The Dhala structure,Bundelkhand craton,Central India—Eroded remnant of a large Paleoproterozoic impact structure     

Jayanta K. PATI  Wolf Uwe REIMOLD  Christian KOEBERL  Puniti PATI 《Meteoritics & planetary science》2008,43(8):1383-1398

Abstract— The newly discovered Dhala structure, Madhya Pradesh State, India, is the eroded remnant of an impact structure with an estimated present‐day apparent diameter of about 11 km. It is located in the northwestern part of the Archean Bundelkhand craton. The pre‐impact country rocks are predominantly granitoids of ?2.5 Ga age, with minor 2.0–2.15 Ga mafic intrusive rocks, and they are overlain by post‐impact sediments of the presumably >1.7 Ga Vindhyan Supergroup. Thus, the age for this impact event is currently bracketed by these two sequences. The Dhala structure is asymmetrically disposed with respect to a central elevated area (CEA) of Vindhyan sediments. The CEA is surrounded by two prominent morphological rings comprising pre‐Vindhyan arenaceous‐argillaceous and partially rudaceous metasediments and monomict granitoid breccia, respectively. There are also scattered outcrops of impact melt breccia exposed towards the inner edge of the monomict breccia zone, occurring over a nearly 6 km long trend and with a maximum outcrop width of ?170 m. Many lithic and mineral clasts within the melt breccia exhibit diagnostic shock metamorphic features, including multiple sets of planar deformation features (PDFs) in quartz and feldspar, ballen‐textured quartz, occurrences of coesite, and feldspar with checkerboard texture. In addition, various thermal alteration textures have been found in clasts of initially superheated impact melt. The impact melt breccia also contains numerous fragments composed of partially devitrified impact melt that is mixed with unshocked as well as shock deformed quartz and feldspar clasts. The chemical compositions of the impact melt rock and the regionally occurring granitoids are similar. The Ir contents of various impact melt breccia samples are close to the detection limit (1–1.5 ppb) and do not provide evidence for the presence of a meteoritic component in the melt breccia. The presence of diagnostic shock features in mineral and lithic clasts in impact melt breccia confirm Dhala as an impact structure. At 11 km, Dhala is the largest impact structure currently known in the region between the Mediterranean and southeast Asia.  相似文献   

Satellite-Derived Regional Apparent Thermal Inertia and Gravity for Mapping Different Rock Types in Parts of Banswara,Rajasthan     

Komal?Rani  Arindam?Guha  Sanjit?Kumar?Pal 《Journal of the Geological Society of India》2018,91(6):671-678

The present study deals with the delineation of lineaments over Sir Creek offshore and its surroundings from EGM2008 gravity data using various derivative techniques owing to their costeffectiveness in prospective hydrocarbon exploration. Initially, 2-D and 3-D synthetic models have been generated with vertical prismatic objects at different depths. The effectiveness of total horizontal derivative (THD) technique has been established by comparing with E-W and N-S Horizontal derivatives and First Vertical derivative techniques. The residuals of Bouguer gravity data have been estimated with different cut-off wavelengths. Further, the residual anomaly map has been enhanced by the derivative techniques for the delineation of the structural features. Possible depths of the delineated lineaments have been estimated using Euler deconvolution of the Bouguer gravity data, which indicates maximum clustering over the delineated lineaments. It is observed that most of the lineaments are in the depth range of 1.0 km to 5.5km, which correlate well with the previous seismic studies. The present study reveals that the major lineament trends in the N-S, E-W and NNW-SSE directions followed by NE-SW, NW-SE and ENE-WSW directions. These major lineament trends are due to the tectonic activities occurred during Precambrian and Cretaceous period. Different small circular features, rectangular features and shorter wavelength features have also been identified, which could be the key parameter for mapping potential location for hydrocarbon exploration.  相似文献   

Satellite based mapping and morphogenetic analysis of the landforms in the tertiary fold belts of parts of Tripura,India     

Swati Singh  Arindam Guha  K. Vinod Kumar  Sandip Bardhan  A. Lesslie  M.V. Ravi Kumar 《国际地球制图》2015,30(9):1016-1032

