Quantitative microstructural characterization of natrojarosite scale formed during high-pressure acid leaching of lateritic nickel ore

Timms, Nicholas E.; Li, Jian; Reddy, Steven M.

doi:10.2138/am.2009.3104

Cited by 10 publications

(4 citation statements)

References 33 publications

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“…Such growth is widely recognised in non-geological materials (e.g. Tiller, 1991) and has been observed recently by EBSD in minerals crystallising from melts and fluids (McLaren and Reddy, 2008;Timms et al, 2009).…”

Section: Formation Of Hopper Crystalsmentioning

confidence: 77%

The structure of and origin of nodular chromite from the Troodos ophiolite, Cyprus, revealed using high-resolution X-ray computed tomography and electron backscatter diffraction

Prichard

Barnes

Godel

et al. 2015

Lithos

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Nodular chromite is a characteristic feature of ophiolitic podiform chromitite and there has been much debate about how it forms. Nodular chromite from the Troodos ophiolite in Cyprus is unusual in that it contains skeletal crystals enclosed within the centres of the nodules and interstitial to them. 3D imaging and electron backscatter diffraction have shown that the skeletal crystals within the nodules are single crystals that are surrounded by a rim of polycrystalline chromite. 3D analysis reveals that the skeletal crystals are partially or completely formed cage or hopper structures elongated along the b 111N axis. The rim is composed of a patchwork of chromite grains that are truncated on the outer edge of the rim. The skeletal crystals formed first from a magma supersaturated in chromite and silicate minerals crystallised from melt trapped between the chromite skeletal crystal blades as they grew. The formation of skeletal crystals was followed by a crystallisation event which formed a silicatepoor rim of chromite grains around the skeletal crystals. These crystals show a weak preferred orientation related to the orientation of the core skeletal crystal implying that they formed by nucleation and growth on this core, and did not form by random mechanical aggregation. Patches of equilibrium adcumulate textures within the rim attest to in situ development of such textures. The nodules were subsequently exposed to chromite undersaturated magma resulting in dissolution, recorded by truncated grain boundaries in the rim and a smooth outer surface to the nodule. None of these stages of formation require a turbulent magma. Lastly the nodules impinged on each other causing local deformation at points of contact.

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Section: Formation Of Hopper Crystalsmentioning

confidence: 77%

The structure of and origin of nodular chromite from the Troodos ophiolite, Cyprus, revealed using high-resolution X-ray computed tomography and electron backscatter diffraction

Prichard

Barnes

Godel

et al. 2015

Lithos

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“…4C) and the presence of subgrain boundaries in quartz (Fig. 4E) do not of necessitate high grade crystal-plastic deformation but can be attributed to growth related defects when the crystals grow into an open space (e.g., Timms et al 2009). of 43 The type 2 veins consist of either fibrous or blocky crystals of calcite and are restricted to the Jeerinah Formation.…”

Section: Petrography Of Carbonate Veinsmentioning

confidence: 99%

In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers

Peters

Piazolo

Webb

et al. 2016

Earth and Planetary Science Letters

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The detection of early life signatures using hydrocarbon biomarkers in Precambrian rocks struggles with contamination issues, unspecific biomarkers and the lack of suitable sedimentary rocks due to extensive thermal overprints. Importantly, host rocks must not have been exposed to temperatures above 250°C as at these temperatures biomarkers are destroyed. Here we show that Archean sedimentary rocks from the Jeerinah Formation (2.63 billion years) and Carawine Dolomite (2.55 billion years) of the Pilbara Craton (Western Australia) drilled by the Agouron Institute in 2012, which previously were suggested to be suitable for biomarker studies, were metamorphosed to the greenschist facies. This is higher than previously reported. Both the mineral assemblages (carbonate, quartz, Fe-chlorite, muscovite, microcline, rutile, and pyrite with absence of illite) and chlorite geothermometry suggest that the rocks were exposed to temperatures higher than 300°C and probably ~ 400°C, consistent with greenschist-facies metamorphism. This facies leads to the destruction of any biomarkers and explains why the extraction of hydrocarbon biomarkers from pristine drill cores has not been successful. However, we show that the rocks are 2 of 43 cut by younger formation-specific carbonate veins containing primary oil-bearing fluid inclusions and solid bitumens. Type 1 veins in the Carawine Dolomite consist of dolomite, quartz and solid bitumen, whereas type 2 veins in the Jeerinah Formation consist of calcite. Within the veins fluid inclusion homogenisation temperatures and calcite twinning geothermometry indicate maximum temperatures of ~ 200°C for type 1 veins and ~ 180°C for type 2 veins. Type 1 veins have typical isotopic values for reprecipitated Archean sea-water carbonates, with δ 13 CVPDB ranging from -3‰to 0‰ and δ 18 OVPDB ranging from -13‰ to -7‰, while type 2 veins have isotopic values that are similar to hydrothermal carbonates, with δ 13 CVPDB ranging from -18‰ to -4‰ and δ 18 OVPDB ranging from -18‰ to -12‰. Evidently, the migration and entrapment of hydrocarbons occurred after peak metamorphism under temperatures congruous with late catagenesis and from fluids of different compositions. The relatively high temperatures of vein formation and the known geotectonic history of the rocks analysed suggest a probable minimum age of 1.8 billion years (Paleoproterozoic). Our results demonstrate that post peak-metamorphic veins provide an exciting opportunity in the search for evidence of early life. The integration of petrological and organic geochemical techniques is crucial for any future studies that use biomarkers to reconstruct the early biosphere.

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“…Formation of the low angle boundaries can be part of the recovery process where dislocations in the crystal lattice migrate to form planar arrays of dislocations (Passchier and Trouw, 2005;Trimby et al, 1998) or they can also be formed during mineral growth (Timms et al, 2009). The two main types of the low angle boundaries are 1) tilt and 2) twist boundaries (Fig.…”

Section: Misorientation Boundary Analysismentioning

confidence: 99%

Relationship between microstructures and grain-scale trace element distribution in komatiite-hosted magmatic sulphide ores

Vukmanovic

Reddy

Godel

et al. 2014

Lithos

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Quantitative microstructural characterization of natrojarosite scale formed during high-pressure acid leaching of lateritic nickel ore

Cited by 10 publications

References 33 publications

The structure of and origin of nodular chromite from the Troodos ophiolite, Cyprus, revealed using high-resolution X-ray computed tomography and electron backscatter diffraction

The structure of and origin of nodular chromite from the Troodos ophiolite, Cyprus, revealed using high-resolution X-ray computed tomography and electron backscatter diffraction

In search of early life: Carbonate veins in Archean metamorphic rocks as potential hosts of biomarkers

Relationship between microstructures and grain-scale trace element distribution in komatiite-hosted magmatic sulphide ores

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