Petrology of the rajmahal traps of the Northwestern Rajmahal Hills,Bihar, India     

P. K. Mukherjee 《Bulletin of Volcanology》1971,35(4):887-906

Nine basaltic lava-flows, which vary in thickness between 60 feet and 300 feet, were established in the NW Rajmahals. The flows were, at places, laid down one above the other and, at others, were found to contain intervening intertrappean horizons. All the flows are essentially of basaltic composition and are made up of labradoritie plagioclase, pigeonitic and augitic pyroxene, opaque ore, primary glass and secondary minerals (palagonite, secondary silica, calcite and zeolite). The phenocrystic plagioclase ranges in composition between An₇₂ and An₆₂, while the constituents of the groundmass range between An₅₀ and An₁₇. The microphenocrysts of pyroxene are mainly augitic and occasionally pigeonitic while the constituents of the groundmass are essentially pigeonitic. The opaque minerals are magnetite and ilmenite. Petrographically, the lava-flows are more or less similar to one another. The first three flows are, however, more remarkably porphyritic and a little coarser in grain size than the six overlying flows. The eighth flow is devoid of palagonite. Calcite occurs only in certain portions of the second flow. There is a gradual increase in the percentage of primary glass from the first to the ninth flow with a corresponding fall in the total percentage of plagioclase and pyroxene. Statistical analysis of the grain size variation in the plagioclases was carried out and the results were found to be directly related to the prevailing rates of cooling in the different flows and also in the different horizons of the same flow. Modal analysis of the nine flows (in all, 98 samples) was carried out and this brought out some interesting results. Samples from three of the flows were analysed chemically and the corresponding norms were calculated. The order of crystallisation of the primary constituents was established from petrographic and petrological studies. The basaltic magma, which gave rise to the lava-flows of this region, does not appear to have undergone any significant differentiation during the course of its cooling and consolidation. The only discernible effect of crystallisati on differentiation was an enrichment of silica (and, perhaps, alkalis) in the residual liquids and no noteworthy enrichment of iron appears to have occurred at any stage.  相似文献   

Stresses produced by a load moving over the rough boundary of a semi-infinite transversely isotropic solid     

Sunita Mukherjee 《Pure and Applied Geophysics》1969,72(1):45-50

Summary Stresses produced due to a moving load over the plane surface (supposed to be rough) of a semi-infinite transversely isotropic medium have been calculated in this paper.  相似文献   

Note on the propagation of waves in infinite spherically-aeolotropic medium produced by a blast in a spherical cavity     

Sunita Mukherjee 《Pure and Applied Geophysics》1968,70(1):39-46

Summary By using the Laplace transform method, solution has been obtained for the elastodynamic problem due to blast pulse on the inner surface of a spherical cavity in an infinite spherically aeolotropic elastic solid. Both types of blast producing radial and rotational waves have been considered.  相似文献   

Rock-water interaction and evolution of sulphide ores in the late Archaean Chitradurga greenstone belt of southern India     

H. N. Bhattacharyay  A. D. Mukherjee  P. K. Bhattacharyay 《Mineralium Deposita》1993,28(5):303-309

Sulphide ore mineralization developed in proximity to iron formations in a cyclic volcano-sedimentary sequence that forms the offshore part of the late Archaean intracratonic basin of the Chitradurga greenstone belt, south India. The chemistry of volcanic suite attests to an extensive rock-water interaction resulting in exchange of Si and Na for divalent cations, including Cu, Pb and Zn. The exchange took place during hydrothermal alteration of basalt prior to its involvement in regional deformation and metamorphism. A hydrothermal convection system extracted Cu, Zn and Pb from sea-floor basalts during a static phase of evolution of the Chitradurga basin and developed the stratabound ore deposit within the pyroclastics and the stringer ores below.  相似文献   

High-pressure silicate liquidus data: Retrieval of partial molar enthalpy and partial molar entropy of mixing,a test of the regular solution formulation,and comments on theP-T modelling of ascending magmas     

Amalbikash Mukherjee  Abhijit Bhattacharya 《Earth and Planetary Science Letters》1980,49(2):231-236

The activity of a silicate liquid component in a melt at an elevated liquidus temperature and pressure may be expressed analytically in terms of the 1-bar liquidus temperature activity and functions of the partial molar volume and partial molar enthalpy of mixing. Alternatively, the activity of the elevated (i.e. higherP-T) liquidus may be expressed in terms of the difference of heat content, heat capacity, entropy and volume of the component in the crystalline form and in the melt. Equating these two expressions, the partial molar enthalpy of mixing and there-from the partial molar entropy of mixing may be determined, provided the liquidus temperatures of the phase in question at both 1 bar and higher pressure and at a constant melt composition are known. Several such retrievals for CaMgSi₂O₆, Mg₂SiO₄, NaAlSi₃O₈, and TiO₂ from experimental phase equilibrium data are presented. It is argued that as the partial molar enthalpy of mixing generally has large values, the regular solution formulation on the basis of a constant function of the activity coefficient would lead to erroneousP-T estimates for ascending magmas.  相似文献   

