Publications
Freshwater Sources of Kerala ? Hydrometeorological Scenarios, Environmental Threats and Management Strategies
SKU:
C-165441
Kerala, the southwestern coastal state of India receives an annual average rainfall of about 3000 mm. However, providing uninterrupted freshwater supply to the community round the year is a major challenge to the water managers in the state because of several factors including high population density, increased human interventions in the river catchments, environmental effects due to climate change, etc. It has now become more and more evident that the nature and contributions of rainfall, especially its pattern, have been changing drastically over the years, aggravating the incidences of floods and landslides in the wet season and water scarcity in the summer months. Although such incidences were minimal in the pre-liberalization period (1956-1990), their recurrence and impacts are getting aggravated in the post-liberalization period - a period that witnessed severe environmental degradation due to rapid urbanization and economic development in the region. As per the records of the gauging stations, the number of no-flow/low flow days are found to be increasing even in the lowland reaches of the major rivers in the state. The adverse impact of unabated groundwater ion/pumping is on the rise in many parts of the state, as the activity is being carried out without due regard to the safe yield and natural recharge capability of the aquifer systems. The rapidly changing water scenario of the state in the pre-and post-liberalization periods needs a thorough investigation, especially in regard to the structure and functions of its near surface terrestrial environment called the Critical Zone. The Critical Zone, the zone extending from tree top to the aquifer bottom, of the state is under immense stress due to many of the aforesaid reasons. The stress in the Critical Zone will have a direct effect on the quality, quantity and availability of the freshwater resources in the surface and subsurface reservoirs, which needs to be addressed adequately for laying down strategies for the conservation and management of the freshwater sources.
Geochemical Study of the Ultramafic-Mafic Plutonic and Volcanic Suites of the Nuggihalli Schist Belt, Western Dharwar Craton
SKU:
C-63393
Petrology, mineral chemistry and whole-rock geochemistry of the intrusive, layered (>3.1Ga) as well as the extrusive volcanic suites of the Nuggihalli Schist Belt (NSB) are presented in this paper. The dunite-metaperiodotite, serpentinite and syngenetic-stratiform chromite association forms the lower part of the Tagadur ultramafic-mafic complex. The upper part of the intrusion is represented by meta-gabbro-meta-anorthosites with vanadiferous titano-magnetite bodies. The extrusive ultramafic rocks are represented by pillowed, spinifex textured peridotites and high-Mg basalts of komatiitic affinity. Petrological studies of the ultramafic rocks reveal primary cumulus textures exhibited by olivine and chromite and secondary alterations, low-grade metamorphism and deformation. The chromitites hosts a variety, of unusual accessory silicate phases such as corundum, diaspore, rutile, zircon, monazite and baryte in addition to olivine, serpentine and amphibole (anthophyllite), chlorite (clinochlore). Native phases such as gold, silver, copper, iron and tin and other Fe-Ni-Cr-Cu alloys are found associated with cumulus chromite grains in the massive chromitites. Trace and REE geochemistry of these ultramafic-mafic suite reveal significant LREE enrichment and depletion, negative Ce and Eu anomalies and flat to enriched HREE pattern suggestive of their derivation from parental komatiitic magmas by high degree of partial melting of a metasomatized depleted mantle source in a subduction zone environment. Trace element and PGE geochemistry of the chromitites indicate that they are PGE poor chromitites but enriched in Au and other base metal alloys, formed under changing oxidizing and reducing conditions resultant of alteration of the primary sulphides by desulphidation processes during the Mesoarchaean. The associated ultramafic (peridotitic) and mafic (basaltic) komatiites devoid of chromite and PGE represent primitive melts, most probably derived from high degrees of partial melting of a common depleted mantle source.
