scholarly journals Dissolution-Repackaging of Hellandite-(Ce), Mottanaite-(Ce)/Ferri-Mottanaite-(Ce)

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 610
Author(s):  
Maria Grazia Perna ◽  
Daria Zaccaria ◽  
Gianluigi Rosatelli ◽  
Francesco Saverio Stoppani ◽  
Ezio Curti ◽  
...  
Keyword(s):  
Molar Fraction ◽  
Element Distribution ◽  
Hydrothermal Fluids ◽  
Group Mineral ◽  
Additional Information ◽  
Secondary Precipitation ◽  
Eu Anomaly ◽  
Mineral Phases ◽  
Co Precipitation

We investigated hellandite-group mineral phases from the Roman Region, alkali syenite ejecta, by multimethod analyses. They show a complex crystallisation history including co-precipitation of hellandite-(Ce) with brockite, resorption, sub-solidus substitution with mottanaite-(Ce), exsolution of perthite-like ferri-mottanaite-(Ce), overgrowth of an oscillatory-zoned euhedral shell of ferri-mottanaite-(Ce) and late, secondary precipitation of pyrochlore in the cribrose hellandite-(Ce) core. LREE/HREE crossover and a negative Eu anomaly in hellandite-group minerals follows fO2 increase during magma cooling. The distinction among the hellandite-group minerals is based on the element distribution in the M1, M2, M3, M4 and T sites. Additional information on miscibility relationship among the hellandite sensu strictu, tadzhikite, mottanaite, ferri-mottanaite and ciprianiite endmembers derives from molar fraction calculation. We observed that change in composition of hellandite-group minerals mimic the ligands activity in carbothermal-hydrothermal fluids related to carbonatitic magmatism.

scholarly journals Spectral Tomography for 3D Element Detection and Mineral Analysis

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 598
Author(s):  
Jose R. A. Godinho ◽  
Gabriel Westaway-Heaven ◽  
Marijn A. Boone ◽  
Axel D. Renno
Keyword(s):  
Energy Spectrum ◽  
3D Imaging ◽  
X Rays ◽  
3D Images ◽  
Characterization Methods ◽  
X Ray ◽  
Additional Information ◽  
Mineral Phases ◽  
Spectral Computed Tomography

This paper demonstrates the potential of a new 3D imaging technique, Spectral Computed Tomography (sp-CT), to identify heavy elements inside materials, which can be used to classify mineral phases. The method combines the total X-ray transmission measured by a normal polychromatic X-ray detector, and the transmitted X-ray energy spectrum measured by a detector that discriminates between X-rays with energies of about 1.1 keV resolution. An analysis of the energy spectrum allows to identify sudden changes of transmission at K-edge energies that are specific of each element. The additional information about the elements in a phase improves the classification of mineral phases from grey-scale 3D images that would be otherwise difficult due to artefacts or the lack of contrast between phases. The ability to identify the elements inside the minerals that compose ore particles and rocks is crucial to broaden the application of 3D imaging in Earth sciences research and mineral process engineering, which will represent an important complement to traditional 2D imaging mineral characterization methods. In this paper, the first applications of sp-CT to classify mineral phases are showcased and the limitations and further developments are discussed.

Genesis of kaolin deposits of Birbhum, West Bengal, India

Clay Minerals ◽  
1969 ◽  
Vol 8 (2) ◽  
pp. 161-170 ◽  
Author(s):  
Bibhuti Mukherjee ◽  
M. G. Rao ◽  
C. Karunakaran
Keyword(s):  
Trace Elements ◽  
West Bengal ◽  
Intimate Relationship ◽  
Element Distribution ◽  
Trace Element Distribution ◽  
Minor And Trace Elements ◽  
Clay Deposit ◽  
Mineral Phases ◽  
Clay Deposits ◽  
Relationship Of

