Structural and physical property characterization in the Wenchuan earthquake Fault Scientific Drilling project — hole 1 (WFSD-1)

Li, Haibing; Xu, Zhiqin; Niu, Yixiong; Guang-sheng, Kong; Yao, Hongbo; Wang, Huan; Si, J.; Sun, Zhilei; Pei, Junling; Gong, Zheng; Chevalier, Marie‐Luce; Liu, Dongliang

doi:10.1016/j.tecto.2013.08.022

Cited by 50 publications

(32 citation statements)

References 20 publications

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“…Along with mercury, Helium isotope data could be helpful to shed new light on the contribution of deep fluids. The drilling mud gas data from Tang et al (2014) have mentioned that fault gouge formed by the Wenchuan Ms 8.0 seismic slip was found in depths between 586 and 593 m depths in the borehole WSFD-1 (Li et al 2014), but highest mercury concentration in the present study is observed in drilled core from 614 m depth. The Hg in drilling mud from the present study appears at somewhat shallower depth, in agreement with the depths from Tang et al (2014).…”

Section: Discussioncontrasting

confidence: 50%

“…Major anomalous peaks of HgT from the drilled cores appear at depth of 614, 731, 993 and 1,107 m. Downhole Logging data and fault density statistic data (Li et al 2014) provides some evidences for long-term fault slip at these depths. HgT concentration peaks indicate that the T3 formation (as shown in Fig.…”

Section: Discussionmentioning

confidence: 90%

“…The depth profile of GEM is characterized as a multiple peak distribution. Major anomalous peaks appear at 590-750 m-depth, corresponding to the principal slip zone (PSZ) and the Yingxiu-Beichuan fault gouge (Li et al 2014). This suggestion is also supported by research results, including helium isotope from Wenchuan drill mud gas samples (Tang et al 2014), which found that the mud gas such as methane and radon yielded low concentrations above the PSZ, whereas yielded high concentrations under the PSZ (Tang et al 2014).…”

Section: Gaseous Elemental Mercury From Drilling Mudmentioning

confidence: 99%

“…Major anomalous peaks of HgT appear at *614, 731, 993, and 1,107 m, respectively, primarily corresponding to the ruptures/fault zones discovered in the WFSD-1 borehole (Li et al 2013), and indicating the long-term high seismic activities of the LMS fault. Downhole Logging data (2014) and fault density statistic data (Li et al 2014) provides some evidences for long-term fault slip at these depths. HgT concentration peaks indicate that the T3 formation experienced big ruptures or strong earthquakes, and deep fluids enriched with mercury invaded into this formation.…”

Section: Introductionmentioning

confidence: 99%

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Mercury indicating inflow zones and ruptures along the Wenchuan Ms 8.0 earthquake fault

Yang¹,

Zhang

Liu³

et al. 2015

Chin. J. Geochem.

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During the Wenchuan Fault Scientific Drilling Project, we determined the values of total mercury (HgT) and gaseous elemental mercury (GEM) from drilled cores and drilling mud, respectively. Geochemical analysis shows HgT values ranging from 0.24 to 6.45 ng/g for the Penguan complex and from 2.90 to 137.54 ng/g for T3 sediment. The average levels of HgT for the Penguan complex and T3 sediments are 1.81 ± 0.26 ng/g and 23.96 ± 4.80 ng/g, respectively. Major anomalous peaks of HgT appear at depth of 614,731,993 and 1,107 m, which correspond to the long-term high seismic activity during crustal deformation in response to tectonic stresses. Gaseous elemental mercury dissolved in drilling mud was also analyzed. We found fluid inflow zones with high GEM at depths of 590-750 m, suggesting that fluid-filled ruptures exist in the LMS fault zone. It indicates that mercury provides geochemical evidence for inflow zones and ruptures/fault zones in the Wenchuan Ms 8.0 earthquake fault.

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Section: Discussioncontrasting

confidence: 50%

Section: Discussionmentioning

confidence: 90%

Section: Gaseous Elemental Mercury From Drilling Mudmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Mercury indicating inflow zones and ruptures along the Wenchuan Ms 8.0 earthquake fault

Yang¹,

Zhang

Liu³

et al. 2015

Chin. J. Geochem.