Geochemistry of Chromian Spinels from the Indo-Myanmar Ophiolite Belt of Northeastern India
SKU:
C-63395
Chromite is commonly used for deciphering the petrogenesis and geodynamic setting of ultramafic rocks. Chromespinels from the Indo-Myanmar ophiolite belt occurring in the form of podiform chromitites associated with the mantle sequence and associated volcanic rocks are studied to characterise their geochemical composition. We have measured major and trace element concentrations of the chrome-spinels. Cr/(Cr+Al) (Cr#) and Mg/(Mg+Fe2+) (Mg#) range from 66 to 70 and 66 to 69 respectively in the chromitite and 47 to 56 and 67 to 70 in volcanic spinel. The computed crystallization conditions show that the studied samples crystallized in an upper mantle environment. Using the chrome spinel compositions, parental magma for the chromitite rock is calculated as boninite, and a MORB for the volcanic sample. Minor and trace element (Ga, Ni, Zn, Co, Mn, V, Sc) concentrations in the analysed spinels are comparable to other podiform chromitites hosted in the mantle section of the ophiolite complexes. Chrome-spinel compositions of the two rocks are used to recognize the probable crystallization condition and nature of the parental magma.
Geochemistry of Gold-Hosting Granitoids from Jonnagiri Greenstone Belt, Eastern Dharwar Craton: Implications on Petrogenesis and Gold Mineralization
SKU:
C-165463
Jonnagiri gold deposit is a lone example of granitoid-hosted orogenic gold deposit in India. Gold mineralization is concentrated within silicified alteration zones along shear zones within the Pagadarayi granodiorite. Geochemical characteristics of unaltered Pagadarayi granodiorite show that, (i) these are granodiorite-tonalite suite of rocks, (ii) contain lower and variable amount of silica (63-72%), (iii) high Fe(Tot), (iv) varying alkali concentrations, (v) large variations in LILE and LREE, particularly K2O, Sr, Ba, Th, La, Ce. Further, in the Harker-type variation diagrams these granitoids show (i) decreasing agpaitic index (molecular Al2O3/Na2O + K2O) with increasing SiO2, (ii) characteristically low Sr/Sr* values, and (iii) no significant correlation of (Ce/Y)N. Hence, these rocks were possibly derived from partial melting of a mafic source with contribution from the LILE-enriched felsic crust. Harker-type variation diagrams plotted against SiO2 show decreasing trend for Fe2O3, MgO, CaO and TiO2 while Na2O increases with increasing silica content. These features are consistent with the initial stage fractional crystallization of plagioclase, pyroxene ? magnetite, followed by hornblende and biotite at a later stage. The higher Na2O, CaO, Sr and lower Cr, Ni, concentrations are similar to the continental arc magmas and therefore, these are grouped under the I-type granitoids which is in agreement with their crystallization from more oxidized melts in relation to major granitoid-hosted gold deposits elsewhere in the world.
Geochemistry of PGE-Bearing Ultramafic Rocks from Ikauna in Madawara Complex, Bundelkhand Craton, Central India
SKU:
C-63397
Based on the field, petrological and geochemical data, the ultramafic rocks near Ikauna in Madawara Igneous Complex are found to occur as E-W trending lensoidal intrusive bodies in a major shear zone predominantly consisting of granite-gneisses in Bundelkhand craton, central India. Cumulates of olivine and pyroxene are the major mineral constituents while the intergranular spaces are occupied by chromite, pyrrhotite, pentlandite and magnetite. These rocks show variation in their chemical composition with moderately low SiO2 and high Mg# (0.67-0.88), with high Ni, Cr and Co. The peridotites are Al-undepleted, while the pyroxenites are Al-depleted-Ti enriched showing chemical affinity towards Komatiitic composition although their textural characters do not reflect the same. SEM-EDS studies indicate presence of fine grained platinum group minerals (PGM) including other precious metal minerals (PMM) as disseminated grains in the interstitial spaces of olivine cumulates and pyroxenes. Ni/Cu, Cu/Pd and Pd/Ir ratios suggests late stage sulfidation prevailed over S-saturation conditions during crystallization of PGE/PMM. The concentrations of platinum group elements (PGE) and Au are variable (Ir 2.4-18.8 ng/g, Ru 34.8-79.6 ng/g, Rh 0.8 - 20 ng/g, Pt 6.8-128.2 ng/g, Pd 6.8-86.8 ng/g and Au 22.8-127.2 ng/g) and their distribution patterns represents relative enrichment of Ru, Pt, Pd compared to Ir and Rh. The trends of REE fractionation and geochemical discrimination diagrams suggest derivation of Ikauna ultramafic rocks at moderate depths from high degree of partial melting from fertile mantle.
