Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

R. Dhana Raju ¹, R. N. Prasad ², D. D. Pande ², A. Panneer Selvam ¹, Mary K. Kumar ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560 072, IN
2 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500 016, IN

Abstract

This study shows δ³⁴S values for the study of co-existing baryte and galena, respectively, are in the ranges of +6.9 to 8.0% and -6.0 to - 9.8%0. Such narrow ranges make biogenic sedimentary source for sulphur less likely and suggest magmatic source. Sulphur isotope values indicate a hydrothermal system with a T of ∼440°C, pH 5±1 and Log f0₂ of -34 to -37.

Keywords

Economic Geology, Sulphur Isotopes, Baryte, Galena, Tamil Nadu.

Full Text

     

R. Dhana Raju ¹, J. S. R. Krishna Rao ¹

Affiliations
1 Department of Geology, Andhra University, Waltair, IN

Abstract

Though much work has been done on the manganese ore deposits of Koduru, Devada, Duvvam and Garividi, no attempt has been made so far to study the powder form occurring as thin beds Intercalated with the primary ore bands. Therefore, an attempt is made in the present paper to know the source of the manganese powder, its depositional environment, mineral constituents and textural features. For this purpose, the manganese powder from Devada was subjected to magnetic separation, and the magnetic and non-magnetic parts were analysed by size analysis, ore microscopic and X-ray studies.

The following are some of the Significant conclusions arrived at from this investigation (1) From the size analysis it is shown that the source of the manganese powder is very near and almost in situ, and the powder was formed due to crushing from the primary bedded ores. (2) The elongation and roundness studies show that most of the grams are not spherical, the average length is about 1.4 to 1.7 times the average width; and this also indicates a near source for the manganese powder. (3) The magnetic part consists of vredenburgite, magnetite and hematite with little pyrolusite, while the non-magnetic part comprises pyrolusite, psilomelane, hematite, hollandite, braunite, bixbyite, geothite and limonite. (4) A new mineral, quenselite (PbMnO₂(OH)) is reported for the first time from this area. (5) The magnetic susceptibility of different powder fractions is correlated with the amount of the sum of vredenburgite and magnetite; of these, coarse fractions contammg much vredenburglte are having high magnetic susceptibilies.

Full Text

     

R. Dhana Raju ¹

Affiliations
1 Department of Geology, Andhra University, Waltair, IN

Abstract

Petrographic study of the granitic rocks of Chipurupalle-Razam area in Srikakulam district of Andhra Pradesh showed that biotite was formed either from orthopyroxene or garnet in reaction with potassium feldspar, under textural disequilibrium conditions. To test whether chemical equilibrium was attained during the formation of biotite, iron distribution coefficient (K_D^Fe2+-Mg) in orthopyroxene-biotite and garnet-biotite mineral phases was considered. K_D of orthopyroxene-biotite pair varies from 1.1 to 2.0, while that of garnet-biotite pair varies from 2.6 to 6.5. After considering the effects of temperature difference and of other elements on the distribution coefficient, the large variation in K_D values in the area was mainly related to the chemical disequilibrium conditions which operated during the biotite formation. An examination of K_D values from different areas showed that in a majority of orthopyroxene-biotite phases and in all garnet-biotite phases, biotite is Mg-rich while the coexisting orthopyroxene or garnet is Fe-rich; and this was explained by the principles of crystal chemistry.

Full Text

     

J. S. R. Krishna Rao ¹, R. Dhana Raju ¹

Affiliations
1 Department of Geology, Andhra University, Waltair, IN

Abstract

Lead-Copper deposits in dolomites, cherty dolomites, quartzites, and calcareous quartzites occur at Bandalamottu, Dhukonda, and Nallakonda of Agnigundala area. The mineralization is mainly controlled by stratigraphic and lithologic features. Galena, sphalerite and pyrite are the dominant ore minerals in dolomites, while chalcopyrite and bornite are dominant in quartzites. Linnaeite, covellite, chalcocite, and bravoite are accessories. In addition to these, X-ray patterns show the presence of violarite, cobaltite, niccolite, stibnite, meneghinite, sternbergite, penroseite, and cuprobismutite. Malachite and azurite are the liberation products of chalcopyrite and bornite during oxidation.

The field and mineralogical associations, textural, petrographic and petrochemical features show that Pb, Zn, and Fe sulphides represent a primary sedimentary genesis, subsequently metamorphosed and recrystallized, while copper mineralization is due to later hydrothermal activity. The presence of linnaeite and bravoite indicates low temperature of the order of 300°C and below, low pressure, and low oxidation for the ore formation.

Full Text

     

J. S. R. Krishna Rao ¹, R. Dhana Raju ²

Affiliations
1 Department of Geology, Andhra University, Waltair, IN
2 Atomic Minerals Division, Dept. of Atomic Energy, Hyderabad, IN

Abstract

Potassium feldspars from the granitic and related rocks occurring in Hyderabad, Salem, Mysore and Waltair areas were subjected to X-ray diffraction studies, both in their natural state and after heating to 1050°C for 8 hrs. The triclinicity (Δ) value in the natural samples varies from 0.98 to 0.74, indicating more or less complete ordered Al/Si distribution, whereas in the heated samples it varies from 0.76 to 0.0, showing increasing disorder with heating. The % Or for these samples as well as for the K-feldspars of Chipurupalle-Razam area was estimated using d-_̅201 following different methods. The % Or obtained from the equations of Wright (1968) very closely agrees with the value obtained from reliable chemical analysis.

