Total exhumation across the Beichuan fault in the Longmen Shan (eastern Tibetan plateau, China): Constraints from petrology and thermobarometry

Airaghi, Laura; Sigoyer, Julia de; Lanari, Pierre; Guillot, Stéphane; Vidal, Olivier; Monié, Patrick; Sautter, Benjamin; Tan, Xibin

doi:10.1016/j.jseaes.2017.04.003

Cited by 28 publications

(57 citation statements)

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“…RSCM was combined with the multiequilibrium thermobarometry based on the thermodynamic properties and solid solutions models of Vidal et al (, ) and Dubacq et al () to model the P ‐ T conditions of the high variance assemblages involving Chl + Wm + Qz + H 2 O in the samples lm230, lm09‐37, sa14‐14, ba15‐12, and ba14‐14, following the procedure described by Airaghi, de Sigoyer, et al () and Lanari et al (). Metamorphic conditions were estimated from the intersection between the P ‐ T equilibrium curves calculated for white mica and (1) the T calculated for Chl in textural equilibrium (lm09‐37 and lm230), or (2) the T estimated for Chl with the thermometer of Massonne and Schreyer (; sample ba15‐10) or the (3) T max estimated with the RSCM (sa14‐2) under the hypothesis that metamorphic white mica reequilibrated at the temperature peak.…”

Section: Analytical and Computational Methodsmentioning

confidence: 99%

“…Metamorphic overprint occurred at 280 ± 30 °C, 7 ± 1 kbar (Pengguan massif) and 370 ± 35 °C, 7 ± 1 kbar (Tonghua massif) at ca. 140–137 Ma (Airaghi, de Sigoyer, et al, ; Airaghi et al, ). Close to the Wulong fault (WuF) the northern slice of the Baoxing massif (Figure b) is also strongly deformed (up to mylonitization; Tian et al, ; this study).…”

Section: Geological Setting and Studied Areasmentioning

confidence: 99%

“…Metamorphic and structural studies carried out in the Danba area (~ 00 km west of the LMS) and in the central LMS (Airaghi, Lanari, et al, ; Billerot et al, ; Dirks et al, ; Harrowfield & Wilson, ; Weller et al, ; Worley & Wilson, ) as well as 40 Ar/ 39 Ar ages on clay mineral in pseudotachylites of the BF (Zheng et al, ) suggest a compressive phase of deformation during the Late Triassic‐Early Jurassic, driven by the closure of the Paleotethys. Recent petrochronological studies have also documented a metamorphic and deformation event in the central LMS at the Early Cretaceous (Airaghi, de Sigoyer, et al, ; Airaghi et al, ). These studies are however still sparse and often restricted to the higher metamorphic units of the belt, limiting our understanding of the Mesozoic thermal and structural evolution of the LMS.…”

Section: Introductionmentioning

confidence: 99%

“…(d) Geological cross section along the profile BB′ for the central Longmen Shan. P ‐ T ‐ t conditions in frames are from Airaghi, Lanari, et al (), Airaghi, de Sigoyer, et al (), and Airaghi et al (). The crustal structure is from the receiver function data of Robert, Pubellier, et al ().…”

Section: Introductionmentioning

confidence: 99%

“…An increasing number of studies propose that part of the crustal thickness of the SPG terrane and of the central and southern Tibetan plateau is acquired during the Mesozoic (e.g., Airaghi, Lanari, et al, ; Airaghi, de Sigoyer, et al, ; Billerot et al, ; Kapp et al, , ; de Sigoyer et al, ; Xue et al, ). Metamorphic and structural studies carried out in the Danba area (~ 00 km west of the LMS) and in the central LMS (Airaghi, Lanari, et al, ; Billerot et al, ; Dirks et al, ; Harrowfield & Wilson, ; Weller et al, ; Worley & Wilson, ) as well as 40 Ar/ 39 Ar ages on clay mineral in pseudotachylites of the BF (Zheng et al, ) suggest a compressive phase of deformation during the Late Triassic‐Early Jurassic, driven by the closure of the Paleotethys.…”

Section: Introductionmentioning

confidence: 99%

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The Mesozoic Along‐Strike Tectonometamorphic Segmentation of Longmen Shan (Eastern Tibetan Plateau)

