M. K. Panigrahi

Influence of different forms of acidities on soil microbiological properties and enzyme activities at an acid mine drainage contaminated site

Assessment of microbial parameters, viz. microbial biomass, fluorescence diacetate, microbial respiration, acid phosphatase, beta-glucosidase and urease with respect to acidity helps in evaluating the quality of soils. This study was conducted to investigate the effects of different forms of acidities on soil microbial parameters in an acid mine drainage contaminated site around coal deposits in Jainta Hills of India. Total potential and exchangeable acidity, extractable and exchangeable aluminium were significantly higher in contaminated soil compared to the baseline (p<0.01). Different forms of acidity were significantly and positively correlated with each other (p<0.05). Further, all microbial properties were positively and significantly correlated with organic carbon and clay (p<0.05). The ratios of microbial parameters with organic carbon were negatively correlated with different forms of acidity. Principal component analysis and cluster analyses showed that the microbial activities are not directly influenced by the total potential acidity and extractable aluminium. Though acid mine drainage affected soils had higher microbial biomass and activities due to higher organic matter content than those of the baseline soils, the ratios of microbial parameters/organic carbon indicated suppression of microbial growth and activities due to acidity stress.

Utilization of Hyperion data over Dongargarh, India, for mapping altered/weathered and clay minerals along with field spectral measurements

Hyperion data acquired over Dongargarh area, Chattisgarh (India), in December 2006 have been analysed to identify dominant mineral types present in the area, with special emphasis on mapping the altered/weathered and clay minerals present in the rocks and soils. Various advanced spectral processes such as reflectance calibration of the Hyperion data, minimum noise fraction transformation, spectral feature fitting (SFF) and spectral angle mapper (SAM) have been used for comparison/mapping in conjunction with spectra of rocks and soils that have been collected in the field using Analytical Spectral Devicess FieldSpec instrument. In this study, 40 shortwave infrared channels ranging from 2.0 to 2.4 μm were analysed mainly to identify and map the major altered/weathered and clay minerals by studying the absorption bands around the 2.2 and 2.3 μm wavelength regions. The absorption characteristics were the results of O–H stretching in the lattices of various hydrous minerals, in particular, clay minerals, constituting altered/weathered rocks and soils. SAM and SFF techniques implemented in Spectral Analyst were applied to identify the minerals present in the scene. A score of 0–1 was generated for both SAM and SFF, where a value of 1 indicated a perfect match showing the exact mineral type. Endmember spectra were matched with those of the minerals as available in the United States Geological Survey Spectral Library. Four minerals, oligoclase, rectorite, kaolinite and desert varnish, have been identified in the studied area. The SAM classifier was then applied to produce a mineral map over a subset of the Hyperion scene. The dominant lithology of the area included Dongargarh granite, Bijli rhyolite and Pitepani volcanics of Palaeo-Proterozoic age. Feldspar is one of the most dominant mineral constituents of all the above-mentioned rocks, which is highly susceptible to chemical weathering and produces various types of clay minerals. Oligoclase (a feldspar) was found in these areas where mostly rock outcrops were encountered. Kaolinite was also found mainly near exposed rocks, as it was formed due to the weathering of feldspar. Rectorite is the other clay mineral type that is observed mostly in the southern part of the studied area, where Bijli rhyolite dominates the lithology. However, the most predominant mineral type coating observed in this study is desert varnish, which is nothing but an assemblage of very fine clay minerals and forms a thin veneer on rock/soil surfaces, rendering a dark appearance to the latter. Thus, from this study, it could be inferred that Hyperion data can be well utilized to identify and map altered/weathered and clay minerals based on the study of the shape, size and position of spectral absorption features, which were otherwise absent in the signatures of the broadband sensors.

