scholarly journals Influence of Genetic Processes on Geochemistry of Fe-oxy-hydroxides in Supergene Zn Non-Sulfide Deposits

Minerals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 602
Author(s):  
Licia Santoro ◽  
Francesco Putzolu ◽  
Nicola Mondillo ◽  
Maria Boni ◽  
Richard Herrington
Keyword(s):  
Trace Element ◽  
Trace Element Composition ◽  
Sulfide Ores ◽  
Critical Metals ◽  
Ore Formation ◽  
Sulfide Deposits ◽  
Icp Ms ◽  
Wide Range ◽  
Significant Enrichment ◽  
Specific Association

In supergene Zn non-sulfide deposits, the Fe-oxy-hydroxides (FeO/OH) are mainly concentrated in the residual zones (gossan) on top of the oxidized ore bodies, although they can also be found throughout the whole weathering profile coexisting with the primary and secondary ore assemblages. Fe-oxy-hydroxides are rarely pure as they form in systems where a wide range of metals, most of them of economic importance (e.g., Zn, Pb, Co, REE, Sc, Ga, Ge, V, etc.), freely circulate and can be “captured” under specific conditions. Although their occurrence can be widespread, and they have a potential to scavenge and accumulate critical metals, FeO/OH are considered gangue phases during the existing processing routes of Zn non-sulfide ores. Moreover, very little is known about the role of the deposit type on the geochemistry of FeO/OH formed in a specific association. Therefore, this paper provides a comprehensive assessment of the trace element footprint of FeO/OH from a number of Zn non-sulfide deposits, in order to define parameters controlling the metals’ enrichment process in the mineral phase. To achieve this, we selected FeO/OH-bearing mineralized samples from four supergene Zn non-sulfide ores in diverse settings, namely Hakkari (Turkey), Jabali (Yemen), Cristal (Peru) and Kabwe (Zambia). The petrography of FeO/OH was investigated by means of scanning electron microscope energy dispersive analysis (SEM-EDS), while the trace element composition was assessed using laser ablation-ICP-MS (LA-ICP-MS). Statistical analyses performed on LA-ICP-MS data defined several interelement associations, which can be ascribed to the different nature of the studied deposits, the dominant ore-formation process and subsequent evolution of the deposits and the environmental conditions under which FeO/OH phases were formed. Based on our results, the main new inferences are: (A) Zinc, Si, Pb, Ga and Ge enrichment in FeO/OH is favored in ores where the direct replacement of sulfides is the dominant process and/or where the pyrite is abundant (e.g., Cristal and Hakkari). (B) When the dissolution of the host-rock is a key process during the supergene ore formation (i.e., Jabali), the buffering toward basic pH of the solutions favors the uptake in FeO/OH of elements leached from the host carbonate rock (i.e., Mn), whilst restricting the uptake of elements derived from the dissolution of sulfides (i.e., Zn, Pb, Ga and Ge), as well as silica. (C) The input of exotic phases can produce significant enrichment in “unconventional” metals in FeO/OH (i.e., Cr and Co at Kabwe; Y at Cristal) depending on whether the optimal pH-Eh conditions are attained. (D) In the Kabwe deposit, FeO/OH records heterogeneous geochemical conditions within the system: where locally basic conditions prevailed during the alteration process, the V and U concentration in FeO/OH is favored; yet conversely, more acidic weathering produced Zn- and Si-bearing FeO/OH.

Deconvolution of the composition of fine-grained pyrite in sedimentary matrix by regression of time-resolved LA-ICP-MS data

2020 ◽  
Vol 105 (6) ◽  
pp. 820-832 ◽  
Author(s):  
Aleksandr S. Stepanov ◽  
Leonid V. Danyushevsky ◽  
Ross R. Large ◽  
Indrani Mukherjee ◽  
Irina A. Zhukova
Keyword(s):  
Trace Elements ◽  
Regression Analysis ◽  
Trace Element ◽  
Sedimentary Rocks ◽  
Trace Element Composition ◽  
Element Composition ◽  
Silicate Matrix ◽  
Time Resolved ◽  
Icp Ms ◽  
Wide Range

