Search

A nickel oxide (NiO)/silver (Ag)/NiO (NAN) transparent conducting electrode (TCE) was deposited on NiO and zinc oxide (ZnO) to fabricate Schottky diodes (SDs). The physical and electrical properties of NAN/NiO and NAN/ZnO SDs were studied. In addition, conventional Au/ZnO SDs were fabricated for comparison. The prepared NAN TCE was of n-type, with more than 40% transmittance and a low sheet resistance of 6.5 Ω sq.−1, indicating that NAN is an exceptional TCE. Secondary ion mass spectrometry revealed that Ag atoms diffused into NiO and ZnO in the NAN/NiO and NAN/ZnO SDs, respectively. Owing to the large number of defects on the ZnO surface, the current–voltage (I–V) characteristics of the Au/ZnO SDs followed a linear curve. However, the reduced number of defects and a large barrier height at the NAN/ZnO interface led to a rectifying I–V curve in NAN/ZnO SDs. In contrast, a near homojunction at the NAN/NiO interface caused a linear I–V curve and a large leakage current in NAN/NiO SDs. These issues resulted in a lower ideality factor (5.32) in NAN/ZnO SDs than that in NAN/NiO SDs (15.14). The NAN/ZnO SDs exhibited a higher barrier height (0.91 eV) than the NAN/NiO SDs (0.55 eV). The mechanism of carrier transport was investigated using a ln(I) versus ln(V) plot. The NAN/NiO SDs only exhibited one region of ohmic conduction. However, two distinct regions were observed in the NAN/ZnO SDs. For V ≤ 0.7 V, the space-charge-limited current dominated; however, the diffusion–recombination model controlled carrier transport at V ≥ 0.7 V. Band diagrams were proposed to elucidate the carrier transport mechanism in NAN/NiO and NAN/ZnO SDs. [ABSTRACT FROM AUTHOR]

Observations over the last few decades from a number of orogenic systems have highlighted the possible importance of tectonic exhumation, i.e., ductile thinning and normal faulting, in exhuming rocks once buried in high-pressure conditions. Taiwan is one of the few active orogens in the world where rocks that once experienced high-pressure metamorphism (> 50 km) are exposed at the Earth's surface, providing a natural laboratory for advancing our understanding of exhumation processes. We integrate previously published studies of the Taiwan orogen with new structural, geochronological, and fluid inclusion microthermometry data to argue that tectonic extrusion and structural thinning played a critical role in exhuming the metamorphic core of the orogen until very recently, ca. 0.7 Ma. We propose a two-stage process for exhuming the high-pressure metamorphic rocks of the Yuli Belt: an initial stage where exhumation is driven primarily by pressure gradients in a subduction channel and a second stage that is initiated as an orogen-parallel regional-scale strike-slip zone, the Tailuko shear zone, is offset by an orogen-normal strike-slip zone. The offset generates an extensional bend that is filled with extruding high-pressure rocks as the upper crust is structurally thinned. Evidence for tectonic thinning comes primarily from a low-angle penetrative foliation that records significant vertical shortening and a suite of sub-vertical late-stage, mineral-filled veins. Isotopic dating indicates that the second stage started ca. 2.4–3.1 Ma and ended at ca. 0.7 Ma when the northern Backbone Range orocline started to form. We propose the low-angle foliation formed in the footwall of a regional-scale extensional shear zone that rooted to the east, beneath the forearc. Combined tectonic and erosional processes may have limited the topographic growth of the orogen from ~3.0 to < 1.0 Ma. [ABSTRACT FROM AUTHOR]