Granitoids around the Malanjkhand copper deposit: types and age relationship

On the basis of field relations, petrography and chemistry, three types of granitoids are recognized at Malanjkhand in and around the copper deposit over an area of about 200 km2. These are (i) a fine grained ‘leucogranite’ of restricted occurrence in the surrounding area (Gr-I); (ii) coarse-grained, grey in most parts, gneissose granitoid of regional extension (Gr-II); and (iii) the pink-feldspar bearing massive type hosting the mineralization with occasional representatives in the surrounding country (Gr-III). Gr-I comes out as a distinct entity on the basis of cross-cutting relation and mineralogical and chemical composition, the Rb-Sr whole rock isochron also giving a younger age than the other two groups irrespective of the regression model used. Gr-II comes out as the oldest unit but its age relationship with Gr-III cannot be established unequivocally. An uncorrelated error regression model establishes the age relationship as Gr-I

Mineralogy of Fe-Precipitates and Their Role in Metal Retention from an Acid Mine Drainage Site in India

Iron-rich precipitates from acid mine drainage (AMD) sites around the Jaintia Hills coalfield, India, were investigated. The ochreous precipitates mainly consist of schwertmannite, goethite, and jarosite. Sorption affinities suggest that Ni, Mn, Cr, Cd, Pb, and Zn are more significant in schwertmannite-bearing ochre than in more crystalline jarosite- and goethite-bearing ochres. The lower crystallinity and higher surface area of schwertmannite-bearing ochreous precipitate result in higher metal retention potential. Fe and Mn concentrations in water may also influence the sorption of metals in the precipitates. The results of the sequential extractions showed that metal mobility is mainly controlled by Fe and Mn oxyhydroxide phases. This information may aid understanding of the natural attenuation of trace metals by ochreous precipitates in AMD-contaminated water.ZusammenfassungEisenhaltige Ablagerungen von saurem Grubenwasser im Umfeld des Kohlereviers Jaintia Hills in Indien wurden untersucht. Die ockerartigen Ablagerungen bestehen hauptsächlich aus Schwertmannit, Goethit und Jarosit. Sorptionsverwandschaften deuten darauf hin, dass Ni, Mn, Cr, Cd, Pb und Zn häufiger in Schwertmannit bildenden Ockern vorkommen als in kristallinen Jarosit und Goethit bildenden Ockern. Die niedrigere Kristallinität und größere Oberfläche der Schwertmannit bildenden ockerartigen Ablagerungen resultieren aus dem höheren Metallrückhaltevermögen. Auch Fe und Mn Konzentrationen im Wasser können die Sorption von Metallen in den Ablagerungen beeinflussen. Die Ergebnisse der sequenziellen Extraktion zeigen, dass die Mobilität von Metallen vornehmlich durch Fe- und Mn-Oxihydrate kontrolliert wird. Diese Information kann zum Verständnis des natürlichen Abbauverhaltens von Spurenmetallen durch ockrige Ablagerungen in durch saures Grubenwasser verunreinigten Wässern beitragen.ResumenSe investigaron precipitados ricos en hierro desde drenajes ácidos de minas (AMD) en la zona de Jaintia Hills coalfield, India. Los precipitados ocres consisten principalmente de schwertmanita, goetita y jarosita. La sorción de Ni, Mn, Cr, Cd, Pb y Zn es más significativa en schwertmanita que en jarosita y en goetita. La menor cristalinidad y mayor área superficial de schwertmanita resulta en un mayor potencial de retención de metales. Las concentraciones de Fe y Mn en agua pueden también influir la sorción de metales en los precipitados. Los resultados de las extracciones secuenciales mostraron que la movilidad del metal es principalmente controlada por las fases de oxohidróxidos de Fe y Mn. Esta información podría ayudar a comprender la atenuación natural de metales trazas por precipitados ocres en aguas contaminadas con AMD.抽象文章研究了印度Jaintia Hill煤田酸性矿山废水中富铁沉淀物的特性。该赭黄色沉淀物主要由施氏矿、针铁矿和黄钾铁矾组成。含施氏矿的赭石与含结晶黄钾铁矾和针铁矿的赭石相比,Ni、Mn、Cr、Cd、Pb和Zn对前者具有更好的亲和性。低结晶度和大比表面积使含施氏矿赭黄色沉淀物具有较高金属阻滞潜力。水中Fe和Mn浓度也会影响沉淀物吸附金属离子能力。顺次提取试验结果表明金属迁移能力主要受铁、锰的氢氧化物形态控制。研究有助于深化理解酸性矿山废水中赭黄色沉淀物对微量金属元素的自然钝化作用。

Metagenomic exploration of microbial community in mine tailings of Malanjkhand copper project, India

