New Delhi annexure-i format for inviting proposal for fresh induction under sap- (drs)

“GEOLOGICAL EVOLUTION OF INDIAN CRUST”

To continue studies in Himalayas and Peninsular Indian Shield areas so as involve maximum number of faculty members under following sub-heads:

1. 
   Petrology, Geochemistry and Tectonics
   
2. 
   Quaternary and Environmental Geology
   
3. 
   Basin Analysis, Palaeobiology and Palaeoceanography
   

A brief overview of work done by the individual Faculty Members and their group related to the thrust areas is given below:

1. 
   Petrology, geochemistry and Tectonics
   

Highlights of the work done by Prof.Anupam Chattopadhyay:

During the period under review (2011-16), I was mostly involved in structural modeling of continental shear/fault zones through fieldwork and experimental modeling. The work done on Gavilgarh-Tan shear zone in central India has revealed that this terrain-bounding shear zone underwent transpressional deformation in Meso-Neoproterozoic, which partitioned into simple shear and pure shear components (Chattopadhyay and Khasdeo 2011). Two types of pseudotachylyte veins (Pt-M and Pt-C) associated with sheared granitoids of GTSZ have been dated in collaboration with the Open University, U.K, and show two fault reactivation events – in Neoproterozoic and Ordovician. These pseudotachylyte vein systems were mapped in detail at outcrop scale and the structural data was used to interpret the seismic source parameters e.g. seismic moment, maximum shear stress at rupture etc. On the basis of these data an estimated paleo-earthquake magnitude was suggested (Chattopadhyay et al. 2014a). The control of polyphase deformation on the gold mineralization in Bhulia-Jagpua belt in Rajasthan, has been worked out (Deol et al. 2014). The Experimental Structural Geology Laboratory has been further expanded, with one post-doc scientist and a few research scholars regularly working with this facility. Experimental investigations on rift faulting, on strain patterns in a transpressional system and on the evolution of thrusts in a contractional orogenic belt have been carried out here. Three major international papers have been published by my research group from the experimental modeling studies (Chattopadhyay and Chakra 2013, Ghosh et al. 2014 and Chattopadhyay et al. 2014b). Monazite dating of deformed and undeformed granites intrusive into the metasedimentary Sausar Group in central India has helped constrain the timing of a major collisional orogeny in Neoproterozoic (Chattopadhyay et al. 2015). In total, I have authored/co-authored eleven peer-reviewed research papers in national and international journals and seven abstracts in conference proceedings during this period. Studies on active faulting in Gavilgarh Fault Zone, central India has just been concluded, on which one Ph.D. student has submitted thesis. The results have been reported in major international/national seminars and one full paper is under publication process.

Highlights of the work done by Dr.Ashima Saikia:

a. Significance of viscous folding in magma mixing.

Mixing between mafic and felsic magmas in shallow level magma chambers is considered as a primary factor triggering volcanic eruptions. Recent developments in microfluidics have enabled us to better understand the complex processes associated with magma mixing from the hybrid rocks of the Ghansura Rhyolite Dome (GRD) of Proterozoic Chotanagpur Granite Gneiss Complex (CGGC), Eastern India.

The hybrid rocks from GRD have formed due to the mixing of a phenocryst-rich basaltic magma and host rhyolite magma. The hybrid products have preserved amphibole-rich microzones (ARM) in contact with fine grained felsic zones. The ARM dominantly consist of amphibole surrounded by other mineral phases like biotite and plagioclase. Amphibole crystals occurring in the core of ARM are actinolite, while those occurring in the rim are of hornblende composition. Veins of amphibole have been observed moving out from the ARM into the felsic zones. An interesting feature about the amphibole veins is that as they venture into the felsic zones amphibole converts to biotite, and also the veins undergo viscous folding. Amphibole display pargasite substitution from the core of the ARM to its margin and further extending into the veins where the mineral is completely replaced by biotite.

