18 research outputs found
Contrasting mechanisms for crustal sulphur contamination of mafic magma: evidence from dyke and sill complexes from the British Palaeogene Igneous Province
This is the final version of the article. Available from the Geological Society via the DOI in this record.he addition of crustal sulphur to magma can trigger sulphide saturation, a process fundamental to the development of some NiāCuāPGE deposits. In the British Palaeogene Igneous Province, mafic and ultramafic magmas intrude a thick sedimentary sequence offering opportunities to elucidate mechanisms of magmaācrust interaction in a setting with heterogeneous S isotope signatures. We present S-isotopic data from sills and dykes on the Isle of Skye. Sharp contrasts exist between variably light Ī“34S in Jurassic sedimentary sulphide (ā35ā° to ā10ā°) and a local pristine magmatic Ī“34S signature of ā2.3āĀ±ā1.5ā°. Flat-lying sills have restricted Ī“34S (ā5ā° to 0ā°) whereas steeply dipping dykes are more variable (ā0ā° to ā2ā°). We suggest that the mechanism by which magma is intruded exerts a fundamental control on the degree of crustal contamination by volatile elements. Turbulent flow within narrow, steep magma conduits, discordant to sediments, and developed by brittle extension or dilation have maximum contamination potential. In contrast, sill-like conduits emplaced concordantly to sediments show little contamination by crustal S. The province is prospective for NiāCuāPGE mineralization analogous to the sill-hosted Norilāsk deposit, and Cu/Pd ratios of sills and dykes on Skye indicate that magmas had already reached S-saturation before reaching the present exposure level.Sulphur isotope analysis was undertaken at the Scottish Universities
Environment Research Centre (SUERC) and funded by an NERC Isotope
Geosciences Facilities Steering Committee grant (IP-1356-1112). H.S.R.H.
would like to acknowledge the financial support of the Natural Environment
Research Council (NERC) for funding this work (studentship NE/J50029X/1)
and open access publication. A.J.B. is funded by NERC funding of the Isotope
Community Support Facility at SUER
Technical note: Lessons from and best practices for the deployment of the Soil Water Isotope Storage System
Soil water isotope datasets are useful for understanding connections between the hydrosphere, atmosphere, biosphere, and geosphere. However, they have been underproduced because of the technical challenges associated with collecting those datasets. Here, we present the results of testing and automation of the Soil Water Isotope Storage System (SWISS). The unique innovation of the SWISS is that we are able to automatically collect water vapor from the critical zone at a regular time interval and then store that water vapor until it can be measured back in a laboratory setting. Through a series of quality assurance and quality control tests, we tested whether the SWISS is resistant to both atmospheric intrusion and leaking in both laboratory and field settings. We assessed the accuracy and precision of the SWISS through a series of experiments in which water vapor of known composition was introduced into the flasks, stored for 14ād, and then measured. From these experiments, after applying an offset correction to report our values relative to Vienna Standard Mean Ocean Water (VSMOW), we assess the precision of the SWISS to be Ā±0.9āā°Ā and Ā±3.7āā°Ā for Ī“18O and Ī“2H, respectively. We deployed three SWISS units at three different field sites to demonstrate that the SWISS stores water vapor reliably enough that we are able to differentiate dynamics both between the sites as well within a single soil column. Overall, we demonstrate that the SWISS retains the stable isotope composition of soil water vapor for long enough to allow researchers to address a wide range of ecohydrologic questions.</p
Age and Geologic Setting of Quartz Vein-Hosted Gold Mineralization at Curraghinalt, Northern Ireland : Implications for Genesis and Classification
Acknowledgments We are grateful to Dalradian Gold Ltd. for providing the sections for petrographic analysis, geochemical data, and general support. We would also like to thank the following: John Still, Alison Sandison, and Jenny Johnston of the School of Geosciences, University of Aberdeen, for assistance with the SEM studies (JS) and with preparing figures (AS and JJ); NERC for ongoing funding of the Argon Isotope facility at SUERC; Jim Imlach and Ross Dymock at SUERC for technical assistance; and Martin Lee at the School of Geographical and Earth Sciences at the University of Glasgow for use of the SEM/CL equipment. The paper has benefitted significantly from comments by the official reviewers and unofficial reviews by Garth Earls, Jamie Wilkinson, Mark Cooper, and Adrian Boyce, and detailed conversations with Ian Alsop (structural geology of the Sperrins) and Nyree Hill and Gawen Jenkin (gold mineralization in the Caledonides). The authors are entirely responsible for the conclusions expressed.Peer reviewedPublisher PD
