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1.
Many tholeiitic dyke-sill intrusions of the Late Cretaceous Deccan Traps continental flood basalt province are exposed in the Satpura Gondwana Basin around Pachmarhi, central India. We present field, petrographic, major and trace element, and Sr–Nd–Pb isotope data on these intrusions and identify individual dykes and sills that chemically closely match several stratigraphically defined formations in the southwestern Deccan (Western Ghats). Some of these formations have also been identified more recently in the northern and northeastern Deccan. However, the Pachmarhi intrusions are significantly more evolved (lower Mg numbers and higher TiO2 contents) than many Deccan basalts, with isotopic signatures generally different from those of the chemically similar lava formations, indicating that most are not feeders to previously characterized flows. They appear to be products of mixing between Deccan basalt magmas and partial melts of Precambrian Indian amphibolites, as proposed previously for several Deccan basalt lavas of the lower Western Ghats stratigraphy. Broad chemical and isotopic similarities of several Pachmarhi intrusions to the northern and northeastern Deccan lavas indicate petrogenetic relationships. Distances these lava flows would have had to cover, if they originated in the Pachmarhi area, range from 150 to 350 km. The Pachmarhi data enlarge the hitherto known chemical and isotopic range of the Deccan flood basalt magmas. This study highlights the problems and ambiguities in dyke-sill-flow correlations even with extensive geochemical fingerprinting.  相似文献   

2.
The crustal depth section obtained from deep seismic soundings along the Koyna II (Kelsi-Loni) profile, which lies near latitude 18°N roughly in the east-west direction in that part of the Deccan Trap Maharashtra State, India, shows a number of reflection segments below the Deccan Traps down to the Moho discontinuity. A deep fault below the Deccan Traps 13 km east of Mahad divides the entire cross-section including the Moho boundary into two crustal blocks. The reflection segments show updip towards the west coast in the western block. The Moho discontinuity which is at a depth of 39 km near the deep fault starts rising towards the coast, reaching a depth of 31.5 km at the west coast. The eastern block is thrown up by 1.5 km with respect to the western block along the deep fault. A structural contour map of the Moho discontinuity for the Koyna reservoir area has been prepared from the present results and the crustal information obtained along the Koyna I profile (Kaila et al., 1979a), shows that the deep fault in the Koyna area is aligned in the NNW-SSE direction.Refraction seismic data analysis by the wave front method reveals that the thickness of the Deccan Trap increases towards the west coast. The Deccan Trap is 600–700 m thick in the eastern region between Nira (SP 130) and Loni (SP 200) and attains a thickness of 1500 m at 10 km east of the west coast. The longitudinal wave velocity in the Deccan Traps along the profile varies from 4.8 to 5.0 km/sec and in the crystalline basement from 6.0 to 6.15 km/sec. A tentative isopach contour map of the Deccan Traps and a tentative structural contour map of the Pre-Deccan Trap contact have been prepared for the Koyna reservoir area from the results along the Koyna II and Koyna I profiles. A flexure aligned in a NNW-SSE direction, in the Pre-Deccan Trap contact, which is an expression of the deep fault into the basement, has been clearly brought out. The flexure coincides in general with the orientation of the Deccan volcanic scarp in this area.  相似文献   