Quantitative estimation of the Al contents in the four tetrahedral sites (T₁O, T₁m, T₂O and T₂m), following the method of Stewart and Ribbe (1969), shows that in orthoclase the Al content is equally distributed between T₁O and T₁m sites, whereas in intermediate and maximum microcline A1 is concentrated more in T₁O site than in T₁m site. Based on the triclinicity values, the K-feldspars from the Chipurupalle-Razam area belong to the high structural state followed by those from Salem, Waltair, Hyderabad, and Mysore areas with low structural states, and the differences in the structural state may be related to the differences in the P-T conditions prevaling at the time of K-feldspar formation in these areas.

Full Text

     

R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, K-366, New Alipore, Calcutta 700053, IN

Abstract

In the Chipurupalle-Razam area, garnetiferous and orthopyroxene-bearing granitic rocks and their associated Khondalite Group constitute the Precambrians of the Eastern Ghats. The mineral assemblages and textural features of the different rock types indicate that the rock types in the area were subjected to at least two periods of metamorphism.

The first period of metamorphism under conditions of granulite facies was around a minimum temperature of the order of 600° to 700°C, but below 800°C, with P_load of about 6 to 7 kb. The second period of metamorphism under the upper almandine-amphibolite facies conditions took place above 550° and below 700°C at about 1.5 kb P_H2O. The bulk composition of the rock is the primary controlling factor for the presence or absence of garnet, orthopyroxene, and sillimanite, as well as the composition of individual minerals like biotite, garnet, and orthopyroxene.

Full Text

     

Sunil Kumar ¹, R. Dhana Raju ², H. M. Varma ², N. K. Dougall ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Skyline View, G S Road, Mawtai, Shiliong 793 008, IN
2 Atomic Minerals Division, Department of Atomic Energy, 110-153, Begumpet, Hyderabad 500 016, IN

Abstract

Rocks of alkaline affinity, namely cancrinite-tinguaite and K-rich trachyte occur as dykes in the Plecambrian gneissic and migmatitic country rocks in the Nongcharam. Darugiri area of the East Garo Hills district Meghalaya Cancrinite-tinguaite is characterized mineralogically by the presence of phenocrysts of high temperature K-feldspar cancrinite nepheline aegirine-augite aeggitine, diopside, biotite and occasional barkevikite in a groundmass consisting of K-feldspar albite anorthoclase, aegirinec aegirinec-augite, nepheline, cancrinite, sodalite and chlorite and chemically by an agpaitic index' of about 1 2 K-rich trachyte exhibits porphytitic texture, and is chemically characterized by low NaO(0 45 wt %), high K₂O(13 25 wt %) resulting to high K ₄O/Na₂O ratio of nearly 3.

This occurrence of alkaline and related rocks together With the earlier reported occurence of an alkaline-carbonatite complex from the nearby Wah Sung valley, Meghalaya points to an alkaline phase of magmatic activity in this part of the Indian subcontinent.

Full Text

   

A. S. Siddiqui ¹, R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, 1-10-153, Begumpet, Hyderabad 500 016, IN

Abstract

In a number of radioactive occurrences near the contact of Buxa and Gondwana rocks in the Subuk-Rishi area of Sikkim Himalayas. uranium mineralization, in the form of hydrothermal veins and disseminations of brannerite-davidite, is recorded in the carbonate rocks of the Buxa. Group (Older Palaeozoic) and quartz arenite of the Lower Gondwana Subgroup. The carbonate rocks are intermediate between a pure limestone and a pure dolonlite, and are phosphatic with P₂O₅ upto 17wt. %, reflected in essential apatite. Radioactivity is relatively more in carbonate rocks than in sandstone, and there is an apparent increase of U with P in both the rock types.

Full Text

     

A. N. Basu ¹, G. S. Sharma ¹, H. M. Varma ¹, R. Dhana Raju ¹, N. K. Dougall ¹, N. V. Raju ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Hyderabad 500016, IN

Abstract

At Maturigiri and Dhurkantagiri, mineralised coarse-grained quartz syenite bodies (up to 10 x 2 m) occur as intrusives along the NNW-SSE trending joints in the gneissic country rock. Mineralogically. the quartz syenite is characterised by over 50% K-feld-spar, lesser plagioclase, quartz, mica, garnet and chlorite, together with accessory uraninite, monazite, molybdenite and pyrite. Uraninite occurs as euhedral to subhedral inclusions and mineralisation is syngenetic. Two types of monazite, Th-poor and Th-rich, are present. Molybdenite occurs as veins along fractures and appears to be of late hydrothermal origin. The mineralogical and textural features suggest that quartz syenite was formed from a residual melt of granitic magma of crustal origin.

Full Text

     

B. Krishnaiah Setty ¹, R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Hyderabad 500 016, IN

Abstract

Taking advantage of the sympathetic variation of magnetite content with that of (i) total heavy minerals, (ii) ilmenite, and (iii) pyriboles in sand samples drawn from the Nizampatnam deposit along the south Andhra coast, regression equations relating magnetite with others are calculated. Using the wt. % of magnetite and these equations, the wt.% of total heavies, ilmenite and Pyriboles are calculated, which closely agree with the observed data, within a difference of 5%. The content of other important but minor heavy minerals like zircon, monazite and rutile need to be estimated by separation and microscopic grain-counting of only two fractions (i.e.) + 200 and -200 mesh-sizes, since these minor minerals are confined in these two fractions. By this method, consumption of heavy liquid and microscopic grain-counting can be substantially reduced by 70%, without sacrificing the accuracy for estimation of reserves of heavy minerals in this deposit.