From mineral chemical, textural and thermometric analyses we infer that when mafic magma, containing phenocrysts of augite, came in contact with felsic magma the two remained as separate entities at first due to pronounced thermal and rheological contrasts. The first interaction that took place between the two phases is diffusion of heat from the hotter mafic magma to the colder felsic magma followed by diffusion of elemental components between them. The diffusion of cations from the felsic to the mafic system like H+, Al3+ and other cations reacted with the clinopyroxene phenocrysts in the mafic magma to form amphibole crystals. The formation of amphibole crystals in the mafic system greatly increased the viscosity of the system allowing the amphibole crystals to venture into the adjacent felsic magma as veins. As these veins traversed in the felsic medium, they were acted upon by compressive stress and underwent viscous folding to enhance mixing between the two magmas.

b.Sphene-centered ocellar texture as a petrological tool to unveil the mechanism facilitating magma mixing.

The sphene-centered ocellar texture is a unique magma mixing feature characterized by leucocratic ocelli of sphene enclosed in a biotite/hornblende-rich matrix (Hibbard, 1991). The ocelli usually consist of plagioclase, K-feldspar and quartz with sphene crystals at its centre. Although geochemical and isotopic data provide concrete evidence for the interaction between two compositionally distinct magmas, the exact processes by which mixing takes place is yet uncertain. So, textural analysis can be used to decipher the behaviour of two disparate magmas during mixing.

Presented work is being carried out on the sphene ocelli, occurring in hybrid rocks of the Nimchak Granite Pluton (NGP), to understand its formation while two compositionally different magmas come in contact and try to equi- librate. The NGPis ca. 1 kmin extent which has been extensively intruded by number of mafic dykes exhibiting well preserved magma mixing and mingling structures and textures in the Bathani Volcano-Sedimentary Sequence (BVSS) located on the northern fringe of the Proterozoic Chotanagpur Granite Gneiss Complex (CGGC) of eastern Indian Shield.

From petrographic and mineral chemical studies we infer that when basaltic magma intruded the crystallizing granite magma chamber, initially the two compositionally different magmas existed as separate entities. The first interaction that took place between the two phases is diffusion of heat from the relatively hotter mafic magma to the colder felsic one followed by diffusion of elemental components like K and incompatible elements from the felsic to the mafic domain. Once thermal equilibrium was attained between the mafic and felsic melts, the rheological contrasts between the two phases were greatly reduced. This allowed the felsic magma to back-vein into the mafic magma. The influx of back-veined felsic melt into the mafic system disrupted the equilibrium conditions in the mafic domain wherein minerals like amphibole, plagioclase and biotite were crystallizing. This led to the incongruent melting of amphibole and biotite to form liquids of sphene composition. Meanwhile, plagioclase continued to grow in the mafic-turned-hybrid system with a different composition after the advent of felsic melt as indicated by compositional zoning in plagioclase crystals. The newly produced sphene-liquid, owing to its higher affinity for felsic phase than mafic, got incorporated into the back-veining felsic melt forming a distinct liquid of its own. The felsic melt also incorporated crystallizing plagioclase grains in it from the mafic matrix. The mixture of felsic melt, sphene-liquid and plagioclase crystals flowed through the biotite, amphibole and plagioclase dominated matrix towards the low pressure zones to occupy the spherical void spaces left behind by escaping of gases/volatiles forming the sphene ocelli.

Highlights of the work done by Prof.J.P.Shrivastava
Stratigraphy, age and duration of Deccan volcanism:

Combined field, petrographic, and major element studies resolves that this lobe comprises 37 lava flows and 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. In addition, our data reveal several flows similar to those of the Mahabaleshwar Formation. Based on the isotopic data the superposition of Mahabaleshwar-like flows over flows withAmbenali- 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.

New age determinations, derived from 40Ar–39Ar incremental heating experiments, for basaltic lava flows from the Mandla lobe, located on the eastern margin of the main Deccan volcanic province, some~1000km from theWestern Ghats escarpment. The most reliable estimates of crystallization ages come from5 plateau ages from plagioclase separates, from a stratigraphically controlled succession of 37 lava flows. We detect no statistically significant age difference from bottom to top (range 63–65 Ma) and calculate a weighted mean age for the section at 64.21 ± 0.33 Ma. These lava flows are significantly younger than the majority of the main Deccan volcanic activity documented from the Western Ghats (67–65 Ma). The new ages are consistent, however, with geochemical correlation of the Mandla lobe lavas with the uppermost succession (Poladpur–Ambenali–Mahabaleshwar Formations) of the SW Deccan, and indicate that this post K/PB youngest phase of flood basalt activity erupted over much of the province.
Highlights of the work done by Prof. N.C.Pant

a. In Central India not only we have been able to identify a UHT metamorphism at ~ 1.6Ga but have also demonstrated that this caused changes differently in accessory minerals such as monazite and zircon (Geological Journal, 2010).