Geological Mapping of Foundation Floor for Nuclear Building of Rajasthan Atomic Power Project, Rawatbhata, India
SKU:
C-95903
Foundation floor mapping is essential for important structures to provide permanent data set for geological interpretations. At Rawatbhata, Rajasthan, two units of 700 MW each Pressurized Heavy Water Reactor (PHWR) type Nuclear Reactors are being constructed adjacent to existing Rajasthan Atomic Power Project (RAPP) units 1 to 6. In order to evaluate the design basis foundation parameters engineering geological mapping on 1:100 scale was carried out for Nuclear Building-7 structures. 1 m x 1 m grids were prepared for mapping of the floors and walls. Based on the field observations and evidences, it was found that the floor area consists of fine to medium grained, compact quartzitic sandstones. The floor region was seen to contain certain iron stained and weathered zone. No evidence of faulting was observed on the surface of the floor areas. However, there were some isolated patches of soft, weathered/altered rock and small fractures in the rocks. Geotechnical assessment of the foundations of RB-7, RAB-7 and ECCS north and south pits was done on the basis of detailed engineering geological mapping, geological drill holes logging data, rock mass permeability values, geophysical profiling and laboratory test results. This permanent foundation record will assist in making better interpretation of post-construction foundation instrumentation data.
Geological Setup for Gold Prospects and Deposits in India
SKU:
C-165460
Gold metallogeny having distinct temporal distribution has a direct relationship with changes in the global tectonic processes. In India too gold metallogeny is episodic from Mesoarchaean to Neoproterozoic peaking in the Neoarchaean and Paleoproterozoic periods. Indian Phanerozoic also show discrete feeble mineralisation which is not of any economic interest. The most productive gold deposits are restricted to Neoarchaean granite-greenstone terranes of Dharwar Craton. Gold deposits/ prospects occur in the eastern as well as western blocks of the Craton, but most productive deposits are in the Eastern Dharwar Craton. Current gold production in the country is mainly from three Neoarchaean deposits in the Hutti-Maski greenstone belt. A small size Mesoarchaean deposit has been located in Singhbhum Craton also. The gold deposits are generally lode type or vein/reef type restricted to shear zones. Secondary shear zones or splays are the loci for mineralisation of commercial interest. Deformed and metamorphosed host rocks exhibit extensive wall rock alteration along the mineralised zones. The deposits are of epigenetic Au or Au-W types with sulphides.During Palaeo and Mesoproterozoic times, gold mineralization occurred in the Fold Belts/Supracrustal belts of the Singhbhum, Bastar and Bundelkhand cratons, namely Aravalli belt, Mahakoshal belt, Singhbhum belt, Kotri belt, Sonakhan belt, Sakoli and Raigarh belts. The mineralization is of Au-Cu and Cu-Au types with basemetals (Cu & Zn) as a dominant component as compared to the gold-only type during Archaean period. Despite the existence of a number of drilled gold and copper-gold resources spread over the three cratons mentioned above, only one mine is being operated at Lawa in Singhbhum Fold Belt which produces a small quantity of about 13kg of gold per annum (as reported in IBM?s Mineral Year Book).VMS type Cu-Au-U metallogenesis reported from Singhbhum Shear Zone, contributing gold as a by-product of copper mining. VMS type Cu-Au prospects abound in Rajasthan. Neoproterozoic (830-850 Ma) Khetri copper deposits exhibit IOCG type Cu-Au mineralisation where gold is recovered as a by-product. Porphyry style Cu-Au-Mo mineralisation is associated in Malanjkhand granite producing gold as a by-product. Mesoproterozoic Cu-Au-Zn prospects are common in the Sakoli Fold Belt. Gold is also found within the Chhotanagpur Gneissic terrain.Palaeoplacer deposits in Quartz Pebble Conglomerate (QPC) are present in Neoarchaean Iron Ore Group (IOG) of Singhbhum Craton and in Bababudan Group of Dharwar craton. Paleoplacer U-Au occurrences are found at the Neoarchaean-Paleoproterozoic boundary exposed at the basal part of Dhanjori basin in Singhbhum Fold Belt. U-Au bearing palaeoplacers, sampled so far, have shown anomalous to interesting gold valuesGold is also reported from the Tertiary laterite covering parts of the Southern Granulite Terrain and Neoarchean greenstone belts in Goa State. Present day placer gold is being recovered locally from eluvial, alluvial and colluvial zones in different parts of the country.