Full Text

   

P. V. Ramesh Badu ¹, B. K. Pandey ², R. Dhana Raju ³

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Nagpur- 440 001, IN
2 Atomic Minerals Division, Department of Atomic Energy, Bangalore - 560 072, IN
3 Atomic Minerals Division, Department of Atomic Energy, Hyderabad - 500 016, IN

Abstract

isotopic date on 12 samples of the Paliam and Darba granites of the Bastar Craton in Central India have defined an isochron age of 2308 ± 48 Ma. with initial Sr-isolopic ratio of 0.7354 ± 0.0097. Mineral ages on perthite, biolile and muscovite from tin- and rare metal-minearlised as well as non-minearlised pegmatites of the Bastar-Koraput Pegmatite belt within this craton have indicated two important dates of about 2050 and 1620 Ma. These dates are interpreted as (a) emplacement of the granite around 2300 Ma., (b) derivation of the pegmatites from this parent granite around 2050 Ma and (c) reselling of Rb-Srsystem at about 1620 Ma., concomitant with the metamorphic/uplift event in the nearby Eastern Ghats. The very high initial ⁸⁷Sr/⁸⁶Sr ratio of 0.735 for granite indicates thai they are crustal derived, possibly from a metasedimentary source.

Keywords

Rb-Sr ages, Geochronology, Pegmatitic Minerals, Bastar-Koraput Belt, Madhya Pradesh, Orissa.

Full Text

     

K. Satyanarayan ¹, R. Dhana Raju ², D. N. Kanungo ³

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500016, IN
2 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560072, IN
3 Atomic Minerals Division, Department of Atomic Energy, Bhubaneswar-751002, IN

Abstract

Geochemistry of ortho-amphibolites from the Degapudi-Kalichedu area of the Nellore Schist Belt (NSB), an Archaean greenstone belt in southeastern India, has indicated their affinity to a low-K tholeiitic magma derived from an LIL-enriched, apatite-bearing mantle by about 5-20% partial melting, followed by fractional crystallization. Amphibolites range from high-Mg-type early differentiates (massive amphibolite and actinolite schist) to low-Mg-type middle-stage differentiates (schistose amphibolite, hornblende schist and related gametiferous hornblende schist). During and subsequent to the generation of their parental magma, the early crystallizing mineral phases are oli vine-clinopyroxene-plagioclase-magnetite-apatite. A back-arc or marginal basin palaeotectonic setting is indicated for NSB by geochemistry of these amphibolites, with precursors of high-Mg-type emplaced in a narrow basin associated with mature subduction zone system and of low-Mg-type in a wider basin associated with youthful subduction zone system.

Keywords

Amphibolites, Tholeiites, Igneous Rocks, Nellore Schist Belt, Andhra Pradesh.

Full Text

     

R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Division, Bangalore-560 072, IN

Abstract

No Abstract.

Full Text

   

Rajendra Singh ¹, R. Dhana Raju ², A. K. Singh ³

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500 016, IN
2 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560 072, IN
3 Atomic Minerals Division, Department of Atomic Energy, Calcutta-700 026, IN

Abstract

A zirconium-rare earth (RE)-thorium-uranium fossil placer with about 60-84% heavy and resistant minerals is recorded in association with quartzite and metagreywacke of the Proterozoic Miri Group from the Boleng area in East Siang District of Arunachal Pradesh. The heavy minerals occur as thin layers with variable thickness of a fraction of a cm to a maximum of 12 cm. The mineralised rocks are hard, highly compact, very heavy (sp. gr. 3.96-4.66), massive (at places, banded) and exhbit clastic texture with rounded to subrounded and well sorted fine grains of heavy minerals pointing to a long distance of transportation. Mineralogically, it consists of 46-61% opaques (mostly Ti-hematite), 9-13% rutile, 3-9% cyrtolite, 0.7-4.5% monazite and 0.2-0.9% thorite, all set in 10-30% sericitic matrix. Chemically, it is markedly different from the widespread unconsolidated coastal and inland placers, and analyses about 43-62% iron oxides, 1.7-5.4% Zr0₂, 0.5-3.1 % (RE,Y)₂O₃, 0.1-0.5% ThO₂, and 0.01-0.9% U₃O₈. Chondrite-normalizcd REE-pattems show light REE enrichment and heavy REE depletion, with (Ce/Yb)_cn ratio of 9-10 and markedly negative Eu-anomaly (Eu/Eu: 0.18-0.22). Generally, consolidated placers (fossil placers) are monazite-rich, whereas unconsolidated placers are, zircon-rich and viewed in this light, the cyrtolite (zircon)-rich fossil placer from the Boleng area is a rare occurrence.

Keywords

Fossil Placer, Radioactivity, Boleng, Arunachal Pradesh.

Full Text

     

G. R. Dikshitulu ¹, B. K. Pandey ², Veena Krishna ², R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560 072, IN
2 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500 016, IN

Abstract

Precambrian Central Gneissic Complex (CGC) in the Kameng district of Arunachal Pradesh comprises the oldest Sela Group thrusting over the Bomdila Group, with the Salari Group being the youngest. Augen gneiss of the Bomdila Group, granite of the Salari Group and hornblende granite gneiss of the Sela Group define Rb-Sr isochron ages of 1914 ± 23, 1536 ± 60 and 481 ± 23 Ma, respectively. The 481 Ma age on the hornblende gneiss from the oldest Sela Group is attributed to the resetting of Rb-Sr clock due to tectonic imprint of the Main Central Thrust (MCT). The 1914 Ma age of the augen gneiss, the oldest reported so far from the Arunachal Himalaya, is either the emplacement age or latest metamorphic event. The 1536 Ma old emplacement age of the granite intruding the black shale of the Salari Group disproves the hitherto considered Gondwana age for the black shale, and, thus, necessitates revision in its chronostratigraphy. (⁸⁷Sr/⁸⁶Sr)_i of the hornblende granite gneiss and Salari granite is high (0.719 and 0.709) indicating a crustal source for these, whereas it is low for the augen gneiss (0.703) suggesting an inherited signature of the upper mantle source together with some crustal contamination. Rb-Sr whole-rock isochron ages from the Arunachal Himalaya are correlatable with those reported from other parts of the Indian Himalaya. These cumulatively point to at least three major periods of activity in the Himalaya at ca. 2060 ± 250, 1530 ± 90 and 530 ± 75 Ma.

