[Show abstract][Hide abstract] ABSTRACT: Adherent epilithic microorganisms recovered from rocks submerged 10 to 20 cm in two different rivers were examined by electron microscopy and enumerated after dispersion in M-9 salts by viable plate counts. Bacterial cells concentrated in microcolonies were often observed attached to the surface of algae, cyanobacteria, and organic detritus. This structured communal mode of growth was common among epilithic microbial communities of different rock types. However, counts of heterotrophic bacteria from limestone (106 to 107 cfu/cm2) were 10- to 100-fold greater than corresponding values from granite, gabbro, rhyolite, basalt, and quartz. Cyanobacteria and algae were an order of magnitude less abundant compared with their bacterial counterparts. These variations in population densities of epilithic microorganisms present on different rocks were inversely related to mineral substrate hardness.Key words: epilithic microorganisms, mineral hardness.
Canadian Journal of Microbiology 02/2011; 35(7):744-747. DOI:10.1139/m89-122 · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: On Ellesmere Island, in the Canadian Arctic, dark-colored biofilms proliferate on moist surfaces, including exposed granodiorite outcrops. Transmission electron microscopy of these biofilms indicates that complex epilithic microbial communities developed, consisting of cyanobacteria and fungi symbiotically associated in a lichen, along with a consortium of free-living algae and gram-negative bacteria. The epilithic cyanobacteria and bacteria were shown to extensively precipitate phosphatic minerals, ranging from relatively large polyphosphate granules (approximately 250 nm in diameter) within their cytoplasmic membranes to smaller iron phosphate grains (generally less than 50 nm in diameter) associated with the periplasmic space and encompassing capsule. Complete encrustation of some bacterial cells by the iron phosphates was observed. Energy-dispersive X-ray spectroscopy suggested that these grains are compositionally similar to the mineral strengite (FePO4∙2H2O). This study clearly indicates that the Arctic supports a thriving microbial community that influences the biogeochemical cycling of PO4 in an environment of low nutrient availability. Nutritional requirements by the microorganisms were actively maintained through a relatively closed recycling mechanism, which restricted the immediate loss of phosphorus from the biofilm.
Canadian Journal of Earth Sciences 02/2011; 31(8):1320-1324. DOI:10.1139/e94-114 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cretaceous coal-bearing sequences from the Moose River basin in northern Ontario and the Peace River basin in northeast British Columbia were analysed for trace- and major-element contents. Modes of occurrence of the trace elements are proposed on the basis of Pearson correlation coefficients and scanning electron microscopy coupled with energy-dispersive X-ray analysis.The Moose River basin lignite was deposited in an alluvial floodplain environment, and the restricted mineralogy, dominated by quartz and kaolinite, reflects derivation from a highly weathered terrain. The bituminous coal from the Peace River basin was deposited in an alluvial to deltaic environment, with a dominant mineralogy including quartz, illite, kaolinite, mixed-layer clays, carbonates, barite, feldspar, and pyrite.Trace-element contents in both deposits are comparable to the average concentration in United States coals. Modes of occurrence of trace elements in the coals are extremely variable and depend on local conditions both during deposition and subsequently. Association with the organic matter is the most common mode of occurrence of trace elements in the Moose River basin lignites, whereas clay minerals are important trace-element sites in the Peace River basin coal.Factors including coal rank, clay mineralogy, nature of the surrounding rocks, and composition of the groundwaters appear to have important influences on the concentrations of the trace elements and their siting in the coals.
Canadian Journal of Earth Sciences 02/2011; 24(5):1038-1052. DOI:10.1139/e87-100 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Most common mantle-derived magmas have densities at Moho pressures that exceed the density of average continental crust. Thus, unless the crust is tightly coupled with the mantle, many such magmas should penetrate at or near the Moho interface. The scale of such a phenomenon can be impressive; recent hot spots may have perturbed more than 5% of the planet's surface. The details of the process will depend on the ease of melting of the base of continents.Underplating can explain continental construction from below; Moho structures, or lack thereof; delamination of the continental basement; partial subduction and density cleaning of crust; the formation of massive anorthosite complexes; and major changes of elevation of continental blocks. In the thermally turbulent Archean, the very dense and hot komatiite magmas must have had even more profound influences.Modern studies of the subduction process show that the mantle must be heterogeneous and that volatiles can be carried to great depths in significant volumes.