Mine tailings from copper mines are considered as one of the sources of highly hazardous acid mine drainage (AMD) due to bio-oxidation of its sulfidic constituents. This study was designed to understand microbial community composition and potential for acid generation using samples from mine tailings of Malanjkhand copper project (MCP), India through 16S rRNA gene based amplicon sequencing approach (targeting V4 region). Three tailings samples (T1, T2 and T3) with varied physiochemical properties selected for the study revealed distinct microbial assemblages. Sample (T3) with most extreme nature (pH < 2.0) harbored Proteobacteria, Actinobacteria, Chloroflexi while the samples (T1 and T3) with slightly moderate nature (pH < 4.0 and > 3.0) exhibited abundance of Proteobacteria, Fimicutes, Actinobacteria and/or Nitrospirae. Metagenomic sequences are available under the BioProject ID PRJNA361456.

Reserve base in relation to crustal abundance of metals: Another look

Abstract When the global “ reserve base ” (instead of global “reserve”) of common metals is considered in relation to their average abundance in the upper continental crust (instead of the bulk continental crust), a striking regularity is revealed. Twenty five common metals considered here fall along four well-defined essentially parallel lines in a “reserve base” versus average abundance diagram. The pattern is inferred to be the reflection of a persistent, first-order control of average abundance over “reserve-base” modified by such factors as: (a) differential preservation potentials of genetic varieties, (b) order-of-magnitude difference in the required “enrichment factors” of the metals, and (c) differential geochemical “adaptability” and “insularity” of the metals. Positive and negative deviations of three of these lines from the main trend line (MTL) can be explained almost quantitatively. Their lateral shift, maintaining near-parallelism with the MTL reveals a fundamental relationship that is neither masked nor distorted by the modifying factors, and distinguishes groups that are more closely related in their response to the modifying factors.

Species diversity variations in Neogene deep-sea benthic foraminifera at ODP Hole 730A, western Arabian Sea

Deep-sea benthic foraminifera are an important and widely used marine proxy to understand paleoceanographic and paleoclimatic changes on regional and global scales, owing to their sensitivity to oceanic and climatic turnovers. Some species of benthic foraminifera are sensitive to changes in water mass properties whereas others are sensitive to organic fluxes and deep-sea oxygenation. Benthic faunal diversity has been found closely linked to food web, bottom water oxygen levels, and substrate and water mass stability. The present study is aimed at analyzing species diversity trends in benthic foraminifera and their linkages with Indian monsoon variability during the Neogene. Species diversity of benthic foraminifera is examined in terms of number of species (S), information function (H), equitability (E) and Sanders’ rarefied values, which were combined with relative abundances of high and low productivity benthic foraminifera at Ocean Drilling Program Hole 730A, Oman margin, western Arabian Sea. The Oman margin offers the best opportunity to understand monsoon-driven changes in benthic diversity since summer monsoon winds have greater impact on the study area. The species diversity was higher during the early Miocene Climatic Optimum (∼17.2–16.4 Ma) followed by a decrease during 16.4–13 Ma coinciding with a major increase in Antarctic ice volume and increased formation of Antarctic Bottom Water. All the diversity parameters show an increase during 13–11.6 Ma, a gradual decrease during 11.6–9 Ma and then an increase with a maximum at 7 Ma. Thereafter the values show little change until 1.2 Ma when all the parameters abruptly decrease. The benthic foraminiferal populations and diversity at Hole 730A were mainly driven by the Indian monsoon, and polar waters might have played a minor or no role since early Neogene period as the Arabian Sea is an enclosed basin.

Volatiles associated with granitoid intrusives around orogenic gold deposits in Ramagiri and Penakacherla regions of Eastern Dharwar Craton, South India