The Central Asian Orogenic Belt (CAOB) formed mainly in the Paleozoic due to the closure of the Paleo-Asian oceanic basins and accompanying prolonged accretion of pelagic sediments, oceanic crust, magmatic arcs, and Precambrian terranes. The timing of subduction–accretion processes and closure of the Paleo-Asian Ocean has long been controversial and is addressed in a geochemical and isotopic investigation of mafic rocks, which can yield important insight into the geodynamics of subduction zone environments. The Xilingol Complex, located on the northern subduction–accretion zone of the CAOB, mainly comprises strongly deformed quartzo-feldspathic gneisses with intercalated lenticular or quasi-lamellar amphibolite bodies. An integrated study of the petrology, geochemistry, and geochronology of a suite of amphibolites from the complex constrains the nature of the mantle source and the tectono-metamorphic events in the belt. The protoliths of these amphibolites are gabbros and gabbroic diorites that intruded at ca. 340–321 Ma with positive εHf (t) values ranging from + 2.89 to + 12.98. Their T DM1 model ages range from 455 to 855 Ma and peak at 617 Ma, suggesting that these mafic rocks are derived from a depleted continental lithospheric mantle. The primitive magma was generated by variable degrees of partial melting of spinel-bearing peridotites. Fractionation of olivine, clinopyroxene and hornblende has played a dominant role during magma differentiation with little or no crustal contamination. The mafic rocks are derived from a Late Neoproterozoic depleted mantle source that was subsequently enriched by melts affected by slab-derived fluids and sediments, or melts with a sedimentary source rock. The Carboniferous mafic rocks in the northern accretionary zone of the CAOB record a regional extensional event after the Early Paleozoic subduction of the Paleo-Asian Ocean. Both addition of mantle-derived magmas and recycling of oceanic crust played key roles in significant Late Carboniferous (ca. 340–309 Ma) vertical crustal growth in the CAOB. Amphibolite–facies metamorphism (P = 0.34–0.52 GPa, T = 675–708 °C) affected these mafic rocks in the Xilingol Complex at ca. 306–296 Ma, which may be related to the crustal thickening by northward subduction of a forearc oceanic crust beneath the southern margin of the South Mongolian microcontinent. The final formation of the Solonker zone may have lasted until ca. 228 Ma. [ABSTRACT FROM AUTHOR]

The Yuli metamorphic belt has been the topic of petrological and geochronological studies for over 40 years and has been interpreted as a Cretaceous mélange. Our study utilizes zircon U-Pb dating of schist and exotic blueschist blocks in the Yuli belt. These new ages indicate that these metamorphic rocks are actually middle Miocene in age and may represent the deeper structural levels of an accretionary prism. Several distinctive detrital zircon U-Pb age populations are recognized from 14 siliceous schists of mélange-hosted rocks that are similar in age population to the Cretaceous, Eocene-Oligocene, and Miocene strata of Taiwan. The wide range of ages is interpreted as a product mixing of various sedimentary strata prior to metamorphism. Three blueschists of a volcanic-arc protolith enclosed within the host rocks yield crystallization ages of 15.4 ± 0.4, 15.5 ± 0.3, and 16.0 ± 0.2 Ma based on zircon U-Pb dating. In consideration of the new data regarding the Cretaceous-Miocene host rocks and the middle Miocene exotic blueschist blocks, it strongly suggests that the Yuli belt formed at deeper levels of an accretionary wedge during subduction of South China Sea oceanic crust at the middle-late Miocene. Subsequently, the rapid uplift of the metamorphic belt was probably related to doubly vergent wedge extrusion due to the Pliocene arc-continent collision. [ABSTRACT FROM AUTHOR]

The Taiwan orogenic belt results from convergence between the Philippine Sea plate and Eurasia plate since the late Cenozoic. An extremely high exhumation rate has been observed in the Backbone Range, which has motivated interpretive models that show underplating as the primary process in driving uplift and thickening. Here we integrate new (U-Th)/He and fission-track dates of detrital zircons with previously published thermochronology to document a significant out-of-sequence thrust in the core of Taiwan orogen. The thrust, informally named the Tayulin fault system, is identified by structural kinematics and offset metamorphic temperature trends, low-temperature thermochronometric dates, and seismic tomography. The OOST appears to be composed of three segments that crop out along the western flank of the Backbone Range. The apparent age-elevation profiles suggest a relatively slow exhumation rate, <1.0 mm/yr, in the early stages from 8 Ma to 2 Ma followed by a stage of significantly higher exhumation rates, ranging from 2.3 to 6.5 mm/yr after 2 Ma. The early slow exhumation stage is related to regional folding and foliation development. In contrast, we suggest the younger rapid exhumation stage is related to slip on the out-of-sequence thrust. • We detect a new Tayulin out-of-sequence thrust (OOST) in Taiwan orogeny. • The exhumation rate is less than 0.1 mm/yr from ca. 8 Ma to 2 Ma in Backbone Range. • Exhumation rate increases to 2.3 mm-6.5 mm/yr after 2 Ma in Backbone Range. • The slow exhumation could be related to the regional-scale folding process. • The OOST plays an important role in the rapid exhumation process after 2 Ma. [ABSTRACT FROM AUTHOR]