Canadian Journal of Earth Sciences 02/2011; 30(5):908-912. DOI:10.1139/e93-075 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acidic effluent containing enhanced concentrations of toxic heavy metals discharges from a cumulative total of 104 ha of mine-tailings waste in Canada. Communities of acidophilic microorganisms, specifically the unicellular alga Euglena sp. and bacteria, thrive in many of the hostile, low-pH effluent environments, which are otherwise devoid of life. The micro organisms concentrate aqueous dissolved metals onto cell walls and at intracellular sites, during the life cycle, and strongly bind metals during early diagenesis. A sequence is observed in which amorphous Fe and Ti concentrated at cell walls are progressively transformed to microcrystalline aggregates of goethite, ferrihydrite, maghemite, magnetite, haematite, lepidocrocite, and ilmenite. The bioprecipitated Ti- and Fe-oxides and oxyhydroxides act as scavengers for heavy metals such as Cu, Pb, Zn, Ni, Cd, and Th. Acidophilic microorganisms play a central role in the toxic-metal budget of mine-tailings waste by efficiently sequestering aqueous metals and by promoting nucleation of oxide minerals whose inorganic formation is kinetically inhibited, thereby retarding toxic-metal dispersion into the natural environment.
Canadian Journal of Earth Sciences 02/2011; 26(12):2731-2735. DOI:10.1139/e89-234 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: High-resolution transmission electron microscopy of clay formation on K-feldspar has revealed the existence of intermediate states between feldspar and crystalline clay products. During the earliest weathering stages of K-feldspar, a primitive clay precursor forms on the feldspar surface that is spotted by ion oxides. This reactive iron is incorporated into the primitive clay precursors, which have an ultrathin 150–200 Å (1 Å = 0.1 nm) circular form and 14–20 Å lattice images or long, curled fiber forms with varied lattice image spacings. The electron diffraction patterns of primitive clay precursors show diffuse rings at 2.65, 2.04, and 1.51 Å, suggesting low crystallinity, random orientation, and partial inheritance of the original structure. EDX step scanning analysis showed that the major-element concentrations of Si, Al, and K tend to decrease from unaltered parts to altered parts of precursors with substantial increase in Fe. Auger depth profiling showed the thickness of the primitive clay layers is 150–300 Å. The primitive clay precursors may well precede formation of spheroidal particles of halloysite, squat cylinders of halloysite or hexagonal crystalline, and tabuler halloysite (7 Å). SEM, XRD, SIMS, and SAM data support the TEM results.
Canadian Journal of Earth Sciences 02/2011; 24(3):506-527. DOI:10.1139/e87-051 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: All biomass contains a significant quantity of metallic constituents, and mineralization in living and dead biodebris may contribute to element transport from the hydrosphere into sediments. The anionic cell walls of bacteria are remarkable in their ability to fix metals and provide sites for nucleation and growth of minerals. Results presented show the types of cell wall polymers that are responsible for metal binding in walls of Gram-positive and Gram-negative bacteria.
Canadian Journal of Earth Sciences 02/2011; 22(12):1893-1898. DOI:10.1139/e85-204 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Monocultures of the freshwater green algae Ankistrodesmus sp. grown at pH 8.1–8.2 and 13–16 °C, in solutions containing 2 ppm U chelated with EDTA, acquired 1000 – 10 000 ppm uranium by dry weight. In some algae, a uranium mineral of cubic habit was detected. At Elliot Lake, Ontario, Euglena sp. thriving in tailings discharge contain on average 184 ppm U. Tailings waters contain high concentrations of dissolved uranium, on average 273 ppb. In natural drainage waters, above and below tailings, dissolved U averages 0.23 ppb. Thames River algae average 28 ppm U, whereas waters have an average dissolved U of 1.46 ppb, representing about twice the global mean riverine value of 0.6 ppb U.
Canadian Journal of Earth Sciences 02/2011; 22(12):1899-1903. DOI:10.1139/e85-205 · 1.34 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: If we are to develop valid models for predicting the future of the global environment, anthropogenic forcing must become the major component of study. The technological developments needed to supply food, water and materials for 10 billion humans will dominate environmental change over thenext decades.
