Continental crust growth induced by slab breakoff in collisional orogens: Evidence from the Eocene Gangdese granitoids and their mafic enclaves, South Tibet

Shu, Chutian; Long, Xiaoping; Yin, Changqing; Yuan, Chao; Wang, Qiang; He, Xiaolan; Zhao, Bingshuang; Huang, Zhipei

doi:10.1016/j.gr.2018.06.004

Cited by 27 publications

(17 citation statements)

References 95 publications

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“…Chondrite and N‐MORB normalization values are from (Sun & McDonough, 1989). Data for ∼50 Ma Lhasa mafic rocks selected from the Daju mafic rocks of Huang et al (2017), the Quxu intermediate rocks of Wang, Qiu, Yu, Lin, and Xu (2019), the Ringqênzê intermediate rocks of Shu et al (2018), the Gangdese intermediate rocks (Nymo area) of Ma, Xu, and Meert (2016), and the Pangduo mafic rocks of Liu et al (2018). Data of Dagzhuka gabbros are from Xia et al (2003).…”

Section: Resultsmentioning

confidence: 99%

“…The low LILE contents of the Lianxiang gabbros also suggest that their source is the asthenospheric mantle (Figure 4). Previous studies have reported that ~50 Ma intermediate and mafic dikes in the southern Lhasa Terrane have ε Nd ( t ) values of −3.5 to +6.2 and 87 Sr/ 86 Sr i ratios of 0.7039–0.7063 (Gao et al, 2008; Huang et al, 2017; Liu et al, 2018; Shu et al, 2018; Wang et al, 2019). These differ from the isotopic composition of the Lianxiang gabbros, which have depleted Sr–Nd isotopic compositions that are similar to the MORB ophiolite suite, indicating that they most likely were derived from an asthenospheric source.…”

Section: Discussionmentioning

confidence: 99%

“…55–50 Ma (Ji et al, 2009; Lee et al, 2009; Wen et al, 2008; Zhu et al, 2015). Shu et al (2018) and Huang et al (2017) recently reported contemporary mafic and felsic rocks in the Daju and Renqinze areas. These observations imply that the ~57 Ma magmatism in Lianxiang is not unique, but part of a larger Cenozoic magmatic event throughout the southern Lhasa Terrane.…”

Section: Discussionmentioning

confidence: 99%

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Neo‐Tethyanslab tearing constrained by PalaeoceneN‐MORB‐like magmatism in southern Tibet

Tian

Huang

et al. 2020

Geological Journal

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Southern Tibet is a key region for investigating the magmatism that occurredduring the collision between India and Asia. The break‐off of the Neo‐Tethyan slab, after the onset of continental collision at ca. 65–60 Ma, affected the lithospheric thermal regime and led to a series of magmatic and tectonic events. Many magmatic rocks generated by slab break‐off have been reported in southern Tibet; however, which of these record the initial slab break‐off (i.e., slab tearing) is still an open question. The Lianxiang gabbros, which intrude an ophiolite in central‐southern Tibet, provide an ideal opportunity to investigate the footprint of the initial slab break‐off. Zircon U–Pb ages show that the Lianxiang gabbros crystallized at 57–53 Ma, coeval with other mafic dikes in southern Tibet. The Lianxiang gabbros are characterized by high Na2O (2.13–5.42 wt%), Al2O3(13.86–17.13 wt%), and V (188–346 ppm) contents and moderate Mg# (40.8–65.9). The gabbrosare slightly depleted in light rare earth elements [LREE; (La/Yb)N= 0.45–0.76], similar to normal mid‐ocean ridge basalt (N‐MORB). They also have low87Sr/86Sriratios (0.703538–0.705698) and highεNd(t) values (9.49–10.68), indicating that they were derived mainly from a shallow asthenospheric mantle source. Combining our results with data from other magmatism at ~57 Ma in the southern Lhasa Terrane, we propose that the N‐MORB‐type rocks reflect the tearing of the Neo‐Tethyan slab. The process of slab break‐off differed between western and eastern southern Tibet, possibly as a result of different lithospheric structures and compositions.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Neo‐Tethyanslab tearing constrained by PalaeoceneN‐MORB‐like magmatism in southern Tibet

Tian

Huang

et al. 2020

Geological Journal

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“…Magma-mixing modeling calculations follow Ersoy and Helvaci [116]. Dotted curves in (c) are from Shu et al [104]. 23 Lithosphere samples are geochemically similar to high-SiO 2 adakitic rocks.…”