Role of fractional crystallization in the descent: Basalt → trachyte     

Amalbikash Mukherjee 《Contributions to Mineralogy and Petrology》1967,16(2):139-148

The role of fractional crystallization in the descent: basalt trachyte is critically examined. For each simple basalt magma type — alkaline, critically undersaturated, and oversaturated — there is a possible trachyte derived by way of fractional crystallization. Olivine removal is the main physical control that may interfere with trachytic trends at low pressure. Higher pressures widen the field of the initial basic compositions from which alkaline trachytes may fractionate. Bowen's hypothesis of trachyte formation from an undercooled basic magma is not supported by recent experimental data. Inefficiency and lack of scope of the fractional crystallization process, in the late stage of differentiation, may lead to an excess of trachytes over trachyandesites. In general, more time, taken in the basic and the salic stages of the descent, due to steeper liquidus and solidus, would result in a greater abundance of the basic and the salic rock types, compared to the intermediate varieties.  相似文献   

Waves produced in an infinite elastic medium due to normal forces and twists on the surface of a burried spherical source     

Jyotirmay Mukherjee 《Pure and Applied Geophysics》1970,82(1):11-18

Summary In this paper, the waves propagated in an infinite medium has been considered by disturbances on the surface of a burried spherical source. The disturbances are produced by two types of forces viz. i) Transient normal force, ii) Transient twist applied on the surface of the source. The solutions are obtained in a very simple form. Graphical representations of some numerical solutions has been added at the end of each problem.  相似文献   

Geochronological constraints on evolution of Singhbhum mobile belt and associated basic volcanics of eastern Indian Shield—reply     

Saumitra Misra 《Gondwana Research》2006,9(4):543-544

  相似文献   

Delineation of arsenic-contaminated zones in Bengal Delta, India: a geographic information system and fractal approach     

Basab Mukhopadhyay  P. K. Mukherjee  Debkumar Bhattacharya  S. Sengupta 《Environmental Geology》2006,49(7):1009-1020

Groundwater extracted from shallow aquifers in the Bengal Delta is contaminated with arsenic. The fluviodeltaic process that creates aquifers, ironically, extends its role to also contaminating them with arsenic. The arsenic distribution maps show a spatial association of arsenic-contaminated wells with palaeo/cut-off/abandoned channels. Weight-on-evidences analysis indicates that the zones of contamination occur around palaeo-channels within a corridor of 500–700 m that contains most of the contaminated wells. These corridors are interpreted to be the zone of channel shifting. Contaminated wells represent point fractal geometry that can be separated into isolated points and clusters. Clusters occur within the zone of channel shifting as obtained by weight-on-evidences analysis. Isolated points occur within floodplain or back swamp areas. Clusters and isolated point fractals are interpreted to reflect the process of arsenic release into groundwater. The migration of biomass within the permeable sandy domain of channel deposits is proposed to be the predominant process in generating clusters. The isolated points represent restricted biomass spreading in less permeable clay-silt dominated floodplains.  相似文献   

Temperatures and winds over tropical middle atmosphere during two contrasting summer monsoons, 1975 and 1979     

B.K. Mukherjee  C.P. Kulkarni  K. Indir  K.K. Dani 《大气科学进展》1989,6(3):325-334

Using the monthly geopotential heights and winds for 700 and 200 hPa for India during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5oN, 76.9oE) during the last week of June and the first week of September for the two contrasting summer monsoon years 1975 (a very strong monsoon year) and 1979 (a very weak monsoon year), a study has been made to examine the mean circulation features of the troposphere over India, and the structures of the temperatures and the winds of the middle atmosphere over Thumba. The study suggested that the axis of the monsoon trough (AMT) at 700 hPa shifted southward in 1975 and northward towards the foothills of the Himalayas in 1979, from its normal position. Superimposed on the low-pressure area (AMT) at 700 hPa, a well-defined divergence was noticed at 200 hPa over the northern India in 1975.The mean temperatures, at 25,50 and 60 km (middle atmosphere) over Thumba were cooler in 1975 than in 1979. While a cooling trend in 1975 and warming trend in 1979 were observed at 25 and 50 km, a reversed picture was noticed at 60 km. There was a weak easterly/ westerly (weak westerly phase) zonal wind in 1975 and a strong easterly zonal wind in 1979. A phase reversal of the zonal wind was observed at 50 km. A tentative physical mechanism was offered, in terms of upward propagation of the two equatorially trapped planetary waves i.e. the Kelvin and the mixed Rossby-gravity waves, to explain the occurrence of the two spells of strong warmings in the mesosphere in 1975.  相似文献