Highlights: [•] Two stage rapid exhumations were revealed in southern segment of the Longmenshan Range, eastern Tibet. [•] The first stage is from ca. 30Ma and the second stage is from 3–5Ma to now. [•] The second stage of rapid exhumation is consistent with the second stage of activity of the Xianshuihe fault. [•] The age distribution of fission track dating is controlled by fault geometry and in-sequence faulting mechanisms. [Copyright &y& Elsevier]

Abstract: We have conducted flexure and sandbox experiments to investigate the 3-D plate interactions in Central Taiwan. The abnormally low-surface-slope mountain belt in Central Taiwan fails to account for the large deflection of the underlying lithosphere. We propose that the northward subduction of the Philippine Sea Plate applies additional bending moments and shear forces to the Eurasian Plate at the plate suture. The interactions between the Eurasian Plate and the Philippine Sea Plate in Central Taiwan could have enhanced the deflection of the continental margin and created a deep tear fault identified in an early study. We have conducted flexure and gravity modeling to confirm that additional downward shear forces are exerted on the Eurasian Plate along the suture zone of the two plates. These forces increase northwardly with the subduction of the Philippine Sea Plate. The fact that the Eurasian Plate deflects with the northward bending of the Philippine Sea Plate implies an eastward subduction of the Eurasian Plate in Central Taiwan. In addition, our model suggests that the bending moment changes from positive (bending upward) to negative (bending downward) southwardly along the Longitudinal Valley. This finding implies a transition from a continental crust to an oceanic one or to a transitional crust southward along the plate suture or/and delamination of a light crust during subduction of the southern part of the Eurasian Plate. The spatial variation in bending moment along the plate suture could also result from a break-off of the east leading edge of the Eurasian Plate near the northern end of the Longitudinal Valley. We have also investigated surface structure by incorporating oblique deflection of the continental margin into our sandbox model. Unlike previous extrusion models, our results show that a salient structure with low-surface-slope mountain ranges can develop even without the presence of a rigid basement high. [Copyright &y& Elsevier]

Abstract: Most researches consider the Taiwan Orogeny to be the result of an oblique arc–continental collision between the Philippine Sea Plate and Eurasia Plate. According to kinematic modeling, the mountains started to build from the north and progressively propagated southward at a rate of 60–90 km/my. Because of the oblique nature of the collision, the influence of the collision on mountain building resulted in the southern Central Range experiencing orogenic processes more recently than in the north. In order to test this model, we studied a critical area using zircon and apatite fission-track data to reveal the early exhumation history of the southern Central Range. We find that exhumation started about 6 Ma, which is earlier than the previously predicted timing of mountain building. We also find that the exhumation history can be separated into two stages: an initial stage starting at ca. 6 Ma and continuing to ca. 1 Ma with a slow uplift rate of <1 mm/yr; and a second stage starting at ca. 1 Ma until the present with a high uplift rate of 4–10 mm/yr. The initial stage of mountain building is considered to be related to accretionary wedge deformation as the South China Sea Plate subducted beneath the Philippine Sea Plate whereas the second stage mountain building resulted from the arc–continental collision. Combining the ages of isotopic dating and fission-track dating in the northern Central Range, we find that the northern Central Range also could start exhumation at ca. 6 Ma and that its exhumation history can also be separated into two stages with similar exhumation patterns and mechanisms to that of the southern Central Range. The most notable difference between the exhumation history of the northern and southern areas of the range is the more extensive degree of exhumation in the north; this could be attributed to the northern Central Range having experienced a longer collision history. [Copyright &y& Elsevier]

