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1.
An attempt is made to work out the sequence stratigraphic frame work of Infra and Intertrappean beds exposed in Soma quarry
section, near Gowripatnam, Rajahmundry area to understand the mode of depositional process in the basin by integrating litho
and biostratigraphic data. The study documents the field data to recognize some of sequence parameters in the field. The sequence
stratigraphic study shows the Sequence Boundary, Transgressive Systems Tract (TST), three shallowing upward sequence, Maximum
Flooding Surface (MFS) and Highstand Systems Tract (HST) deposits got exposed as a result of basinal rise and fall. 相似文献
2.
The Rajahmundry Traps, Andhra Pradesh: Evaluation of their petrogenesis relative to the Deccan Traps
Ajoy K. Baksi 《Journal of Earth System Science》2001,110(4):397-407
Geochemical and geochronological data for rocks from the Rajahmundry Traps, are evaluated for possible correlation with the
main Deccan province. Lava flows are found on both banks of the Godavari River and contain an intertrappean sedimentary layer.
Based on40Ar/39 Ar age data, rocks on the east bank are post K-T boundary, show normal magnetic polarity, and belong to chron 29N. Their
chemistry is identical to lavas in the Mahabaleshwar Formation in the Western Ghats, ∼1000km away. It was suggested earlier
that the genetic link between these geographically widely separated rocks resulted from lava flowing down freshly incised
river canyons at ∼ 64 Ma. For the west bank rocks, recent paleomagnetic work indicates lava flows below and above the intertrappean
(sedimentary) layer show reversed and normal magnetic polarity, respectively. The chemical composition of the west bank flow
above the intertrappean layer is identical to rocks on the east bank. The west bank lava lying below the sedimentary layer,
shows chemistry similar to Ambenali Formation lava flows in the western Deccan.40Ar/39 Ar dating and complete chemical characterization of this flow is required to elucidate its petrogenesis with respect to the
main Deccan Province. 相似文献
3.
Rajahmundry Traps has been under geo-scientific investigations for over half a century; yet sketchy information is available
on morphology and internal architecture of lavas. This study bridges this gap by describing the morphology of lava pile of
Duddukuru area following Hawaiian scheme that relates a lava-type with a particular emplacement style. 相似文献
4.
G. Nagendra Babu M. Sai Baba Mary K. Kumar Yamuna Singh P. V. Ramesh Babu P. S. Parihar 《Journal of the Geological Society of India》2013,81(4):447-450
For the first time we report bastnaesite and hydroxyl bastnaesite (lanthanum cerium fluoro-carbonate) from the Kanigiri granite. The host granitoids are of A-type and vary in composition from quartz syenites to peralkaline granites. Rare metal and rare earth-bearing minerals identified by X-ray diffraction (XRD) studies in Kanigiri granite are bastnaesite and hydroxyl bastnaesite, besides columbite-tantalite, monazite, fergusonite, thorite and euxenite. Petromineralogical studies have also revealed the presence of bastnaesite. The presence of bastnaesite in Kanigiri granite suggests that the host felsic rocks may also form a potential source for light rare earth mineral, bastnaesite, apart from the already known rare-metal minerals. 相似文献
5.
Y. Janardan Rao I. S. N. Murthy C. Sree Ramulu 《Contributions to Mineralogy and Petrology》1973,41(1):57-60
Sphene coronites around magnetite are recorded in the granodiorite of Hyderabad. The metamorphic origin of the corona is discussed. 相似文献
6.
C. Sivaprakash 《Contributions to Mineralogy and Petrology》1981,77(2):121-128
Mineral assemblages, rock and mineral chemistry, and mineral reactions, in calc-silicate rocks from Koduru area, Andhra Pradesh, India are discussed. Mineralogical and bulk chemical differences indicate 3 calc-silicate rock types — type I with K feldspar+calcite+wollastonite+quartz+scapolite+diopsidess +andraditess+sphene, has relatively high rock oxidation ratios. Type II is a highly calcic variety with high rock MgFe ratios, and has K feldspar+calcite+wollastonite+quartz+scapolite + diopsidess±grossularitess+sphene+zoisite. Type III has K feldspar +calcite+wollastonite+quartz+scapolite+diopsidess +sphene+hornblende+magnetite, and has relatively low oxidation ratio and low MgFe ratio. The 3 calc-silicate rock types have originated as mixtures of limestone/dolomite/marl.Diopside was produced by a reaction involving Ca-amphibole +calcite+quartz, and reversed during retrogression. Andraditess in type I rocks was produced at the expense of hedenbergitic component of pyroxene in a continuous reaction as a consequence of increase in the oxygen content of the original sediment relative to type III. Calcite+quartz reacted to give wollastonite. During cooling an influx of water caused scapolite to alter to zoisite. 相似文献
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Neerja Jha K. Pauline Sabina N. C. Mehrotra 《Journal of the Geological Society of India》2011,77(2):167-174
High fluoride content in the groundwater is reported from parts of the Gad River Basin, Sindhudurg district, coastal Maharashtra,
India. The fluoride content of up to 5 mg/l has been found in the groundwater in laterite, basalt and the Precambrian basement
(gneiss) aquifers in the region. The presence of high fluoride in groundwater well above the permissible levels for consumption
poses a serious health threat to the rural populace in the region. The presence of tourmaline bearing pegmatites in the Precambrian
basement is considered as a potential fluorine source. Deep circulation of fluoride rich groundwater between the latetritised
basalts and the underlying crystalline basement could be responsible for the occurrence of fluoride in both the shallow and
deeper aquifers of the region. 相似文献
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10.