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“…Most of the sedimentary cover from Neoproterozoic to Cenozoic on top of the basement has been eroded, except for those in wedge at the hanging block of the WMF [ Burchfiel et al ., ]. The YBF is located at the eastern boundary of the Pengguan complex, along which only brittle fault rocks have been reported before [ Li et al ., ; H. Wang et al ., ]. To the east of the Pengguan complex, carbonates dominate the Mesozoic successions, whose lithology is remarkably different from the Songpan‐Ganze unit but were deposited during the same time span as the thick flysch sediments (Figure c). The Sichuan basin is located at the western flank of the Yangtze unit (Figure b), which turned into an independent foreland basin from a passive continental margin in the Late Triassic.…”

Section: Geological Settingmentioning

confidence: 99%

New geochronology constraints on timing and depth of the ancient earthquakes along the Longmen Shan fault belt, eastern Tibet

Zheng

Sun

et al. 2016

Tectonics

Self Cite

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Pseudotachylyte is an ideal target to directly date ancient earthquake associated with regional faulting. Here we perform step‐heating 40Ar/39Ar, clay mineral K‐Ar, and zircon fission track (ZFT) analyses on the pseudotachylyte samples collected from the Yingxiu‐Beichuan coseismic rupture of the Longmen Shan fault belt (LSFB) to provide time constraints for the tectonic evolution of the LSFB during the Indosinian orogeny. 40Ar/39Ar results from the matrix show that the frictional melting occurred 226–235 Ma ago. Combined with mylonite dating of the host rock, the age of the ancient earthquakes is constrained at 231–238 Ma, with a formation depth of 10–14 km. As a response to the earthquakes, a series of soft‐sediment deformation structures are widely preserved in the Middle and Late Triassic strata along the Yingxiu‐Beichuan fault (YBF), indicating that the LSFB was seismically active since the Late Anisian and persisted episodically until the end of the Indosinian orogeny. Both clay mineral K‐Ar and ZFT analyses record a younger deformation or alteration with an age of approximately 195 Ma, corresponding to a postcollisional orogeny. These new data represent the first direct evidence of the regional thrusting (YBF) in the central LSFB during the Indosinian orogeny, concurrent with the initial ductile deformation of the western boundary fault. Tectonic inheritance then strongly influenced the evolution of the LSFB as most of the Mesozoic faults are reactivated by major Tertiary tectonic deformations.

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Rock magnetic expression of fluid infiltration in the Yingxiu‐Beichuan fault (Longmen Shan thrust belt, China)

Yang

Duan

et al. 2016

Geochem Geophys Geosyst

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Fluid infiltration within fault zones is an important process in earthquake rupture. Magnetic properties of fault rocks convey essential clues pertaining to physicochemical processes in fault zones. In 2011, two shallow holes (134 and 54 m depth, respectively) were drilled into the Yingxiu-Beichuan fault (Longmen Shan thrust belt, China), which accommodated most of the displacement of the 2008 Mw 7.9 Wenchuan earthquake. Fifty-eight drill core samples, including granitic host rock and various fault rocks, were analyzed rock-magnetically, mineralogically, and geochemically. The magnetic behavior of fault rocks appears to be dominated by paramagnetic clay minerals. Magnetite in trace amounts is identified as the predominant ferrimagnetic fraction in all samples, decreasing from the host rock, via fault breccia to (proto-)cataclasite. Significant mass-losses (10.7-45.6%) are determined for the latter two with the ''isocon'' method. Volatile contents and alteration products (i.e., chlorite) are enriched toward the fault core relative to the host rocks. These observations suggest that magnetite depletion occurred in these fault rocksexhumed from the shallow crust-plumbed by fluid-assisted processes. Chlorite, interpreted to result from hydrothermal activity, occurs throughout almost the entire fault core and shows high coefficients of determination (R 2 > 0.6) with both low and high-field magnetic susceptibility. Close relationships, with R 2 > 0.70, are also observed between both low and high-field magnetic susceptibility and the immobile elements (e.g., TiO 2 , P 2 O 5 , MnO), H 2 O 1 , and the calculated mass-losses of fault rocks. Hence, magnetic properties of fault rocks can serve as proxy indicators of fluid infiltration within shallow fault zones.

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Structural and physical property characterization in the Wenchuan earthquake Fault Scientific Drilling project — hole 1 (WFSD-1)

Cited by 50 publications

References 20 publications

Mercury indicating inflow zones and ruptures along the Wenchuan Ms 8.0 earthquake fault

Mercury indicating inflow zones and ruptures along the Wenchuan Ms 8.0 earthquake fault

New geochronology constraints on timing and depth of the ancient earthquakes along the Longmen Shan fault belt, eastern Tibet

Rock magnetic expression of fluid infiltration in the Yingxiu‐Beichuan fault (Longmen Shan thrust belt, China)

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