A preliminary assessment of the application of Sr, Nd, Pb, He and N isotope analysis to fluid inclusions in kimberlite olivine: A new approach to trace deep-mantle sources

2020 ◽  
Author(s):  
Andrea Giuliani ◽  
Janne M. Koornneef ◽  
Peter Barry ◽  
Patrizia Will ◽  
Henner Busemann ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Trace Element ◽  
Mass Spectrometer ◽  
Fluid Inclusions ◽  
Noble Gas ◽  
Isotope Analysis ◽  
Helium Isotope ◽  
New Approach ◽  
Deep Mantle ◽  
Mantle Sources

<p>Kimberlites are the deepest melts that reach Earth’s surface and, therefore, can provide unique insights into the composition and evolution of the convective mantle through time. Application of isotope geochemistry to trace the composition of kimberlite sources has thus far been hindered by the ubiquitous alteration and incorporation of xenocrystic material in kimberlite rocks. Bulk-kimberlite analyses are typically considered reliable for Nd and Hf isotopes due to their overwhelmingly higher concentrations in kimberlite melts compared to common mantle and crustal contaminants. Conversely, Sr and Pb isotope compositions of bulk kimberlite samples are seldom considered representative of their parental melts thus requiring analysis of robust magmatic phases, primarily perovskite. Addressing the primary (i.e. magmatic) isotopic composition of volatile elements, such as N and noble gases, requires analyses of volatile-rich phases, and fluid inclusions in olivine represent a typical primary target in mantle-derived magmas. However, fluid inclusions in kimberlitic olivine are dominantly secondary in origin. Secondary inclusions can form at any time after crystallisation of their mineral host, which requires assessment of the origin of trapped fluids (i.e. pristine magmatic fluids, crustal fluids of external derivation, or combination thereof) before their isotopic composition can be used to make inferences about kimberlite mantle sources.</p><p>Here we present trace-element and Sr-Nd-Pb-He-N isotopic compositions of multiple olivine aliquots representing two different magmatic units of the ~88 Ma Wesselton kimberlite (Kimberley, South Africa). The Sr and Nd isotopic composition of olivine analysed by isotope-dilution (ID) TIMS are within the narrow range of perovskite <sup>87</sup>Sr/<sup>86</sup>Sr (0.7043-0.7046) and whole-rock <sup>143</sup>Nd/<sup>144</sup>Nd (eNd<sub>i</sub> = 0.4–2.2) for the Kimberley kimberlites. These results indicate that the secondary fluid inclusions, which dominate the incompatible trace-element budget of olivine separates, have a pristine magmatic origin devoid of crustal contribution.</p><p>Helium isotope compositions were measured by laser heating of 1.6 to 9.8 mg of olivine using an ultrahigh-sensitivity compressor-source noble gas mass spectrometer. <sup>3</sup>He/<sup>4</sup>He ratios are between 1.6 R<sub>A</sub> and 3.7 R<sub>A</sub> (where R<sub>A</sub> indicates the atmospheric <sup>3</sup>He/<sup>4</sup>He ratio), values more radiogenic than MORBs but comparable to HIMU OIBs. These results indicate a high time-integrated (U+Th)/He ratio in the source of the Kimberley kimberlites, which is consistent with the moderately high (i.e. HIMU-like) time-integrated U/Pb ratio implied by elevated initial <sup>206</sup>Pb/<sup>204</sup>Pb in Wesselton olivine (19.1-19.5), Kimberley kimberlites (up to 19.9) and megacrysts in southern African Cretaceous kimberlites (up to 20.5). The combination of low <sup>3</sup>He/<sup>4</sup>He, moderately radiogenic <sup>87</sup>Sr/<sup>86</sup>Sr, and negative d<sup>34</sup>S values (-2.6‰ to -5.7‰) require a contribution from subducted recycled material in the source of the Kimberley kimberlites. Conversely, a preliminary N isotope analysis of Wesselton olivine by in-vacuo crushing using a noble gas mass spectrometer returned a mantle-like d<sup>15</sup>N of -2.9‰, which might suggest limited recycling of surface N (d<sup>15</sup>N >0‰) in the source of these kimberlites. We conclude that the combination of Sr-Nd-Pb and He-N isotope tracing of fluid inclusions in olivine can provide a robust new approach to address the composition of kimberlite sources and, therefore, the evolution of the deep mantle through time.</p>

scholarly journals Technical Note: Noble gas extraction procedure and performance of the Cologne Helix MC Plus multi-collector noble gas mass spectrometer for cosmogenic neon isotope analysis