Mantle heat drives hydrothermal fluids responsible for carbonate-hosted base metal deposits: evidence from 3He/4He of ore fluids in the Irish Pb-Zn ore district
There is little consensus on whether carbonate-hosted base metal deposits, such as
the world-class Irish Zn+Pb ore field, formed in collisional or extensional tectonic
settings. Helium isotopes have been analysed in ore fluids trapped in sulphides
samples from the major base metal deposits of the Irish Zn-Pb ore field in order to
quantify the involvement of mantle-derived volatiles, that require melting to be realised,
as well as test prevailing models for the genesis of the ore fields. 3He/4He ratios
range up to 0.2 Ra, indicating that a small but clear mantle helium contribution is
present in the mineralising fluids trapped in galena and marcasite. Sulfides from ore
deposits with the highest fluid inclusion temperatures (~200Ā°C) also have the highest
3He/4He (> 0.15 Ra). Similar 3He/4He are recorded in fluids from modern continental
regions that are undergoing active extension. By analogy we consider that the
hydrothermal fluids responsible for the carbonate-hosted Irish base metal
mineralization circulated in thinned continental crust, undergoing extension, and
demonstrates that enhanced mantle heat flow is ultimately responsible for driving fluid
convection
InterCarb: a community effort to improve interlaboratory standardization of the carbonate clumped isotope thermometer using carbonate standards
Increased use and improved methodology of carbonate clumped isotope thermometry has greatly enhanced our ability to interrogate a suite of Earth-system processes. However, interlaboratory discrepancies in quantifying carbonate clumped isotope (Ī47) measurements persist, and their specific sources remain unclear. To address interlaboratory differences, we first provide consensus values from the clumped isotope community for four carbonate standards relative to heated and equilibrated gases with 1,819 individual analyses from 10 laboratories. Then we analyzed the four carbonate standards along with three additional standards, spanning a broad range of Ī“47 and Ī47 values, for a total of 5,329 analyses on 25 individual mass spectrometers from 22 different laboratories. Treating three of the materials as known standards and the other four as unknowns, we find that the use of carbonate reference materials is a robust method for standardization that yields interlaboratory discrepancies entirely consistent with intralaboratory analytical uncertainties. Carbonate reference materials, along with measurement and data processing practices described herein, provide the carbonate clumped isotope community with a robust approach to achieve interlaboratory agreement as we continue to use and improve this powerful geochemical tool. We propose that carbonate clumped isotope data normalized to the carbonate reference materials described in this publication should be reported as Ī47 (I-CDES) values for Intercarb-Carbon Dioxide Equilibrium Scale
Mantle heat drives hydrothermal fluids responsible for carbonate-hosted base metal deposits: evidence from 3He/4He of ore fluids in the Irish Pb-Zn ore district
There is little consensus on whether carbonate-hosted base metal deposits, such as
the world-class Irish Zn+Pb ore field, formed in collisional or extensional tectonic
settings. Helium isotopes have been analysed in ore fluids trapped in sulphides
samples from the major base metal deposits of the Irish Zn-Pb ore field in order to
quantify the involvement of mantle-derived volatiles, that require melting to be realised,
as well as test prevailing models for the genesis of the ore fields. 3He/4He ratios
range up to 0.2 Ra, indicating that a small but clear mantle helium contribution is
present in the mineralising fluids trapped in galena and marcasite. Sulfides from ore
deposits with the highest fluid inclusion temperatures (~200Ā°C) also have the highest
3He/4He (> 0.15 Ra). Similar 3He/4He are recorded in fluids from modern continental
regions that are undergoing active extension. By analogy we consider that the
hydrothermal fluids responsible for the carbonate-hosted Irish base metal
mineralization circulated in thinned continental crust, undergoing extension, and
demonstrates that enhanced mantle heat flow is ultimately responsible for driving fluid
convection
How did it get there? Searching for "the feeder" at the Navan Zn+Pb deposit, Ireland
No abstract available
The age and geological setting of quartz vein-hosted gold mineralisation at Curraghinalt, Northern Ireland: Implications for genesis and classification.
How did it get there? Searching for "the feeder" at the Navan Zn+Pb deposit, Ireland
No abstract available