In situ LA-ICPMS U–Pb dating of cassiterite without a known-age matrix-matched reference material: Examples from worldwide tin deposits spanning the Proterozoic to the Tertiary

Neymark, Leonid A.; Holm-Denoma, Christopher S.; Moscati, Richard J.

doi:10.1016/j.chemgeo.2018.03.008

Cited by 86 publications

(82 citation statements)

References 75 publications

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“…Recent studies (e.g. Liu et al, 2007;Moscati and Neymark, 2019;Neymark et al, 2018;Yuan et al, 2011Yuan et al, , 2008Zhang et 675 https://doi.org/10.5194/gchron-2019-22 Preprint. Discussion started: 16 January 2020 c Author(s) 2020.…”

Section: Discussionmentioning

confidence: 99%

“…Comparison of the ID-TIMS T-W lower intercept dates with the LA-ICP-MS Pb-Pb isochron dates used to derive the fractionation factor (Neymark et al, 2018) indicates an absolute offset ~0.4 % older for the LA-ICP-MS Pb-Pb isochron data. The equivalent ID-TIMS 204 Pb/ 206 Pb-207 Pb/ 206 Pb isochron date for this study yields 1540.9 ± 3.6 Ma that is broadly in concert with that derived by the LA-ICP-MS data (Neymark et al, 2018). 315…”

Section: Spg-iv Ad Hoc Rm Cassiteritementioning

confidence: 98%

“…CC BY 4.0 License. utilised by Neymark et al (2018) for dates that cluster close to Concordia, anchoring the common Pb component of the T-W ischron to the mean 207 Pb/ 206 Pb value of 11 galena analyses from the ore system (1.0104 ± 0.0062) (Larin et al, 1990) generates a lower intercept date of 1536.6 ± 1.0 (MSWD = 1.02).…”

Section: Spg-iv Ad Hoc Rm Cassiteritementioning

confidence: 99%

“…In zircon geochronology a deficit in 206 Pb due to 230 Th disequilibrium (Schärer, 1984) can be reasonably corrected using a reasonable assumption of the mineral/melt partition coefficient or an estimate of melt Th/U, and an estimate of mineral Th/U, typically based on assumed 208 Pb/ 232 Th-206 Pb-238 U concordance for zircon ID-TIMS data. Cassiterite typically has extremely low 232 Th relative to U (Th/U = <10 -4 545 Neymark et al, 2018). This geochemical feature may be derived from preferential partitioning of U into the ore fluids, and/or preferential partitioning of U upon precipitation of cassiterite leading to a deviation from secular equilibrium.…”

Section: Cassiterite U-pb Ages and Effects Of Initial U-th Disequilibmentioning

confidence: 99%

“…A high proportion of LA-ICP-MS U-Pb cassiterite datasets record over-dispersion (e.g. ~2/3 of samples, typically analysed from single crystals, reported by Neymark et al, 2018) suggesting that these are also not strict binary mixtures. We postulate that some of the over-dispersion can be attributed variable initial Pb isotopic compositions within cassiterite that is inherited from the hydrothermal systems.…”

Section: Cassiterite U-pb Ages and Effects Of Initial U-th Disequilibmentioning

confidence: 99%

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High-precision ID-TIMS Cassiterite U-Pb systematics using a low-contamination hydrothermal decomposition: implications for LA-ICP-MS and ore deposit geochronology

Tapster¹,

Bright²

2020

Preprint

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Abstract. Cassiterite (SnO2) is the most common ore phase of Sn. Typically containing 1&#8211;100&#8201;&#181;g/g&#8201;U and relatively low concentrations of common Pb the mineral has been increasingly targeted for U-Pb geochronology, principally via micro-beam methods, to understand the timing and durations of granite related magmatic-hydrothermal systems throughout geological time. However, due to the extreme resistance of cassiterite to most forms of acid digestion, to date, there has been no published method permitting the complete, closed system decomposition of cassiterite under conditions where the basic necessities of measurement by isotope dilution can be met, leading to a paucity of reference, and validation materials. To address this a new low blank (<&#8201;1&#8201;pg Pb) method for the complete acid decomposition of cassiterite utilising HBr in the presence of a mixed U-Pb tracer, U and Pb purification, and TIMS analyses has been developed. Decomposition rates have been experimentally evaluated under a range of conditions. A careful balance of time and temperature is required due to competing effects (e.g. HBr oxidation) yet decomposition of 500&#8201;&#181;m diameter fragments of cassiterite is readily achievable over periods comparable to zircon decomposition. Its acid resistant nature can be turned into an advantage, by leaching common Pb-bearing phases (e.g. sulfides, silicates) without disturbing the U-Pb systematics of the cassiterite lattice. The archetypal Sn-W greisen deposit of Cligga Head, SW England, is used to define accuracy relative to CA-ID-TIMS zircon U-Pb ages and demonstrate the potential of this new method, for resolving high resolution timescales (<&#8201;0.1&#8201;%) of magmatic-hydrothermal systems. However, analyses also indicate that the isotopic composition of initial common Pb varies significantly, both between crystals and within a single crystal. This is attributed to significant fluid-rock interactions and the highly F-rich acidic nature of the hydrothermal system. At micro-beam precision levels, this issue is largely unresolvable and can result in significant inaccuracy in interpreted ages. However, this method can, for the first time, be used to properly characterise suitable reference materials for micro-beam cassiterite U-Pb analyses, thus improving the accuracy of the U-Pb cassiterite chronometer as a whole.

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Section: Discussionmentioning

confidence: 99%

Section: Spg-iv Ad Hoc Rm Cassiteritementioning

confidence: 98%

Section: Spg-iv Ad Hoc Rm Cassiteritementioning

confidence: 99%

Section: Cassiterite U-pb Ages and Effects Of Initial U-th Disequilibmentioning

confidence: 99%

Section: Cassiterite U-pb Ages and Effects Of Initial U-th Disequilibmentioning

confidence: 99%

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High-precision ID-TIMS Cassiterite U-Pb systematics using a low-contamination hydrothermal decomposition: implications for LA-ICP-MS and ore deposit geochronology

Tapster¹,

Bright²

2020

Preprint

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Neoproterozoic tin mineralization in South China: geology and cassiterite U–Pb age of the Baotan tin deposit in northern Guangxi

Zhang

et al. 2019

Miner Deposita

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U–Pb geochronology of tin deposits associated with the Cornubian Batholith of southwest England: Direct dating of cassiterite by in situ LA-ICPMS

Moscati

Neymark

2019

Miner Deposita

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In situ LA-ICPMS U–Pb dating of cassiterite without a known-age matrix-matched reference material: Examples from worldwide tin deposits spanning the Proterozoic to the Tertiary

Cited by 86 publications

References 75 publications

High-precision ID-TIMS Cassiterite U-Pb systematics using a low-contamination hydrothermal decomposition: implications for LA-ICP-MS and ore deposit geochronology

High-precision ID-TIMS Cassiterite U-Pb systematics using a low-contamination hydrothermal decomposition: implications for LA-ICP-MS and ore deposit geochronology

Neoproterozoic tin mineralization in South China: geology and cassiterite U–Pb age of the Baotan tin deposit in northern Guangxi

U–Pb geochronology of tin deposits associated with the Cornubian Batholith of southwest England: Direct dating of cassiterite by in situ LA-ICPMS

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