moderate-resolution wide-wavelength images (MWI), Hongze Lake, total suspended particulate matter (TSPM), remote sensing Total suspended particulate matter (TSPM) is an important indicator of water quality.Remote sensing has advantages of wide range and high time efficiency.The use of satellites to monitor TSPM concentration is of great significance for the study of water quality and eutrophication.Using the measured data on the ground and taking Hongze Lake as the research area, we compared and analyzed seven types of suspended particulate matter concentration estimation model based on Tiangong-II wide-band moderate-resolution widewavelength images (MWI), selected the TSPM concentration estimation model suitable for the MWI data of Hongze Lake, and verified the accuracy and applicability of MWI data products.The results show that the linear model constructed by using the band ratio combination of B5/B9 MWI data as a variable has a high estimation accuracy, with a determination coefficient of 0.94, an average absolute error percentage of 12.27%, and a root mean square error of 2.97 mg/L.Compared with the TSPM estimation results from the moderate-resolution imaging spectroradiometer data obtained on the same day, the two estimation results were similar, and the change trend of TSPM concentration is basically consistent.The TSPM concentration in Hongze Lake has an obvious spatial difference.Huaihe River Bay is affected by its inflow into the lake, and its TSPM concentration is the highest.The concentration in the east of the gulf of Lihe Bay was also affected by Huaihe River Bay.Owing to eutrophication, the TSPM concentration of Chengzi Bay is relatively high in some areas.
Abstract The cause of magmatic tempo in an active plate margin remains controversial, partly due to lack of structural analysis. During 130–105 Ma, the magmatism in the South China Block (SCB) was significantly reduced (lull) and restricted around the Changle‐Nan'ao Belt (CNB) while the magmatism was highly active (flare‐up) in North China. For unveiling the tectonic role on magmatism, a multidisciplinary study including field and microscopic structural observations, magnetic fabric measurement (AMS), and zircon/monazite dating was conducted on the plutons with oriented minerals in the CNB. Structural analysis and AMS results show a highly clustered NE‐striking vertical foliation developed during the emplacement indicating a syn‐emplacement NW‐SE shortening regime. The geochronology results confirm that the emplacement occurred during 130–105 Ma. Regional geologic correlation indicates that the collision between the Dangerous Grounds‐West Philippines Block and SCB was responsible for this shortening regime. The collected depleted zircon ε Hf(t) data suggest that a possible collision‐triggered slab break‐off caused the syn‐collisional magmatic activity around the CNB. This study shows that the magmatic lull in the SCB was coeval with a crustal shortening regime due to the arrival of a microcontinent carried by the subduction slab, while the magmatic flare‐up was coeval with an extensional regime due to the subduction roll‐back and retreat as evidenced by the Cretaceous evolution of the SCB before and after the collision and that of North China which is unaffected by the collision. The cause of magmatic tempo in the continental margin is largely due to the tectonic evolution of underlain subduction slabs.
[1] The present-day topography of the Tian Shan range is considered to result from crustal shortening related to the ongoing India-Asia collision that started in the early Tertiary. In this study we report evidence for several episodes of localized tectonic activity which occurred prior to that major orogenic event. Apatite fission track analysis and (U-Th)/He dating on apatite and zircon indicate that inherited Paleozoic structures were reactivated in the late Paleozoic-early Mesozoic during a Cimmerian orogenic episode and also in the Late Cretaceous-Paleogene (around 65–60 Ma). These reactivations could have resulted from the accretion of the Kohistan-Dras arc or lithospheric extension in the Siberia-Mongolia zone. Activity resumed in the late Mesozoic prior to the major Tertiary orogenic phase. Finally, the ongoing deformation, which again reactivates inherited tectonic structures, tends to propagate inside the endoreic basins that were preserved in the range, leading to their progressive closure. This study demonstrates the importance of inherited structures in localizing the first increments of the deformation before it propagates into yet undeformed areas.
In Northern Africa, Zn-Pb ore deposits are numerous, and Zn ores of supergene origin
have been long extracted for local use using calcination to smelt the metals. While the
renewal of interest in non-sulfide ores coincides with improvements in mineral
processing, the recent opening of a Zn-oxides production plant in Morocco attests to the
multipartite will to revive interest in the non-sulfide ores disseminated throughout the
Atlas Mountains, as it represents a direct source of employment and an opportunity to
create infrastructure in remote places.
Six non-sulfide Zn-Pb ore deposits, namely Toulal, Ait Labbes, Tadaghast, Beni Tajite,
Bou Arhous, Tizi n'Firest, (representing an overall production of ca. 1Mt at 24% Zn)
hosted in the Lower Jurassic reef to para-reef limestone have been investigated in the
Moroccan High Atlas, to understand processes and timing of their formation. Ore
occurs either in veins associated with a faulted anticline, or in orthogonal fractures or
stratabound horizons in tilted strata. A vertical zoning from deep Zn-Pb sulfide
stratabound lenses to shallow non-sulfide deposits has been reported. Zn (Pb)
carbonates, Zn silicates and hydrated associated minerals directly replace the sulfide ore
bodies or filled cavities along fractures related to the Atlasic events.