b. From an Archean Craton (Bundelkhand), we have been able to demonstrate conditions of mineralogical transformation which would have been only possible at depths greater than 70 kms or high pressure conditions. The significance of this HP event is that we have dated monazite which overprint this fabric and reflect two growth ages- 2.78 and 2.45 Ga. Thus, this represents first report of processes akin to present day subduction from any Indian Archean domain (Contribution to Mineralogy and Petrology, 2011). Further work (unpublished) from this cratonic block has shown ~2.5Ga continent-continent collision signatures.

c.From Dharwar craton also we have reported for the first time a granulite grade metamorphism in EDC at ~2.62 Ga (Geological Journal, 2011).

d.We have dated 3 billion year old monazites in metapelitic granulites. The sample is from the interface of a Proterozoic orogenic belt (Eastern Ghats Mobile Belt or EGMB) and an Archean craton (Singhbhum craton). The former is considered a granulite terrain of ~ 1.1 Ga age while the latter is a granite-greenstone terrain of Archean age. Using petrological and geochronological evidence we have demonstrated these to be lower crustal component of an Arcehan craton. (Geological Journal, 2012)

e.I have attempted to carry out the bulk chemical characterization of micro domains in thin sections to understand the geological processes. Electron beams of 50, 20 and 1 micron meters were calibrated as well as employed to analyze in-situ micro domains (scales of tens of microns). This allows computation of effective bulk compositions and can be used in understanding features such as coronas. We employed this technique in pseudotachylites to demonstrate disequilibrium melting and also to show formation of two different melts in close proximity (Contribution to Mineralogy and Petrology, 2011).

f.In a combined sedimentological-petrological study we have demonstrated that two synchronous Proterozoic basins (Gwalior and Bijawar) sourcing from same provenance produce dissimilar sequences indicating a strong basin level control on deposition (Geol. Soc. London Book Chapter, 2015).

g.Suturing of east and west Gondwana is a significant geological event and is well marked in African continent by the East African Orogen (EAO). However, its southward continuation is still not well understood as its projection in east Antarctic shield divides this craton into two distinct geological entities. Our recent work using petrological and geochronological data shows landward extension of EAO in east Antarctica in the Wohlthat Mountains in central Dronning Maud Land (Precambrian Research, 2013).

1. 
   Quaternary and Environmental Geology
   

Highlights of the work done by Prof.C.S.Dubey
Work on Arsenic in Delhi, Chattisgarh, Singrauli Industrial Area and West Bengal, its contamination and treatment has culminated in filling an Intellectual Property India Patent, Government of India and thereby published on their website on 08/01/2016 under the title “Arsenic Treatment Technology in Contaminated Water with Scolecite” (File No. 4145/DEL/2015). Research interest in the geological study of Himalayas, spanning from western to eastern, and its dynamics in the face of changing environment and change in climate patterns led to publication of 15 papers in renowned research journals and periodicals, in the last 5 years.Have also considerable research experience on Earthquake liquefaction and vulnerability mapping based on geo-technical studies of Delhi region. This has resulted in producing a thesis for Ph.D in 2015.
Highlights of the work done by Prof. J.P.Shrivastava
Nuclear Waste Management:

Nuclear waste loaded and natural (analogue) glasses were studied to understand neo-formed mineral species, formed in equilibrium with the physico-chemical conditions existing in the geological repository. To predict alteration-phases, dissolution equations for average vitrification system (AVS), barium borosilicate (BBS) and obsidian glasses were calculated, considering glass composition, pressure, temperature and pH conditions. Progress of reaction plotted against saturation index indicates saturation with solid phases – chamosite, chalcedony and Ca-beidellite in obsidian; greenalite and fayalite in AVS; and coffinite in BBS glass. Activities and molalities of aqueous species together with the number of moles of each mineral species produced and degenerated during the progress of the reaction (as a function of time) are discussed here.