Abstract Pyrite is a common mineral in sedimentary rocks and is the major host for many chalcophile trace elements utilized as important tracers of the evolution of the ancient hydrosphere. Measurement of trace element composition of pyrite in sedimentary rocks is challenging due to fine-grain size and intergrowth with silicate matrix and other sulfide minerals. In this contribution, we describe a method for calculation of trace element composition of sedimentary pyrite from time-resolved LA-ICP-MS data. The method involves an analysis of both pyrite and pyrite-free sediment matrix, segmentation of LA-ICP-MS spectra, normalization to total, regression analysis of dependencies between the elements, and calculation of normalized composition of the mineral. Sulfur is chosen as an explanatory variable, relative to which all regressions are calculated. The S content value used for calculation of element concentrations from the regressions is calculated from the total, eliminating the need for independent constraints. The algorithm allows efficient measurement of concentrations of multiple chalcophile trace elements in pyrite in a wide range of samples, including quantification of detection limits and uncertainties while excluding operator bias. The data suggest that the main sources of uncertainties in pyrite composition are sample heterogeneity and counting statistics for elements of low abundance. The analysis of regression data of time-resolved LA-ICP-MS measurements could provide new insights into the geochemistry of the sedimentary rocks and minerals. It allows quantification of ratios of elements that do not have reference material available (such as Hg) and provides estimates on the content of non-sulfidic Fe in the silicate matrix. Regression analysis of the mixed LA-ICP-MS signal could be a powerful technique for deconvolution of phase compositions in complex multicomponent samples.

scholarly journals Composition of iron oxides in Archean and Paleoproterozoic mafic-ultramafic hosted Ni-Cu-PGE deposits in northern Fennoscandia: application to mineral exploration

2020 ◽  
Vol 55 (8) ◽  
pp. 1515-1534
Author(s):  
M. Moilanen ◽  
E. Hanski ◽  
J. Konnunaho ◽  
T. Törmänen ◽  
S.-H. Yang ◽  
...  
Keyword(s):  
Trace Element ◽  
Iron Oxides ◽  
Oxide Phase ◽  
Massive Sulfide ◽  
Sulfide Liquid ◽  
Monosulfide Solid Solution ◽  
Sulfide Deposits ◽  
Northern Fennoscandia ◽  
Pge Mineralization ◽  
Wide Range

Abstract Using electron probe microanalyzer (EPMA) and laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS), we analyzed major and trace element compositions of iron oxides from Ni-Cu-PGE sulfide deposits hosted by mafic-ultramafic rocks in northern Fennoscandia, mostly focusing on Finland. The main research targets were the Archean Ruossakero Ni-(Cu) deposit; Tulppio dunite and related Ni-PGE mineralization; Hietaharju, Vaara, and Tainiovaara Ni-(Cu-PGE) deposits; and Paleoproterozoic Lomalampi PGE-(Ni-Cu) deposit. In addition, some reference samples from the Pechenga (Russia), Jinchuan (China), and Kevitsa (Finland) Ni-Cu-PGE sulfide deposits, and a barren komatiite sequence in the Kovero area (Finland) were studied. Magnetite and Cr-magnetite show a wide range of trace element compositions as a result of the variation of silicate and sulfide melt compositions and their post-magmatic modification history. Most importantly, the Ni content in oxide shows a positive correlation with the Ni tenor of the sulfide phase in equilibrium with magnetite, regardless of whether the sulfide assemblage is magmatic or post-magmatic in origin. The massive sulfide samples contain an oxide phase varying in composition from Cr-magnetite to magnetite, indicating that Cr-magnetite can crystallize directly from sulfide liquid. The Mg concentration of magnetites in massive sulfide samples is lowest among the samples analyzed, and this can be regarded as a diagnostic feature of an oxide phase crystallized together with primitive Fe-rich MSS (monosulfide solid solution). Our results show that magnetite geochemistry, plotted in appropriate discrimination diagrams, together with petrographical observations could be used as an indicator of potential Ni-(Cu-PGE) mineralization.

scholarly journals Encrustation and trace element composition of <i>Neogloboquadrina dutertrei</i> assessed from single chamber analyses, implications for paleotemperature estimates

2012 ◽  
Vol 9 (8) ◽  
pp. 10615-10644 ◽  
Author(s):  
L. Jonkers ◽  
L. J. de Nooijer ◽  
G.-J. Reichart ◽  
R. Zahn ◽  
G.-J. A. Brummer
Keyword(s):  
Trace Element ◽  
Planktonic Foraminifera ◽  
Trace Element Composition ◽  
Element Composition ◽  
Dominant Factor ◽  
Temperature Changes ◽  
Icp Ms ◽  
Neogloboquadrina Dutertrei ◽  
Crust Thickness ◽  
Outer Crust

Abstract. Crust formation is a common phenomenon in planktonic foraminifera. Because of their different formation mechanism and hence composition, crusts affect the overall test composition and therefore complicate the use of crust-bearing foraminifera in paleoceanography. Such species are often used to estimate subsurface paleotemperatures and although the influence of the crust on the trace element/Ca ratio is recognised, it has not been systematically explored between and within tests. Here we use laser ablation ICP-MS to assess the variability in trace element composition of the crust of Neogloboquadrina dutertrei within individual chambers, as well as the effect of compositional heterogeneity of the crust on whole test chemistry. Compositionally, the outer crust differs from inner layer by lower Mg/Ca and Mn/Ca, but is indistinguishable in Sr/Ca. Crust thickness decreases towards the younger chambers and it may be entirely absent from the last chamber. In contrast to Mn/Ca and Sr/Ca, crustal Mg/Ca ratios show a tendency towards higher values on the younger chambers. These patterns in crust thickness and in crust Mg/Ca indicates that temperature is not the dominant factor controlling crust composition. Temperature estimates based on N. dutertrei, and presumably other crust-forming species too, are therefore biased towards too low values. Through comparison of modern and glacial tests we show that this bias is not constant and that changes in the crust thickness and/or in the Mg/Ca values can spuriously suggest temperature changes.

