Extrusion tectonics driven by the collision of Indian-Eurasian continents and the relative motion among microcontinents (e.g. South China, Simao-Indochina blocks) has led to multi-phase and complex ...geological activity and structures in Northern Vietnam. While extensively studied, its detailed crustal architecture in association with multiple large-scale shear zones and plate boundaries remains unclear and is key to resolving long-lasting tectonic debates. This study constructs the first 3-D regional S-wave velocity (Vs) model with consistent P-wave velocity (Vp) and Vp/Vs ratio models by jointly using the crustal and head waves (e.g. Pg/Sg and Pn/Sn phases) from an augmented earthquake catalog combining the Vietnam National Earthquake Catalog (VNCAT) and the data from multiple adjacent seismic networks. The quality of phase picking and earthquake location incorporating seismic data from various sources are carefully examined and collected for the tomographic inversion. We use a stepwise joint inversion scheme to subsequently constrain the earthquake location, 1-D and 3-D velocity models. The output models suggest that the Song Ma suture represents a better candidate for the Indochina-South China boundary rather than the Red River Shear Zone. The latter seems to act as a crustal structure while the former and the Dien Bien Phu Fault are likely lithospheric ones. Several other geologic features such as the Tu Le volcanic basin, the Song Hong basin, and the Day Nui Con Voi metamorphic complex are also clearly depicted and discussed in the model. This new set of the Vp, Vs, and Vp/Vs models could further contribute to better assessment to seismic hazards in the northern Vietnam.
•Incorporating later arrival phases to better constrain earthquake locations in Vietnamese National Earthquake Catalog.•Joint inversion of crustal and Moho-head waves to investigate whole crustal structures in Northern Vietnam.•Our current velocity models hinting at the Song Ma Suture a primary boundary between South China and Indochina Blocks.
The definitive account of one of the most important battles of the twentieth century, and the Black River borderlands' transformation into Northwest Vietnam This new work of historical and political ...geography ventures beyond the conventional framing of the Battle of Ði?n Biên Ph?, the 1954 conflict that toppled the French empire in Indochina. Tracking a longer period of anticolonial revolution and nation-state formation from 1945 to 1960, Christian Lentz argues that a Vietnamese elite constructed territory as a strategic form of rule. Engaging newly available archival sources, Lentz offers a novel conception of territory as a contingent outcome of spatial contests.
The Paleotethyan evolution of the Southeast Asia has become better understood in recent years. Questions remain, however, over the role of the Dien Bien Phu Suture Zone in the evolution of the ...Indochina Block and whether the Song Ma Suture represents the boundary between the Indochina Block and the South China Block. Granitoid geochronological and geochemical data obtained in northern Laos provide new information vis-à-vis these arguments. Zircon U–Pb ages together with whole rock, trace and rare earth element data from 27 granitic rocks from five complexes allow us to conclude that these granites are typical of I-type Indosinian volcanic arc granites. However, the 234–256Ma I-type granites mismatch the initiation age obtained from the ductile shear zone of the Dien Bien Phu Fault, thus repudiating the existence of the Dien Bien Phu Suture Zone. This then implies that the Qamdo–Simao and Indochina blocks were united. The geochemical and geochronological data further suggest that the main crust in the Indochina Block formed in the Late Paleoproterozoic to Early Mesoproterozoic, much later than the Archean crustal formation age identified east of the Song Ma Suture. Moreover, the 440–404Ma and 234–256Ma I-type granites suggest that the boundary between Indochina and South China should be the Jinsha River Suture–Song Ma Suture–Kontum Massif, instead of the Jinsha River Suture–Song Chay Suture. Finally, the Emeishan basalt and granite complexes both form part of the South China tectonic units subducting westward under the Qamdo–Simao and Indochina blocks.
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•The 234–256Ma and 440–404Ma granites from northern Laos are I-type granites.•The ages of Laotian granites mismatch the initiation age of the Dien Bien Phu Fault.•The South China Block subducted southward under the Simao-Indochina Block ca. 250Ma.
