Pasbakhsh P.,Sunway University |
Churchman G.J.,University of Adelaide |
Keeling J.L.,Geological Survey of Western Australia
Applied Clay Science | Year: 2013
There is increasing research interest on new industrial applications for the clay mineral halloysite where greater use is made of its natural tubular morphology, nano-scale diameter and contrasting chemistry on external and internal surfaces. Halloysite nanotubes, commonly referred to as HNTs, have potential applications as microfibre fillers, carriers for the supply and controlled or sustained release of active agents for drug delivery and anticorrosion coatings, in nanoreactors or nanotemplates, and for the uptake of contaminants or pollutants. In this study, various properties were measured on 6 halloysites from different geographical and geological environments from Australia, New Zealand and the USA. From the results, inferences were drawn on their comparative suitability for new uses. The characterisation included identification of impurities by X-ray diffraction (XRD), morphology, surface area and pore volume by electron microscopy and nitrogen absorption, the determination of exchangeable cations, and measurement of zeta potential over a wide range of pH. Halloysite content in individual samples ranged from 84 to 98%. Impurities included minor quartz, cristobalite, kaolinite, gibbsite, alunite, iron oxides and anatase. Variation in halloysite morphology and the levels of impurities had the most effect on surface area and internal pore volume. Samples with low levels of impurities and regular, thin-walled tubes reported the highest pore volumes associated with the cylindrical cavity or lumen in halloysite tubes. Surface areas varied from 22 to 81m2.g-1 and the proportion of pore space associated with the HNT lumen ranged from 11 to 39%. When the properties of the 6 different halloysites were assessed relative to the requirements for halloysite as nanotubes for either additives or carriers, one showed exceptional characteristics for both types of application but it occurs only rarely. Another halloysite that is moderately suitable for use as an additive but not a carrier occurs in a large deposit. The other samples each showed some limitations of suitability for use as an additive and/or as a carrier. © 2012 Elsevier B.V.
Zhou C.H.,Zhejiang University of Technology |
Keeling J.,Geological Survey of Western Australia
Applied Clay Science | Year: 2013
This brief overview comments on recent trends in scientific research and development of clay minerals and was stimulated by the compilation of papers for this special issue to pay tribute to the 34th International Geological Congress held in 2012. The essentially geological context of the conference was a reminder that increased understanding of the genesis and evolution of clays and clay minerals provides insights that have applications in mining, environmental management, paleoclimate, Earth and extraterrestrial sciences. The requirement for multidisciplinary knowledge, including geology, mineralogy, chemistry and materials science, and modern instrumentation and analysis of clay minerals, is essential to a full understanding of the genesis, role and potential new uses for these fine-grained industrial minerals. Latest studies are typically focused on processing and modifying of clay minerals as adsorbents, catalysts, and biomaterials. The emphasis for future work is on advanced clay-based nanomaterials for use in new approaches to sustainable energy, green environment, and human health. © 2013 Elsevier B.V.
Pirajno F.,Geological Survey of Western Australia |
Pirajno F.,University of Western Australia
Journal of Geodynamics | Year: 2010
In the orogenic belts of the Central Asian Orogenic Belt (CAOB), many mafic and felsic plutons are temporally and spatially associated with orogen-scale strike-slip faults. The CAOB is a huge and complex orogenic collage of accreted terranes that was formed in the Early to Mid-Palaeozoic. In the CAOB, orogen-scale strike-slip faults extend for 100-1000. s of kilometres marking the boundaries of tectonic units and terranes. I use examples from southern Siberia and NW China to illustrate the important role that strike-slip faults have in localising intraplate magmatism and associated metallogeny. Cases from the Altay-Sayan in southern Siberia, the Altay and Tianshan orogens in NW China, are compelling for providing good evidence of the control that strike-slip structures exert for the emplacement of magmas and related mineral systems. These strike-slip faults controlled the emplacement of mafic-ultramafic intrusions, alkaline mafic and felsic magmatism in the period 280-240. Ma, which coincides with mantle plume(s) activity that led to the emplacement of the Tarim and Siberian large igneous provinces (LIPs). Mineral systems that are associated with these LIPs include magmatic Ni-Cu in sill-like intrusions, concentrically zoned mafic-ultramafic intrusions (e.g. Kalatongke, the second largest Ni-Cu sulphide deposit in China, after Jinchuan), epithermal systems, breccia pipes, polymetallic hydrothermal veins, granitoid-related greisen and rare earth pegmatites, as well as kimberlite fields. In the Altay-Sayan and NW China regions, orogen-scale translithospheric strike-slip faults provided the channels for the emplacement of magmas, resulting from lateral flow of mantle melts along the base of the lithosphere. This lateral flow is interpreted to have resulted from the impingement of mantle plumes to the base of the lithosphere of what was, to all intents and purposes, a stationary plate. Lateral flow from mantle plumes head was sustained or facilitated, during stages of extension and movements along orogen-scale strike-slip faults. In the Altay-Sayan and NW China, decompression melting of the mantle material produced mafic-ultramafic magmas that were emplaced along the comparatively narrow conduits of the strike-slip zones, forming concentrically zoned complexes that locally, where favourable conditions allowed it (e.g. crustal contamination), host magmatic Ni-Cu sulphides. Flow of mantle melts into translithospheric strike-slip structures also caused partial melting of a thinned and metasomatised lithosphere, resulting in alkaline magmatic products and a wide range of related mineral systems, from polymetallic veins to greisens. Partial melting of the lower crust also produced A-type granitic magmas that locally vented to the surface, forming calderas hosting epithermal and porphyry systems, as observed in NW China. © 2010 Elsevier Ltd.
