Geochemistry

Staff List – MLP-6201-28(CM) Geochemistry Division

S.No

Name

Designation

1

Dr.(Mrs.) C. Manikyamba Group Head & Senior Principal Scientist

2

Dr. M. Rammohan

Principal Scientist

3

Dr. D. Srinivasa Sarma

Principal Scientist

4

Dr.M.Satyanarayanan

Senior Scientist

5

Dr.A.Kehsav Krishna

Senior Scientist

6

Dr.Tarun Khanna

Scientist

7

Dr. B. Dasaram

Senior Technical Officer

8

Dr. K.S.V. Subramanyam

Senior Technical Officer

9

Mr. Vamsi Krishna. G

Senior Technical Officer

10

Dr. S. S. Sawant

Technical Assistant

11

Dr. D. Purushottam

Technical Assistant

12

Mr. D. Linga

Technical Assistant

13

Mr. ParashaRamulu V

Technical Assistant

14

Mr. Abdul Samad

Lab Assistant

15

Mr. D. Raghunandan

Lab Assistant

16

Mr. J.R. Reddy

Lab Assistant



On-going Projects of Geochemistry Group

  • Integrated geological, petrological, geochemical and paleomagnetic studies and metallogeny in the selected geodynamic provinces of India (MLP 6201-28 (CM)
  • India Deep Earth Exploration Programme (INDEX) W.P. 2.2Precambrian crustal growth and evolution of central - eastern Indian cratons
  • Geochemistry of Andaman-Nicobar ophiolites and their tectonic significance (GENIAS Project: W.P No. 3.6) (DSS)
  • Ni-Cu-PGE mineralization in Central Indian Cratons, SHORE-PSC0205-WP4.2 (MSN)
  • Geological, geochemical and PGE Investigations of Precambrian mafic magmatism of Singhbhum Craton, Eastern India: implications on Mantle processes (CM)
  • Biogeochemical and atmospheric changes during Archean and Proterozoic: Geochemical and isotopic studies from greenstone belts of Dharwar craton and Cuddapah basin (CM)
  • Petrogenesis of mafic and ultramafic magmatism at Madawara Igneous Complex, Bundelkhand Craton: Implications for Platinum Group Elements (PGE) Metallogeny (MSN)
  • Integrated Geological, Geochemical, Isotopic and Geophysical studies over the Paleoproterozoic Mahakoshal Fold Belt, Central India: Implications on Crustal Evolution and Metallogeny (MSN)
  • Geology, Geochemistry and Isotopic Studies in the Veligallu granite-greenstone terrane, eastern Dharwar craton, India: Implications for Archean Mantle Evolution, Metallogenesis and Crustal Growth Processes (TCK)
  • Analytical Facilities Available

    WD -XRF Philips MagiX PRO PW 2440

    X-ray fluorescence spectrometeris a widely used method for the bulk chemical analysis of rocks, soils and sediments. The primary advantage of the method is that it is non-destructive and many elements can be analyzed in rapid succession without different sample preparation for each element. Elemental composition for inorganic constituents can be determined using an X-ray fluorescence spectrometer.

    X-ray fluorescence (XRF) spectrometry can be effectively used to measure major and trace elements (Si, Al, Na, Mg, Ca, Fe, P, S, As, Ba, Cd, Se, Co, Cu, Mo, Ni, Pb, Rb, Sr, U, Th, V, Zn and Zr) in rocks, soils and sediments from few ppm to % level.

    Dissolving of rock/mineral/ore samples for preparing solutions is critical and important for trace, Rare earth elements (REE) & PGE (platinum Group elements) analysis by HR-ICP-MS. The following facilities are available in Wet Chemical Lab to digest the rock sample powders effectively

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    High Resolution Inductively Coupled Plasma Mass Spectroscopy (HR-ICP-MS) Laboratory of Geochemistry Division

    PB280001.JPGPrecise estimation of Trace, REE as well as Platinum Group Elements up to pg/g levels in geological materials at three different resolutions 300/4000/10000.

    The instrument is attached with a laser ablation (LA) system, a desolating nebulizer system and an auto-sampler for precise determination of trace elements and isotopic ratios in rock samples, for conducting geochemical/geochronological applications. It is the third such system available in the country, a first high resolution device to have coupled with laser ablation system and fully funded by CSIR at NGRI.