In the present study, satellite-based mapping and morphogenetic analysis of eastern part of Tripura has been attempted. Landforms are delineated based on conjugate analysis of satellite-imaged and satellite-derived digital elevation data. Further, landforms were classified based on hierarchical three-tier classification system where genesis is used as a criteria to classify the landforms in the first level followed by nature of their dissection and the geometric forms of the landform in second and third level, respectively. During the analysis, it has been observed that most of the landforms are structural in origin and their orientations are guided by the geological lineaments although the variations in the dissection pattern of the landforms are related to the changes in the underlying lithology. The implementation of quantitative analysis using hypsometric integral and ruggedness index of geomorphic parameters indicates that the landforms are immature but have been evolving towards maturity.  相似文献   

Solar Maximum Mission   总被引：1，自引：0，他引：1  

J. David Bohlin  Kenneth J. Frost  Peter T. Burr  Arun K. Guha  George L. Withbroe 《Solar physics》1980,65(1):5-14

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Chromium isotopes identify the extraterrestrial component in impactites from Dhala impact structure,India     

Aryavart Anand  Anuj Kumar Singh  Klaus Mezger  Jayanta Kumar Pati 《Meteoritics & planetary science》2023,58(5):722-736

The Dhala structure in north-central India is a confirmed complex impact structure of Paleoproterozoic age. The presence of an extraterrestrial component in impactites from the Dhala structure was recognized by geochemical analyses of highly siderophile elements and Os isotopic compositions; however, the impactor type has remained unidentified. This study uses Cr isotope systematics to identify the type of projectile involved in the formation of the Dhala structure. Unlike the composition of siderophile elements (e.g., Ni, Cr, Co, and platinum group elements) and their inter-element ratios that may get compromised due to the extreme energy generated during an impact, Cr isotopes retain the distinct composition of the impactor. The distinct ε⁵⁴Cr value of −0.31 ± 0.09 for a Dhala impact melt breccia sample (D6-57) indicates inheritance from an impactor originating within the non-carbonaceous reservoir, that is, the inner Solar System. Based on the Ni/Cr ratio, Os abundance, and Cr isotopic composition of the samples, the impactor is constrained to be of ureilite type. Binary mixing calculations also indicate contamination of the target rock by 0.1–0.3 wt% of material from a ureilite-like impactor. Together with the previously identified impactors that formed El'gygytgyn, Zhamanshin, and Lonar impact structures, the Cr isotopic compositions of the Dhala impactites argue for a much more diverse source of the objects that collided with the Earth over its geological history than has been supposed previously.  相似文献   

Dimensionality reduction of hyperspectral data using spectral fractal feature     

Kriti Mukherjee  Jayanta Kumar Ghosh  Ramesh Chand Mittal 《国际地球制图》2013,28(6):515-531

A new approach for dimensionality reduction of hyperspectral data has been proposed in this article. The method is based on extraction of fractal-based features from the hyperspectral data. The features have been generated using spectral fractal dimension of the spectral response curves (SRCs) after smoothing, interpolating and segmenting the curves. The new features so generated have then been used to classify hyperspectral data. Comparing the post classification accuracies with some other conventional dimensionality reduction methods, it has been found that the proposed method, with less computational complexity than the conventional methods, is able to provide classification accuracy statistically equivalent to those from conventional methods.  相似文献   

Hydrogeomorphological mapping in ground water exploration using remotely sensed data — a case study in keonjhar district, orissa     

S Das  S C Behera  A Kar  P Narendra  S Guha 《Journal of the Indian Society of Remote Sensing》1997,25(4):247-259

Identification of fractures/lineaments and hydrogeomorphic units is prerequisite for undertaking ground water exploration and development in any terrain. Use of satellite remote sensing techniques coupled with aerial photo-interpretation greatly aid in planning ground water exploration, and pin pointing well sites In this study, airborne and space borne data was used for qualitative evaluation of ground water resources and a critical appraisal of such study in combination with hydrogeological and hydrogeophysical techniques for ground water exploration and development in Keonjhar district of Orissa. The study area has been divided into various geomorphic units based on visual interpretation of Landsat (TM) false colour composite on. 1:2,50,000 scale and the ground water potential of each of the units is qualitatively assessed. Digital image processing techniques such as principal component analysis and brightness index were used for generating classified outputs. The features like valley fills, pediments ete appeared clearly on the classified image. Directional filtering brought out minor fractures/lineaments crisply. The study has revealed the significance of different hydrogeomorptuc units and lineaments in Controlling ground water potential of the area. The findings were corroborated by resalts of drilling and resistivity soundings.  相似文献   

