Petrogenesis of early Late Cretaceous Asa-intrusive rocks in central Tibet, western China: post-collisional partial melting of thickened lower crust

Luo, An‐Bo; Wang, Ming; Cai, Li; Xie, Chao-Ming; Fan, Jian‐Jun; Zhang, Tianyu; Liu, Jin-Heng; Wang, Wei

doi:10.1007/s00531-019-01744-4

Cited by 17 publications

(6 citation statements)

References 72 publications

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“…Most of these ophiolites appear in the form of fault blocks in the flysch, and some of them are intruded by acidic dykes. Previously, 90 Ma acid rocks and 103 Ma basic magma events have been reported in the study area (Liu, Y. M. et al 2018;Zeng et al 2019;Luo et al 2019).…”

Section: Geological Backgroundmentioning

confidence: 68%

“…The appearance of flysch shows that the evolution of the ocean had entered the stage of subduction and accretion at this time (Stow & Shanmugam, 1980). The main lithology of the Upper Cretaceous Jingzhushan Formation is a red sandy conglomerate, in which there are typical reports of molasse formation, indicating that the evolution of the orogenic belts had entered the final collision stage (Liu, Y. M. et al 2018;Luo et al 2019). The ophiolite in the study area is well formed, and an Early Cretaceous age was obtained from a gabbro (Zeng et al 2018).…”

Section: Geological Backgroundmentioning

confidence: 82%

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Slab break-off origin of 105 Ma A-type porphyritic granites in the Asa area of Tibet

Wang

Zeng

et al. 2020

Geol. Mag.

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The study of the petrogenesis of some magmatic rocks with special geochemical attributes provides effective information for us to explore the deep geodynamic background of their formation. A series of granitic porphyry dykes have been found in the mélange zone of the Asa region in southern Tibet, whose genesis may be closely related to the evolution of the Meso-Tethyan Ocean. Regional geodynamic evolution is investigated by whole-rock geochemical analysis, zircon U–Pb dating and Lu–Hf isotopic analysis of two porphyritic granites. The Asa porphyritic granites have high SiO2 (74.29–78.65 wt %) and alkalis (Na2O + K2O = 6.51–9.35 wt %) contents, and low Al2O3 (11.60–14.51 wt %), CaO (0.04–0.19 wt MgO (0.01–0.10 wt %) contents. They are enriched in Zr, Nb, Ce, Y and Hf and depleted in Ti, Ba, Sr and P, consistent with A-type granites. The samples are relatively rich in LREEs, with LREE/HREE ratios of 1.73–3.04. They display negative Eu anomalies (Eu/Eu* = 0.24–0.28) and obvious Ce anomalies in some samples. Zircon U–Pb analyses show that the porphyritic granites formed in late Early Cretaceous time, 107.4 to 105.5 Ma. Zircon εHf(t) values are in the range of 6.9 to 12.0. These data indicate that the porphyritic granites were sourced from interaction between mantle-derived and juvenile lower crust-derived melts, with the addition of oceanic sediment-derived melts. This occurred when the subducting Bangong–Nujiang oceanic crust split to create a slab window. Rising asthenosphere triggered re-melting of lower crust basalts, resulting in the formation of the late Early Cretaceous A-type granites around Asa.

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Section: Geological Backgroundmentioning

confidence: 68%

Section: Geological Backgroundmentioning

confidence: 82%

Slab break-off origin of 105 Ma A-type porphyritic granites in the Asa area of Tibet

Wang

Zeng

et al. 2020

Geol. Mag.

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“…In contrast, if the melts were derived from partial melting of a lower crust that was still attached to the bottom of the crust, they would hardly interact with the underlying mantle peridotite thus generating low‐Mg # adakitic rocks (Karsli et al, 2010, Sun, Hu, Zhu, et al, 2015, Yi et al, 2018). Available data indicate that the Late Cretaceous high‐Mg # (e.g., the Sebuta adakitic rocks) and coeval low‐Mg # (e.g., Azhang and the Baingoin adakitic rocks) adakitic rocks coexist along the central‐northern Lhasa block (Liu, Wang, Yang, et al, 2018; Luo et al, 2019; Sun, Hu, Zhu, et al, 2015; Wang et al, 2014, 2019; Yi et al, 2018; Yu et al, 2011). This feature is in favour of crustal delamination in the Late Cretaceous.…”