Hickman A.H.,Geological Survey of Western Australia
Island Arc | Year: 2012
The oldest part of the Pilbara Craton is 3.80-3.55Ga crust. Between 3.53 and 3.22Ga, mantle plume activity resulted in eight successive volcanic cycles forming the Pilbara Supergroup. Large volumes of granitic magma were intruded during the same period. By 3.22Ga, a thick continental crust, the East Pilbara Terrane, had been established. Between 3.22 and 3.16Ga, rifting of the East Pilbara Terrane separated off two additional terranes (Karratha and Kurrana), with intervening basins of oceanic crust. After 3.16Ga, the three terranes began to converge, resulting in both obduction of oceanic crust (Regal Terrane) and, in another area, subduction to form a 3.13Ga island arc (Sholl Terrane). At 3.07Ga, the Karratha, Regal, and Sholl Terranes collided to form the West Pilbara Superterrane, and this collided with the East Pilbara Terrane. The 3.05-2.93Ga De Grey Superbasin was deposited as a succession of basins: Gorge Creek, Whim Creek, Mallina, and Mosquito Creek. Eventual closure of the basins, between 2.94 and 2.93Ga, formed two separate orogenic belts on either side of the East Pilbara Terrane. Post-orogenic granites were intruded between 2.89 and 2.83Ga. The 2.78-2.63Ga Fortescue Basin developed in four stages: (i) rifting of the Pilbara Craton; (ii) folding and erosion; (iii) large igneous province (LIP) volcanism; and (iv) marine sedimentation on a passive margin. A review of all known evidence for early life in the Pilbara Craton is provided. In hydrothermal settings, most of the evidence occurs as filamentous and spheroidal microfossils, organic carbon, microbial mats, and rare stromatolites. By contrast, shallow-water marine sedimentary rocks contain a diverse range of stromatolites, and microbial mats. Lacustrine and shallow-water marine carbonate rocks in the Fortescue Basin contain abundant and morphologically diverse stromatolites, widespread microbial mats, and organic carbon. © 2012 Blackwell Publishing Asia Pty Ltd.
Van Kranendonk M.J.,Geological Survey of Western Australia
Journal of African Earth Sciences | Year: 2011
A thick, upward-younging stratigraphy and presence of crustal contamination in even the oldest rocks of the Barberton greenstone belt precludes crust formation through tectonic stacking of oceanic lithosphere above a subduction zone. Rather, structural and geochronological evidence for simultaneous formation of dome-and-keel structure in the footwall of the belt, greenstone-down extensional shearing and radially inward-plunging lobe-cusp folds around the belt margins, and recumbent folds and thrusts in the core of the belt is uniquely explained by sinking of thick, dense greenstones into partially molten granitic middle crust during partial convective overturn at 3.26-3.22. Ga. High-pressure (P), moderate-temperature (T) metamorphism in vertically-lineated greenstone septae around granite domes contrasts with moderate P-T assemblages in the cores of the same domes in the footwall, reflecting initial sinking of cool greenstone drips from the base of the belt. These data suggest crust formation as a long-lived volcanic plateau affected by intracrustal modification. © 2011.