Fractal-based dimensionality reduction of hyperspectral images   总被引：3，自引：0，他引：3  

Jayanta Kumar Ghosh  Ankur Somvanshi 《Journal of the Indian Society of Remote Sensing》2008,36(3):235-241

The spectral reflectance of any pixel in a remote sensing image depends on the characteristics of the particular land cover (LC) present in the Instantaneous Field of View (IFOV) of the sensor. The fractal dimension of the spectral reflectance curve (SRC) of any pixel can thus be visualized as a representation of the characteristics of the LC. Based on this, a fractalbased method for reduction of the dimensionality of Hyperspectral (HS) images has been investigated. The fractal dimension (FD) of SRC has been calculated by adopting a method based on Hausdorff metric that reduces the dimensionality from N HS bands to a single feature incorporating the characteristics associated with each of the bands. Further, it has been established that FD values can be used as a feature to identify anomaly in water cover.  相似文献   

Alteration patterns related to gold mineralization and their relation to CO2/H2O ratios     

T. B. Dubé  J. Guha  M. Rocheleau 《Mineralogy and Petrology》1987,37(3-4):267-291

Summary The pattern of hydrothermal alteration associated with a gold prospect located within a differentiated iron-rich gabbro sill in the Chibougamau region has been investigated in order to establish the alteration mechanism. The gold mineralization, occurring in east-west trending shear zone, shows a close spatial relationship to zones of intense alteration. Ankerite-sericite-pyrite/ankerite-fuchsite-chlorite/ankerite-sericite-chlorite, and chlorite-calcite-magnetite form four distinct alteration facies which extend outward from the mineralized zones. Detailed mineralogical, petrological and chemical studies show that the iron content of chlorite increases whereas the iron content of the carbonate decreases from the mineralized zone outwards. The hydrothermal alteration pattern is shown to be derived from a single fluid with a high initial CO₂/H₂O ratio. At first, reducing reactions prevailed and, with progressive fluid-rock interaction, the CO₂/H₂O ratio was lowered and oxidation reactions dominated.

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Alterationsmuster in beziehung zur goldmineralisation und dem CO₂/H₂O- Verhältnis

Zusammenfassung Hydrothermale Alterationen in Zusammenhang mit einer Goldvererzung eines differenzierten eisenreichen gabbroischen Sills im Chibougamaugebiet wurden untersucht, um den Umwandlungsmechanismus zu ermitteln. Die Goldvererzung in der Ost-West verlaufenden Scherzone ist eng mit Zonen intensiver Alteration verbunden. 4 deutlich unterscheidbare Alterationsfazics, die mit zunehmender Entfernung von der Vererzung auftreten, sind: Ankerit - Serizit - Pyrit/Ankerit - Fuchsit - Chlorit/Ankerit -Serizit - Chlorit und Chlorit - Kalzit - Magnetit. Detailierte mineralogische, petrographische und geochemische Untersuchungen zeigen, daß sich von der Vererzung weg der Eisengehalt im Chlorit, erhöht, gleichzeitig aber in Karbonaten verringert. Die hydrothermale Alteration ist auf eine einzige fluide Phase mit ursprünglich hohem CO₂/ H₂O-Verhältnis zurückzuführen. Vorherrschend waren zunächst reduzierende Reaktionen. Mit zunehmender Wechselwirkung zwischen Fluid und Gestein erniedrigte sich das CO₂/H₂O-Verhältnis und oxidierende Reaktionen nahmen zu.

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With 9 Figures  相似文献   

On the propagation of certain types of surface waves in a non-homogeneous elastic layer     

Jayanta Bhattacharya 《Pure and Applied Geophysics》1969,73(1):93-98

Summary The propagation of a certain type of surface waves in a non-homogeneous elastic layer of finite thickness lying in welded contact with a semi-infinite homogeneous elastic medium has been investigated in this paper. The surface wave is characterised by the fact that the dilatation and the vertical displacement component are both zero. It has been proved that such disturbance can propagate only when the phase velocity of the wave is greater than the shear wave velocity and the group velocity is inversely proportional to the phase velocity.  相似文献