Terra Nova 06/2007; 4(3):284 - 287. DOI:10.1111/j.1365-3121.1992.tb00816.x · 2.32 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Stable isotope and geochemical data are used here to differentiate between contemporaneous abiotic and microbial processes leading to formation of modern carbonate- (calcite, aragonite and magnesite) and silicate-rich (kerolite) mineralization in basaltic sea caves on the island of Kauai, Hawaii. Strontium isotope and Ca/Sr ratios in meteoric water and cave carbonates suggest that the majority of Sr and Ca are derived from rock–water interaction within the host basalts situated above the caves. Oxygen and hydrogen isotope ratios and chemical compositions of cave and surface waters indicate that evaporation does not control cave-water composition. However, evaporation of drops and thin films of water in microenvironments can lead to precipitation of some phases. This behaviour is suggested by the covariance in δ18O and δ13C values of some carbonates, especially magnesite, which is considered to be a late-stage evaporative precipitate. Modelling of water evolution suggests that evaporation can be a cause of supersaturation for magnesite, kerolite and some Ca carbonates. However, the highly elevated δ13C values (up to +8.2) of some Ca carbonates, compared to average dissolved inorganic carbon δ13C values (~−12), are best explained as the product of microbial photosynthesis, in particular by cyanobacteria, present in the upper layers of active microbial mats on cave surfaces. The preferential uptake of 12C by cyanobacteria is recorded in the low δ13C values (−29.1 to −22.6) of organic matter in mats and mineralized microbialites. The resulting 13C-enrichment of dissolved inorganic carbon is recorded in the elevated δ13C values of these Ca carbonates. A positive correlation exists between the δ13C values of the carbonates and coexisting organic matter. The large enrichment in 13C of carbonate minerals, relative to dissolved inorganic carbon, and its covariance with the δ13C values of coexisting organic matter are useful for identification of carbonate-rich mineralization resulting from autotrophic microbial activity.
[Show abstract][Hide abstract] ABSTRACT: Intracellular crystals of aragonite have been identified by selected area electron diffraction (SAED) in a species of the freshwater filamentous alga Spirogyra from the Thames River, Ontario, Canada. The crystals are 2 to 24 μm in diameter, and characterized by a unique cross-shaped morphology, in which needle-like, or prismatic outgrowths develop from a common axis. Crystals may be dispersed throughout filaments, but tend to cluster as aggregates towards the centre.
[Show abstract][Hide abstract] ABSTRACT: Chemical and mineral studies were carried out on weathered materials from six profiles developed on granites located in different areas of Brazil.Quartz and K-feldspar are the most abundant minerals overall. Kaolinite is the most common secondary mineral and is principally a feldspar weathering product. Mica breakdown is associated with smectite formation in semi-arid regions. In more humid regions mica weathering products include interlayered mica-vermiculite, vermiculite and kaolinite. Changes in the concentrations of Si, Al and K reflect the weathering behaviour of quartz, kaolinite, K-feldspar respectively, although K mobilities sometimes appear to be governed by processes related to the formation of secondary minerals. Ca and Mg are the first elements to exhibit depletion and their removal rates are very fast relative to K. P is also among the most mobile elements. Cr, Co, Ni, Cu, Zn, Rb, Sr, Y, Zr, Nb, Ba and Pb concentrations were measured. The first row transition metals are the most depleted. Rb and Sr are retained relative to Na, Mg, and Ca, and Ba accumulates as weathering proceeds. Y, Zr, Nb and Pb concentrations show little variation.The conclusion is that the factors controlling deep leaching are complex and the common notion that weathering rates are higher at lower latitudes should be reassessed.
European Journal of Soil Science 07/2006; 34(4):841 - 851. DOI:10.1111/j.1365-2389.1983.tb01076.x · 2.39 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We are living in a new period of earth history. I was impressed by the writing of
Vladimir Vernadsky, 1929, in his book The Biosphere. He said we were in a
transition to a new geological era which he termed the psychozoic era. As he
stated, mankind as a whole would become a new and powerful geological entity
able to transform the planet. I very much liked the words of Sir Crispin Tickell
in his British Association lecture of 1993 \“I was recently asked if I was an
optimist or pessimist. The best answer was given by someone else. He said that
he had optimism of the intellect but pessimism of the will. In short, we have
most of the means for coping with the problems we face, but are distinctly short
on our readiness to use them. It is never easy to bring the long term into the
short term. Our leaders, whether in politics or business, rarely have a time
horizon of more than five years”. I have been fortunate that I have walked in
over 60 nations. When you walk you see, smell, the problems and you meet
people of all types.
