The source of phosphate in the oxidation zone of ore deposits: Evidence from oxygen isotope compositions of pyromorphite

Burmann, Fabian; Keim, Maximilian F.; Oelmann, Yvonne; Teiber, Holger; Marks, Michael A.W.; Markl, Gregor

doi:10.1016/j.gca.2013.07.042

Cited by 13 publications

(8 citation statements)

References 49 publications

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“…Furthermore, due to their extremely low solubility products, they retain this information for a long time, probably even during fluvial transport. The growth of pyromorphite is invariably related to microbial transformation of phosphate ions (Burmann et al 2013). These minerals form a bridge between a physical surface process such as rain or snow melt, the microbial interaction with this circulating surface water, and the transport and precipitation of heavy metals typically (but not necessarily) derived from weathered inorganic ore deposits.…”

Section: Discussionmentioning

confidence: 99%

“…Our data set shows maximum V contents in pyromorphite, mimetite or a member of the hedyphane group of about 0.8 wt% V 2 O 5 corresponding to about 4 mol% of vanadinite and about 15% of phosphate or 15% of arsenate in vanadinite. We assume that our samples formed at or below 30 °C (Burmann et al 2013). …”

Section: Trace Element Compositionmentioning

confidence: 99%

“…The study of Burmann et al (2013) used the oxygen isotope composition of phosphate in pyromorphites from some of the localities also used in the present study to decipher the source of the phosphate. The authors came to the conclusion that most of the phosphate has been biologically modified and that no purely inorganic phosphate (e.g., from apatite dissolution in the host rocks of ore deposits) can be identified in pyromorphites.…”

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Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

Markl

Marks

Holzäpfel

et al. 2014

American Mineralogist

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More than 150 samples of pyromorphite, mimetite, vanadinite, and minerals of the hedyphane-group (which collectively are summarized here under the term PyGM for pyromorphite-group minerals) from the Schwarzwald mining district, southwest Germany, have been analyzed by electron microprobe and LA-ICP-MS. In this largest study of its kind, the relations of PyGM composition to host rock and fluid compositions and the amount of solid solution between the various end-members were investigated. In addition, we report the colors of the many analyzed mineral compositions. Here is a list of the most important results.• Pyromorphite and mimetite are completely miscible.• At conditions of the oxidation zone in ore deposits, the solvus between pyromorphite and vanadinite appears to asymmetrical with up to about 3 mol% of vanadinite component in pyromorphite and up to about 39 mol% of pyromorphite component in vanadinite in cases where both minerals coexist.• Due to a lack of suitable samples, the solvus between vanadinite and mimetite could not be completely constrained, but we report vanadinite analyses with up to 12 mol% mimetite and 8 mol% pyromorphite component.• There is complete miscibility between pyromorphite and phosphohedyphane and between mimetite and hedyphane.• F-rich varieties appear only to exist in hedyphanes and phosphohedyphanes, while pyromorphites, mimetites, and vanadinites are Cl-or OH-dominated.• We report for the first time analyses suggesting the occurrence of an OH-end-member corresponding to mimetite.• While pyromorphites are preferably green and mimetites yellow, this is not at all a diagnostic feature, as many exceptions exist; major elements are not correlated at all with the color of a specific crystal.• Most PyGM are strongly zoned and display, for example, significant variations in Ca that are likely to be related to variations of the compositions of various fluid pulses from which the crystals formed.• PyGM composition is generally uncorrelated with host rock composition, but PyGM enrich other metals like REE, Cr, Sb, Bi, or U up to a factor of 10 6 ; therefore, they can be regarded as very sensitive recorders of the metal inventory of an oxidation zone and they even record metals only present as traces in the primary ore deposit very reliably.• REE patterns of PyGM show significant variability even at one location; this may suggest that each zone of a PyGM crystal records the REE pattern of a single fluid pulse or it may indicate fractionation of the REE during PyGM growth. In the absence of conclusive data, the former possibility appears the more likely one.• PyGM are extremely efficient filters for heavy metals from supergene solutions in and in the vicinity of ore deposits.