Abstract Knowledge of how strain is partitioned and accommodated in crustal shortening provides fundamental constraints on evaluating tectonic models of orogenic plateaus. A number of tectonic models have been proposed for the central Longmen Shan along the eastern Tibetan Plateau margin, including mid-crustal channel flow, upper crustal shortening, and whole crust shearing. However, it remains controversial whether these models work in the Min Shan – northern Longmen Shan area, and if so, how the models function in three dimensions. One straightforward test is to evaluate the timing and rate of uplift on the principle crustal faults. Here we present 36 fission track dates from this region. Our data show that the southeastern Min Shan has experienced the most rapid exhumation in this area since the late Miocene, due to slip along the Huya thrust and coeval northwestward tilting of the Min Shan fault block. Further, we identify a "maximum exhumation belt" (MEB) along Min Shan and Longmen Shan that is characterized by the greatest amount of exhumation in the late Cenozoic and the formation of 5000+ m peaks along the eastern Tibetan Plateau margin. Interestingly, the MEB overlies the "Moho ramp" between the Tibetan Plateau and the Sichuan Basin. The parallelism between the MEB and the Moho ramp leads us to a crustal-scale tectonic model, in which the Tibetan upper crust undergoes shortening and thrusting and the lower crust undergoes pure-shear thickening. Moreover, a ∼15° angle exists between the trend of the MEB and that of the Longmen Shan, implying that the Longmenshan thrust belt is a reactivated structure, which explains the along-strike variations of fault kinematics and activity. We conclude that the eastern Tibetan crust is partially decoupled, and future studies need to quantify strain partitioning in both the upper and the lower crust during continental orogenesis. Highlights • Rapid exhumation (∼0.9 mm/yr) and northwestward tilting occurred in Min Shan. • A maximum exhumation belt (MEB) overlaps the Moho ramp along the plateau margin. • The parallelism implies deep crustal deformation influences surface exhumation. • The MEB has ∼15° angle with the Longmen Shan, indicative of tectonic reactivation. • Partially decoupled upper and lower crust and a fully coupled crust and mantle. [ABSTRACT FROM AUTHOR]

The Cenozoic orogenic process of the Longmen Shan (LMS) and the kinematics of major faults along the LMS are crucial for understanding the growth history and mechanism of the eastern Tibetan Plateau. Three major faults, from west to east, are present in the central segment of the LMS: the Wenchuan-Maoxian Fault (WMF), the Beichuan-Yingxiu Fault (BYF), and the Jiangyou-Guanxian Fault (JGF). Previous researchers have placed great impetus on the Pengguan Massif, between the WMF and BYF. However, limited low-temperature thermochronology data coverage in other areas prevents us from fully delineating the tectonic history of the LMS. In this study, we collect 22 samples from vertical profiles in the Xuelongbao Massif and the range frontal area located at the hanging walls of the WMF and JGF respectively, and conduct apatite and zircon fission track analyses. New fission track data reveal that the Xuelongbao Massif has been undergoing rapid exhumation with an average rate of ~ 0.7–0.9 mm/yr since ~ 11 Ma, and the range frontal area began rapid exhumation at ~ 7.5 Ma with total exhumation of ~ 2.5–4.5 km. The exhumation histories indicate that the three major faults (WMF, BYF and JGF) in the central LMS are all reverse faults, and show a basinward in-sequence propagation from middle Miocene to present-day. Such a pattern further implies that upper crustal shortening is the primary driver for the LMS' uplift during the Late Cenozoic. Nevertheless, middle-lower crustal deformation is difficult to be constrained by the exhumation histories, and its contribution to LMS' uplift cannot be ruled out. [ABSTRACT FROM AUTHOR]

We adopted 106 campaign-mode GPS observations and 310 precise leveling measurements between 2002 and 2010 to understand the present-day crustal deformation in mudstone area and to estimate the earthquake potential of the Hsiaokangshan (HKSF) and the Chishan faults (CHNF) in southwest Taiwan. Horizontal velocities east of the CHNF are ~ 66 mm/yr, 270° and gradually decrease westward to ~ 15 mm/yr, N259°. A horizontal velocity gradient of ~ 15 mm/yr is shown between the HKSF and CHNF. Subsidence rates west of the HKSF and east of the CHNF are ~ 5–10 mm/yr, while the uplift is observed between these two faults in the highest elevation with the maximum rate of ~ 18 mm/yr. The observed deformation patterns are difficult to be fully modeled by 2D kinematic fault model. Field relationships within the vertical shear zones of the mudstone therefore indicate that the deformation pattern may be also controlled by a relic onshore mud diapir that is still experiencing vertical uplift. Consistency between the geological and geodetic vertical velocities, weak rock strength, and no destructive earthquakes over the last 100 years imply that faults (HKSF) within the mudstone area are creeping. However, the CHNF or the associated décollement may still have earthquake potential. [ABSTRACT FROM AUTHOR]