Keywords

Rb-Sr Whole-Rock Ages, Geochronology, Central Gneissic Complex, Arunachal Himalaya.

Full Text

     

G. R. Dikshitulu ¹, R. Dhana Raju ²

Affiliations
1 Atomic Minerals Division, Hyderabad - 500 016, IN
2 Atomic Minerals Division, Bangalore - 560 072, IN

Abstract

The Central Gneissic Complex (CGC) in the Kameng district, Arunachal Pradesh comprises the oldest Sela Group, followed by the Bomdila Group and the youngest Salari Group. The Sela Group consists of migmatite, hornblende granite gneiss, two-mica granite and profuse intrusions of tounnaline granite (Tertiary ?). Along the Main Central Thrust (MCT), the Sela Group overlies the Bomdila Group consisting of augen gneiss, quartzite. quart-mica schist, marble and basic intrusive rocks. The Bomdila Group, in turn, overlies the Salari Group that comprises black shales and intrusive high-Ca granites. Radioelement (U, Th and K) contents, detennined by gamma-ray spectrometry. of 28 granitic and migmatitic samples of CGC indicate that the tourmaline granite and two-mica granite, augen gneiss have the highest U values as compared to that of others. Th content is more in the augen gneiss and hornblende gneiss than in other rock types. In case of K, two-mica granite and tourmaline granite have higher contents than the rest. Radioactive heat, computed from each ofthese radioelements, is highest in the tourmaline granite and two-mica granite, with the other rock types having low to intermediate values. The average total heat generation of CGC is of the order of 9.3 Heat Generation Units (HGU). A value of about 7 HGU is generally taken as the separating value between hot and cold crust and, hence, the higher value of 9.3 HGU for CGC points to the presence of hot crust in the Arunachal Himalaya. The radioactive heat generation and the published high heat flow values in the CGC indicate steep geothermal gradients in the area, which may help in remobilisation and subsequent precipitation/concentration of U in favourable locales.

Keywords

Radioactivity, Central Gneissic Complex, Arunachal Pradesh.

Full Text

     

R. Dhana Raju ¹, Madhuparna Roy ¹, Arjun Panda ¹, M. Vasudeva Rao ¹

Affiliations
1 Regional Centre for Exploration and Research, Atomic Minerals Division, Department of Atomic Energy, Bangalore-560 072, IN

Abstract

In the uranium prospect at Tummalapalle in the southwestern part of Cuddapah basin, fluid flow during contact metamorphism is documented in a vein-mineral-assemblage of a metadolerite intruding the carbonate rocks and shale of the Vempalle Formation of the mid-Proterozoic Lower Cuddapah Supergroup. The minerals in the vein are calcite, quartz, Mg-chlorite and Fe-chlorite formed in that order due to fluid-infiltration-driven volatilization reactions involving CO₂- and H₂O- fluid having an external source in the nearby sedimentary rocks. The observed sequential vein-mineral assemblage is considered as a petrographic evidence of 'infiltrating fluid mechanism during metamorphism', proposed first by Ferry (1980), as well as for 'batch volatilization' of Valley (1986).

Keywords

Metamorphism, Uranium Mineralisation, Cuddapah Basin, Andhra Pradesh.

Full Text

     

A. Panneer Selvam ¹, R. N. Prasad ², R. Dhana Raju ¹, R. M. Sinha ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560072, IN
2 Atomic Minerals Division, Department of Atomic Energy, Hyderabad-500016, IN

Abstract

Metaluminous granitoids of the South Khasi batholith (SKB) in the West Khasi Hills district of Meghalaya define a Rb-Sr whole-rock isochron age of 757 ± 60 Ma, with (⁸⁷Sr/⁸⁶Sr) of 0.71069 ±0.00092. SKB and other granitoids of Meghalaya like Mylliem, Nongpoh and Kyrdem have many common features such as the presence of basic enclaves of hornblende gneiss and amphibolite, lateto post-tectonic nature, predominance of biotite amongst mafic silicates, overall metaluminous nature and high (⁸⁷Sr/⁸⁶Sr) of more than 0.709. All these indicate much similarity in the genesis of their melts due to partial melting of lower crustal rocks. The Rb-Sr isochron ages of SKB and other granitoids in Meghalaya point to a major tectonomagmatic activity during ca. 760-480 Ma, which is almost coeval with ca. 800-500 Ma Mid-Upper.Pan-African activity. The data, thus imply the possible imprint of the widespread Pan-African activity in northeastern India, besides southern India.

Keywords

South Khasi Batholith (Meghalaya), Rb-Sr Isochron Age, Geochronology, Pan-African Activity.