Omprakash S. Sarate 《Journal of the Geological Society of India》2010,76(6):557-564
The quantitative maceral study of the Queen seam from Mailaram coalfield of Godavari valley has displayed alternate coal bands
rich in vitrinite/liptinite or inertinite. The random vitrinite reflectance (Ro max. %) of these coals, from top part ranges from 0.50 to 0.64%. However, the bottom part of the seam has indicated lower
reflectance, between 0.49 and 0.52%. Thus, the Queen seam, in general, has attained high volatile bituminous C rank. The study
indicates that the depositional site has been a slowly sinking basin that witnessed alternate dry (oxidizing) and wet (reducing)
spells. This subsequently caused fluctuation in water table of the basin and the formation of oxic and anaoxic moor condition,
where accumulated vegetal resource transformed into mixed and fusic coal types in due course of time. Being high in liptinite
and vitrinite contents and low mineral matter, the Queen seam of Mailaram coalfield has high economic potential. 相似文献
11.
B. Anu Radha M. A. Rasheed P. L. Srinivasa Rao M. S. Kalpana A. M. Dayal 《Journal of the Geological Society of India》2011,78(5):477-483
A geochemical study of surface sediments from Pranhita-Godavari Basin, Andhra Pradesh, India was carried out using light hydrocarbon
compounds to assess the hydrocarbon potential of the basin. Suite of 80 soil samples were collected from the depth of 2.5
m and analyzed for adsorbed light gaseous hydrocarbons namely methane (CH4), ethane (C2H6) and propane (C3H8) in Gas chromatograph. Compound specific Carbon isotope ratios for CH4 and C2H6 were also determined using GC-C IRMS (Gas Chromatograph Combustion Isotope Mass Spectrometer). The presence of moderate to
low concentrations of methane (CCH4 C_{CH_4 } : 1 to 138 ppb), ethane (H4{H_4 }: 1 to 35 ppb) and propane (CC3 H8 C_{C_3 H_8 } : 1 to 20 ppb) was measured in the soil samples. Carbon isotopic composition of d13 CCH4 \delta ^{13} C_{CH_4 } ranges between −27.9 to −47.1 ‰ and d13 CC2 H6 \delta ^{13} C_{C_2 H_6 } ranged between −36.9 to −37.2 ‰ (V-PDB) indicating that these gases are of thermogenic origin. Study of soil samples suggests
the area has good potential for hydrocarbon. 相似文献
12.
The Indian subcontinent has the largest semi-arid tropical (SAT) area among developing nations. The State of Andhra Pradesh
falls under the SAT region in India and is mostly covered by compact and hard rocks, characterized by seasonal rainfall of
a highly fluctuating nature, in both space and time. As a consequence of the green revolution and an increase in industrial
activity, there has been an increase in the utilization of groundwater resources during the last two decades in Andhra Pradesh.
The development has also caused a number of problems, such as water table decline, decrease in well yields and seawater intrusion.
Although major irrigation projects have contributed to improved agricultural production, the associated problems of waterlogging,
salinization and loss of valuable bioresources have led to the gradual degradation of the land, affecting agricultural productivity.
Surface water and groundwater have also been polluted in several parts of the State because of untreated discharge of effluents
from the industries into nearby streams or open lands. A brief account of the overall scenario of the hydrogeological framework
and geo-environmental effects on the groundwater regime in Andhra Pradesh is presented. Possible management practices and
conservation methods are suggested.
Received: 9 August 1999 · Accepted: 10 July 2000 相似文献
13.
The basic volcanic group exposed in the Kadiri schist belt includes high Mg-basalt, basalt, basaltic andestite and dacite. The basalts are tholeiitic in composition and high Mg-basalts, basaltic andesites and dacites show calc-alkaline affinity. Major and trace element characteristics suggest that the volcanic suite has been derived from an initial tholeiitic magma which has given rise to an early basaltic type and a later calc-alkaline type of rocks. An island arc and active continental margin tectonic setting was inferred for these rocks. 相似文献
14.
