Publication Date:
2024-01-22
Description:
The Tibetan Plateau is growing by both vertical uplift and horizontal extension. It is a continuing debate how the
Tibetan Plateau interacts with its surrounding plates and blocks. Due to intense tectonic activity, which produced
catastrophic earthquakes, the tectonic zone between the northeast margin of the horizontal extending Tibetan
Plateau and the stable Ordos Block has garnered considerable interest. This study investigated the spatial distribution
of gas geochemical anomalies (e.g., high flux of CO2 in correspondence of the main faults) at regional
scale together with the seismic tomography in correspondence of this tectonic zone with the aim to figure out the
domain of convergent boundary between the Ordos block and Tibetan plateau, and trace the tectonic discontinuities
which are able to transfer fluids through the crustal layers between the two main geological units. From
northwest to southeast, obvious difference of spatial distributions of geochemical and geophysical features in the
tectonic zone between the northeast margin of the Tibetan Plateau and the Ordos Block is inferred. The northeast
area (Zone A) is dominated by thrust and strike-slip faults with clear velocity boundary underneath, where low
crack density (ε), saturation rate (ξ) and Poisson’ ratio (σ) in the middle-lower crust coincided with the low
values of heat flow and CO2 emissions, tectonic compression and regional locked-fault can be inducements. The
southeast area (Zone C) is dominated by extensional tectonics with roughly E-W fast-velocity direction (FVD) of
P-wave azimuthal anisotropy, where high permeability and porosity can be deduced from crustal high ε, ξ and
relatively high σ anomalies, resulting in high heat flow, CO2 concentrations and fluxes at the surface, and predominantly
crustal-derived gases. The intermediate area (Zone B) also dominated by thrust and strike-slip faults
is an extraordinary zone, where intensely locked-fault were clearly revealed, while the predominant anisotropic
FVDs in the middle crust changed obviously, more contribution of shallow gas component was detected, and CO2
flux, heat flow, and regional ε, ξ, and σ in the upper crust were higher, compared with those in Zone A, which
indicated the regional crushing fragmentation underneath Zone B. The adopted multidisciplinary approach
demonstrated that Zone B is the convergent boundary between the Tibetan Plateau and the Ordos Block.
Description:
Published
Description:
121386
Description:
OST3 Vicino alla faglia
Description:
JCR Journal
Keywords:
fluids
;
earthquakes
;
helium
;
Tibetan plateau
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