Deccan basaltic glass is associated with the differentiation centre of the vast basaltic magmas erupted in a short time span. Its suitability as a radioactive waste containment chiefly depends on alteration behaviour; however, detailed work is needed on this glass. Therefore, the basaltic glass was treated under hydrothermal-like conditions and then studied to understand its alteration. Moreover, comparison of these results with the naturally altered glass is also documented in this paper. Solutions as well as residue obtained after glass alteration experiments were analysed. Treated glass specimens show partial to complete release of all the ions during alteration; however, abundant release of Si and Na ions is noticed in case of almost all the specimens and the ionic release is of the order of Na > Si > K > Ca > Al = Mg > Fe > Mn > Ti. Scanning electron images of the altered residue show morphologies of smectite, montmorillonite and illite inside as well as outside of the secondary layers, and represent paragenesis of alteration minerals. It has been noticed that the octahedral cation occupancies of smectite are consistent with the dioctahedral smectite. The secondary layer composition indicates retention for Si, Al, and Mg ions, indicating their fixation in the alteration products, but remarkably high retention of Ti, Mn and Fe ions suggests release of very small amount of these elements into the solution. By evolution of the secondary layer and retention of less soluble ions, the obstructive effect of the secondary layer increases and the initial constant release rate begins slowly to diminish with the proceeding time. It has been found that devitrification of glass along the cracks, formation of spherulite-like structures and formation of yellowish brown palagonite, chlorite, calcite, zeolite and finally white coloured clays yielded after experiments that largely correspond to altered obsidian that existed in the natural environment since inception ~66 Ma ago.

Obsidian glass alteration experiments under near hydrothermal conditions were performed to study mechanism and conditions of formation of altered minerals. X-ray diffraction patterns and cell dimensions of the specimens treated at 150, 200 and 3000C (pH = 8.03) revealed appearance of three main minerals - illite (9.5-10 Å), chlorite (7.04 Å) and halloysite (10.25Å). Further increase in the pH favours matrix dissolution with the formation of secondary altered layers. SEM-EDS study show that the alteration causes smoothing of the grain surfaces. These surfaces exhibits etch pits and series of depressions, formed by the process of dissolution. SEM - Back Scattered Electron images of obsidian specimens show thin laminae of smectite, with foliated bulky rims and cellular honeycomb texture, formed by precipitation from the solution as well as by direct transformation of glass during alteration. This mechanism is resulting from the alteration of alkalis by ionic inter-diffusion with H3O+ and H+ and inward diffusion of H2O, leading to free diffusion of silica into solution and then to a local rearrangement of the glass framework. Thus, a direct transformation of glass into clay minerals is the major reaction mechanism as evidenced by the mechanism of glass dissolution and subsequent mineral precipitation. conditions. Neo-formed minerals were compared with naturally altered minerals to assess its performance.

Altered specimens show partial to complete leaching of glass, where ionic release is of the order of Na>Si>K>Ca>Al = Mg>Mn>Ti. SEM-BSE images show distinct microstructures and mineral paragenesis of smectite, chlorite, nontronite, and illite inside and outside of the secondary layers - show retention of Si, Al, and Mg ions, fixation in the alteration products after their meager release to the solution. Secondary minerals-palagonite, chlorite, calcite, zeolite and white colored clays - formed after experiments largely correspond to altered obsidian in the natural environment since ~ 65 Ma.

CO₂ Sequestration:

Rock specimens from Deccan flood basalts have been reacted in the laboratory under high pCO2 (5 and 10 bars), total pressure (vessel pressure between 10 and 20 bars), and temperature (100 and 200°C) conditions for 50, 60, 70, and 80 hours. XRD and SEM-EDS analyses show that calcite, aragonite, siderite and magnesite, and clays are derived from the alteration of Deccan basalts under water-saturated, hydrothermal-like conditions. Alteration reactions were accompanied by significant variation in the pH of the reacting aqueous solution, dependent upon time, pCO2, and temperature variables of the experiment. Neo-formed secondary products also include significant amounts of smectite, chlorite, and smectite/chlorite mixed layer clays.

