A Hybrid Neuro-Fuzzy Model for Mineral Potential Mapping

A GIS-based hybrid neuro-fuzzy approach to mineral potential mapping implements a Takagi–Sugeno type fuzzy inference system in a four-layered feed-forward adaptive neural network. In this approach, each unique combination of predictor patterns is considered a feature vector whose components are derived by knowledge-based ordinal encoding of the constituent predictor patterns. A subset of feature vectors with a known output target vector (i.e., unique conditions known to be associated with either a mineralized or a barren location), extracted from a set of all feature vectors, is used for the training of an adaptive neuro-fuzzy inference system. Training involves iterative adjustment of parameters of the adaptive neuro-fuzzy inference system using a hybrid learning procedure for mapping each training vector to its output target vector with minimum sum of squared error. The trained adaptive neuro-fuzzy inference system is used to process all feature vectors. The output for each feature vector is a value that indicates the extent to which a feature vector belongs to the mineralized class or the barren class. These values are used to generate a favorability map. The procedure is applied to regional-scale base metal potential mapping in a study area located in the Aravalli metallogenic province (western India). The adaptive neuro-fuzzy inference system demarcates high favorability zones occupying 9.75% of the study area and identifies 96% of the known base metal deposits. This result is significant both in terms of reduction in search area and the percentage of deposits identified.     

INITIATION OF SHELL MOTION ON SAND BEDS: AN EXPERIMENTAL STUDY

1 INTRODUCTION Bivalve shells are found in biologically productive coastal regions encompassing the surf zone, tidal entrance and estuarine waters near the entrances. An example of a beach composed exclusively of shells (about 97% of the surficial sedimentary material) is the beach at John o'Groats in Scotland (Raymond and Hutchins, 1932; Komar, 1976). Southern Gulf Coast of Florida in USA (Runsak et al., 1966; Austin, 1971) and the banks of Lower Medway estuary in England (Kirby,…     

Volcanology and eruptive styles of Barren Island: an active mafic stratovolcano in the Andaman Sea,NE Indian Ocean

Barren Island (India) is a relatively little studied, little known active volcano in the Andaman Sea, and the northernmost active volcano of the great Indonesian arc. The volcano is built of prehistoric (possibly late Pleistocene) lava flows (dominantly basalt and basaltic andesite, with minor andesite) intercalated with volcaniclastic deposits (tuff breccias, and ash beds deposited by pyroclastic falls and surges), which are exposed along a roughly circular caldera wall. There are indications of a complete phreatomagmatic tephra ring around the exposed base of the volcano. A polygenetic cinder cone has existed at the centre of the caldera and produced basalt-basaltic andesite aa and blocky aa lava flows, as well as tephra, during historic eruptions (1787–1832) and three recent eruptions (1991, 1994–95, 2005–06). The recent aa flows include a toothpaste aa flow, with tilted and overturned crustal slabs carried atop an aa core, as well as locally developed tumuli-like elliptical uplifts having corrugated crusts. Based on various evidence we infer that it belongs to either the 1991 or the 1994–95 eruptions. The volcano has recently (2008) begun yet another eruption, so far only of tephra. We make significantly different interpretations of several features of the volcano than previous workers. This study of the volcanology and eruptive styles of the Barren Island volcano lays the ground for detailed geochemical-isotopic and petrogenetic work, and provides clues to what the volcano can be expected to do in the future.     

B2114+022: a distant radio source gravitationally lensed by a starburst galaxy

We have discovered a radio source (B2114+022) with a unique structure during the course of the JVAS gravitational lens survey. VLA, MERLIN, VLBA and MERLIN+EVN radio maps reveal four compact components, in a configuration unlike that of any known lens system, or, for that matter, any of the ∼15 000 radio sources in the JVAS and CLASS surveys. Three of the components are within 0.3 arcsec of each other while the fourth is separated from the group by 2.4 arcsec. The widest separation pair of components have similar radio structures and spectra. The other pair also have similar properties. This latter pair have spectra which peak at ∼5 GHz. Their surface brightnesses are much lower than expected for synchrotron self-absorbed components.
Ground-based and Hubble Space Telescope optical observations show two galaxies ( z =0.3157 and 0.5883) separated by 1.25 arcsec. The lower redshift galaxy has a post-starburst spectrum and lies close to, but not coincident with, the compact group of three radio components. No optical or infrared emission is detected from any of the radio components down to I =25 and H =23 . We argue that the most likely explanation of the B2114+022 system is that the post-starburst galaxy, assisted by the second galaxy, lenses a distant radio source producing the two wide-separation images. The other two radio components are then associated with the post-starburst galaxy. The combination of the angular sizes of these components, their radio spectra and their location with respect to their host galaxy still remains puzzling.     