Keywords: the Psychozoic era, education needed for all people, diversity, energy
and waste reduction, soil quality.
[Show abstract][Hide abstract] ABSTRACT: Ore deposit structural analysis, using a combination of structural geology and geostatistics, has direct application in the mining industry. Its main goal is to integrate structural measurements and assay data to create a method in which structurally controlled deposits are modeled numerically. This provides guidance to grade control and pit optimization during mining, improves prediction of orebody geometry and orientation, and provides more effective exploration strategies for surrounding areas. The method leads to a better understanding of how mineralized fluids percolated and were focused at the Ouro Fino Mine, a shear zone-hosted gold deposit in Minas Gerais State, Brazil. In this mine, gold is distributed along permeability pathways within rock fabrics that were produced or modified during the Brasiliano orogeny, when the Espinhaço–Araçuaı́ sequence was inverted towards the São Francisco craton during a basement-involved fold-and-thrust regime. The resulting permeable zones are conformable with the C surface, within which two other clusters of fabric elements control the large-scale features of the mineralization: (1) a cluster of fabric elements (mineral, stretching and intersection lineations) that plunges SE; and (2) a sub-horizontal cluster along folds and intersection lineations and the strike of the shear zone.
[Show abstract][Hide abstract] ABSTRACT: A comagmatic suite of lamproites, ultramafic lamprophyres, and minettes was intruded at ∼100 Ma into thick siliciclastic sequences deposited in five intracratonic basins which developed during Gondwana rifting in eastern India. Lamproites are dominated by microphenocrysts of Ti-rich phlogopite, and olivine pseudomorphed by serpentine and talc, with variable modal abundances of aegirine, amphibole, apatite, carbonates, Cr-spinel, fluorite, perovskite, priderite, and titanomagnetite. Compositionally, lamproites are characterized by extremely high contents of TiO2 (4.2–10 wt%), K2O, and P2O5, over a range of Mg# from 80 to 75, in keeping with lamproites worldwide. They have high abundances of Ba, Th, U, and REE (1019–5400 ppm), with pronounced fractionation of REE, where La/Smcn=3.5–5.6, and Gd/Ybcn=7.3–18, consistent with residual garnet in the mantle source. Nitrogen isotope compositions range from +1.6 to +8.7‰ with an average of 3.8‰, and N contents average 107 ppm. Mantle δ15N averages −5‰, with a N content of 2 ppm, whereas continental crust varies from 2 to 6‰ with 30–90 ppm N. Atmospheric N2 is sequestered by N-fixing microorganisms, and stored as kerogen with an average δ15N of +3‰ in sedimentary rocks. Some of the organic N is converted to NH4+ which substitutes for K in crustal K-silicates. The 15N-enriched lamproites are interpreted to have formed from partial melting of enriched harzburgitic mantle lithosphere by decompressional melting accompanying extension. Enrichment resulted from subduction–erosion of continental crust, or subduction of sediments, low-degree partial melting, hybridization of the melts with mantle lithosphere and incubation, prior to decompressional melting. Consequently, some crustal N is recycled to the mantle.
[Show abstract][Hide abstract] ABSTRACT: A continuously accumulated section (the Yanyu section) of Red Clay and loess–palaeosol sequence from the southernmost Chinese Loess Plateau was selected for this study of palaeoclimate of the late Pliocene to early Pleistocene period. Termination of the Red Clay accumulation and onset of loess deposition was coincident with the beginning of extensive Northern Hemisphere glaciation at 2.6 Ma. Field observations and compositional analyses suggest an aeolian origin for the Red Clay, much like the processes experienced by the loess–palaeosol sequence. Pedogenic analysis indicates that the late Pliocene Red Clay first experienced complete decalcification and illuviation (mechanical translocation of clays) in all horizons, including the present carbonate precipitation zones, but other chemical alterations have been rather weak and even weaker than experienced by the overlying loess-derived palaeosols. In great contrast to the Pleistocene climate characterised by frequent and large-amplitude fluctuations between cold–dry and warm–wet, a relatively steady warm–dry climate condition is implied for the late Pliocene. Dustfall rate assessment indicates a much lower accumulation rate during the late Pliocene than in the early Pleistocene, in agreement with a notable systematic coarsening from the Red Clay to the overlying loess and palaeosols. Together, these features suggest that the dust transport agent, the northwesterly winds, were weaker over the late Pliocene. The transition from Red Clay to loess possibly marked a significant and rapid shift in the climatic system in east Asia.