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Section: Discussionmentioning

confidence: 99%

Section: Trace Element Compositionmentioning

confidence: 99%

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confidence: 99%

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Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

Markl

Marks

Holzäpfel

et al. 2014

American Mineralogist

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“…7a) compounds are incorporated during pyromorphite precipitation. Note that all P fixed in pyromorphite is considered to be derived from the soil as it seems to be modified by biological activity (see Burmann et al 2013). The phosphorous flux varies with the seasons higher fluxes in the summer and autumn contrast with lower fluxes in the spring and winter.…”

Section: Fluid Evolution Of Natural Water Samplesmentioning

confidence: 99%

“…This feature is used to remediate leadcontaminated soils by adding phosphate to the contaminated site (e.g., Cotter-Howells et al 1994;Ruby et al 1994;Basta and McGowen 2004). Based on oxygen isotopes, Burmann et al (2013) showed that almost the entire quantity of phosphate fixed in pyromorphite is biologically modified. Because of these biological processes it remains unclear, whether there is an important direct inorganic source of phosphate (like dissolution of apatite).…”

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Weathering of galena: Mineralogical processes, hydrogeochemical fluid path modeling, and estimation of the growth rate of pyromorphite

Keim

Markl

2015

American Mineralogist

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In many natural and anthropogenically affected environments, alteration of galena produces thermodynamically more stable secondary lead phases. These secondary minerals control the mobility of the toxic heavy metal lead in water. These textural, paragenetic, and stability relations have not been investigated in detail in the literature yet. An extensive petrographic study of 41 thin sections of weathered, zoned galena and adjacent country rock from the Schwarzwald mining area, southwest Germany, is presented. The observed textures were evaluated using PHREEQC fluid path modeling and sequences of stable secondary mineral assemblages were predicted.The most common secondary (supergene) lead minerals of interest here are cerussite, anglesite, and pyromorphite group minerals (PyGM; pyromorphite, mimetite, and vanadinite). These lead phases show a spatially well-ordered zoned texture around the preexisting/relic galena. Cerussite and anglesite commonly occur either as in situ replacement of galena and/or as euhedral crystals in cavities of former, partially dissolved galena. The PyGM are present either as crusts around the margin of the former/relic galena or are common as infiltration products into the host rock/gangue. During progressive weathering anglesite typically disappears first followed by cerussite. Finally, only the highly insoluble PyGM persist as a perimorphose. Hence, a spatially and temporally zoning texture is formed.Thermodynamic models of various fluid evolution paths using PHREEQC show the influence of temperature, pH, variable P CO2 , phosphorous contents and/or different mineral reactions on the sequence of formation and stability of the secondary lead phases. Already small changes in one or more of these parameters can lead to different mineral assemblages or sequences of secondary lead minerals. Over almost the whole relevant pH range, PyGM are the most stable lead phases, precipitating at very low ion activities explaining their textural position. Whether cerussite or anglesite forms, depends mainly on the pH value of the supergene fluids, which is affected by the quite variable fluid pathways. Furthermore a solubility diagram for a typical near-surface fluid was calculated, showing that anglesite is the most soluble phase, followed by cerussite and PyGM. This again reflects the microscopic observations.As a further step, the time span for the formation of a natural millimeter-thick pyromorphite crust was evaluated using subsoil phosphorous fluxes from the literature. The calculation indicates that millimeter-thick pyromorphite crusts can be formed in few tens to about hundred years, which is in agreement with observations in the nature.In this study, a framework for predicting stable secondary lead mineral assemblages and textures by fluid path modeling is given. These models are potentially important for predicting the retention and mobilization of lead in systems around contaminated sites or natural ore deposits.

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Innovative methods in soil phosphorus research: A review

Kruse

Abraham

Amelung

et al. 2015

J. Plant Nutr. Soil Sci.

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294

195

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Phosphorus (P) is an indispensable element for all life on Earth and, during the past decade, concerns about the future of its global supply have stimulated much research on soil P and method development. This review provides an overview of advanced state-of-the-art methods currently used in soil P research. These involve bulk and spatially resolved spectroscopic and spectrometric P speciation methods (1 and 2D NMR, IR, Raman, Q-TOF MS/MS, high resolution-MS, NanoSIMS, XRF, XPS, (µ)XAS) as well as methods for assessing soil P reactions (sorption isotherms, quantum-chemical modeling, microbial biomass P, enzymes activity, DGT, 33P isotopic exchange, 18O isotope ratios). Required experimental set-ups and the potentials and limitations of individual methods present a guide for the selection of most suitable methods or combinations.

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The source of phosphate in the oxidation zone of ore deposits: Evidence from oxygen isotope compositions of pyromorphite

Cited by 13 publications

References 49 publications

Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

Weathering of galena: Mineralogical processes, hydrogeochemical fluid path modeling, and estimation of the growth rate of pyromorphite

Innovative methods in soil phosphorus research: A review

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