    Scanning Electron Microscope – with EDS

    A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition. The electron beam is generally scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image. SEM can achieve resolution better than 1 nanometre. Specimens can be observed in high vacuum, in low vacuum conditions.

    Sulfur Analyser Lab

    sufur anaSulfur Analyzer Lab is used for determination of Sulfur concentration in rocks, minerals, ores and other geological materials. This system can determine Sulphur as low as 1 ppm in rock samples

    Significant research activities

    Studies in Singhbhum Craton:

    Distinct signatures of Archean-Proterozoic geodynamic process are preserved in discrete crustal provinces that constitute the Singhbhum Craton. The ~3.4 Ga IOG lavas from the Jamda Iron Ore basin and ~ 2.25 Ga Malangtoli lavas exhibit calc-alkaline and tholeiitic to calc-alkaline compositional characters respectively. These two types of basalts reflect different emplacement histories, and characterized by a porphyritic texture with an overall comparable mineralogical composition overprinted by greenschist to lower amphibolite facies metamorphism. Mantle normalized multi-element patterns of IOG and low MgO Malangtoli lavas exhibit negative anomalies at Nb, Zr, Hf and Ti that are attributed to subduction processes in an intraoceanic arc setting.  The parent magma for the IOG lavas were derived by <1-1% partial melting within garnet lherzolite domain whereas the genesis of Malangtoli basalts involved 3-<10% partial melting from spinel to garnet lherzolite stability field. PGE abundance in the IOG lavas was controlled by sulphide fractionation whereas that in the Malangtoli samples is ascribed to fractionation of chromite and sulphide. The sulphur saturated, PGE depleted character of the IOG lavas attest to low degrees of partial melting and crustal contamination of magma.  Variable degrees of partial melting and crustal contamination account for the sulphur saturated to undersaturated nature of the low and high MgO Malangtoli basalts having a wide variation in their PGE content. The IOG basalts show an affinity towards intraoceanic arc setting whereas the genesis of low- and high MgO basalts of Malangtoli are associated with arc-related subduction component and enriched MORB-type asthenospheric mantle. These are generated at transitional arc to rift-controlled back arc tectonic regime in a basinal environment that developed proximal to an active convergent margin setting.

    Singhbhum Craton

    Studies in Bastar Craton:

    The regional tectonic framework and stratigraphic positioning of the volcano-sedimentary sequence of Proterozoic DongargarhSupergroup of Bastar Craton, Central India suggests a protracted period of episodic magmatic activity with interludes of marine transgression/regression events that collectively occupy a considerable duration of the Proterozoic time span. Till date there is no significant comprehensive database that has been collectively reported from all the five volcanic formations of the DongargarhSupergroup, which infused conflicts in the interpretation of its geodynamic setting. Our ongoing comprehensive geochemical studies in the Dongargarh terrane potentially suggest the possibility that the basalts and andesites, which are intercalated with the shelf facies sedimentary horizons, may likely represent the evolution of the Dongargarh synclines in a marginal sea basin.  The basalts are consistent with an intraoceanic arc origin whilst the andesites were erupted proximal to the continental margin. The volcanic rocks exhibit geochemical footprint from ocean to continent transition.

    Granites of Kotri belt:
    The granites of Kotri belt are porphyritic, predominantly consisting of quartz, K-feldspar and biotite (Fig. 1). These are having high silica and low contents of CaO, MgO, TiO2, and P2O5. Total alkali content ranges from 9.3 wt% to 11 wt. % while Al2O3 ranges from 11 to 13 wt. %. K2O varies between 6.25 to 7.38 wt.% and is higher than Na2O.   K2O/ Na2O ratio indicate that they are potash-rich alkaline granites. The granites are characterized by high concentrations of Ba, Rb, U and Th (Fig. 2A) while high field strength elements like Zr and Y show moderate abundances. The granites are enriched in LREE and show prominent negative Eu anomaly indicating a significant role of plagioclase fractionation from the parent magma.  Trace element patterns depict negative Nb, Ta and Sr anomalies (Fig. 2B).  Petrographic studies and geochemical data record the presence of biotite and normative agerine and diopside which illustrate their I-type nature. A within-plate, rift relatedanorogenic tectonic setting is envisaged for the generation of these granites (Fig.3).