Section: Geological Setting and Petrographymentioning

confidence: 94%

Eocene–Oligocene Crustal Thickening-Collapse of the Eastern Tibetan Plateau: Evidence from the Potassic Granitoids in SW China

et al. 2021

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The eastern Tibetan Plateau is a key part of the eastern India–Asia collisional zone, a region that records multiple overprinting tectonic and magmatic events. This study presents new geochronological, geochemical, and Sr–Nd–Hf–O isotopic data for Cenozoic potassic granitoids in eastern Tibet, southwestern China, which recorded the tectonic evolution of the eastern Tibetan Plateau. These potassic granitoids are formed between 37.6 and 32.9 Ma and are geochemically subdivided into the following: Group 1, adakite-like granites; Group 2, syenites; and Group 3, low-εNdt granitoids. The Group 1 samples are similar to high-silica adakites in that they have variable SiO2 contents (63.31–73.62 wt.%) and high Sr/Y and La/Yb ratios. These samples have εNdt and εHft values that range from −5.8 to −0.6 and from −4.3 to +5.2, respectively, with δ18O values of 6.78‰–7.36‰. The Group 2 samples are syenites, contain 56.36–63.86 wt.% SiO2 and high concentrations of Y and Yb, and have εNdt values from −8.4 to −2.4, εHft values from −6.1 to +1.1, and δ18O values of 6.37‰–6.89‰. The Group 3 samples have a narrow range of SiO2 concentrations (62.27–64.59 wt.%), high Sr/Y and La/Yb ratios, δ18O values of 6.31‰–6.82‰, and low εNdt and εHft values (−12.6 to −10.9 and −11.4 to −6.6, respectively) that are similar to the values obtained for the contemporaneous Yao’an lamprophyres. These data indicate that the Group 1 samples are formed from magmas sourced from a heterogeneous and thickened region of the lower crust containing an enriched mantle component. Group 2 magmas were most likely derived from contemporaneous mafic melts sourced from an ancient region of the lithospheric mantle previously modified by the incorporation of recycled components. The Group 3 samples have distinct Sr–Nd–Hf isotopic compositions that are indicative of derivation from magmas generated by the fractional crystallization of lower crustal melts sourced from ancient enriched mantle of the Yangtze Block. Combining these new data with the results of previous research suggests that the Cenozoic potassic igneous rocks of eastern Tibet were formed as a result of the thinning of the lithospheric mantle and an associated crustal collapse event, potentially representing a regional late Eocene to early Oligocene transition from compression to transtension in the eastern Tibetan Plateau. These potassic igneous rocks are contemporaneous with or are younger than igneous rocks in the Qiangtang Block, suggesting that the magmatic response to the India–Asia collisional event was initiated in the central Tibetan Plateau before propagating towards the eastern margin of this region.

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“…There is a narrow belt of mafic‐ultramafic rocks (mainly gabbro) intruding into the southern Gangdese batholith from Xietongmen in the west to Quxu in the east (Figure f), which were constrained by zircon U‐Pb dating to 53–40 Ma (Dong et al, ; Ji et al, ; Ma et al, ; Meng et al, ). From field observations, since the Gangdese granitoids often have abundant mafic enclaves and are combined with synchronous mafic intrusions, it has been widely accepted that magma mixing/mingling between the mafic and felsic magma happened around 50 Ma (Dong et al, ; Ji et al, ; Jiang et al, ; Luo et al, ; Meng et al, ; Mo et al, ), which contributed to the growth of the continental crust in the Gangdese arc (Mo et al, , ; Shu et al, ; Zhou et al, ).…”

Section: Geological Settingsmentioning

confidence: 99%

Aeromagnetic Anomalies in Central Yarlung‐Zangbo Suture Zone (Southern Tibet) and Their Geological Origins

Wang

Yao

2020

JGR Solid Earth

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Two subparallel east‐west trending linear aeromagnetic anomalies are observed along the central Yarlung‐Zangbo suture zone in southern Tibet. The Yarlung‐Zangbo suture zone represents the boundary of the Eurasian and Indian plates and records the subduction of the Neo‐Tethyan oceanic slab and subsequent continental collision. The two magnetic lineaments are spatially associated with the Gangdese batholith and Xigaze ophiolites, which are separated by the Xigaze fore‐arc basin that is filled with nonmagnetic sedimentary sequences. The Mesozoic‐Cenozoic Gangdese batholith is characterized by widespread I‐type granitoids. The Xigaze ophiolites are dominated by serpentinized mantle peridotites. To investigate the geological origins and deep structures of the magnetic sources of the two magnetic lineaments, a 3‐D inversion of aeromagnetic anomaly data was undertaken. By analyzing our inversion model and further magnetic modeling, it is proposed that the Gangdese batholith has a magmatic root with higher magnetization than the exposed granitoids, indicating that the deeper part of the Gangdese batholith may contain more mafic constituents than the shallow part. The subsurface part of the Xigaze ophiolites resembles a thin slab dipping to the south, implying that the deep‐seated Xigaze ophiolites are also serpentinized and retain complete structure.

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Continental crust growth induced by slab breakoff in collisional orogens: Evidence from the Eocene Gangdese granitoids and their mafic enclaves, South Tibet

Cited by 27 publications

References 95 publications

Neo‐Tethyanslab tearing constrained by PalaeoceneN‐MORB‐like magmatism in southern Tibet

Neo‐Tethyanslab tearing constrained by PalaeoceneN‐MORB‐like magmatism in southern Tibet

Eocene–Oligocene Crustal Thickening-Collapse of the Eastern Tibetan Plateau: Evidence from the Potassic Granitoids in SW China

Aeromagnetic Anomalies in Central Yarlung‐Zangbo Suture Zone (Southern Tibet) and Their Geological Origins

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