3.
《Gondwana Research》2002,5(3):649-665
The Mandla lobe in the eastern part of the Deccan volcanic province represents an isolated lava pile having a thickness of ∼900 m. The large thickness of this lava pile and its spatial detachment from the western Deccan outcrop points to a plausible second source. The stratigraphic configuration of the central and eastern Deccan lava sequences and their possible stratigraphic correlation are primarily based on geology and chemical signatures of the lava flows. Based on variations in the incompatible element ratios, the lava sequences of Chindwara, Jabalpur-Seoni and Jabalpur-Piparia sections were classified into four informal formations showing similarity with the southwestern formations. Major and trace element abundances in fifteen lava flows of Jabalpur area are similar to that of the southwestern Deccan lava flows. It has been found that the Ambenali Fm. and a few Khandala and Bushe Fm. flows are present in the northeastern Deccan. The regional mapping and detailed petrographic studies coupled with the lateral tracing have enabled the recognition of thirty-seven physically distinct lava flows and is justified by their major-elemental chemistry. The ‘intraflow variations’ studied in some of the flows is very low for most of the major oxides. These thirty-seven lava flows are grouped into eight chemical types. The order of superposition in this sequence reflects that the older flows occur in the west of the outlier at the Seoni-Jabalpur-Sahapura sector whereas, the younger flows are confined to the Dindori-Amarkantak sector in the east. The spatial disposition of the lava flows suggests that the structural complexity in the lava flow sequence in the Mandla lobe lies between Jabalpur and Dindori. The juxtaposition of distinct groups of lava flows are observed near Deori (flows 1 to 4 abeted aginst flows 5 to 14) and Dindori areas. At Dindori and towards its south the distinct lava packages (flows 15 to 27 and flows 28 to 37) are juxtaposed along the course of Narmada river. The possible explanation for this could be the presence of four post-Deccan faults at Nagapahar, Kundam, Deori and Dindori areas. The vertical shift of chemically distinct lava packages at different sectors in the outlier contravenes the idea of small regional dip and favours the presence of four NE-SW trending post-Deccan faults. Major geochemical breaks, when traced out from section to section, exhibit shifting in heights by approximately 150 m near Nagapahar and 300 m near Deori and Dindori areas. The field, petrographic and major-oxide data sets considered in conjuction with the magnetic chron reversal heights, support the inference that four faults trending NE-SW are present in the Mandla lobe.A commonality in the mineralo-chemical attributes of the infra (Lametas)-/inter-trappean as well as weathered Deccan basalt further favours their derivation from Deccan basalt, implying the availability of Deccan basalt during the Maastrichtian Lameta sedimentation. This observation does not match with the models suggesting an extremely short duration of Deccan volcanism (<0.5 Ma) at the KTB, but is congruent with the models advocating a more prolonged Deccan volcanism.  相似文献   

4.
Flow mapping and physical volcanology of 15 basaltic lavas exposed in three critical road pass sections (ghats) in the Koyna-Warna region of the western Deccan Traps is presented in this paper. Transitional lavas like rubbly pahoehoe are most common morpho-type exposed in these ghat sections. Sinking of rubbly breccia into flow interiors and formation of breccia-cored rosette are common in some lava flows. Few rubbly lavas exhibit slabby tendencies. The amount and nature of the associated rubble is variable and result from the mechanical fracturing and auto-brecciation of the upper vesicular crust in response to distinctive stages in the cooling, crystallization and emplacement history of individual lava flows. Occurrence of aa and pahoehoe morpho-types in the lava flow sequence is subordinate. Three prominent pahoehoe flows separated by red bole horizons are seen in the upper parts of the Kumbharli ghat. These are thick, P-type sheet pahoehoe. The pahoehoe lavas represent compound flow fields that grew by budding, endogenous lava transfer and inflation. Presence of pahoehoe lavas in the Koyna-Warna region hints at possible hitherto unrecorded southern extension of Bushe-like flow fields. This study reconfirms the existence of pahoehoe-slabby-rubbly-aa flow fields and transitions even in the upper echelons of the Deccan Trap stratigraphy. The study of morphology and internal structure of lava flows exposed at the ghat sections in the Koyna-Warna region could guide subsurface core-logging that is critical in deciphering the physical volcanology and emplacement dynamics of basaltic lava flows penetrated by drill holes sunk under the scientific deep drilling programme.  相似文献   

5.
Intracratonic South Rewa Gondwana Basin occupies the northern part of NW–SE trending Son–Mahanadi rift basin of India. The new gravity data acquired over the northern part of the basin depicts WNW–ESE and ENE–WSW anomaly trends in the southern and northern part of the study area respectively. 3D inversion of residual gravity anomalies has brought out undulations in the basement delineating two major depressions (i) near Tihki in the north and (ii) near Shahdol in the south, which divided into two sub-basins by an ENE–WSW trending basement ridge near Sidi. Maximum depth to the basement is about 5.5 km within the northern depression. The new magnetic data acquired over the basin has brought out ENE–WSW to E–W trending short wavelength magnetic anomalies which are attributed to volcanic dykes and intrusive having remanent magnetization corresponding to upper normal and reverse polarity (29N and 29R) of the Deccan basalt magnetostratigrahy. Analysis of remote sensing and geological data also reveals the predominance of ENE–WSW structural faults. Integration of remote sensing, geological and potential field data suggest reactivation of ENE–WSW trending basement faults during Deccan volcanism through emplacement of mafic dykes and sills. Therefore, it is suggested that South Rewa Gondwana basin has witnessed post rift tectonic event due to Deccan volcanism.  相似文献   