Geology and Geochemistry of Ultramafic-Mafic Rocks from Antarghatta Belt, Western Dharwar Craton, Karnataka: Implications for PGE Mineralization and Future Targets
SKU:
C-63399
The mafic-ultramafic (MUMF) suite of rocks of Archaean age occur as discontinuous pods north of Arsikere up to south of Vedavathi river in western Dharwar Craton, Karnataka. The mafic-ultramafic enclaves consist of meta-peridotites, tremolite-actinolite schists, serpentinites, amphibolites and metabasalts with gabbro dykes. The rocks have undergone green schist to amphibolites facies metamorphism. Our studies have shown nodular and ocellar, pillows, jack straw textures in these ultramafic-mafic suite (the talc-serpentine rocks). Talc-serpentine and tremolite-actinolite schists contain chromite and titanomagnetite concentrated at the grain boundaries. The overall major element composition of these rocks shows a high MgO (22-40 %) and total iron (8-10 %) contents and some samples also exhibit komatiitic affinity. The distribution of chromite grains in amphibole and associated matrix is also noticed. High contents of Ni and Cr (∼3000, 2800 ppm) were obtained in some of these rocks. The REE data show slightly fractionated patterns with enriched LREE (LREE/HREE ∼5.0) and negative europium anomalies. The reported Pt and Pd values are 6500 and 190 ppb. The element relationships indicate that different types of hydrothermal fluids re-distributed Ni, Cu, and (Pt+Pd) in different ways, which may have led to local concentration of Pt and Pd. The overall geochemical data and (Pt+Pd) contents imply that, at Antarghatta ultramafic belt, different genetic types of (Pt+Pd) enrichment processes were active. (1) Small amounts of immiscible sulphide melt collected relatively high amounts of PGE (relatively high (Pt+Pd) at low Ni and Cu contents) and represent a low sulphur type silicate PGE mineralization, but no major sulphide liquation event may have happened that would lead to a potential economic mineralization. (2) A hydrothermal Ni-enrichment trend (at low Cu) is reflected by the presence of millerite, which enriches the rocks beyond the Ni in the silicate minerals and the slightly higher values of Ni where elevated chromium values occur. (3) Where Cu (at low Ni contents) gets enriched by fluids, often (Pt+Pd) is enriched as well. Thus, the Antarghatta ultramafic belt warrants a multi-disciplinary approach to understand the critical parameters and processes involved in the genesis of Ni-Cu-(PGE) associated with these komatiites.
Geology and Mineral Resources of Kerala (3rd Edition – Revised) 2023
SKU:
55843
This revised and enlarged edition of the Geology of Kerala incorporates new information on coastal geomorphology, mudbanks and mineral resources in addition to a chapter on Environmental Geology with special reference to Kerala. This publication is an ideal introduction to the geology of Kerala for the benefit of all earth science students and researchers alike.
Geology of Bihar and Jharkhand
SKU:
55860
This book provides an exhaustive account of the geology of the two States that occupy a crucial position in the Indian Peninsular Shield. The book is authored by an experienced geologist with first-hand knowledge of the geology of the composite Bihar State.
The book attempts to weave the fascinating story of the geological evolution of a vital segment of the Indian Shield, which is also richly endowed with diverse mineral resources.
Geology of Himachal Pradesh
SKU:
166665
The Himalaya, stretching from the Nanga Parbat (8126 m) in the west to the Namche Barwa (7756 m) in the east, forms an arcuate mountain belt and a rampart for the Indian subcontinent along its northern margin (Fig. 1.1). It comprises the earth's largest mountain range with its varied geotectonic zones (Fig. 1.2). From time immemorial the Himalaya has been the source of poetic and spiritual inspiration. It has, ever since the advent of man, sustained several civilizations that flourished on the plain that bordered along its southern margin with its perennial rivers, lush green forests along its slopes and the fertile soil of the land that lay at its feet.