The mineral phases and the distribution of major, minor and trace elements in the clays and bed rocks of two bore-holes at Adda and Chaubatta of the Birbhum area have revealed an intimate relationship of the kaolin-rich clays with the bed-rock of Adda. The possibility of a common origin for the clay deposits at Chaubatta, lying close to the Rajmahal trap formations, and at Adda, lying close to the Archaean boundary, has been inferred from trace element distribution and other factors. A genetic relationship of the clay deposit at Adda with the bed-rock, altered Archaean gneiss, has been established, but there is no significant relationship of the Chaubatta clay deposit with its bed-rock, the weathered basalt.The lateritic cappings above the kaolin-rich clays of Adda and Chaubatta areas are explained as being formed from kaolinite in the weathering sequence as the end-product of intensive desilication under conditions of intensive leaching and increasing acidity near the surface.

scholarly journals Ag-Pb-Sb Sulfosalts and Se-rich Mineralization of Anthony of Padua Mine near Poličany—Model Example of the Mineralization of Silver Lodes in the Historic Kutná Hora Ag-Pb Ore District, Czech Republic

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 430 ◽  
Author(s):  
Pažout ◽  
Sejkora ◽  
Šrein
Keyword(s):  
Solid Solution ◽  
Czech Republic ◽  
Chemical Element ◽  
Hydrothermal Fluids ◽  
Tectonic Events ◽  
Mineral Phases ◽  
Ore Mineralization ◽  
Ore Mineralogy ◽  
Low Sulfidation ◽  
Ore District

Significant selenium enrichment associated with selenides and previously unknown Ag-Pb-Sb, Ag-Sb and Pb-Sb sulfosalts has been discovered in hydrothermal ore veins in the Anthony of Padua mine near Poličany, Kutná Hora ore district, central Bohemia, Czech Republic. The ore mineralogy and crystal chemistry of more than twenty silver minerals are studied here. Selenium mineralization is evidenced by a) the occurrence of selenium minerals, and b) significantly increased selenium contents in sulfosalts. Identified selenium minerals include aguilarite and selenides naumannite and clausthalite. The previously unknown sulfosalts from Kutná Hora are identified: Ag-excess fizélyite, fizélyite, andorite IV, andorite VI, unnamed Ag-poor Ag-Pb-Sb sulfosalts, semseyite, stephanite, polybasite, unnamed Ag-Cu-S mineral phases and uytenbogaardtite. Among the newly identified sulfides is argyrodite; germanium is a new chemical element in geochemistry of Kutná Hora. Three types of ore were recognized in the vein assemblage: the Pb-rich black ore (i) in quartz; the Ag-rich red ore (ii) in kutnohorite-quartz gangue; and the Ag-rich ore (iii) in milky quartz without sulfides. The general succession scheme runs for the Pb-rich black ore (i) as follows: galena – boulangerite (– jamesonite) – owyheeite – fizélyite – Ag-exces fizélyite – andorite IV – andorite VI – freieslebenite – diaphorite – miargyrite – freibergite. For the Ag-rich red ore (ii) and ore (iii) the most prominent pattern is: galena – diaphorite – freibergite – miargyrite – pyragyrite – stephanite – polybasite – acanthite. The parallel succession scheme progresses from Se-poor to Se-rich phases, i.e., galena – members of galena – clausthalite solid solution – clausthalite; miargyrite – Se-rich miargyrite; acanthite – aguilarite – naumannite. A likely source of selenium is in the serpentinized ultrabasic bodies, known in the area of “silver” lodes in the South of the ore district, which may enable to pre-concentrate selenium, released into hydrothermal fluids during tectonic events. The origin of the studied ore mineralization is primarily bound to the youngest stage of mineralization of the whole ore district, corresponding to the Ag-Sb sequence of the ´eb´ ore type of the Freiberg ore district in Saxony (Germany) and shows mineralogical and geochemical similarities to low-sulfidation epithermal-style Ag-Au mineralization.

scholarly journals Ocean Alkalinity Enhancement – Avoiding runaway CaCO<sub>3</sub> precipitation during quick and hydrated lime dissolution