6.
Ground magnetic data collected over Chikotra River in the peripheral region of Deccan Volcanic Province (DVP) of Maharashtra located in Kolhapur district was analysed to throw light on the structural pattern and distribution of magnetic sources within the basin. In order to isolate the magnetic anomalies showing varying trend and amplitude, several transformation operations including wavelength filtering, and upward continuation has been carried out on the reduced to pole anomaly map. Qualitative interpretation of these products help identify the distribution of magnetic sources, viz., the Deccan basalts, dolerite intrusives and older greenstone and schist belts in the subsurface. Present study suggests that the Chikotra basin is composed of three structural units; a NE–SW unit superposed on deeper NW–SE unit with randomly distributed trap flows on the surface. One of the major outcome of the present study is the delineation of almost 900-m thick Proterozoic Kaladgi sediments below the Deccan trap flows. The NE–SW magnetic sources may probably represent intrusives into the Kaladgi sediments, while the deeper NW–SE trends are interpreted as the northward extension of the Dharwars, underneath the Deccan lava flows, that forms the basement for the deposition of Kaladgi sediments.  相似文献   

7.
Landslide is one of the devastating natural phenomenon that threatens human life and property. Every year a number of persons lost their lives due to the landslides. Therefore, a better understanding and characterization of landslide is very essential for adopting mitigation strategies to contain the adversities of this natural hazard. Information on landslides from different climatic setup are very essential for better understanding of the influence of weathering, rainfall, or topography on landslide generation. Weathering is one of the important causative factor for landslide generation in the moderate topography or inactive mountainous terrain. The Western Ghats including the Deccan Traps, an inactive mountain range, receives torrential rainfall. Intense rainfall in these areas enhances the weathering processes and fabricates thick soil covers. Mahabaleshwar area, Maharashtra was chosen as a case study, where high elevated part is covered by lateritic layer and each lava flow unit is separated by a thin weathered bed of red bole. The area experiences series of landslides during the summer monsoon months. Mainly two types of landslides have been identified in the area confined with the red bole bed and powdery lateritic soil. The first type of landslides occur at higher elevations (≥1200m) where horizontal beds of permeable laterites underlined by impermeable thick basalt beds. The rain water infiltrates down and spread laterally within the permeable lateritic beds. It finally spouts at lower plateau elevations and triggers mainly debris flows. The other category of landslides occurs where the weathered red bole bed separates two successive lava flows. The percolating water from the secondary porosities (joints and inter connected vugs) comes out from the contact zones of basalt and red bole bed in the form of seepages. It erodes the red bole bed and as a result the overlying masses hang and consequently lead to rock fall. The Chemical Index of Alteration (CIA) of the representative samples from landslide locations indicates significant weathering. The CIA values for the fine lateritic soil are up to 98% whereas for the red bole bed it varies from 77 to 85%. This suggests a high chemical weathering and higher erodibility. The association of active landslide locations with the red bole bed and fine lateritic soil suggests a close relation between weathering and landslide occurrences in the area.  相似文献   

8.
The Deccan trap basalt, laid down by multiple lava flows during upper Cretaceous to Paleocene times forms the basement of current study in Cambay basin. As such, there is great interest and value in fracture detection and evaluation of fractured basement reservoirs in the Cambay basin. The procedure for identification and evaluation of natural as well as induced fractures in basaltic basement of the Cambay basin is presented in this work. In this study formation micro-imager (FMI) and extended range micro-imager (XRMI) log data for fracture identification is used. The Deccan trap basaltic basement of the study area, comprising five wells in the Tarapur-Cambay block, has potential for holding commercial hydrocarbon due to the presence of fractures and weathered basement. Both image logs (FMI, XRMI) identify three types of fracture including open (conductive), partially open and closed (resistive) fractures, of which open and partially open fractures are important for hydrocarbon accumulation. Fracture dip ranges from 10° to 80°. Image logs have also identified washout, breakout and drilling-induced fracture zones. The strike direction of the open natural fractures for four wells varies from N60°E to N30°E whereas the strike direction of most natural fracture in the fifth well is oriented towards N20°W. The orientations of drilling-induced fractures and breakouts may be interpreted for the in-situ stress direction over the logged interval. Drilling-induced tensile fractures, identified over the depth interval of 1969–1972 m, and borehole breakouts over the interval of 1953–1955 m in one well, suggest an orientation of maximum in-situ horizontal compressive stress (SH) lies in the north-south direction. The azimuths of open natural fractures in the same well vary from north-south to N30°E. It is expected that the direction of fluid flow will be controlled by open natural fractures and therefore would be in a direction parallel to the SH direction, which is orthogonal to the minimum horizontal stress (Sh) direction. The orientations observed are consistent with the present day SH direction in the study area of Cambay basin.  相似文献   