    Geochemistry
    The felsic volcanic rocks of Kotri belt are porphyritic, predominantly consisting of quartz, plagioclase phenocrysts that are set in a fine grained matrix (Fig. 4).  These are characterized by higher SiO2, moderate Al2O3, low to moderate Fe2O3and low TiO2. Higher SiO2 along with relatively lower MgO and CaO contents attest to the felsic nature of these volcanic rocks.  The studied samples have K2O content dominant over the Na2O reflecting a mild potassic character. These rocks are rhyolites and show distinct alkaline to peralkaline compositions. Incompatible trace element abundances of these rocks suggest an overall enrichment in large ion lithophile elements (LILE) and relative depletion in high field strength elements (HFSE). Among transitional elements, the rhyolites characteristically have overall depleted Ni and Cr concentrations. Chondrite normalized REE patterns (Fig. 5A) exhibit pronounced LREE enrichment with strong LREE/HREE fractionation and prominent negative Eu anomalies. Primitive mantle normalized incompatible trace element patterns (Fig.5B) of these rhyolites show distinct negative anomalies at Nb, Sr, P and Ti and positive anomalies at Th, U.  The overall geochemical characteristics of the felsic volcanic rocks indicate an active continental margin setting (Fig. 6). We have identified auriferous quartz reefs hosted in felsic volcanic rocks along the Kotri lineament at several places.  We have also recorded a sulphide rich metapyroxenitic dyke hosting Ni-Cu-PGE mineralization occurring in association with a differentiated gabbro sequence at Bhagwantola at Kotri region. 

    Troctolites of ChhattisgarhBasin:

      • The Proterozoic ultramafic intrusions in Lailanga region are represented by coarse grained olivine-trocolite and metapyroxenite which are associated with abundant mafic gabbros and K-rick granites.
      • SEM-EDS studies on troctolites show phases of native gold, Cr-Ni magnetite, galena, Cr-spinels, baryte, pyrite and pyrrhotite occurring as inclusions in host silicates such as olivine and cpx (Fig.8).
      • The metapyroxenites show exotic mineral phases of native gold, Cr-spinels, pyrrhotite, galena, zircon and rare halite crystals exhibiting radiating as well as flower type crystals (Fig.9).
      • Presence of above phases in these ultramafic intrusions indicates the role played by magmatic and hydrothermal fluids in their evolution.

      Studies on Bundelkhand granitoids

      Different phases of granitoids of Bundelkhand Craton were systematically identified based on the field and petrographic characteristics, and obtained their geochemical systematics. U-Pb zircon geochronological and Lu-Hf isotopic systematics for selective samples demonstrates the role of crustal recycling processes and the involvement of older crust (~3000 Ma) in the generation of Bundelkhand granitoids.

      Plot of Crystalisation age against ɛHft for three granitoids of Bundelkhand Craton. All the samples show –veɛHft values suggestive of their derivation from recycled crust.

      Batul Belt
      The mafic-ultramafic intrusive magmatic complexes and associated Ni-Cu-PGE mineralization in the Proterozoic Betul-Chhindwara belt, Central India, indicated visible sulfide mineralization (Ni-Cu sulfides, pyrite, chalcopyrite and pyrrhotite) at Dhappa-Temra, Bacha-Bareta, Sarni-Ghatakeda and Kherli-Nagdev sections within the Padhar Complex. Geophysical investigations were carried out wherein ground geophysical electrical resistivity and HERT surveys identified sulfide horizons.


      Madawara Igneous Complex (MIC)
      The late Archean-early Proterozoic ultramafic-mafic intrusions and the host litho units (granite gneisses) were studied for their mineralogical, petrological, geochemical and geophysical including structural data components through an integrated approach to delineate ultramafic bodies within the host environment and PGE enriched zone in MIC, Dunite, harzburgite, lherzolite and websterite are commonly occurring ultramafic rocks which show high MgO, Ni, Cr, PGE and extremely low in Al2O3, CaO, K2O, TiO2 and V contents and display komatiitic affinity. Our studies indicate that PGE are enriched in source magma at moderate to deeper depths at low sulphur fugacity by high degree of partial melting of mantle.