Full Text

     

R. Dhana Raju ¹, Minati Roy ¹, Madhuparna Roy ¹, S. G. Vasudeva ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Bangalore 560072, IN

Abstract

Two types of uranium mineralisation occur in the south-western part of Cuddapah basin, viz., stratabound type hosted by impure dolostone of the Vempalle Formation of the Papaghni Group and structuralIy-controlled type hosted by deformed basement grani toid. The carbonate-hosted type occurs over a 140 km-long belt from Reddipalle in the west to Maddimadugu in the east with promising mineralisation at Tummalapalle, Rachakuntapalle and Gadankipalle. It is sandwiched between a Iower massive limestone and upper shale and cherty limestone. The rnineralised carbonate rock is a stromatolite-bearing 'siliceous, calcitic doIostone ' (SCD+phosphate) associated with other impure dolostones, quartzite, chert, phyllite, conglomerate, and intrusive dolerite a nd basalt. Uranium mineralisation occurs along the bedding plane, carbonate-phosphate conlact, micro-stylolites, grain boundaries of clasts and within pelioids, mainly in the form ultrafine pitchblende, in intimate association with pyrite and as disseminations in cellophane-rich parts, besides as minor phases ot'coffi~itea nd U-Ti compIex. The associated ore minerats include pyrite, molybdenite, chalcopyrite, bornite, digenite and covellite. The fertile basement granite fs.1.) is the source of uranium and the mineralisation, which appears to be polygenetic(syn-, dia- and epi-genetic), is controIled by impure nature of dotostone and organic activity. The mineralisation in the southern part of the belt in Cuddapa h district is typically molybdenum-rich, whereas the northern portion, in parts of Anantapur district, is characterised by high content of copper. The rnineralised SCD in the S/SE parts is also marked by high content of P, V and Pb, in addition to Mo. There is a good positive correlation of U with Pand V (r : 0.98 and more).

The structurally-controlled uranium mineralisation occurs around Rayachoti (outside the SW margin of Cuddapah basin) along a number of fracture zones within the basement granitoid, and is hosted by mylonites and cataclasites indicative of intense dislocation metamorphism. Of many such zones, the one between T. Sundupalle and Sanipaya is promising and has a strike extension of about 16 km. This mineralisation is epigenetic hydrothermal vein-type, mainly represented by coffinite, pitchblende, U-Ti. complex and secondary uranium minerals.

Keywords

Uranium Mineralisation, Stratabound Deposit, Hydrothermaltype, Cuddapah Basin, Andhra Pradesh.

Full Text

     

R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Division, Bangalore, IN

Abstract

No Abstract.

Full Text

   

Minati Roy ¹, R. Dhana Raju ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy Hyderabad-500016, IN
2 Atomic Minerals Division, Department of Atomic Energy, Bangalore-560 072, IN

Abstract

The phosphatic siliceous dolostone (PSD) predominantly comprises ferroan dolomite that occurs as (a) micritic mosaic within the groundmass, intraclasts, peloids and ooids; (b) fibrous dolomite coating (a); and (c) clear dolomite filling cavities, and is secondary in nature formed due to dolomitisation of precursor high-Mg calcite. Stratigraphic position, sedimentary structures, structures of dolomite, process of dolomitisation and association with collophane and silicate clasts indicate a shallow marine intertidal depositional environment for PSD.

Keywords

Petrography, Sedimentology, Uranium, Vempalle Formation, Cuddapah Basin Andhra Pradesh.

Full Text

     

G. R. Dikshitulu ¹, R. Dhana Raju ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Begumpet, Hyderabad - 500016, IN
2 Atomic Minerals Division, Department of Atomic Energy, Begumpet, Nagarabhavi, nangalore - 560072, IN

Abstract

Petrology and geochemistry (major, minor and trace elements including REE) of the different granitoids from Central Gnessic Complex indicate that, (a) the dominant Palaeoproterozoic migmatite, hornblende granite gneiss, two-mica granite and augen gneiss are syn-kinematic, autochthonous, peraluminous, low-Ca granodiorite, with the first three being of S-type formed by highdegree (>50%) anatexis of sediments of psammopelitic composition, whereas the augen gneiss is I-type formed by partial melting of a basic rock of mantle affinity coupled with notable crustal contamination and affected by soda metasomatism; (b) the minor Mesoproterozoic Salari granite is late-kinematic, allochthonous, metaaluminous, epidote-bearing, high-Ca monzogranite of I-type formed by partial melting of basic rock from crustal depth; (c) the youngest (ca. 30 Ma) tourmaline granite is post-kinematic, allochthonous, strongly peraluminous, high-level syenogranite of S-type, with its parental melt derived from a peraluminous granitoid by anatexis induced by large volume of volatiles and fluids, and (d) tectonically, these granitoids are of 'syn-collision' type.

Keywords

Petrology, Geochemistry, Granitoids, Anmachal Himalaya.

Full Text

     

R. Dhana Raju ¹

Affiliations
1 Osmania University, Hyderabad - 7, IN

Abstract

No Abstract.

Full Text

   

R. Dhana Raju

Abstract

No Abstract.

Full Text

   

R. Dhana Raju ¹

Affiliations
1 6-3- 124, Hastinapuri, Sainikpuri P 0 . Secunderabad - 500 094, IN