9.
Fluid driven metasomatism and mass transfer from the earth’s mantle have played an important role in the evolution of the lower continental crust in many geodynamically active areas. The epicentral region of the disastrous 1993 Killari earthquake (M 6.2), concealed below a thick suite of Deccan volcanics in central India, appear to be one such region. In connection with the study of seismotectonics of the earthquake prone Deccan volcanic region, we have carried out systematic and detailed geochemical and mineralogical investigation on core samples from the basement, obtained from the 617m deep KLR-1 borehole, drilled in the epicentral region of Killari. Our investigations indicate that the basement, concealed below 338m thick Deccan volcanics, is made up of CO2, Cl, FeO and CaO-rich, high density (2.82 g/cm3) — high velocity (avg. Vp: 6.2 km/s) moderately retrogressed upper amphibolite to granulite facies mid crustal rocks, which were subjected to pervasive Ca-metasomatism due to infiltration of mantle fluids. Graniticgneissic layer, typical of the upper crust, seems to be totally absent from this earthquake region. Chondrite normalized trace and rare earth elemental patterns display negative Eu anomalies together with LILE enrichment. Similarly, spider diagrams for incompatible elements show depletion in Zr, Hf, Y, Ta and Nb relative to the primitive mantle, indicating possible alterations of such relatively immobile elements at relatively high temperatures. Selective enrichment is also observed in transitional elements like Cu and Zn, indicating the possible role of chlorine in metal transport. The present study suggests that regional metasomatism beneath the Deccan Traps, which apparently alters the basic fabric of the rock during recrystallisation and makes it weak, may have a link with the nucleation of large earthquakes.  相似文献   

10.
Boreholes are the only sources for direct measurements of geological and geophysical characteristics of the shallow subsurface of the earth. Borehole imaging tool “Acoustic Televiewer (ATV)” is an advanced probe, which records 3D image of the bore hole wall and is used to obtain oriented images of bore hole and provides substantial information regarding lithology, structural information, detection of fractures and casing of the borehole. The images are highly sensitive to the presence of fractures, the delineation of which becomes accurate and reliable based on these acoustic images. Features identified on log-derived images can be correlated with core samples or can be used as substitute in the poor core recovery zones. In the present study, ATV log from a deep borehole drilled at Khadi Kolavan in Koyna-Warna region of Ratnagiri district, Maharashtra located west of the Western Ghat escarpment in the Deccan Volcanic province, India, is used for interpretation of structural characteristics of the formation. The same was correlated with other conventional logging methods such as resistivity and full waveform sonic (FWS) as well as core logging and rock quality designations (RQD) which generated new understanding of the basement and basalt cover in this region.  相似文献   

11.
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12.
Chemical analysis of nine Deccan flow basalts at Anjar, Kutch, western India, indicates that all, except the uppermost flow F-9, are alkaline. In their major and trace element composition, the alkali basalts resemble Ocean island basalts (OIB). Similarities of many diagnostic trace element ratios (e.g. Sm/Nd, Ba/Nb,Y/Nb and Zr/Nb) are similar to those found in the Réunion Island basalts. The uppermost basalt is tholeiitic and chemically resembles the least contaminated Deccan basalt (Ambenali type). The Anjar basalts have iridium concentration ranging between 2 and 178 pg/g. Some of these values are higher by about an order of magnitude compared to the Ir concentration in other basalts of the Deccan. A synthesis of chemical, palaeomagnetic and geochronologic data enables us to construct a chemical and magnetic stratigraphy for these flows. The three flows below the iridium enriched intertrappean bed (IT III) show normal magnetic polarity whereas all except one of the upper basalts show reversed magnetic polarity. The sequence seems to have started in polarity zones 31N and probably continued up to 28R or 27R. The results presented here support the view that Deccan volcanism in Kutch occurred on a time span of a few million years.  相似文献   