Field observation has been complemented by a multidisciplinary approach (Raman,
SEM, EPMA) for mineralogical characterization, revealing a similar paragenetic
evolution for all deposits, as follows: 1) formation of the protore sulfides, 2) early
supergene weathering with formation of Zn-Pb-bearing carbonates and iron
oxi-hydroxides replacing protore sulfides or in the form of karst-related internal
sediment and 3) late supergene weathering with deposition of Zn-carbonates,
Zn-silicates and hydrated phases. Direct replacement of Zn-Pb sulfides strongly
controlled by pyrite oxidation is accompanied by precipitation of zinc non-sulfide
minerals in cavities or karst-related internal sediment filling.
A complementary rock magnetism study from the Toulal and Ait Labbes ore deposits
have been carried out. It shows that magnetite and minor hematite and goethite are the
magnetic carriers. Measurement of the anisotropy of the magnetic susceptibility (AMS)
from both ore and karstic internal sediments has revealed consistent directions and
horizontal magnetic fabrics, with the magnetic lineation usually paralleling the direction
of the calamine veins. The attitude of the AMS parameters (PJ and T) suggests an
absence of significant deformation supporting the theory that the magnetic fabric
originates from sedimentary dynamics within the veins. High temperature components
of primary origin have been isolated from the localities. The reverse and normal
directions of this component are antipodal and similar within error for both calamines
and karst-related internal sediments, suggesting that non-sulfide ore deposits and
karst-related internal sediments are contemporaneous. We therefore calculated an
average paleomagnetic direction for each locality. The corresponding poles are
consistent with the last 30 Ma of the Apparent Polar Wander Path (APWP) of Africa.
These promising results pave the way for an efficient method to constrain the age of Zn
supergene deposits.
The proposed three-step scenario can be placed within the tectonic evolution of the
Moroccan High Atlas belt. Deposition of primary sulfides is contemporaneous with
opening of the Tethyan and Atlantic oceans. During the Tertiary, intracontinental
deformation has given rise to the High Atlas fold-and- thrust belt and to regional uplift.
As a result, Zn-Pb sulfides, hosted in carbonates experienced oxidation under an arid
climate (with short intermediate humid episodes facilitating karst development) to form
karst-related Zn-Pb non-sulfide ore bodies.
Fold-and-thrust belts are hot topics in the research of orogens. However, the single geological or geophysical discipline often provides multisolutions on the geometry of a fold-and-thrust belt. We introduce here a multidisciplinary method combining geological and geophysical methods, take the Hutubi River section as a case to study the geometry of the fold-and-thrust belt in the northern piedmont of Tianshan. Firstly, we have carefully taken geological survey and got structural data on the surface. Secondly, petroleum seismic profile was re-interpreted based on the surface data and drilled wells. However, the seismic profile is absent in the contact zone between the mountain and the Junggar basin. We therefore carried out gravity measurements and forward modeling along this profile with the densities of the basement and sediments. The result shows that the northern flank fault of Tianshan doesn't exist along the Hutubi River profile, and the basin sediments could be continually followed from the basin to the mountain interior. This indicates that the tectonic structures in the contact zones between the mountain and the basin are variable, as the western section in the Jingou River section shows that the Tianshan basement thrusts northward on the basin sediments. Based on the balance-section technology, the restored section shows 4. 8 km of shortening. Comparing with previous results, this indicates the heterogeneous deformation along the northern piedmont of Tianshan. It also implies that this multidisciplinary method could be widely used in the fold-and-thrust belt.
Summary Dynamic Resolution Time-Lag FWI (DR-TLFWI) aims to use both diving waves and reflections for velocity update with optimized low- and high-wavenumber components from shallow to deep section. The proposed method builds contrast into the velocity model, enabling the simulation of reflections. The iterative velocity update scheme of DR-TLFWI handles multiples hence it can work with raw seismic data. The tomographic term of the velocity gradient from the reflection energy (low-wavenumber components) is typically much weaker than other components, due to additional reflections taking place during wave propagation. We propose to compensate these additional reflections by the corresponding illumination volume derived in each iteration of the FWI scheme. As such, a dynamic weighting can be devised for the different components in the FWI kernel to optimize the contributions across low- and high-wavenumber components of the velocity model. We use the time-lag objective function to avoid the dominance of strong amplitudes. Both synthetic and field dataset applications show that DR-TLFWI can reasonably update the velocity models from shallow section to deep beyond the reach of diving waves, especially when input data has a limited offset range. The images are improved accordingly with reduced structural undulations.
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