et al. 2018

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The Longmen Shan belt (eastern border of the Tibetan plateau) constitutes a tectonically active region as demonstrated by the occurrence of the unexpected 2008 Mw 7.9 Wenchuan and 2013 Mw 6.6 Lushan earthquakes in the central and southern parts of the belt, respectively. These events revealed the necessity of a better understanding of the long‐term geological evolution of the belt and its effect on the present dynamics and crustal structure. New structural and thermobarometric data offer a comprehensive data set of the paleotemperatures across the belt and P‐T estimates for low‐grade metamorphic domains. In the central Longmen Shan, two metamorphic jumps of 150–200 °C, 5–6 kbar and ~50 °C, 3–5 kbar acquired during the Early Mesozoic are observed across the Wenchuan and Beichuan faults, respectively, attesting to their thrusting movement and unrevealing a major decollement between the allochtonous Songpan‐Garze metasedimentary cover (at T > 500 °C) and the autochtonous units and the basement (T < 400 °C). In the southern Longmen Shan, the only greenschist facies metamorphism is observed both in the basement (360 ± 30 °C, 6 ± 2 kbar) and in the metasedimentary cover (350 ± 30 °C, 3 ± 1 kbar). Peak conditions were reached at ca. 80–60 Ma in the basement and ca. 55–33 Ma in the cover, ca. 50 Ma after the greenschist facies metamorphic overprint observed in the central Longmen Shan (ca. 150–120 Ma). This along‐strike metamorphic segmentation coincides well with the present fault segmentation and reveals that the central and southern Longmen Shan experienced different tectonometamorphic histories since the Mesozoic.

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Section: Analytical and Computational Methodsmentioning

confidence: 99%

Section: Geological Setting and Studied Areasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Mesozoic Along‐Strike Tectonometamorphic Segmentation of Longmen Shan (Eastern Tibetan Plateau)

et al. 2018

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Mesozoic Crustal Thickening of the Longmenshan Belt (NE Tibet, China) by Imbrication of Basement Slices: Insights From Structural Analysis, Petrofabric and Magnetic Fabric Studies, and Gravity Modeling

et al. 2017

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This work first presents field structural analysis, anisotropy of magnetic susceptibility (AMS) measurements, and kinematic and microstructural studies on the Neoproterozoic Pengguan complex located in the middle segment of the Longmenshan thrust belt (LMTB), NE Tibet. These investigations indicate that the Pengguan complex is a heterogeneous unit with a ductilely deformed NW domain and an undeformed SE domain, rather than a single homogeneous body as previously thought. The NW part of the Pengguan complex is constrained by top‐to‐the‐NW shearing along its NW boundary and top‐to‐the‐SE shearing along its SE boundary, where it imbricates and overrides the SE domain. Two orogen‐perpendicular gravity models not only support the imbricated shape of the Pengguan complex but also reveal an imbrication of high‐density material hidden below the Paleozoic rocks on the west of the LMTB. Regionally, this suggests a basement‐slice‐imbricated structure that developed along the margin of the Yangtze Block, as shown by the regional gravity anomaly map, together with the published nearby seismic profile and the distribution of orogen‐parallel Neoproterozoic complexes. Integrating the previously published ages of the NW normal faulting and of the SE directed thrusting, the locally fast exhumation rate, and the lithological characteristics of the sediments in the LMTB front, we interpret the basement‐slice‐imbricated structure as the result of southeastward thrusting of the basement slices during the Late Jurassic‐Early Cretaceous. This architecture makes a significant contribution to the crustal thickening of the LMTB during the Mesozoic, and therefore, the Cenozoic thickening of the Longmenshan belt might be less important than often suggested.

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Differential Exhumation Across the Longriba Fault System: Implications for the Eastern Tibetan Plateau

et al. 2018

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The deformation processes at work across the eastern margin of the Tibetan Plateau remain controversial. The interpretation of its tectonic history is often polarized between two deformation models: ductile flow in the lower crust and shortening and crustal thickening accommodated by brittle structures in the upper crust. Many geological investigations on this plateau margin focused on the Longmen Shan, at the western edge of the Sichuan Basin. However, the Longriba fault system (LFS) located 200 km northwest and parallel to the Longmen Shan structures provides an opportunity to understand the role of hinterland faults in eastern Tibet geodynamics. For this reason, we investigate the exhumation history of rocks across the LFS using (U‐Th)/He and fission track ages from apatite and zircon. Results show a significant contrast in cooling histories across the Maoergai fault, the southernmost fault of the LFS. South of the Maoergai fault, the bedrock records a rapid increase in exhumation rate since ~10–15 Ma. In contrast, the area north of the fault has experienced steady cooling since ~25–35 Ma. We attribute this cooling contrast to ~2 km of differential rock uplift across the Maoergai fault, providing the first evidence of activity of the LFS in the Late Cenozoic. Our results indicate that deformation of the eastern Tibetan margin has been partitioned into the LFS and the Longmen Shan over an ~200 km wide block, which should be incorporated in future studies on the region's deformation, and in both above‐mentioned deformation models.

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Total exhumation across the Beichuan fault in the Longmen Shan (eastern Tibetan plateau, China): Constraints from petrology and thermobarometry

Cited by 28 publications

References 62 publications

The Mesozoic Along‐Strike Tectonometamorphic Segmentation of Longmen Shan (Eastern Tibetan Plateau)

The Mesozoic Along‐Strike Tectonometamorphic Segmentation of Longmen Shan (Eastern Tibetan Plateau)

Mesozoic Crustal Thickening of the Longmenshan Belt (NE Tibet, China) by Imbrication of Basement Slices: Insights From Structural Analysis, Petrofabric and Magnetic Fabric Studies, and Gravity Modeling

Differential Exhumation Across the Longriba Fault System: Implications for the Eastern Tibetan Plateau

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