Gabbros at Purimetla occur in close association with the alkaline pluton. Petrography and petrochemistry of these gabbros
indicate their tholeiitic nature. Chemical variation of these tholeiites suggests that an initial undersaturated tholeiitic
magma yielded oversaturated fractions in the final stages of differentiation. Their regional distribution suggests that basic
magmatism preceded the emplacement of the alkaline rocks in the Prakasam alkaline province. 相似文献
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Fluoride-bearing groundwater in Gummanampadu Sub-basin, Guntur District, Andhra Pradesh, India 总被引:1,自引:0,他引:1
The functional factors responsible for fluoride (F?)-bearing groundwater used for drinking as well as for cooking in the area of Gummanampadu Sub-basin, Guntur District, Andhra Pradesh, India are discussed. The study area is a part of an Archean Gneissic Complex, consisting of banded-biotite-hornblende-gneisses, over which the Proterozoic Cumbhum quartzites, shales, phyllites, and dolomitic limestones occur. The chemistry of groundwater is dominated by carbonates (HCO3 ? and CO3 2?) at a higher pH. This results in a higher total alkalinity over total hardness, causing an excess alkalinity. Sodium ion is dominated among the cations (Ca2+, Mg2+, and K+). The concentration of F? (2.1–3.7 mg/L) is higher than that of desirable national limit (1.2 mg/L) prescribed for drinking purpose. A significant positive correlation exists between F? and pH as well as that between F? and HCO3 ? + CO3 2?. This indicates that the alkaline condition is the prime conducive factor for dissolving F?-bearing minerals more effectively leading to a higher concentration of F? in the groundwater. Furthermore, a positive chloro-alkaline index reflects the ion exchange, and an oversaturation with respect to CaCO3 indicates the evaporation. In addition, a negative relation between the well depth and F? shows the effect of solubility and/or leaching of salts in different depth levels. These factors regulate the concentration of F? in the groundwater. On the other hand, a positive correlation of F? with SO4 2? as well as with K+ shows the human land use activities (namely, use of chemical fertilizers, disposal of domestic wastes, etc.), which add F? to the groundwater. A significant number of the residents of the study area suffer from the health disorders related to fluorosis, which is a consequence of higher concentration of F? in the drinking water. Thus, this study emphasizes the need for supply of safe drinking water, nutritional diet, rainwater-harvesting structures, and public education to realize “health for all” motto of World Health Organization. 相似文献
19.
Sukanta GOSWAMI Pradeep K. UPADHYAY Purnajit BHATTACHARJEE Malaiandi G. MURUGAN 《《地质学报》英文版》2017,91(6):1992-2006
Plate tectonic activity has played a critical role in the development of petrotectonic associations in the Kadiri schist belt. The calc alkaline association of basalt, andesite, dacite and rhyolite(BADR) is the signature volcanic rock suite of the convergent margin. The N-S belt has gone below the unconformity plane of Cuddapah sediments. In the northern part geochemical and structural attributes of the Kadiri greenstone belt is studied along with microscopic observations of selected samples. Harker diagram plots of major elements generally indicate a liquid line of descent from a common source, such that BADR rocks are derived from a common parent magma of basaltic to andesitic composition. These calc-alkaline volcanic rocks are formed at convergent margins where more silicic rocks represent more highly fractionated melt. All the litho-units of this greenstone belt indicate crush and strain effects. The stretched pebbles in the deformed volcanic matrix with tectonite development along with associated greenschist facies metamorphism, alteration and hydration is remarkable. Flow foliation plane with N-S strike and very low angle(5° to 10°) easterly dip and N-S axial planar schistosity formed due to later phase isoclinal folding can be clearly identified in the field. Basic intrusives are quite common in the surrounding area. All the observations including the field setting and geochemistry clearly demonstrate ocean-continent subduction as the tectonic environment of the study area. 相似文献
20.
Over-exploitation of groundwater results in decline of water levels, leading to intrusion of salt water along the coastal
region, which is a natural phenomenon. A groundwater quality survey has been carried out to assess such phenomena along the
coast of Visakhapatnam, Andhra Pradesh, India. Brackish groundwaters are observed in most of the wells. The rest of the wells
show a fresh water environment. The factors responsible for the brackish groundwater quality with respect to the influence
of seawater are assessed, using the standard ionic ratios, such as Ca2+:Mg2+, TA:TH and Cl−:HCO−
3. Results suggest that the brackish nature in most of the groundwaters is not due to the seawater influence, but is caused
by the hydrogeochemical process. Some influence of seawater on the groundwater quality is observed along the rock fractures.
The combined effect of seawater and urban wastewaters is due to the inferior quality of groundwater in a few wells, where
they are at topographic lows close to the coast. 相似文献