Within the Sanbagawa metamorphic belt, the timing of high-pressure and retrograde metamorphism is controversial. Recently, an area in the Asemi River region (central Shikoku, Japan) was delineated that had been subjected to ecologite facies metamorphism prior to retrograde metamorphism in the epidote-amphibolite facies which provides a new opportunity to constrain the age of high-pressure metamorphism. Detrital zircon from this area yields ages as young as 84 ± 4 Ma. Hence, the protoliths were deposited not earlier than ca. 88 Ma and thus, eclogite facies and retrograde metamorphism occurred after 88 Ma, probably at 86–82 Ma as indicated by the age of metamorphic zircon and K-Ar and Ar-Ar ages for white mica. [ABSTRACT FROM AUTHOR]

Deep tectonic processes are key integral components in the evolution of mountain belts, while observations of their temporal development are generally obscured by thermal resetting, retrograde alteration and structural overprinting. Here we recorded an integrated rock time-temperature history for the first time in the pro-wedge part of the active Taiwan arc-continent collision starting from sedimentation through cleavage-forming state to its final exhumation. The integrated thermal and age results from the Raman Spectroscopy of Carbonaceous Material (RSCM) method, zircon U-Pb laser ablation dating, and in-situ 40 Ar/ 39 Ar laser microprobe dating suggest that the basal accretion process was crucial to the development of the Taiwanese orogenic wedge. The basal accretion process commenced early in the mountain building history (∼6 Ma) and gradually migrated to greater depths, as constrained by persistent plate convergence and cleavage formation under nearly isothermal state at similar depths until ∼ 2.5 Ma recorded in the early-accreted units. Such development essentially contributed to mountain root growth by the increased depth of the wedge detachment and the downward wedge thickening during the incipient to full collision stages in the Taiwan mountain belt. [ABSTRACT FROM AUTHOR]

Erosion and tectonic uplift are widely thought to be coupled through feedbacks involving orographic precipitation, relief development, and crustal weakening. In many orogenic systems, it can be difficult to distinguish whether true feedbacks exist, or whether observed features are a consequence of tectonic forcing. To help elucidate these interactions, we examine Gongga Shan, a 7556 m peak on the eastern margin of the Tibetan Plateau where cosmogenic 10 Be basin-wide erosion rates reach >5 mm/yr, defining a region of localized rapid erosion associated with a restraining bend in the left-lateral Xianshuihe Fault. Erosion rates are consistent with topography, thermochronometry, and geodetic data, suggesting a stable pattern of uplift and exhumation over at least the past 2–3 My. Transpression along the Xianshuihe Fault, orographically enhanced precipitation, thermally weakened crust, and substantial local relief all developed independently in the Gongga region and existed there prior to the uplift of Gongga Shan. However, only where all of these conditions are present do the observed topographic and erosional extremes exist, and their relative timing indicates that these conditions are not a consequence of rapid uplift. We conclude that their collocation at 3–4 Ma set into motion a series of feedbacks between erosion and uplift that has resulted in the exceptionally high topography and rapid erosion rates observed today. [ABSTRACT FROM AUTHOR]

The Tananao Schist Belt is a low-pressure metamorphic complex comprised of three lithological units of marble, schist formation, and granite, in ascending order of proportion. Previous studies have found that the schist formation was formed during the Mesozoic. However, there is a lack of geochronological data to corroborate the schist protolith and metamorphic ages. In this study, we have used U Pb zircon geochronology to provide a time frame for the creation of the schist formation and metamorphism, as well as a new tectonic model. Twenty-three schist and eleven meta-magmatic samples were used for U Pb dating by LA-ICP-MS. Results from the youngest peak age of detrital zircon indicate that the schist formed in a new depositional age of 120–110 Ma and, therefore, is different from the previously estimated age of the Paleozoic-Mesozoic. Additionally, the block-in-matrix schist indicates an age that ranges from 270 to 80 Ma and was inferred from the chaotic deposits to be a metamorphic mélange. The Tananao Schist Belt appears to represent an arc-trench system that formed during the Cretaceous in the South China Block margin. Moreover, the youngest U Pb age of 80 Ma from the leucogranite dike and schist, constrains the upper age limit for a metamorphism that is younger than the previously accepted age of 100–90 Ma. The contact layer between Permian-Triassic marble and the overlying early Cretaceous schists remains a chloritoid bed that is, therefore, considered to be a paleosol at the unconformity, which formed over an extended duration of 60 ± 30 Ma. The stratigraphic contact indicates a long period of erosion during the Jurassic and suggests that a tectonic event occurred. However, we propose that two important metamorphic events took place prior to, and following, the schist formation during the Jurassic and late Cretaceous orogenic events. [ABSTRACT FROM AUTHOR]