13.
A potassium-rich Alkalic Suite from the Deccan Traps,Rajpipla, India   总被引：4，自引：0，他引：4  
The Rajpipla Alkalic Suite is the most potassium-enriched group of basaltic rocks so far described from the Deccan Traps. In the same area however early tholeiitic flows and late tholeiitic dykes show the potassium-poor nature characteristic of most Deccan Trap magmas. The rocks of the alkalic suite are highly porphyritic and their major element variation can be interpreted in terms of crystal fractionation dominated by clinopyroxene. Plagioclase, which is an important phenocryst phase, has fractionated only in relatively small amounts as a result of a lack of density contrast between it and the liquids. A dyke-like form for the magma chambers in which fractionation has taken place is postulated to account for the abundance of highly porphyritic types. The Rajpipla area is also notable as being one of the few Deccan localities where rhyolites are found.Abbreviations AB ankaramitic basalt - PB porphyritic basalt - PTB porphyritic trachybasalt - FPM feldsparphyric mugearite - M mugearite - TR trachyte - P. RHY potassic rhyolite - Th. B. tholeiitic basalt - Th. D. tholeiitic dolerite - Af alkali feldspar  相似文献   

14.
The Mandla lobe is a 900 m thick lava pile that forms a 29,400 km2 northeastern extension of the Deccan Traps. Earlier, combined field, petrographic, and major element studies have shown that this lobe comprises 37 lava flows. Using a combination of trace elements (Ba, Ti, Zr, Rb, Sr) and Nb/Zr values, we group the flows into six chemical types (A–F) that are separated stratigraphically. Combined trace element and Nd-Pb-Sr isotopic data, document the presence of lavas resembling those of the Poladpur Formation and less abundantly, the Ambenali Formation of the southwestern Deccan are in conformity with the earlier reconnaissance work. In addition, our data reveal several flows similar to those of the Mahabaleshwar Formation, the type sections of which are located?~?900 km to the southwest. Based on the isotopic data the superposition of Mahabaleshwar-like flows over flows with Ambenali- and Poladpur-like characteristics is in the same stratigraphic order seen in the southwestern Deccan type section. However, from the stratigraphy indicated by the Discriminant Function Analysis (DFA) results and the serious discrepancy between the DFA and isotopic data, it seems that few Mandla lobe flows are different and not in the same stratigraphic order as in the southwestern part of the province. To some extent the differences may be explained by faulting along four large post-Deccan normal faults near Nagapahar, Kundam, Deori, and Dindori areas across which offsets of ~150 m have been measured. This post-emplacement faulting accounts for the presence of several chemically Mahabaleshwar-like lavas at the base of the ~900 m thick Mandla lobe pile, at a lower elevation than a thick sequence dominated by chemically Poladpur-like flows. However, presence of common signature lavas (similar to that in the northeastern Deccan) cannot be ruled out in this area. They are similar to Poladpur-type lavas both chemically and isotopically. They appear in different formations and erupted at different times other than Poladpur Formation. Close similarities in petrogenetic processes between the two regions are indicated, although it is not clear whether any of the Mandla lobe lavas are far-traveled counterparts of flows cropping out in the southwestern Deccan, or whether some magma migrated laterally in dike systems over great distances. Feeder dykes have not been found in the study area except for Chakhla-Delakhari Intrusive Complex (CDIC) in Satpura region that shows major and trace elemental similarities with the Seoni lavas, although, long distance transport of magma is yet to be proved. The Poladpur-like Mandla lobe flows appear to be different flows from those of the Poldapur Formation in the southwest, as they are somewhat different in isotopic (higher 206Pb/204Pb) composition. They also differ from any known flows in the other southwestern formations, but are broadly similar to flows found in sections across the northern Deccan west of the Mandla lobe.  相似文献   

15.
Crustal or mantle xenoliths are not common in evolved, tholeiitic flood basalts that cover huge areas of the Precambrian shields. Yet, the occasional occurrences provide the most direct and unequivocal evidence on basement composition. Few xenolith occurrences are known from the Deccan Traps, India, and inferences about the Deccan basement have necessarily depended on geophysical studies and geochemistry of Deccan lavas and intrusions. Here, we report two basalt dykes (Rajmane and Talwade dykes) from the central Deccan Traps that are extremely rich in crustal xenoliths of great lithological variety (gneisses, quartzites, granite mylonite, felsic granulite, carbonate rock, tuff). Because the dykes are parallel and only 4 km apart, and only a few kilometres long, the xenoliths provide clear evidence for high small-scale lithological heterogeneity and strong tectonic deformation in the Precambrian Indian crust beneath. Measured 87Sr/86Sr ratios in the xenoliths range from 0.70935 (carbonate) to 0.78479 (granite mylonite). The Rajmane dyke sampled away from any of the xenoliths shows a present-day 87Sr/86Sr ratio of 0.70465 and initial (at 66 Ma) ratio of 0.70445. The dyke is subalkalic and fairly evolved (Mg No. = 44.1) and broadly similar in its Sr-isotopic and elemental composition to some of the lavas of the Mahabaleshwar Formation. The xenoliths are comparable lithologically and geochemically to basement rocks from the Archaean Dharwar craton forming much of southern India. As several lines of evidence suggest, the Dharwar craton may extend at least 350–400 km north under the Deccan lava cover. This is significant for Precambrian crustal evolution of India besides continental reconstructions.  相似文献   