2021 ◽  
Author(s):  
Benedikt Ritter ◽  
Andreas Vogt ◽  
Tibor J. Dunai
Keyword(s):  
Mass Spectrometer ◽  
Noble Gas ◽  
Primary Standard ◽  
Isotope Analysis ◽  
Extraction Procedure ◽  
Technical Note ◽  
High Mass ◽  
Experimental Setup ◽  
And Performance ◽  
The University

Abstract. We established a new laboratory for noble gas mass spectrometry that is dedicated for the development and application to cosmogenic nuclides at the University of Cologne (Germany). At the core of the laboratory are a state-of-the-art high mass resolution multicollector Helix MCPlus (Thermo-Fisher) noble gas mass spectrometer and a novel custom-designed automated extraction line. The Mass-spectrometer is equipped with five combined Faraday Multiplier collectors, with 1012 Ω and 1013 Ω pre-amplifiers for faraday collectors. We describe the extraction line and the automized operation procedure for cosmogenic neon and the current performance of the experimental setup. Performance tests were conducted using gas of atmospheric isotopic composition (our primary standard gas); as well as CREU-1 intercomparison material, containing a mixture of neon of atmospheric and cosmogenic composition. We use the results from repeated analysis of CREU-1 to assess the performance of the current experimental setup at Cologne. The precision in determining the abundance of cosmogenic 21Ne is equal or better than those reported for other laboratories. The absolute value we obtain for the concentration of cosmogenic 21Ne in CREU is indistinguishable from the published value.

scholarly journals Construction of a Newly Designed Small-Size Mass Spectrometer for Helium Isotope Analysis: Toward the Continuous Monitoring Of 3He/4He Ratios In Natural Fluids

2012 ◽  
Vol 1 (2) ◽  
pp. A0009-A0009 ◽  
Author(s):  
Ken-ichi Bajo ◽  
Hirochika Sumino ◽  
Michisato Toyoda ◽  
Ryuji Okazaki ◽  
Takahito Osawa ◽  
...  
Keyword(s):  
Mass Spectrometer ◽  
Continuous Monitoring ◽  
Isotope Analysis ◽  
Helium Isotope

First assessment of the noble gas and CO2 isotopic composition of fluid inclusions hosted in mantle xenoliths from El Hierro (Canary Islands) 

2021 ◽  
Author(s):  
Andres Sandoval Velasquez ◽  
Andrea Luca Rizzo ◽  
Alessandro Aiuppa ◽  
Maria Luce Frezzotti ◽  
Samantha Remigi ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Oceanic Crust ◽  
Canary Islands ◽  
Fluid Inclusions ◽  
Upper Mantle ◽  
Noble Gas ◽  
Mantle Metasomatism ◽  
Mantle Xenoliths ◽  
Local Source ◽  
El Hierro

<p>Studying the isotopic composition of fluids trapped in mantle xenoliths opens avenues to understanding the origin and cycling of volatiles in the Earth’s upper mantle. Here, we present the first isotopic results for noble gases and CO<sub>2</sub> in fluid inclusions (FI) trapped in mantle xenoliths from El Hierro the youngest island of the Canarian archipelago. Our results are based on 6 mantle xenolith samples (3 Spinel-lherzolites and 3 Spinel-harzburgites) collected from the El Julan cliff valley (Oglialoro et al., 2017), from which we hand-picked crystals of Ol, Opx, and Cpx. Isotopic determinations were performed at the INGV (Sezione di Palermo) noble gas and stable isotopes laboratories, following the preparation methods and analytical procedures described in Rizzo et al. (2018 and references therein).</p><p>The Ne-Ar isotopic compositions reveal the presence of an atmospheric component in the FI. Most of the samples exhibit <sup>4</sup>He/<sup>20</sup>Ne ratios > 60, <sup>20</sup>Ne/<sup>22</sup>Ne ratios between 9.84 and 10.49, <sup>21</sup>Ne/<sup>22</sup>Ne ratios from 0.0295 to 0.0330, and <sup>40</sup>Ar/<sup>36</sup>Ar > 800, suggesting mixing between MORB-like mantle fluids and an air-derived component. We argue this latter may (at least in part) derive from upper mantle recycling of atmospheric fluids via paleo-subduction event(s). Excluding samples possibly affected by diffusive fractionation processes, the average Rc/Ra ratio (<sup>3</sup>He/<sup>4</sup>He ratio corrected for atmospheric contamination) measured in El Hierro xenoliths is ~7.45 + 0.26 Ra, within the MORB range (8 + 1 Ra; Graham, 2002). The He homogeneous signature of these xenoliths agrees well with the <sup>3</sup>He/<sup>4</sup>He compositions previously reported in lava phenocrysts and cumulates (Day and Hilton, 2011) and is slightly below the maximum ratios measured in groundwater samples during the 2012 volcanic unrest (~8.2 Ra; Padron et al., 2013). All these pieces of evidence argue against a primordial source involved in the local lithospheric mantle. Putting these data in the context of previous literature results for FI and surface gases in the Canary Islands (La Palma, La Gomera, Tenerife, Gran Canaria, and Lanzarote), we identify an eastward <sup>3</sup>He/<sup>4</sup>He decreasing trend that parallels a corresponding increase of the oceanic crust thickness. In addition to the mantle heterogeneity, we propose that part of the <sup>3</sup>He/<sup>4</sup>He east-to-west variation along the archipelago is caused by the variable thickness of the oceanic crust (and hence, different interactions with <sup>4</sup>He-rich crustal fluids during emplacement).</p><p>The FI δ<sup>13</sup>C(CO<sub>2</sub>) isotopic composition ranges from -2.38 to -1.23‰ in pyroxenes and -0.2 to +2.0‰ in olivine. These unusually positive δ<sup>13</sup>C compositions support the existence of a recycled crustal carbon component in the local source mantle, likely pointing to mantle metasomatism (Oglialoro et al., 2017) from fluids carrying carbon from subducted sediments and/or altered oceanic crust (AOC).</p>