Section: Discussionmentioning

confidence: 99%

“…The (La/Yb) N ratios of magmatic rocks are usually used to infer the thickness of the crust where these rocks formed (Cao, Zhang, Santosh, et al, 2019; Hu et al, 2019; Luo et al, 2019; Wang et al, 2015; Zhu et al, 2017). Low (La/Yb) N ratios of the Early Cretaceous calc‐alkaline rocks occurring in the central‐northern Lhasa terrane suggest a normal crustal thickness (mostly thinner than 50 km; Figure 15).…”

Section: Discussionmentioning

confidence: 99%

“…(a) Tectonic map of China, showing the location of Tibet (modified after Cao, Zhang, Santosh, et al, 2019); (b) the tectonic subdivision of the Tibet Plateau, showing the major sutures and terranes (modified after Pan et al, 2012; Yin & Harrison, 2000). Ages are compiled from Cao, Zhang, Santosh, et al (2019), Chen, Xu, et al (2015), Liu, Wang, et al (2018), Luo et al (2019), Sun, Hu, Zhu, et al (2015), Wang et al (2014, 2019), Yi et al (2018) and Yu et al (2011) [Colour figure can be viewed at wileyonlinelibrary.com]…”

Section: Geologic Background and Samplesmentioning

confidence: 99%

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Formation of Late Cretaceoushigh‐Mggranitoid porphyry in central Lhasa, Tibet: Implications for crustal thickening prior to India–Asia collision

Dai

Huang

et al. 2020

Geological Journal

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The Tibetan Plateau is characterized by the largest crustal thickness on Earth, although the timing of formation of the plateau remains debated. In this study, we present in situ laser ablation-inductively coupled plasma-mass spectrometry zircon U-Pb ages and Hf isotopes, and whole-rock geochemical data on porphyritic granitoids of Sebuta in the central Lhasa block. Our zircon U-Pb data indicate that these rocks emplaced at ca. 89 Ma, in the early Late Cretaceous. Geochemically, the Sebuta biotite granite porphyry can be broadly divided into two subtypes, namely metaluminous porphyry and peraluminous porphyry. The metaluminous porphyry has high SiO 2 , Al 2 O 3 , Sr, low Y and Yb contents, and high Sr/Y and La N /Yb N ratios, showing adakitic features. These rocks have high K 2 O and Th contents, low Ti/Eu and Nd/Sm ratios, indicative of a continental crust affinity. Positive zircon ε Hf (t) values, along with high Mg # , Cr and Ni, imply that the Sebuta adakitic porphyry was most likely derived from partial melting of a delaminated thickened juvenile lower crust, and that the initial melts interacted with mantle peridotite during ascent. The field features, petrographic characteristics, formation age, ore-bearing potential, and Hf isotope of the peraluminous porphyry are similar to those of the Sebuta adakitic porphyry, indicating that the peraluminous porphyry was likely formed by contamination with ancient crustal material and fractional crystallization from the same primary adakitic magmas which generated the Sebuta adakitic porphyry. Residual phases of amphibole + plagioclase + garnet + rutile in the source region, together with previous studies, suggest that the crust beneath the centralnorthern Lhasa block experienced thickening during the early Late Cretaceous, and had already been thickened to more than 50 km by the Late Cretaceous (ca. 89 Ma).

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The Meso-Tethys Ocean: The nature, extension and spatial-temporal evolution

Fan,

Zhang,

Zhou

et al. 2024

Earth-Science Reviews

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Petrogenesis of early Late Cretaceous Asa-intrusive rocks in central Tibet, western China: post-collisional partial melting of thickened lower crust

Cited by 17 publications

References 72 publications

Slab break-off origin of 105 Ma A-type porphyritic granites in the Asa area of Tibet

Slab break-off origin of 105 Ma A-type porphyritic granites in the Asa area of Tibet

Formation of Late Cretaceoushigh‐Mggranitoid porphyry in central Lhasa, Tibet: Implications for crustal thickening prior to India–Asia collision

The Meso-Tethys Ocean: The nature, extension and spatial-temporal evolution

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