Abstract

India has a coastline of over 7,500 km, with a large Delta-Region behind it along its East Coast and practically no delta along its West Coast Scientists of the Atomic Minerals Directorate (AMD) for Exploration and Research of the Department of Atomic Energy, by their more than 5-decade old reconnoitory surveys and detailed exploration have identified many dune and beach placer Heavy Minerals (HMs ilmenite,rutile, monazite, zircon, garnet, sillimanite, etc ) sand deposits along the East Coast in the States of Orissa, Andhra Pradesh and Tamil Nadu. A few big deposits amongst these are bang exploited by some Govt and Private agencies. As these HMs have numerous industrial, including hitech, applications with further requirement to establish their additional exploitable resource-base, its time to explore for concealed deposits in the hiherto unexplored areas. In this backdrop, it is suggested that the Delta-Region of the East Coast could be a target. Within this, strandplain behind the shoreline and prograding deltas of the Rivers like Mahanadi and Godavai, which are characterized by palaeo-strandlines associated with Palaeo-Sand bodies, all within a zone of 30 km inland from the present day shoreline, appear to be potential for such exploration. This is supported by AMD's recent identification of notable concentration (2-64 wt %, average 16 wt %) of HMs in Palaeo-sand ridges in the Paradeep sector of Orissa and of lesser concentration in parts of the Krishna-Godavari delta in Andhra Pradesh. An exploration programme, involving sequentially (a) mapping of the areas of strandplain and prograding deltas within 30 km inland from the present day shortline by High-Resolution satellite imageries and aerial photographs, (b) shallow seismic survey, (c) Low-Flying Aero-Radiometric/magnetic surveys, (d) reconnoitory ground survey and sampling, (e) sub-surface exploration, first by reconnoitory and then by Exploratory-Evaluation drilling and (f) determnation of grade, mode and resource of HMs, is proposed for this purpose.

Keywords

Delta, Placer Heavy Mineral Sand Deposits, East Coast, India.

Full Text

     

R. Dhana Raju ¹, G. S. Ravi ², K. Shivkumar ³, L. S. R. Reddy ⁴, Sabita Rohatgi ⁴

Affiliations
1 Hon Visiting Prof, Dept of Applied, Geochemistry, Osmania University, Hyderabad - 500 007, IN
2 Atomic Minerals Directorate for Exploration & Research, Department of Atomic Energy, Visakhapatnam-530 018, IN
3 Atomic Minerals Directorate for Exploration & Research, Department of Atomic Energy, Nagpur-440 001, IN
4 Atomic Minerals Directorate for Exploration & Research, Department of Atomic Energy, Hyderabad- 500 016, IN

Abstract

Estimation of industrial and strategic heavy minerals (HMs) in sands, viz, ilmenite, rutile, garnet, sillimanite, zircon and monazite, is usually carried out by Microscopic Gram-Counting (MGC) technique on heavy Liquid- and Magnetically-Separated fractions. This method is slow, laborious, Time-Consuming, costly, toxic and causes Eye-Strain. Its precision and accuracy depend on Microscope-Operator's skills in mineral identification and preparation, by microsplitting of representative portions of fractions for analysis. Instead, we are proposing here a WDXRFS-Based relatively simple, rapid, low-cost, non-toxic, eye Strain-Free and precise method. This involves (a) magnetic separation of a sand sample into 3 Sub-Samples that are magnetic at 0 4 and 1 2 A and Non-Magnetic at 1 2 A, (b) WDXRFS analysis of these for the oxides and elements in the formulae of HMs, and (c) computation of the contents of HMs, assuming their stoichiometric composition. The contents of HMs in sand samples, determined by this method, are in general agreement with that from MGC method on natural sand samples and prepared samples, with an overall error of <20%and coefficient of correlation (r) of -0 98. Furthermore, our method gives additional information on end-member composition of garnet, Th-content of monazite and proportion of Ortho- to Clino- in pyroxenes.

Keywords

XRF Method, Heavy Minerals, Quantification, Beach Sands.

Full Text

   

R. Dhana Raju ¹

Affiliations
1 Kavalipuram - 534 222 West Godavari Dist., A. P, IN

Abstract

No Abstract.

Full Text

   

R. Dhana Raju ¹

Affiliations
1 - 1-10-284/1, Begumpet, Hyderabad - 500 016, IN

Abstract

No Abstract.

Full Text

   

R. Dhana Raju ¹

Affiliations
1 Kavalipuram - 534 222, W Godavari District Andhra Pradesh, IN

Abstract

No Abstract.

Full Text

   

R. Dhana Raju ¹, E. V. S. S. K. Babu ²

Affiliations
1 Department of Atomic Energy, Begumpet, Hyderabad - 500 016, IN
2 National Geophysical Research Institute, Hyderabad - 500 007, IN

Abstract

Rare Earth Elements (REE) geochemistry of uranium-bearing phases from two genetically different types of uranium mineralisation is presented here. These include the syn-magmatic type, hosted by part of the Suryamalai or Sankari granite in the Kullampatti area, Tamil Nadu and hydrothermal vein type, hosted by both basement granitoid and its overlying Shahabad Limestone in the Bhima basin at Gogi, Karnataka. The study is based on the Electron Microprobe (EMP) analysis of selected REEs from different U-bearing phases, viz., uraninite, its pseudomorphic altered product of gummite, pitchblende and coffinite. Those hosted by granite, compared to that in limestone, have higher contents of XREE. Those in syn-magmatic type contain HREE>LREE and vice-versa in hydrothermal type. The former pattern is reflected in the co-existing Y- and HREE-bearing multiple oxides of fergusonite, samarskite and betafite. Furthermore, U-bearing organic matter and smectite-illite clay at Gogi contain higher contents of LREE. Pitchblende in both granite and limestone shows perceptible positive Ce-anomaly whereas the coffinite in limestone shows negative Ce-anomaly.

In the plot of EREE vs. chondrite-normalised LREE/HREE, except for those in the granite-hosted syn-magmatic type, the rest of U-phases as well as uraninite from other types (taken from literature) define a trend of positive correlation. The minimum-end of the ZREE is represented by the unconformity-type of Collins Bay, Canada and Pine Creek deposits, Australia, and the maximum-end of SREE by hydrothermal vein type in the granite at Gogi. The syn-magmatic granite-hosted uraninite from Kullampatti, Rossing and Faraday plot close to each other, but away from the main positive trend toward a higher EREE.

