deposits in southern Tibet

2021 ◽  
Author(s):  
Chen-Hao Luo ◽  
Rui Wang ◽  
Roberto F. Weinberg ◽  
Zengqian Hou
Keyword(s):  
Lithospheric Mantle ◽  
Lower Crust ◽  
Isotopic Ratios ◽  
Crustal Growth ◽  
Deposit Formation ◽  
Southern Tibet ◽  
Porphyry Deposit ◽  
Arc Magmas ◽  
Magmatic Rocks ◽  
Three Stages

Crustal growth is commonly associated with porphyry deposit formation whether in continental arcs or collisional orogens. The Miocene high-K calc-alkaline granitoids in the Gangdese belt in southern Tibet, associated with porphyry copper deposits, are derived from the juvenile lower crust with input from lithospheric mantle trachytic magmas, and are characterized by adakitic affinity with high-Sr/Y and La/Yb ratios as well as high Mg# and more evolved isotopic ratios. Researchers have argued, lower crust with metal fertilization was mainly formed by previous subduction-related modification. The issue is that the arc is composed of three stages of magmatism including Jurassic, Cretaceous, and Paleocene−Eocene, with peaks of activity at 200 Ma, 90 Ma, and ca. 50 Ma, respectively. All three stages of arc growth are essentially similar in terms of their whole-rock geochemistry and Sr-Nd-Hf isotopic compositions, making it difficult to distinguish Miocene magma sources. This study is based on ∼430 bulk-rock Sr-Nd isotope data and ∼270 zircon Lu-Hf isotope data and >800 whole-rock geochemistry analyses in a 900-km-long section of the Gangdese belt. We found large scale variations along the length of the arc where the Nd-Hf isotopic ratios of the Jurassic, Cretaceous, and Paleocene−Eocene arc rocks change differently from east to west. A significant feature is that the spatial distribution of Nd-Hf isotopic values of the Paleocene−Eocene arc magmas and the Miocene granitoids, including metallogenic ones, are “bell-shaped” from east to west, with a peak of εNd(t) and εHf(t) at ∼91°E. In contrast, the Jurassic and Cretaceous arc magmas have different isotopic distribution patterns as a function of longitude. The isotopic spatial similarity of the Paleocene−Eocene and Miocene suites suggests that the lower crust source of the metallogenic Miocene magmas is composed dominantly of the Paleocene−Eocene arc rocks. This is further supported by abundant inherited zircons dominated by Paleocene−Eocene ages in the Miocene rocks. Another important discovery from the large data set is that the Miocene magmatic rocks have higher Mg# and more evolved Sr-Nd-Hf isotopic compositions than all preceding magmatic arcs. These characteristics indicate that the involvement of another different source was required to form the Miocene magmatic rocks. Hybridization of the isotopically unevolved primary magmas with isotopically evolved, lithospheric mantle-derived trachytic magmas is consistent with the geochemical, xenolith, and seismic evidence and is essential for the Miocene crustal growth and porphyry deposit formation. We recognize that the crustal growth in the collisional orogen is a two-step process, the first is the subduction stage dominated by typical magmatic arc processes leading to lower crust fertilization, the second is the collisional stage dominated by partial melting of a subduction-modified lower crust and mixing with a lithospheric mantle-derived melt at the source depth.

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