The nature of magmatic fluid has been tested well in varied type of auriferous deposits. However, in context of orogenic gold deposits, there are not many studies that clearly point out the nature of fluids exsolved out of crystallizing granitoids. This study compares the fluid of late-stage magmatic origin with that causative for mineralization in gold camps of Ramagiri and Penakacherla in Eastern Dharwar Craton. Various types of fluid inclusion assemblages (FIAs) were identified in granitoid matrix quartz, pegmatites, quartz segregations and greenstone-hosted goldquartz veins. The aqueous-carbonic (CH4-poor) and carbonic (CH4- and H2O-poor) inclusions are most common in pegmatites and quartz segregations, while the matrix quartz grains are generally devoid of CO2-bearing inclusions. On the other hand, auriferous veins in greenstone rocks show predominance of low to moderate salinity, aqueous-carbonic (variably CH4-bearing) inclusions. Inconsistencies in H2O/CO2 ratio and final homogenization properties of aqueous-carbonic inclusions within individual FIAs, apart from common occurrence of the FIA comprising aqueous-carbonic, carbonic and aqueous biphase inclusions, point to immiscibility in the ore fluid regime. Based on estimated microthermometric results, we attempt to deduce the evolution path of magmatic fluid with respect to that of fluid in ore zone. On this basis, a case for magmatic derivation of the ore fluid has been put forward. The difference in magmatic and auriferous fluid in terms of CO2/CH4 ratio are justifiable and allows us to visualize that aqueous-carbonic composition of orogenic gold fluid does not signify its exclusive origin through any particular process (or source), for example metamorphism.

Ductile shear zones

European Union through the European Regional Development Fund, based on COMPETE 2020 (Programa Operacional da Competitividade e Internacionalizacao), project ICT (UID/GEO/04683/ 2013) with reference POCI-01-0145-FEDER-007690 and national funds provided by Fundacao para a Ciencia e a Tecnologia.“Tabular or sheetlike, planar or curviplanar zones in which rocks are more highly strained than rocks adjacent to the zone” are called ductile shear zones. Identification and study of ductile shear zones are important since major plate boundaries are defined by such shear zones. We need to study such zones since along them partially molten rocks can flow. Secondly, viscous dissipation related to such zones has been investigated. The ductile shear sense/sense of movement from such zones can be deciphered mainly from asymmetric sigmoid, parallelogram and lenticular clasts and intrafolial folds. See Passchier and Trouw for review on ductile shear zones. In addition to such shear sense indicators, this chapter also presents near-symmetric clasts that form possibly within shear zones but that do not give the shear sense.

Comparative geochemical, magnetic susceptibility, and fluid inclusion studies on the Paleoproterozoic Malanjkhand and Dongargarh granitoids, Central India and implications to metallogeny

The Malanjkhand granodiorite (MG) hosting economic copper mineralization and the hitherto barren Dongargarh granitoids (DG) have subtle differences in their petrographic and bulk geochemical features. The two plutons are contiguous and occur in the northern part of the Bhandara Craton in Central India with intervening volcanosedimentary sequence of the Dongargarh Supergroup amidst older gneisses. The Dongargarh granitoids studied in two smaller units have higher bulk magnetic susceptibility than the Cu-bearing MG; the majority of samples studied from the latter being ilmenite-series rocks. DG crystallized at higher pressures compared to MG. Plagioclase composition ranges from albite to high bytownite in MG, whereas its compositional range is restricted to high andesine in DG. However, both intrusions give identical temperature ranges estimated by binary feldspar thermometry. Biotite in MG shows higher Fe/Mg ratios, as well as a greater range of compositional variation, than that in DG. MG has a moderately fractionated rare earth element distribution pattern without any significant Eu anomaly, showing depletion in mid-range rare earth elements (REE) and no depletion in heavy REE. DG is characterized by a prominent negative Eu anomaly. Geochemical features indicate subtle differences in the nature of source rocks and/or melting processes responsible for the generation of the two granitoids. MG displays more consistent bulk chemical features and is possibly a result of crystallization from a homogeneous granodioritic melt. DG displays a greater diversity and possibly incorporated a significant felsic crustal component that contributed to the parent melt. A fluid inclusion study of quartz grains from the granitoids and barren quartz veins occurring in MG indicates identical low-temperature nature of the fluid in both cases. They differ from the fluid in the mineralized zone in MG in the absence of a high-temperature component and CO2 in the fluid. Late-stage fluids in DG and associated barren quartz veins compare well with those from MG. The hydrothermal activity following the granite emplacement seems to have operated under identical temperature conditions, and the aqueous fluid at the two occurrences seems to have been broadly similar. In both cases, internal evolution of the exsolved fluid to low temperatures and moderate salinity are visualized. Based on the existing information, the lack of ore potential in DG may be attributed to the metal and volatile (water + halogens) deficient nature of the parental granitic melt.