[Show abstract][Hide abstract] ABSTRACT: An experimental study on the phase relationships of three potassium-rich ultramafic rocks from the Damodar Valley, Gondawana
basins, has been performed under upper mantle P–T conditions (1.0–2.5 GPa, 700–1200 °C). The Mohanpur lamproite and Satyanarayanpur
minette, both from the Raniganj basins, have been investigated with the addition of 15 wt% H2O. No water was added in the experiments done on an olivine minette from the Jarangdih coal mine, Bokaro Basin, which originally
contains 15 wt% CO2 and 2.86 wt% H2O.
In all cases, olivine is the liquidus phase followed by phlogopite. The subsolidus assemblage for the three rocks is a phlogopite-bearing
harzburgite, associated with apatite, Mg-ilmenite and carbonates for the Jarangdih rock; apatite, chromian spinel and carbonates
and priderite (only between 1.0 and 1.2 GPa) in the case of the Mohanpur lamproite, and finally apatite, chromian spinel,
rutile, and carbonate in the Satyanarayanpur sample.
Although orthopyroxene is absent in the natural potassium-rich ultramafic rocks, its presence in the run products of the Jarangdih
rock is possibly related to a reaction between olivine and a CO2-bearing fluid phase. The presence of orthopyroxene in the run products of Mohanpur and Satyanarayanpur rocks may be due to
a reaction between K-feldspar, olivine and a vapour phase to produce phlogopite and orthopyroxene.
On the basis of present experimental investigation and isotopic studies made by previous investigators, it has been suggested
that these K-rich rocks have crystallized from melts derived by vein-plus-wall-rock melting of a phlogopite-bearing harzburgite
Mineralogy and Petrology 01/2002; 74(2):343-360. DOI:10.1007/s007100200010 · 1.60 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: ● NaHCO3 ● 2H2O) with minor thermonatrite (Na 2CO3 ● H2O) are commonly developed on less vegetated portions of the Indo- Gangetic Plains of the state of Uttar Pradesh in India. Being highly soluble, the presence of trona alone explains the high alkalinity of the soil (pH 10.5). Occa- sional flooding followed by fast evaporation in this extensive flood plain is a possible cause of the formation of this mineral. Carbonate build-up will have a major impact on the Gangetic ecosystem in the future, causing declining bioproductivity.
[Show abstract][Hide abstract] ABSTRACT: Modern microbial mats and microbialites are described from basaltic sea caves on the island of Kauai, HI. The mats grow on the ceilings and walls in the photic zone of several open caves where fresh water seeps out of the rock. Scanning (SEM) and transmission electron microscopy (TEM) showed that the active mats are dominated by filamentous and nonfilamentous cyanobacteria in the surface layers and heterotrophic bacteria in deeper layers. Energy dispersive X-ray analysis revealed that copious amounts of extracellular polymeric substances (EPS) are rich in Mg, Si, O, and Ca, likely concentrated from solution. Petrographic microscopy and electron microprobe analysis of the mineralized microbialites showed textures reminiscent of stromatolitic laminations, consisting mainly of alternating calcium carbonate (calcite and aragonite) and magnesium-rich silicate (kerolite). Thin coatings rich in magnesite, hydromagnesite and monohydrocalcite surround the microbialites on the rock surfaces and are likely inorganic in origin. Within the mats, minerals tend to form and concentrate within, or around, dense matrices of EPS. Microenvironments with geochemical conditions favorable for mineral crystallization likely develop in the mats as a result of the mucilaginous extracellular material and the development of bacterial microcolonies. In addition, copious amounts of extracellular polymers bind ions from solution and provide nucleation sites for mineral crystallization and growth. This combination of biological and inorganic processes can explain the occurrence of the secondary minerals in these caves, as well as the stromatolitic textures of the microbialites.
Chemical Geology 09/2000; 169(3). DOI:10.1016/S0009-2541(00)00213-8 · 3.48 Impact Factor