      Mahakoshal Fold Belt (MFB)
      Studies on Mahakoshal Volcanics reveal that the western region metabasalts display geochemical characteristics of Arc –type (island-arc basalts (IAB) and eastern region exhibit dominantly OceanIsland Basalt (OIB)/OIT geochemical characteristics of Plume type. Studies on U-Pb dating of MKB lithologies reveal western part (Narsingapur areas) show unusual younger 1.0 Ga U-Pb ages suggests their Neoproterozoic evolution and southeastern part of the MKB at Singrauli region show older ages in the range of 1800 Ma. Studies on stable isotopic compositions of C and O reveal new stromatolite horizon in the metacarbonate bands north of Kareli in the western part of MFB. The metacarbonate rocks of western region (Jabalpur-Sleemnabad areas) show a lower C & O isotope values which suggests their correlation with Meso to Neoproterozoic marine carbonates.


      Studies in the Dharwar Craton:

      The felsic volcanic rocks of Shimoga and Chitradurga greenstone belts of western Dharwar craton are potassic rhyolites consisting of alkali feldspar, quartz as essential minerals and chlorite, biotite and opaques as accessory phases.  These rocks exhibit enrichment in LILE and depletion in HFSE and show prominent negative Nb-Ta, Zr-Hf and Ti anomalies with moderate fractionation in LREE and flat HREE.  The consistent negative Eu anomalies in these rocks suggest plagioclase fractionation in their source.  Field and petrographic observation along with geochemical signatures suggest their generation in an active continental margin setting. According to the existing models, mantle plume magmatism, subduction zone processes and plume arc accretion have been proposed as dominant processes contributing to the crustal growth of various cratons. Our studies indicate that the rhyolites of EDC are intraoceanic island arc type while the WDC rhyolites show an affinity towards an active continental margin setting.

      Sediment infill volcanic breccia:

      Field and petrological studies in the Shimoga belt let to identification of significant rock type called sediment-infill volcanic breccias.  This rock consists of clasts of felsic volcanic rock that were embedded within carbonate sediment.  These are typically monomictic and are made up of a class-supported framework.  They occur in the upper part of volcanic sequence and were found by infiltration of fine carbonate sediments into the clasts produced due to explosive volcanic activity.  The undisturbed carbonate matrix suggest that the sedimentary component infilled the void spaces of a pre-existing clastic framework.  These are associated with Volcanic Hosted Massive Sulphide Deposits (VHMS) and reflect on pyroclastic volcanism and sulphide mineralization at a shallow marine shelf. 

      Manganiferous deposits of Chitradurga, Shimoga and Sandur greenstone belts in western Dharwar Craton

      mineralization in Chitradurga is associated with carbonates and ferrugeneous and manganeferous shales where there is a division between iron and Mn formations observed at many places indicative of oxidizing conditions.  Mn formations took place as pockets due to supergene enrichment processes.  High grade Mn is reported from Shimogafollowed by Sandur.  The Mn content is relatively less in Chitradurga.

      The geological, petrological and geochemical studies suggest a transition in the geodynamic conditions marked by ocean-ocean subduction, migration of oceanic arc towards a continent followed by ocean-continent collision which altogether contributed towards the crustal evolution of Dharwar craton.

      Veligallu Greenstone Belt:

      The Veligallu basalts are tholeiitic in nature and on the basis ofgeochemistry are classified as back-arc basalts.  Geochemical modeling suggests that the Veligallu basalts weregenerated by low degree partial melting of a depleted MORBsource.The Veligallu high Mg-andesites represent the products ofpartial melting of a slab-melt hybridized mantle wedgeperidotite.The geochemical characteristics of the adakitic rocks are consistent with a slab-melt origin analogous to the Cenozoic high-silicaadakites.A complex interplay of arc magmatic processes generatedthe basalts, high Mg-andesites and adakites in the Veligallubelt. These complex arc magmatic processes culminatedinto the evolution of the Neoarchean Veligallu greenstone terrane in a rifted back-arc environment. This event appears to have significantly contributed to the peak of crustal growth activity inthis part of the Dharwar craton at 2.7 Ga

      Studies on Andaman ophiolites

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