In simple oxides of uranium, LREE, MREE and HREE, appear to co-exist or substitute, respectively, for Ca, Th and U, as indicated by the corresponding increasing trends. During post-magmatic alteration of uraninite to gummite and samarskite to betafite, there is a notable depletion of especially the HREE. During coffinitisation of pitchblende or replacement of coffinite by pitchblende, there is a similar depletion, especially the LREE in the former and the MREE in the latter.

Full Text

     

R. Dhana Raju ¹

Affiliations
1 Kavalipuram - 534 222 W. Godavari Dist., A.P., IN

Abstract

No Abstract.

Full Text

   

S. Viswanathan ¹, R. Dhana Raju ², E. V. S. S. K. Babu

Affiliations
1 Flat B-203, Block-B, United Avenue Apts., South End, 7-1-29, Ameerpet, Hyderabad - 500 016, IN
2 3-27, Kavalipuram, (via) Velpur-Tanuku - 534 222, West Godavari District, Andhra Pradesh, IN

Abstract

No Abstract.

Full Text

   

R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research Department of Atomic Energy Begumpet, Hyderbad - 500 016, IN

Abstract

No Abstract.

Full Text

   

R. Dhana Raju ¹, Mary K. Kumar ², E. V. S. S. K. Babu ¹, S. A. Pandit ²

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Hyderabad - 500 01 6, IN
2 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Bangalore - 560 072, IN

Abstract

Uranium mineralisation in the Neoproterozoic Bhima basin todate has been found near Ukinal and at Gogi. U-mineralised phosphatic horizon near Ukinal includes the lithounits of phosphatic micritic limestonelchert and siliceous, calcareous phosphorite, some of which are manganiferous and glauconite-bearing. Uranium in these phosphatic rocks, correlatable with P₂O₅content (r>0.9), occurs mostly in collophanc and is difficult to extract. This mineralisation is sedimentary-diagenetic.

Mineralisation at Gogi is more promising. This occurs within the major E-W trending Gogi-Kurlagere fault, near to its intersection with a NE-SW trending fault and is hosted by both brecciated, siliceous limestone and deformed basement rock represented by low-Ca biotite granite-granodiorite. Over 80% of the mineralisation at Gogi occurs as veins, veinlets and fracture-fills, composed of coffinite, lesser pitchblende, accessory U-Ti-Si complex (only in granitoid), associated intimately with reductants like sulphides and organic matter, and also clays (illite, smectite). Pitchblende is of two generations, both replaced by and replacing coffinite, and these two U-minerals, in turn, arc replaced by U-Ti-Si complex. The U-minerals occurring in limestone are Th-poor and are characterised by variable contents of U, Pb, Si and lanthanides (LREE>HREE), and as compared to those in granitoid are marked by higher contents of U, Pb, Fe and lower contents of Si and lanthanides. Amongst the sulphides, pyrite is predominant and occurs in three modes, viz., coarse euhedral-subhedral, framboidal and reticulate. The rest comprise marcasitc, chalcopyrite and galena in accessory to minor amount. These sulphides carry notable contents of Co, Ni, Se As, Ag and Au, with enrichment of Ag, Co, Ni in chalcopyrite followed by pyrite (more in framboidal type), Se in galena and Au more in sulphides from the granitoid. These high-value metals can be recovered as by-products during extraction of U. The organic n~atteris heterogenous and contains U, Si, Ca, Al, Pb and Fe, with the one rich in U is also high in the other elements. Radioactive clay contains U, P and REE. Both radioactive organic matter and clay are almost free of Th and Zr, with LREE>HREE. Paragenetically, the uranium minerals were formed later than the sulphides and organic matter. U-mineralisation at Gogi is poly-phase and poly-metallic, hydrothermal vein type with an Eh of -0.2 to -0.3V, pH of 7 to 8, and temperature of <200°C. The controls for this U-mineralisation are: (a) fertile granitoid as source, (b) structurally weak and permeable zones of faults, folds, brittle-ductile deformation and unconformity, along basin margin, (c) presence of strong reductants of organic matter and sulphides, (d) impervious and reactive cover rock of limestone and (e) dyke activity in the basement which may have acted as heat source and created necessary geothermal gradient for remobilisation and precipitation of U. These can be taken as guides for U-exploration in similar geologic set-up.

Keywords

U-Mineralisation, Hydrothermal, Neoproterozoic, Bhima Basin, Gogi, Ukinal, Karnataka.

Full Text

     

R. Dhana Raju ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Hyderabad - 500 016, IN

Abstract

No Abstract.

Full Text

   

A. V. Jeyagopal ¹, R. Dhana Raju ², P. B. Maithani ¹, Anjan Chaki ¹

Affiliations
1 Atomic Minerals Directorate for Exploration and Research, Department of Atomic Energy, Begumpet, Hyderabad - 500 016, IN
2 Atomic Minerals Directorate for Exploration and Research, 6-3-124, Hastinapuri, Secundarabad - 500 094, IN

Abstract

The Mesoproterozoic Papaghni Group in the Cuddapah basin of southern Andhra Pradesh comprises mainly arenaceous, argillaceous and calcareous sediments. These sediments occur in sequences that are mappable on large scale (15000) and the sequences are idenified by unconfornities which are recognised by conglomerate/breccia beds in Vempalle Formation (Papaghni Group). Each sequence starts with near shore arenaceous and argillaceous sediments and ends up with relatively deeper marine chemical precipitate, viz dolomitic sediment, with these three constituting one cycle of sediments. The thickness of each cycle ranges from about twenty meters to hundreds of meters and three such cycles of sedimentation are identified. On the basis of the identification of cyclic sedimentation and bounding unconfornuties it is proposed that the Vempalle Formation of Papaghni Group may be classified into Lower, Middle and Upper members, which denote recurrence of similar depositional settings during the Vempalle sedimentation.