16.
《International Geology Review》2012,54(12):1094-1116
Rhyolite, trachyte, pitchstone, and granophyre dikes are associated with mafic dolerite dikes and basaltic flows of the northwestern part of the Deccan flood basalt province in the Saurashtra Peninsula, India. Felsic dikes, exposed in the Rajula area of Saurashtra, are similar in age to the basaltic flows of neighboring Palitana. The ages of both the felsic and mafic rocks straddle the ~65 Ma Cretaceous-Tertiary boundary and correspond to the main Deccan flood basalt episode. Palitana is centered on an elongated gravity high whose major axis is NE-SW, and Rajula is located on its southwestern flank. Unlike the younger Bombay felsic rocks from the western coast of India, which have been explained as partial melts of gabbros in deep crustal sills or previously erupted basalts, the incompatible-element characteristics of the Rajula rocks indicate that the Rajula rhyolites, trachytes, and dacites may have been generated by an almost complete melting of upper crustal rocks at the southwestern flank of the Rajula-Palitana-Sihor magmatic body. High potential temperatures of the Deccan plume, quick migration of the hot basaltic parent magma through lithospheric weak trends, and collection and residence of magma in upper-crustal magma chambers before eruption may have produced the right conditions to melt the upper crust in the vicinity of the Rajula-Palitana-Sihor magma chamber. On the other hand, the andesite located northeast of the magmatic body possibly evolved by assimilation of upper-crustal wall rocks accompanied by 5-10% crystallization of a Rajula-type basalt near the wall of the magma chamber. The Sihor rhyolites may also have been derived from the Sihor basalts through fractional crystallization accompanied by crustal assimilation. The Rajula granophyres, however, do not show any involvement of the upper crust in their genesis. These may have a history similar to that of the Bombay rocks and may have erupted in response to rifting along the Cambay rift.  相似文献   

17.
Cambay basin is an intra-cratonic rift graben formed as a result of rifting which was occurred in late Cretaceous with Deccan lava eruption through linear trending NNW to SSE directional basin. The Deccan basalt forms the basement over which more than 7–11 km thick piles of Tertiary sediments have been deposited during syn-rift and post-rift phases of basin development. Cambay basin has been considered as one of the significant hydrocarbon prolific basin in India. The biggest challenge in current days for this basin is further exploration or exploration under development stage in small marginal field or unexplored left out areas in the basin part as most of the areas are already explored/discovered by various small to big E&;P (exploration &; production) industrial players. In this present study one such small marginal field has been chosen for “Exploration under Development” portfolio in mid Cambay basin. The amount of oil-in-place volume, investment and techno-economics analysis of small marginal field has made this study area. In view of further hydrocarbon exploration in this area this kind of study will provide a robust support in limited dataset. The reservoir sand quality of the study area is discrete, thin and less permeable. This kind of sand body detection through classical seismic interpretation approach is difficult and there will be always a big amount of uncertainties for findings the pay reservoir sand. In view of the limitation of available data and challenging geological setup of the reservoir, a quantitative approach has been taken to detect the thin reservoir sand in this study area. Primarily coloured inversion technique has been applied on post-stack seismic data based upon well to seismic correlation and reservoir sand detection in seismic interpretation and well log property analysis. This technique has produced higher detectability impedance/property volume with respect to normal post-stack seismic data signature. Based on high contrast impedance/elastic property further seismic based attribute analysis on reservoir section has been performed. The attribute analysis has been made along surface and 3D seismic data level, provided clear image about the thin hydrocarbon sand reservoir. Based upon quantitative interpretation approach coloured inverted volume the prospect was chosen for further drilling in the study area and drilling of that sand was turned to be a hydrocarbon discovery prospect. The unconventional approaches e.g. coloured inversion with limited dataset for this kind of small marginal field has potential to find the hydrocarbon.  相似文献   