scholarly journals Technical Note: Noble gas extraction procedure and performance of the Cologne Helix MC Plus multi-collector noble gas mass spectrometer for cosmogenic neon isotope analysis

Geochronology ◽  
2021 ◽  
Vol 3 (2) ◽  
pp. 421-431 ◽  
Author(s):  
Benedikt Ritter ◽  
Andreas Vogt ◽  
Tibor J. Dunai
Keyword(s):  
Mass Spectrometer ◽  
Noble Gas ◽  
Primary Standard ◽  
Isotope Analysis ◽  
Extraction Procedure ◽  
Technical Note ◽  
High Mass ◽  
Thermo Fisher Scientific ◽  
And Performance ◽  
Set Up

Abstract. We established a new laboratory for noble gas mass spectrometry that is dedicated to the development and application to cosmogenic nuclides at the University of Cologne (Germany). At the core of the laboratory are a state-of-the-art high-mass-resolution multicollector Helix MC Plus (Thermo Fisher Scientific) noble gas mass spectrometer and a novel custom-designed automated extraction line. The mass spectrometer is equipped with five combined Faraday multiplier collectors, with 1012 and 1013 Ω pre-amplifiers for faraday collectors. We describe the extraction line and the automated procedure for cosmogenic neon and the current performance of the experimental set-up. Performance tests were conducted using gas of atmospheric isotopic composition (our primary standard gas), as well as CREU-1 intercomparison material, containing a mixture of neon of atmospheric and cosmogenic composition. We use the results from repeated analysis of CREU-1 to assess the performance of the current experimental set-up at Cologne. The precision in determining the abundance of cosmogenic 21Ne is equal to or better than those reported for other laboratories. The absolute value we obtain for the concentration of cosmogenic 21Ne in CREU is indistinguishable from the published value.

scholarly journals New on-line method for water isotope analysis of speleothem fluid inclusions using laser absorption spectroscopy (WS-CRDS)

2014 ◽  
Vol 10 (1) ◽  
pp. 429-467 ◽  
Author(s):  
S. Affolter ◽  
D. Fleitmann ◽  
M. Leuenberger
Keyword(s):  
Isotopic Composition ◽  
Fluid Inclusions ◽  
Isotope Analysis ◽  
Isotope Ratio Mass Spectrometry ◽  
Laser Absorption ◽  
On Line ◽  
Injection Unit ◽  
Water Measurement ◽  
Δd And Δ18o ◽  
Water Gas