Abstract: We integrated a regional tomography model, 20-year seismicity and earthquake focal mechanisms of the 4 March 2010 M L 6.4 Jiashian earthquake source region to delineate the seismogenic structure and mechanics of a relatively rare damaging inland earthquake that occurred in the southwestern fold-and-thrust belt of Taiwan. The main shock of the Jiashian earthquake occurred at a depth of 23km beneath the slate belt of the southern Central Range with a sinistral thrust mechanism. Based on seismic tomography and seismicity, the Jiashian earthquake sequence occurred in the Chishan transfer fault zone, which we interpret to be located near the transition zone between the subducted Eurasian plate to the south and the arc–continent Taiwan collision to the north. The distribution of the Jiashian aftershocks define a WNW-ESE striking fault plane that dips 30–40° NNE which is consistent with the optimal fault plane of the GPS-derived coseismic slip model. Focal mechanisms and inverted stress results of the earthquake sequence indicate both thrust and strike–slip motions with the maximum compressive stress at nearly 90° to the regional compressive stress and thus sub-parallel to the strike of the Taiwan orogen. We propose that the 2010 Jiashian earthquake resulted from rupturing of a buried oblique fault within the Chishan transfer fault zone at the subduction–collision transition zone in southern Taiwan. The orogen-parallel P-axis of the 2010 Jiashian earthquake represents collision-related lateral compression, although a local stress deviation is also possible. [Copyright &y& Elsevier]

Abstract: Support vector machine (SVM) modeling is based on statistical learning theory. It involves a training phase with associated input and target output values. In recent years, the method has become increasingly popular. The main purpose of this study is to evaluate the mapping power of SVM modeling in earthquake triggered landslide-susceptibility mapping for a section of the Jianjiang River watershed using a Geographic Information System (GIS) software. The river was affected by the Wenchuan earthquake of May 12, 2008. Visual interpretation of colored aerial photographs of 1-m resolution and extensive field surveys provided a detailed landslide inventory map containing 3147 landslides related to the 2008 Wenchuan earthquake. Elevation, slope angle, slope aspect, distance from seismogenic faults, distance from drainages, and lithology were used as the controlling parameters. For modeling, three groups of positive and negative training samples were used in concert with four different kernel functions. Positive training samples include the centroids of 500 large landslides, those of all 3147 landslides, and 5000 randomly selected points in landslide polygons. Negative training samples include 500, 3147, and 5000 randomly selected points on slopes that remained stable during the Wenchuan earthquake. The four kernel functions are linear, polynomial, radial basis, and sigmoid. In total, 12 cases of landslide susceptibility were mapped. Comparative analyses of landslide-susceptibility probability and area relation curves show that both the polynomial and radial basis functions suitably classified the input data as either landslide positive or negative though the radial basis function was more successful. The 12 generated landslide-susceptibility maps were compared with known landslide centroid locations and landslide polygons to verify the success rate and predictive accuracy of each model. The 12 results were further validated using area-under-curve analysis. Group 3 with 5000 randomly selected points on the landslide polygons, and 5000 randomly selected points along stable slopes gave the best results with a success rate of 79.20% and predictive accuracy of 79.13% under the radial basis function. Of all the results, the sigmoid kernel function was the least skillful when used in concert with the centroid data of all 3147 landslides as positive training samples, and the negative training samples of 3147 randomly selected points in regions of stable slope (success rate=54.95%; predictive accuracy=61.85%). This paper also provides suggestions and reference data for selecting appropriate training samples and kernel function types for earthquake triggered landslide-susceptibility mapping using SVM modeling. Predictive landslide-susceptibility maps could be useful in hazard mitigation by helping planners understand the probability of landslides in different regions. [Copyright &y& Elsevier]