Keywords

Cyclic Sedimentation, Papaghni Group, Cuddapah Basin, Andhra Pradesh.

Full Text

     

R. Dhana Raju ¹, M. Jagannadha Rao ²

Affiliations
1 Secunderabad, IN
2 Visakhapatnam, IN

Abstract

No Abstract.

Full Text

   

R. Dhana Raju ¹, S. Vijayalakshmi ², T. R. Mahalingam ², C. R. M. Rao ³, Madhuparna Roy ⁴

Affiliations
1 Atomic Minerals Division, Dept. of Atomic Energy, Bangalore - 560 072, IN
2 Indira Gandhi Centre for Atomic Research, Dept. of Atomic Energy, Kalpakkam - 603 102, IN
3 Chemical Laboratory, Geological Survey of India, Madras - 600 032, IN
4 Atomic Minerals Division, Dept. of Atomic Energy, New Delhi - 110066, IN

Abstract

Platinum Group Elemental (PGEs-Pt, Ir, Pd, Rh and Ru) contents, determined by ICP-MS, are reported in a rare REE-Th-Zr-Ti-rich ultrabasic tremolite-actinolite rock from Vattalakki, Kerala. Data on PGE, together with unusually high contents of REE, Th, Zr and Ti at percent level, indicate this rock as 'anomalous'.

Keywords

Economic Geology, PGE, REE-Rich Metaultramafite, Kerala.

Full Text

     

R. Dhana Raju ¹, R. N. Prasad ², D. D. Pandey ², A. V. Jeyagopal ², R. D. Deshmukh ¹

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, Bangalore - 560072, IN
2 Atomic Minerals Division, Department of Atomic Energy, Hyderabad - 500016, IN

Abstract

Baryte at Vemula near to the southwestern margin of Cudapah Basin occurs as a vein-type deposit discordant to both the carbonate rocks of Vempalle formation and its intrusive dolerite. S-isotopic data on the baryte have a range of δ³⁴S_CDT between +16.2‰ and +23.3‰ whereas the coexisting chalcopyrite has a restricted range between +10.9‰ and +11.4‰. The average value of δ³⁴S of Vemula baryte (+20.8‰) differs much from that of magmatic rocks (0‰ to +2.5‰), metamorphic rocks (+3‰) and sediments of continental margins, platform areas and geosynclines (-12.5‰ -17,1‰), but is similar to that of sea water (+20‰) which appears to be the source for sulphur. The narrow range of δ³⁴S of baryte and chalcopyrite points to a uniform source with their sulphur possibly derived from sea water sulphate by bacteriogenic reduction.

Keywords

Economic Geology, Baryte, Sulphur Isotope, Cuddapah Basin, Andhra Pradesh.

Full Text

     

S. K. Bhattacharya ¹, M. M. Sarin ¹, Minati Roy ², R. Dhana Raju ³

Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN
2 Atomic Minerals Division, Dept. of Atomic Energy, Hyderabad - 500 016, IN
3 Atomic Minerals Division, Dept. of Atomic Energy, Bangalore 560 072, IN

Abstract

The dolostones show a narrOw range of δ¹³C values but a large range of δ¹³O values. The small spread of δ¹³C from 0.1‰ to -0.9‰ is typical of marine carbonates, whereas the large range of δ¹³O from -7‰ to -14‰ represents characteristic Proterozoic marine carbonates some of which were exposed to alteration by fresh continental waters. A diagenetic environment of mixed marine and fresh water for the dolostone alteration is also supported by earlier studies in sedimentary structures and petrography. The ²³⁴U/²³⁸U activity ratio of 0.7 in some of the mineralised samples shows the effect of ongoing chemical leaching of uranium from discrete uranium minerals like pitchblende and coffinite.

Full Text

     

R. Dhana Raju ¹, B. S. Negi ²

Affiliations
1 Atomic Minerals Division, Department of Atomic Energy, 1-1-153, Begumpet, Hyderabad 500 016, IN
2 Atomic Minerals Division, Department of Atomic Energy, West Block VII, R. K. Puram, New Delhi 110022, IN

Abstract

The Andaman ophiolite suite, consists of ultramafic to mafic plutonites, basic volcanics and chert beds. Ophiolites were emplaced as linear belts along major and deep 'seated N-S-trending fault zones in eugeosynclinal flysch series of the Port Blair Group. Ultramafic plutonites include dominant serpentinile and minor dunite, harzburgite and Tare pyroxenite, with the last three exhibiting different degrees of serpentinization. Among the mafic and related plutonites, olivine-gabbro and gabbro are dominant. A layered complex, comprising olivine-gabbro, gabbro, anorthositic gabbro and anortho- site. is recorded near Kodiaghat in South Andaman island.

Low grade metamorphic effects under the greenschist facies conditions and metasomatic alteration, of varying intensity culminating finally in near-total serpentinization together with high-temperature contact metamorphism are recorded.

A model involving partial melting of a CO₂-Saturated upper mantle material of 'Spinel-peridotite at about 20 K bar pressure leading to the formation of an alkalic basalt that got separated and extruded first from a probable hot-spot within the Indian Ocean Plate is suggested. This was followed by the intrusion of ultramafics along deep seated N-S trending fault zones in the eugeosyncline involving vertical tectonics. The Andaman ophiolites were not involved in any obduction or large scale lateral migration, and hence may be considered as belonging to an autochthonous-type, in contrast to many on-land allochthonous ophiolites.

Full Text