Abstract. A new online method to analyse water isotopes of speleothem fluid inclusions using a wavelength scanned cavity ring down spectroscopy (WS-CRDS) instrument is presented. This novel technique allows us to simultaneously measure hydrogen and oxygen isotopes for a released aliquot of water. To do so, we designed a new simple line that allows the on-line water extraction and isotope analysis of speleothem samples. The specificity of the method lies in the fact that fluid inclusions release is made on a standard water background, which mainly improves the δD reliability. To saturate the line, a peristaltic pump continuously injects standard water into the line that is permanently heated to 140 °C and flushed with dry nitrogen gas. This permits instantaneous and complete vaporisation of the standard water resulting in an artificial water background with well-known δD and δ18O values. The speleothem sample is placed into a copper tube, attached to the line and after system stabilisation is crushed using a simple hydraulic device to liberate speleothem fluid inclusions water. The released water is carried by the nitrogen/standard water gas stream directly to a Picarro L1102-i for isotope determination. To test the accuracy and reproducibility of the line and to measure standard water during speleothem measurements a syringe injection unit was added to the line. Peak evaluation is done similarly as in gas chromatography to obtain δD and δ18O isotopic composition of measured water aliquots. Precision is better than 1.5‰ for δD and 0.4‰ for δ18O for water measurement for an extended range (−210 to 0‰ for δD and −27 to 0‰ for δ18O) primarily dependent on the amount of water released from speleothem fluid inclusions and secondarily on the isotopic composition of the sample. The results show that WS-CRDS technology is suitable for speleothem fluid inclusion measurements and gives results that are comparable to Isotope Ratio Mass Spectrometry (IRMS) technique.

scholarly journals Minimising12C3+interference on4He+measurements in a noble gas mass spectrometer

2015 ◽  
Vol 30 (6) ◽  
pp. 1400-1404
Author(s):  
James Schwanethal
Keyword(s):  
Mass Spectrometer ◽  
Noble Gas ◽  
Ion Source ◽  
Helium Isotope ◽  
Isotope Measurements

New insights into interferences on helium isotope measurements, using a noble gas mass spectrometer, as a function of ion source trap current and filament voltage.

Elemental, lead and sulfur isotopic compositions of galena from Kola carbonatites, Russia – implications for melt and mantle evolution

2015 ◽  
Vol 79 (2) ◽  
pp. 219-241 ◽  
Author(s):  
K. Bell ◽  
A. N. Zaitsev ◽  
J. Spratt ◽  
S. Fröjdö ◽  
A. S. Rukhlov
Keyword(s):  
Isotopic Composition ◽  
Mantle Source ◽  
Noble Gas ◽  
Isotope Ratios ◽  
Pb Isotope ◽  
Mantle Evolution ◽  
Isotopic Compositions ◽  
Kola Alkaline Province ◽  
Mantle Sources ◽  
Heterogeneous Mantle

AbstractGalena from four REE-rich (Khibina, Sallanlatvi, Seblyavr, Vuoriyarvi) and REE-poor (Kovdor) carbonatites, as well as hydrothermal veins (Khibina) all from the Devonian Kola Alkaline Province of northwestern Russia was analysed for trace elements and Pb and S isotope compositions. Microprobe analyses show that the only detectable elements in galena are Bi and Ag and these vary from not detectable to 2.23 and not detectable to 0.43 wt.% respectively. Three distinct galena groups can be recognized using Bi and Ag contents, which differ from groupings based on Pb isotope data. The Pb isotope ratios show significant spread with 206Pb/204Pb ratios (16.79 to 18.99), 207Pb/204Pb (15.22 to 15.58) and 208Pb/204Pb ratios (36.75 to 38.62). A near-linear array in a 207Pb/204Pb vs.206Pb/204Pb ratio diagram is consistent with mixing between distinct mantle sources, one of which formed during a major differentiation event in the late Archaean or earlier. The S isotopic composition (δ34S) of galena from carbonatites is significantly lighter (–6.7 to –10.3% Canyon Diablo Troilite (CDT) from REE-rich Khibina, Seblyavr and Vuoriyarvi carbonatites, and – 3.2% CDT from REE-poor Kovdor carbonatites) than the mantle value of 0%. Although there is no correlation between S and any of the Pb isotope ratios, Bi and Ag abundances correlate negatively with δ34S values. The variations in the isotopic composition of Pb are attributed to partial melting of an isotopically heterogeneous mantle source, while those of δ34S (together with Bi and Ag abundances) are considered to be process driven. Although variation in Pb isotope values between complexes might reflect different degrees of interaction between carbonatitic melts and continental crust or metasomatized lithosphere, the published noble gas and C, O, Sr, Nd and Hf isotopic data suggest that the variable Pb isotope ratios are best attributed to isotopic differences preserved within a sub-lithospheric mantle source. Different Pb isotopic compositions of galena from the same complex are consistent with a model of magma replenishment by carbonatitic melts/fluids each marked by quite different Pb isotopic compositions.

Development of an In-Situ Mass Spectrometer for Stable Isotope Analysis

2003 ◽  
Author(s):  
R. T. Short ◽  
Gottfried P. Kibelka ◽  
Robert H. Byrne ◽  
David Hollander
Keyword(s):  
Stable Isotope ◽  
Mass Spectrometer ◽  
Stable Isotope Analysis ◽  
Isotope Analysis
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