Quantifying the present–day kinematics of southeastern Tibet is important for understanding the tectonic evolution of the Tibetan Plateau. In this study, we established a three–dimensional finite ...element model to estimate fault slip and strain rates in the southeastern Tibetan Plateau based on Global Navigation Satellite Systems (GNSS) observations. Our model yields an overall good fit to the GNSS velocity field with residuals of 0.83 mm/yr and 0.85 mm/yr for the east and north components, respectively, comparable to the uncertainties of 0.67 mm/yr and 0.61 mm/yr. The model–derived strike–slip rates of the Xiaojiang fault, Nanhua–Chuxiong fault, Qujiang fault, central segment of Red River fault, southeastern segment of Red River fault and Dien Bien Phu fault are 13.7 ± 0.7 mm/yr, 1.9 ± 0.6 mm/yr, 3.4 ± 1.1 mm/yr, 1.5 ± 0.5 mm/yr, 1.2 ± 0.4 mm/yr and 1.6 ± 0.4 mm/yr, respectively, which are consistent with previous geological results, implying that the short–term fault motions estimated from GNSS data can reflect the long–term fault slip in the southeastern Tibetan Plateau. The shear strain rate is localized along the Xiaojiang fault, which agrees with predictions of the tectonic extrusion model (i.e., the lateral extrusion of internally rigid blocks along strike-slip faults). Strain orientations in the western part of southeastern Tibetan Plateau are characterized by clockwise rotation. Comparison of the surface strain rates, crustal stress, and seismic anisotropy reveals general consistency between deformation of the surface and upper crust. The eastern part of southeastern Tibetan Plateau has small residuals, and the present–day crustal deformation can be explained by rigid block motion. However, the western part of the study area has relatively large residuals, implying that other processes, such as gravitational spreading, may influence deformation in the area. We propose a hybrid model that combines rigid block motion with continuum deformation to explain the contemporary crustal deformation of southeastern Tibetan Plateau.
•We established a three-dimensional finite element model to analyze the fault slip and strain rates in southeastern Tibet.•We find good agreement between the GNSS and geologic slip rates in southeastern Tibetan Plateau.•Comparison of strain rate, stress, seismic anisotropy reveals consistency between deformation of surface and upper crust.
The Dien Bien Phu (DBP) Fault strikes nearly perpendicular to the general tectonic framework, separating northwest Vietnam into two compartments. The DBP and Muong Lay granites are exposed ...respectively east and west of the fault. The U/Pb age of 277±2Ma obtained for the Muong Lay granite is similar to the age of the Chieng Khuong complex exposed within the Song Ma structure east of the DBP Fault. These two magmatic intrusions are considered as belonging to a same tectonic structure related to the subduction of the Song Ma Ocean under the Indochina Block during the Indosinian orogeny. The DBP Fault with a total post Permian dextral offset of 30–40km shifts the Song Ma Suture. It could then be connected to the Ailao Shan–Shuanggou suture to the north. The undeformed DBP granite gave a U/Pb age of 230±1Ma sealing the Indosinian deformation on the fault. The Ladinian–Carnian activity of the fault is confirmed by the 40Ar/39Ar (biotite) age of 228±4Ma obtained from the paragneiss forming the fault zone. A geodynamic model is proposed to describe the various tectonic phases recorded by on the DBP Fault. It associates field data, stratigraphic observations, and geochronology analyses (U/Pb, Ar/Ar, fission tracks). Following the Late Triassic exhumation of the granite and the end of the Indosinian orogeny marked by the Norian unconformity, the granite was buried under Jurassic and Lower Cretaceous sediments. A strong cooling event during the early Late Cretaceous (100Ma) is associated with the reactivation of the DBP Fault and the accommodation of a southward thrusting of the Song Da terrane onto the Truong Son Belt. This newly recognised tectonic phase could be associated to the subduction of the Paleo-Pacific plate under the Indochina Block. No data are available yet to constrain the Tertiary evolution of the DBP system. However, the Tertiary deformation is likely similar to the Cretaceous one.
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•The SE corner of the Simao block is a continuation of the Song Da structure.•The Dien Bien Phu fault was active at 230 Ma and has been reactivated at 100Ma.•The DBP fault accommodates the thrusting of the Song Da terrane onto the Truong Song.