scholarly journals Texture and Trace Element Composition of Rutile in Orogenic Gold Deposits

2021 ◽  
Vol 116 (8) ◽  
pp. 1865-1892
Author(s):  
Marjorie Sciuba ◽  
Georges Beaudoin
Keyword(s):  
Trace Element ◽  
Trace Element Composition ◽  
Gold Deposits ◽  
Element Composition ◽  
Partial Least Square ◽  
Orogenic Gold ◽  
Orogenic Gold Deposits ◽  
Hydrothermal Deposits ◽  
Wide Range ◽  
Strong Control

Abstract Rutile from a wide range of orogenic gold deposits and districts, including representative world-class deposits, was investigated for its texture and trace element composition using scanning electron microscopy, electron probe microanalysis, and laser ablation-inductively coupled plasma-mass spectrometry. Deposits are hosted in various country rocks including felsic to ultramafic igneous rocks and sedimentary rocks, which were metamorphosed from lower greenschist to middle amphibolite facies and with ages of mineralization that range from Archean to Phanerozoic. Rutile presents a wide range of size, texture, and chemical zoning. Rutile is the dominant TiO2 polymorph in orogenic gold mineralization. Elemental plots and partial least square-discriminant analysis suggest that the composition of the country rocks exerts a strong control on concentrations of V, Nb, Ta, and Cr in rutile, whereas the metamorphic facies of the country rocks controls concentrations of V, Zr, Sc, U, rare earth elements, Y, Ca, Th, and Ba in rutile. The trace element composition of rutile in orogenic gold deposits can be distinguished from rutile in other deposit types and geologic settings. Elemental ratios Nb/V, Nb/Sb, and Sn/V differentiate the rutile trace element composition of orogenic gold deposits compared with those from other geologic settings and environments. A binary plot of Nb/V vs. W enables distinction of rutile in metamorphic-hydrothermal and hydrothermal deposits from rutile in magmatic-hydrothermal deposits and magmatic environments. The binary plot Nb/Sb vs. Sn/V distinguishes rutile in orogenic gold deposits from other geologic settings and environments. Results are used to establish geochemical criteria to constrain the source of rutile for indicator mineral surveys and potentially guide mineral exploration.

scholarly journals Advanced in situ geochronological and trace element microanalysis by laser ablation techniques

2006 ◽  
Vol 10 ◽  
pp. 25-28 ◽  
Author(s):  
Dirk Frei ◽  
Julie A. Hollis ◽  
Axel Gerdes ◽  
Dan Harlov ◽  
Christine Karlsson ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Laser Ablation ◽  
Trace Element ◽  
Inductively Coupled Plasma ◽  
Age Dating ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Wide Range ◽  
Plasma Mass Spectrometry

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was developed in 1985 and the first commercial laser ablation systems were introduced in the mid 1990s. Since then, LA-ICP-MS has become an important analytical tool in the earth sciences. Initially, the main interest for geologists was in its ability to quantitatively determine the contents of a wide range of elements in many minerals at very low concentrations (a few ppm and below) with relatively high spatial resolution (spot diameters of typically 30–100 μm). The potential of LA-ICP-MS for rapid in situ U–Th–Pb geochronology was already realised in the early to mid 1990s. However, the full potential of LA-ICP-MS as the low-cost alternative to ion-microprobe techniques for highly precise and accurate in situ U–Th–Pb age dating was not realised until the relatively recent advances in laser technologies and the introduction of magnetic sectorfield ICP-MS (SF-ICPMS) instruments. In March 2005, the Geological Survey of Denmark and Greenland (GEUS) commissioned a new laser ablation magnetic sectorfield inductively coupled plasma mass spectrometry (LA-SF-ICP-MS) facility employing a ThermoFinnigan Element2 high resolution magnetic sectorfield ICP-MS and a Merchantek New Wave 213 nm UV laser ablation system. The new GEUS LA-SF-ICP-MS facility is widely used on Survey research projects in Denmark and Greenland, as well as in collaborative research and contract projects conducted with partners from academia and industry worldwide. Here, we present examples from some of the these ongoing studies that highlight the application of the new facility for advanced geochronological and trace element in situ microanalysis of geomaterials. The application of LASF-ICP-MS based in situ zircon geochronology to regional studies addressing the Archaean geology of southern West Greenland is presented by Hollis et al. (2006, this volume).

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