18.
Leone Melluso  John J. Mahoney  Luigi Dallai   《Lithos》2006,89(3-4):259-274
Near-primitive picritic basalts in the northwestern Deccan Traps have MgO > 10 wt.% and consist of two groups (low-Ti and high-Ti) with markedly different incompatible element and Nd–Sr–Pb isotope characteristics. Many elemental characteristics of the low-Ti picritic basalts are similar to those of transitional or normal ocean ridge basalts. However, values of ratios like Ba/Nb (13–30) and Ce/Pb (4–11), and isotopic ratios (e.g., εNd(t) + 0.3 to − 6.3, (207Pb/204Pb)t 15.63–15.75 at (206Pb/204Pb)t 18.19–18.84, δ18Oolivine as high as + 6.2‰) are far-removed from ocean-ridge-type values, indicating a significant contribution from continental crust. The crustal signature could represent crustal contamination of ascending magmas; alternatively, it could represent a minor component within the Indian lithospheric mantle of anciently subducted sedimentary material or fluids derived from subducted material. In contrast, the high-Ti picritic basalts are chemically and isotopically rather similar to recent shield lavas of the Réunion hotspot (e.g., εNd(t) + 2 to + 4) and to volcanic rocks along the postulated pre-Deccan track of this hotspot in Pakistan. Neither type of picritic basalt is parental to the voluminous flows comprising the bulk of the Deccan Traps. However, many of the Deccan primary magmas could have been derived from mixtures of a high-Ti-type, Réunion-like source component and a component more similar to, or even more incompatible-element-depleted than, average ocean-ridge mantle.  相似文献   

19.
Deccan Traps spread over large parts of south, west and central India, possibly hiding underneath sediments with hydrocarbon potential. Here, we present the results of seismic refraction and wide-angle reflection experiments along three profiles, and analyze them together the results from all other refraction profiles executed earlier in the western part of Narmada–Tapti region of the Deccan Volcanic Province (DVP). We employ travel time modelling to derive the granitic basement configuration, including the overlying Trap and sub-trappean sediment thickness, if any. Travel time skips and amplitude decay in the first arrival refraction data are indicative of the presence of low velocity sediments (Mesozoic), which are the low velocity zones (LVZ) underneath the Traps. Reflection data from the top of LVZ and basement along with the basement refraction data have been used to derive the Mesozoic sediment thickness.In the middle and eastern parts of the study region between Narmada and Tapti, the Mesozoic sediment thickness varies between 0.5 and 2.0 km and reaches more than 2.5 km south of Sendhwa between Narmada and Tapti Rivers. Thick Mesozoic sediments in the eastern parts are also accompanied by thick Traps. The Mesozoic sediments along the present three profiles may not be much prospective in terms of its thickness, except inside the Cambay basin, where the subtrappean sediment thickness is about 1000–1500 m. In the eastern part of the study area, the deepest section (>4 km) has thick (∼2 km) Mesozoic sediments, but with almost equally thick Deccan Trap cover. Results of the present study provide important inputs for future planning for hydrocarbon exploration in this region.  相似文献   

20.
There is a growing interest in deciphering the emplacement and environmental impact of flood basalt provinces such as the Deccan, India. Observations of active volcanism lead to meaningful interpretations of now-extinct volcanic systems. Here, I illustrate and discuss the morphology and emplacement of the modern and active lava flows of Kilauea volcano in Hawaii, and based on them, interpret the compound pahoehoe lavas of the Deccan Traps. The latter are vastly larger (areally extensive and voluminous) than Kilauea flows, and yet, their internal architecture is the same as that of Kilauea flows, and even the sizes of individual flow units often identical. Many or most compound flows of the Deccan Traps were emplaced in a gentle, effusive, Kilauea-like fashion. Bulk eruption rates for the Deccan province are unknown, and were probably high, but the local eruption rates of the compound flows were no larger than Kilauea’s. Large (≥ 1000 km3) individual compound pahoehoe flows in the Deccan could have been emplaced at Kilauea-like local eruption rates (1 m3/sec per metre length of fissure) in a decade or less, given fissures of sufficient length (tens of kilometres), now exposed as dyke swarms in the province.  相似文献   

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