ORCID Profile
0000-0002-2281-8896
Current Organisation
University of Brighton
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Publisher: Elsevier BV
Date: 03-2019
Publisher: Geological Society of America
Date: 09-02-2018
DOI: 10.1130/G39801.1
Publisher: Springer Science and Business Media LLC
Date: 18-11-2016
DOI: 10.1038/SREP37377
Abstract: Carbonatites, usually occurring within intra-continental rift-related settings, have strong light rare earth element (LREE) enrichment they rarely contain economic heavy REE (HREE). Here, we report the identification of Late Triassic HREE-Mo-rich carbonatites in the northernmost Qinling orogen. The rocks contain abundant primary HREE minerals and molybdenite. Calcite-hosted fluid inclusions, inferred to represent a magmatic-derived aqueous fluid phase, contain significant concentrations of Mo (~17 ppm), reinforcing the inference that these carbonatitic magmas had high Mo concentrations. By contrast, Late Triassic carbonatites in southernmost Qinling have economic LREE concentrations, but are depleted in HREE and Mo. Both of these carbonatite types have low δ 26 Mg values (−1.89 to −1.07‰), similar to sedimentary carbonates, suggesting a recycled sediment contribution for REE enrichment in their mantle sources. We propose that the carbonatites in the Qinling orogen were formed, at least in part, by the melting of a subducted carbonate-bearing slab, and that 10 Ma younger carbonatite magmas in the northernmost Qinling metasomatized the thickened eclogitic lower crust to produce high levels of HREE and Mo.
Publisher: Informa UK Limited
Date: 03-04-2017
Publisher: Springer Science and Business Media LLC
Date: 25-10-2019
DOI: 10.1038/S41529-019-0099-9
Abstract: Accelerated low water corrosion is a form of marine steel corrosion caused by bacterial activity. It has a global spread and is potentially responsible for billions of pounds of damage. We have determined in detail both the chemistry of corrosion products and the associated microbiology at a UK site. The corrosion products form a layered structure with iron sulfides at the steel surface and iron oxides and sulfates in contact with water. The iron sulfides are formed by reaction of steel with hydrogen sulfide formed by sulfate-reducing bacteria and are oxidised through a series of sulfur oxidation states by sulfide-oxidising bacteria, forming acid at all stages and encompassing the whole of the bacterial sulfur cycle. The bacteria involved are endemic in anoxic bed sediment, and the process is a response to the presence of steel as an electron donor, and the generation of anoxic microenvironments within corrosion products.
Publisher: Mineralogical Society
Date: 11-12-2019
DOI: 10.1180/MGM.2019.79
Abstract: Sulfur-bearing monazite-(Ce) occurs in silicified carbonatite at Eureka, Namibia, forming rims up to ~0.5 mm thick on earlier-formed monazite-(Ce) megacrysts. We present X-ray photoelectron spectroscopy data demonstrating that sulfur is accommodated predominantly in monazite-(Ce) as sulfate, via a clino-anhydrite-type coupled substitution mechanism. Minor sulfide and sulfite peaks in the X-ray photoelectron spectra, however, also indicate that more complex substitution mechanisms incorporating S 2– and S 4+ are possible. Incorporation of S 6+ through clino-anhydrite-type substitution results in an excess of M 2+ cations, which previous workers have suggested is accommodated by auxiliary substitution of OH – for O 2– . However, Raman data show no indication of OH – , and instead we suggest charge imbalance is accommodated through F – substituting for O 2– . The accommodation of S in the monazite-(Ce) results in considerable structural distortion that may account for relatively high contents of ions with radii beyond those normally found in monazite-(Ce), such as the heavy rare earth elements, Mo, Zr and V. In contrast to S-bearing monazite-(Ce) in other carbonatites, S-bearing monazite-(Ce) at Eureka formed via a dissolution–precipitation mechanism during prolonged weathering, with S derived from an aeolian source. While large S-bearing monazite-(Ce) grains are likely to be rare in the geological record, formation of secondary S-bearing monazite-(Ce) in these conditions may be a feasible mineral for dating palaeo-weathering horizons.
Publisher: Geological Society of London
Date: 24-11-2021
Abstract: The Nalunaq deposit, Greenland, is a hypozonal, shear zone-hosted, Au deposit. The shear zone has previously been interpreted as having undergone four stages of deformation, accompanied by fluid flow and vein formation. Coupled with previous trapping T estimates, fluid inclusion data are consistent with the trapping of fluids with salinities between 28 and 45 wt% NaCl equiv., from 300 to 475°C during D 2 and D 3 , with pressure varying between c. 800 and 100 MPa. The range reflects pressure cycling during seismic slip-related depressurization events. D 4 fluids were lower salinity and trapped from 200 to 300°C, at c. 50–200 MPa during late-stage normal faulting. The variation in major element chemistry is consistent with the ingress of hypersaline, granitoid equilibrated fluids into the shear zone system and mixing with fluids that had reacted with the host metamorphic rocks. D 4 -stage fluids represent the ingress of meteoric fluids into the system. Gold contents in inclusion fluids range from c. 300 to 10 mg kg −1 . These data are consistent with the high- P–T solubility of Au as AuHS(H 2 S) 3 0 complexes, and Au deposition by decompression and cooling. The high salinities also suggest Au transport as chloride complexes may have been possible. Gold distribution was modified by the release of chemically bound or nanoscale Au during sulfide oxidation at the D 4 stage.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Martin Smith.