Proposed river-linking project of India: a boon or bane to nature

India is a vast country and is highly diversified in terms of natural resources and socio-economic setup. Moreover, its water resources are unevenly distributed in space and time. With increasing population and increasing aspiration for improved standard of living, there is an acute pressure on the demand and availability of water. Though the idea of interlinking of rivers is not a new concept in India, it had rather persisted long back as much as in other countries of ancient civilization. National Water Development Agency (NWDA) has given the real shape to the proposal of the interlinking of rivers of the country. In India the river-linking project in a sensible and scientific manner will not only allow the prevention of the colossal wastage of a vitally important natural resource, mitigate the flood and inundation by detaining flowing surface water of rainy seasons, but also ensure availability of water to drier areas; combating both flood and drought simultaneously. Moreover, this project will generate 34,000 MW of hydropower and irrigation of an additional 35 million hectares (135,135 square miles) of land. Though linking of rivers may initially appear to be a costly proposition in ecological, geological, hydrological and economical terms, in the long run the net benefits coming from it will far outweigh these costs or losses. However, in the absence of any definite international legal framework, Bangladesh has raised objections against the project. This paper aims at looking at this long-term plan, the project proposal, its involvement and impact not only on the states of India, India as a whole, but also on its neighbouring nations which are linked with India through the waterways, and share the common climatic conditions and economic status.     

Tectonostratigraphy and base-metal mineralization controls, Aravalli province (western India): New interpretations from geophysical data analysis

Analysis and synthesis of multi-disciplinary geoscience information from geological literature/maps and from digitally-processed aeromagnetic and gravity data pertinent to the Aravalli province were carried out to address some hitherto unresolved questions about the tectonostratigraphy of this Archaean–Proterozoic metallogenic province. Based on the magnetic anomalies, several tectonic domains were identified. These domains, bounded by regional-scale geophysical lineaments, have distinct crustal, lithological, metamorphic, and metallogenic characteristics and correlate broadly with lithostratigraphic belts identified by several earlier workers. New interpretations on the tectonostratigraphy and the base-metal mineralization controls in the Aravalli province are as follows. The Hindoli sequences, in the eastern parts of the province, constitute an independent Palaeo–Proterozoic tectonic domain and do not form part of the Archaean basement complex. The base-metal-bearing metasedimentary enclaves in the central parts of the province also constitute an independent Palaeo–Proterozoic tectonic domain, which is quite distinct from the surrounding (basement complex?) rocks. The base-metal-bearing metavolcano-sedimentary sequences in the western parts of the province constitute an independent Neo–Proterozoic tectonic domain. The base-metal deposits in the province are spatially associated with the regional-scale lineaments and with the mafic metavolcanic rocks deduced from the aeromagnetic data. The regional-scale lineaments, which possibly represent Proterozoic crustal-scale faults, are plausible structural controls on the base-metal mineralization in the province. The mafic metavolcanic rocks are plausible heat-source controls on the SEDEX- and/or VMS-type base-metal mineralizations and are possible metal-source controls on the VMS-type base-metal mineralization in the province.     

Social capital,trust, and collective action in post-earthquake Nepal

According to the first generation of theories of collective action, utility-maximizing individuals encountering conditions of nonexcludability and nonrivalry free ride rather than cooperate as their dominant strategy. But scholars have documented innumerable successful and unsuccessful collective action efforts after disasters around the world that contradict that idea. We square the findings of disaster research with the second generation of collective action research by demonstrating how important social capital is for understanding voluntary collective action. We apply structural equation modeling and mediation analysis to data we collected from Sindhupalchowk, Nepal, after its 2015 earthquake to show that bonding social capital has the mediated effect of engendering mutual trust and in turn enabling collective action. Further, we demonstrate direct effects of both bonding and bridging/linking social capital on collective action following disasters. We portray social capital as essential in enabling self-governance and fostering resilience in postdisaster scenarios in which the collective burdens of reconstruction and recovery necessitate concerted efforts on the part of the private sector, citizens, and public institutions.