Highlights of the work done by Prof.N.C.Pant

a.In inaccessible areas (e.g. sub-ice areas in east Antarctica) ocean sediments reflect the geology of the provenance as well as the processes that leads to sediment formation and deposition. Essentially using mineralogic approach, we have been able to infer the nature of geology of eastern Wilkes Land in east Antarctica and also been able to comment on the processes (including climate variability’s) leading to the deposition. (Geological Society of London Special Publication, 2013; Int. Jour. Earth Sciences, 2014). One Ph.D. from this work has already been awarded. We have also inferred a major bollide impact in Wilkes Land basin based on meteorite fragments recovered from ocean sediments (Under review).

b.Taking this approach a step further for the study of Quaternary sediments in the Himalayas, I have recently been awarded a project worth ~98 lakhs by Ministry of Earth Sciences.

c.North Delhi Fold Belt (NDFB) represents a significant Proterozoic ororgenic belt in northwest Indian shield. It also contains significant sulphide mineralization. We were first to date the metamorphism in this belt in 2008. In a still continuing work we have now constrained the metamorphism and mineralization both of which are of more than one generation and we have identified a Neoproterozoic contact metamorphic effect which is mainly responsible for the relatively enriched mineralization (Episodes, 2013; Geol. Surv. Ind. Sp. Publication, 2015). In course of this work we have used mineralogical approach to document sub-greenschist facies metamorphism in the Raialo Group and proposed that these rocks are not part of the Delhi Supergroup (Jour. Geol. Soc. Ind., 2015). One Ph.D. from this work is submitted.

d.In Himalayas, one of the youngest orogen, we are looking at eclogites mainly from the point of view of deducing the processes and geochemical pathways involved during the transit of crustal rocks to depths of over 150 kilometers and their subsequent exhumation. We have modified the P-T-t path for these rocks using mainly the amphibole compositions (Int. Jour. Earth Sciences, 2014). In eastern Himalayas, a dual P-T path was worked out in the LHS sequence located in the footwall part of the MCT in western Arunachal Himalaya (Lithos, 2014).

Highlights of the work done by Prof. Pankaj Srivastava

Clay minerals record from Late Quaternary drill cores of the Ganga Plains and their implications for provenance and climate change in the Himalayan foreland: This study documents the coupling of provenance and climate change over the last 100 ka manifested in clay mineralogy of sediments from two cores (~50 m deep) in the Ganga–Yamuna interfluve in the Himalayan Foreland Basin, India. Depth distribution of the texture and clay mineral assemblage in the two cores show notable differences on account of pedogenesis and sediment supply over the last 100 ka. Core sediments from the northern part of the interfluve (IITK core) are micaceous and dominated by hydroxyl-interlayered dioctahedral low-charge smectitea (LCS) in fine clay fraction but by trioctahedral high-charge smectite (HCS) in silt and coarse clay fractions. In contrast, core sediments from the southern part of the interfluve (Bhognipur core) are poor in mica and both LCS and HCS are recorded in the upper 28 m of the core while the lower part is dominantly LCS in all size fractions. The paleosols in the two cores formed in the sub-humid to semi-arid climatic conditions resulting in clay minerals such as 1.0–1.4 nm minerals, vermiculite, HCS and also preserved the LCS, hydroxyl-interlayered vermiculite (HIV) and pseudo-chlorite (PCh), and kaolin that formed earlier in a humid climate. The preservation of LCS, HIV, kaolin and PCh is a clear indicator of climate shift from humid to semi-arid in the Ganga Plains as their formation does not represent contemporary pedogenesis in the alkaline chemical environment induced by the semi-arid climate. As the simultaneous formation of both HCS and LCS is not possible at the expense of mica, the abundance of LCS sediments from both the cores suggests the role of plagioclase weathering in the formation of LCS. In the upper 28 m of the Bhognipur core, the presence of both HCS and LCS in the fine clays suggests a change in sediment provenance from cratonic to a dominantly Himalayan source during Holocene. The climatic records inferred from the typical clay mineral assemblages of the two interfluve cores are consistent with the Marine Isotope Stages (MIS). The humid interglacial stages (MIS 5, 3, and 1) are marked by dominance of HIV, PCh, and LCS whereas the dominance of HCS together with pedogenic carbonate (PC) is noted in semi-arid stages (MIS 4 and 2).