Several models have been proposed to describe the tectonic evolution of SE Tibet and its marginal areas. Hence, high‐resolution crustal velocity models are essential to address this controversy. With ...waveform data from 73 broadband stations in southwest China and northern Vietnam, we invert for a 3‐D shear wave velocity model of the crust and uppermost mantle from ambient noise tomography. Our model reveals that the midlower crustal low‐velocity zone in the Xiaojiang Fault Zone extends farther southward across the Red River Fault to Vietnam and is approximately bounded by the Xiaojiang and Dien Bien Phu faults to the east. We suggest that the observed low‐velocity zone represents a mechanically weak zone in the mid‐lower crust, which may serve as a channel for efficient southward material transport in SE Tibet. With our results and previous evidence, we propose a combined model that integrates rigid block extrusion and crustal channel flow to describe the large‐scale material transport in SE Tibet. We further propose a two‐phase material transport model in SE Tibet after the India‐Eurasia plate collision: (1) rigid block extrusion between the right‐lateral Sagaing Fault and left‐lateral Red River Fault during the early Oligocene‐early Miocene and (2) a combined model of rigid block extrusion and material channel flow in the mid‐lower crust from the late Miocene to the present. The southward crustal material transport is likely to be diverted along two major channels around the more rigid crust beneath the inner zone of the Emeishan large igneous province.
Key Points
The crustal low‐velocity zone in southwest China spreads from north to south and extends across the Red River Fault into northern Vietnam
A combined model of rigid block extrusion and ductile material channel flow can explain material transport patterns in SE Tibet well
Integrating with previous studies, we propose a two‐phase model for large‐scale material transport in SE Tibet
Following the French reoccupation of Indochina at the end of World War II, the pro-Communist Vietnamese nationalists, or Viet Minh, launched a grassroots insurgency that erupted into a full-fledged ...war in 1949. After nearly ten years of savage combat, the western world was stunned when Viet Minh forces decisively defeated the French Union army at the battle of Dien Bien Phu in May 1954. Logistics dominated every aspect of the First Indochina War, dictating the objectives, the organization of forces, the timing and duration of the operations, and even the final outcome.
InA War of Logistics, Charles R. Shrader meticulously examines both French Union and Viet Minh logistical units during the period of active conventional warfare, as well as external support provided to the French by the United States and to the Vietnamese by China. Although the Vietnamese had few advantages over their opponents, their military leaders brilliantly employed a highly committed network of soldiers and civilians, outfitted to accommodate the challenging terrain on which they fought.
Drawing on extensive research such as declassified intelligence documents, the reports of French participants, and accounts by Viet Minh leaders, including Vo Nguyen Giap and Ho Chi Minh,A War of Logisticsprovides in-depth coverage of the often-ignored but critically important topic of logistics in modern military campaigns.
Constraining the timing of fault zone origin and movement history is of fundamental geotectonic importance to understand the evolution and processes of the brittle fault structures. The authors ...present in this paper authigenic illite K-Ar age data from the fault gouge samples, collected from the Dien Bien Phu Fault (DBPF) in the Dien Bien province, Vietnam as well as in a major strike-slip fault zone in South-East Asia; all of which played important roles in the structural formation and geotectonic development of northwestern Vietnam. The gouge fault samples were separated into four grain-size fractions (<0.1μm, 0.1–0.4μm, 0.4–1.0μm and 1.0–2.0μm).
The K-Ar ages of the fractions were divided into two age groups, from 26 to 29Ma and 130Ma. The timing of the fault movements is defined at 26±0.24Ma, 29±0.61Ma, 130.1±1.27Ma and 130.7±1.29Ma. This indicates that the Dien Bien Phu Fault underwent two movements, first in the Early Cretaceous, with an age of about 130Ma and second in the Oligocene (Paleogene), with an age of about 26–29Ma. The ductile deformation of the DBPF terminated during the Early Cretaceous. These studies also indicate slow exhumation of the Dien Bien granitoid complex during the Cretaceous times.
The Oligocene ages indicate that the DBPF had been reactivated by the SE extrusion and clock-wise rotation of the Indochina block, caused by the collision of the Indian and Eurasian plates. This tectonic event led to the DBPF brittle-sinistral movement, causing the exhumation phase along the fault. This movement period (ca. 26–29Ma) is coexistent with 600–700km sinistral shearing along the Red River–Ailao Shan fault.
This is the first report determining the absolute age constraints of multi-activated tectonic events, affecting the Dien Bien Phu Fault using the K-Ar dating method for the gouge samples.
•The first report determining absolute age constraints of multi-activated tectonic events affecting the Dien Bien Phu Fault.•The direct evidence of transpressive NNE–SSW strike-slip and oblique-slip movements by the Dien Bien Phu Fault is provided.•The timings of the fault movements are defined at 26±0.24 Ma, 29±0.61 Ma, 130.1±1.27 Ma and 130.7±1.29 Ma.•Stage of 26–29 Ma reflects major tectonic development of South East Asia following collision of India with Eurasia.
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