Chemical and boron isotopic composition of hydrothermal tourmaline from the Panasqueira W-Sn-Cu deposit, Portugal

Codeço, Marta S.; Weis, Philipp; Trumbull, Robert B.; Pinto, Filipe; Lecumberri-Sánchez, Pilar; Wilke, Franziska

doi:10.1016/j.chemgeo.2017.07.011

Cited by 73 publications

(38 citation statements)

References 46 publications

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“…When the nature of cassiterite-bearing greisen systems, such as Cligga Head, is taken into account, the ability to generate atypical Pbc isotopic compositions is less surprising. Geisenisation at the margins of the 525 cassiterite-bearing veins represents extensive, destructive, fluid-rock interaction and elemental exchange during alteration of host rocks by high temperature ~450-300°C, highly acidic, fluorine-rich (HF) fluids (Burt, 1981;Codeço et al, 2017;Lecumberri-Sanchez et al, 2017). As at Cligga Head, W-Sn greisen bordered vein magmatic-hydrothermal deposits are commonly hosted by, or are proximal to thick continentally derived sedimentary packages that likely 530 represent the source of Sn enrichment prior to magma genesis (Romer and Kroner, 2016).…”

Section: Comparison Of Hf Leached and Non-hf Leached Cassiterite Frommentioning

confidence: 99%

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: Comparison Of Hf Leached and Non-hf Leached Cassiterite Frommentioning

confidence: 99%

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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“…Therefore, to the possible exception of the narrower banding in the large crystals (which could well be explained by self-organization), it must be concluded that the oscillatory zoning in the Panasqueira rutile crystals was essentially developed under external constraints. As crystallization temperature is not expected to have much varied [63], and unless pressure variations exert a major control on element partitioning into the rutile, which is thought to be unlikely, it results that the zoning reflects variations in the composition of the hydrothermal fluid.…”

Section: Oscillatory Zoning: External or Internal Control?mentioning

confidence: 99%

Rutile from Panasqueira (Central Portugal): An Excellent Pathfinder for Wolframite Deposition

et al. 2018

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Abundant W-rich rutile in the tourmalinized wall-rocks from the Panasqueira W-deposit appears to be a marker of the onset of the main wolframite depositing event. Rutile displays spectacular zoning, both sector (SZ) and oscillatory (OZ). An extensive set of compositional data obtained on crystals, beforehand studied using back-scattered electron images and X-ray maps, was used to address (i) the effects of SZ on differential trapping of minor elements, and (ii) the significance of the OZ in deciphering fluid sources and fluid circulation dynamics. Particular attention was paid to Sn, W (Nb, Ta) concentrations in rutile as pathfinders of the W deposition. Concerning the sector zoning, W is more incorporated than (Nb, Ta) onto more efficient faces, whereas Sn contents are nearly not impacted. The net effect of the sector zoning is thus a progressive increase of the relative weight of Sn from pyramid to prism faces, in combination with a less significant increase in the relative weight of Nb + Ta. The oscillatory zoning concerns most minor elements: W, Nb (Ta), Fe, V, Cr and Sn. In the frequent doublets, the clear bands are in general enriched in W relatively to the dark ones, whereas the inverse is true for Nb and Ta. The doublets may be viewed as the result of the successive influx of (i) a W-rich, Nb + Ta poor fluid, abruptly replaced by (or mixed to) (ii) a Nb + Ta-rich and W-poor fluid. The Nb + Ta-rich fluid could be in turn related to a rare-metal granite layer observed atop of the Panasqueira granite.

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“…Targeting of mineralized systems requires the integration of geological, geophysical and geochemical data sets and their interpretation in the light of an ore deposition model (McCuaig et al, 2010;McCuaig and Hronsky, 2014). With the development of analytical tools, mineralogical compositions of both gangue and ore minerals are increasingly used to footprint the presence of proximal orebodies (Belousova et al, 2002;Codeço et al, 2017;Harlaux et al, 2018a;Neiva, 2008). W mineral deposits include quartz veins, stockworks, greisens, skarns and breccia pipes spatially associated with granitic bodies, and are thought to result from magmatic and hydrothermal processes, combined (Bobos et al, 2018;Harlaux et al, 2015;Kelly and Rye, 1979;Ramboz et al, 1985;Smith et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

“…It includes intragranitic (e.g., Smith et al, 1996) and country rock (e.g., Kelly and Rye, 1979) veins with a wide range of geometries, widths and extensions (e.g., Giuliani, 1985). Quartz and wolframite can be accompanied by various gangue (e.g., tourmaline, Codeço et al, 2017) and ore (e.g., cassiterite, Noronha et al, 1992) minerals. Wolframites have compositions ranging from hübnerite (MnWO 4 ) to ferberite (FeWO 4 , e.g., Harlaux et al, 2018a;Lecumberri-Sanchez et al, 2017).…”

Section: Introductionmentioning

confidence: 99%

The H/F ratio as an indicator of contrasted wolframite deposition mechanisms

Michaud

Pichavant

2019

Ore Geology Reviews

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Understanding wolframite deposition mechanisms is a key to develop reliable exploration guides for W. In quartz veins from the Variscan belt of Europe and elsewhere, wolframites have a wide range of compositions, from hübnerite-(MnWO 4 ) to ferberite-rich (FeWO 4 ). Deposition style, source of Mn and Fe, distance from the heat/fluid source and temperature have been proposed to govern the wolframite H/F (hübnerite/ferberite ratio) defined as 100 at. Mn / (Fe + Mn). The Argemela mineralized district, located near the world-class Panasqueira W mine in Portugal, exposes a quartz-wolframite vein system in close spatial and genetic association with a rare-metal granite.Wolframite is absent as a magmatic phase, but W-rich whole-rock chemical data suggest that the granite magma is the source of W. Wolframite occurs as large homogeneous hübnerites (H/F = 64-75%) coexisting with montebrasite, K-feldspar and cassiterite in the latest generation of intragranitic veins corresponding to magmatic fluids exsolved from the granite. Locally, early hübnerites evolve to late more Fe-rich compositions (H/F = 45-55%). In a country rock vein, an early generation of Fe-rich hübnerites (H/F = 50-63%) is followed by late ferberites (H/F = 6-23%). Most Argemela wolframites have H/F ratios lower than at Panasqueira and other Variscan quartz-vein deposits which dominantly host ferberites. In greisens or pegmatitic veins, wolframites generally have intermediate H/F ratios. In those deposits, fluid-rock interactions, either involving country rocks (quartz-veins) or granite (greisens) control W deposition. In contrast, at Argemela, wolframite from intragranitic veins was deposited from a magmatic fluid. Differentiation of highly evolved peraluminous crustal magmas led to high Mn/Fe in the fluid which promoted the deposition of hübnerite. Therefore, the H/F ratio can be used to distinguish between contrasted deposition environments in perigranitic W ore-forming systems. Hübnerite is a simple mineralogical indicator for a strong magmatic control on W deposition.

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Chemical and boron isotopic composition of hydrothermal tourmaline from the Panasqueira W-Sn-Cu deposit, Portugal

Cited by 73 publications

References 46 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

Rutile from Panasqueira (Central Portugal): An Excellent Pathfinder for Wolframite Deposition

The H/F ratio as an indicator of contrasted wolframite deposition mechanisms

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