     

Petrology and geochemistry of the Mesoproterozoic Vattikod lamproites,Eastern Dharwar Craton,southern India: evidence for multiple enrichment of sub-continental lithospheric mantle and links with amalgamation and break-up of the Columbia supercontinent

Numerous lamproite dykes are hosted by the Eastern Dharwar Craton, southern India, particularly towards the northwestern margin of the Cuddapah Basin. We present here a comprehensive mineralogical and geochemical (including Sr and Nd isotopic) study on the lamproites from the Vattikod Field, exposed in the vicinity of the well-studied Ramadugu lamproite field. The Vattikod lamproites trend WNW–ESE to NW–SE and reveal effects of low-temperature post-magmatic alteration. The studied lamproites show porphyritic texture with carbonated and serpentinized olivine, diopside, fluorine-rich phlogopite, amphibole, apatite, chromite, allanite, and calcite. The trace-element geochemistry (elevated Sr and HFSE) reveals their mixed affinity to orogenic as well as anorogenic lamproites. Higher fluorine content of the hydrous phases coupled with higher whole-rock K₂O highlights the role of metasomatic phlogopite and apatite in the mantle source regions. Trace-element ratios such as Zr/Hf and Ti/Eu reveal carbonate metasomatism of mantle previously enriched by ancient subduction processes. The initial ⁸⁷Sr/⁸⁶Sr-isotopic ratios (calculated for an assumed emplacement age of 1350 Ma) vary from 0.7037 to 0.7087 and ?Nd range from ??10.6 to ??9.3, consistent with data on global lamproites and ultrapotassic rocks. We attribute the mixed orogenic–anorogenic character for the lamproites under study to multi-stage metasomatism. We relate the (1) earlier subduction-related enrichment to the Paleoproterozoic amalgamation of the Columbia supercontinent and the (2) second episode of carbonate metasomatism to the Mesoproterozoic rift-related asthenospheric upwelling associated with the Columbia breakup. This study highlights the association of lamproites with supercontinent amalgamation and fragmentation in the Earth history.     

Petrographic and Geochemical Study of Gurha Lignites,Bikaner Basin,Rajasthan, India: Implications for Thermal Maturity,Hydrocarbon Generation Potential and Paleodepositional Environment

In the present study an attempt has been made to characterize the Gurha lignites employing petrographic and geochemical techniques on a large number of lignite samples. The data generated has been discussed to understand the hydrocarbon generation potential as well as the evolution of the paleomires of these lignites. The present investigation indicates that these lignites are mainly dominated by the huminite followed by inertinite and liptinites occurs in meager concentration. The huminite reflectance values rank the Gurha lignite as a low-rank B lignite.Petrographic result indicates these lignites are thermally immature in nature and comprised of Type-III kerogen and may generate only gas on maturation which is further supported by the rock-eval pyrolysis. The plots of rock eval data also indicates the same. The GI and TPI as well as GWI and VI values and the petrography-based facies critical models indicate that these lignites originated mostly under wet forest swamp condition. The microscopic constituents have also shown that these lignites are from herbaceous plants in wet forest swamp environment and ombrotrophic hydrological condition. The presences of framboidal pyrite in the study area infer the marine influence which also supported by the presence of high sulphur content.     

Petrogenesis of the crater-facies Tokapal kimberlite pipe,Indrvati Basin,Central India

New geochemical data of the crater-facies Tokapal kimberlite system sandwiched between the lower and upper stratigraphic horizons of the Mesoproterozoic Indr avati Basin are presented.The kimberlite has been subjected to extensive and pervasive low-temperature alteration.Spinel is the only primary phase identifiable,while olivine macrocrysts and juvenile lapilli are largely pseudomorphed(talc-serpentinecarbonate alteration).However,with the exception of the alkalies,major element oxides display systematic fractionation trends; likewise,HFSE patterns are well correlated and allow petrogenetic interpretation.Various crustal contamination indices such as(SiO2+Al2O3+Na2O)/(MgO+ K2O) and Si/Mg are close to those of uncontaminated kimberlites.Similar La/Yb(79-109) of the Tokapal samples with those from the kimberlites of Wajrakarur(73-145) and Narayanpet(72-156),Eastern Dharwar craton,southern India implies a similarity in their genesis.In the discriminant plots involving HFSE the Tokapal samples display strong affinities to Group II kimberlites from southern Africa and central India as well as to ‘transitional kimberlites' from the Eastern Dharwar craton,southern India,and those from the Prieska and Kuruman provinces of southern Africa.There is a striking similarity in the depleted-mantle(TDM) Nd model ages of the Tokapal kimberlite system,Bastar craton,the kimberlites from NKF and WKF,Eastern Dharwar craton,and the Majhgawan diatreme,Bundelkhand craton,with the emplacement age of some of the lamproites from within and around the Palaeo-Mesoproterozoic Cuddapah basin,southern India.These similar ages imply a major tectonomagmatic event,possibly related to the breakup of the supercontinent of Columbia,at 1.3-1.5 Ga across the three cratons.The ‘transitional'geochemical features displayed by many of the Mesoproterozoic potassic-ultrapotassic rocks,across these Indian cratons are inferred to be memories of the metasomatising fluids/melts imprinted on their source regions during this widespread event.