2021 ◽  
Author(s):  
Charly Andre Moras ◽  
Lennart Thomas Bach ◽  
Tyler Cyronak ◽  
Renaud Joannes-Boyau ◽  
Kai Georg Schulz
Keyword(s):  
Hydrated Lime ◽  
Mineral Dissolution ◽  
Atmospheric Co2 ◽  
Natural Seawater ◽  
Co2 Uptake ◽  
Heterogeneous Precipitation ◽  
Critical Knowledge ◽  
Secondary Precipitation ◽  
Mineral Phases ◽  
Carbon Dioxide Co2

Abstract. Ocean Alkalinity Enhancement (OAE) has been proposed as a method to remove carbon dioxide (CO2) from the atmosphere and to counteract ocean acidification. It involves the dissolution of alkaline minerals such as quick lime, CaO, and hydrated lime, Ca(OH)2. However, a critical knowledge gap exists regarding their dissolution in natural seawater. Particularly, how much can be dissolved before secondary precipitation of calcium carbonate (CaCO3) occurs is yet to be established. Secondary precipitation should be avoided as it reduces the atmospheric CO2 uptake potential of OAE. Here we show that both CaO and Ca(OH)2 powders (> 63 µm of diameter) dissolved in seawater within a few hours. However, CaCO3 precipitation, in the form of aragonite, occurred at a saturation (ΩAr) threshold of about 5. This limit is much lower than what would be expected for typical pseudo-homogeneous precipitation in the presence of colloids and organic materials. Secondary precipitation at unexpectedly low ΩAr was the result of so-called heterogeneous precipitation onto mineral phases, most likely onto CaO and Ca(OH)2 prior to full dissolution. Most importantly, this led to runaway CaCO3 precipitation by which significantly more alkalinity (TA) was removed than initially added, until ΩAr reached levels below 2. Such runaway precipitation would reduce the CO2 uptake efficiency from about 0.8 moles of CO2 per mole of TA down to only 0.1 mole of CO2 per mole of TA. Runaway precipitation appears to be avoidable by dilution below the critical ΩAr threshold of 5, ideally within hours of the addition to minimise initial CaCO3 precipitation. Finally, model considerations suggest that for the same ΩAr threshold, the amount of TA that can be added to seawater would be more than three times higher at 5 °C than at 30 °C, and that equilibration to atmospheric CO2 levels during mineral dissolution would further increase it by a factor of ~6 and ~3 respectively.

scholarly journals Neptunium Reactivity During Co-Precipitation and Oxidation of Fe(II)/Fe(III) (Oxyhydr)oxides

Geosciences ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 27 ◽  
Author(s):  
Hannah E. Roberts ◽  
Katherine Morris ◽  
J. Frederick W. Mosselmans ◽  
Gareth T. W. Law ◽  
Samuel Shaw
Keyword(s):  
Green Rust ◽  
Solution Chemistry ◽  
Natural Environments ◽  
Edge Structure ◽  
X Ray ◽  
End Point ◽  
Mineral Phases ◽  
Oxidation In Air ◽  
Co Precipitation ◽  
X Ray Absorption

Fe(II) bearing iron (oxyhydr)oxides were directly co-precipitated with Np(V)O2+ under anaerobic conditions to form Np doped magnetite and green rust. These environmentally relevant mineral phases were then characterised using geochemical and spectroscopic analyses. The Np doped mineral phases were then oxidised in air over 224 days with solution chemistry and end-point oxidation solid samples collected for further characterisation. Analysis using chemical extractions and X-ray absorption spectroscopy (XAS) techniques confirmed that Np(V) was initially reduced to Np(IV) during co-precipitation of both magnetite and green rust. Extended X-Ray Absorption Fine Structure (EXAFS) modelling suggested the Np(IV) formed a bidentate binuclear sorption complex to both minerals. Furthermore, following oxidation in air over several months, the sorbed Np(IV) was partially oxidised to Np(V), but very little remobilisation to solution occurred during oxidation. Here, linear combination fitting of the X-Ray Absorption Near Edge Structure (XANES) for the end-point oxidation samples for both mineral phases suggested approximately 50% oxidation to Np(V) had occurred over 7 months of oxidation in air. Both the reduction of Np(V) to Np(IV) and inner sphere sorption in association with iron (oxyhydr)oxides, and the strong retention of Np(IV) and Np(V) species with these phases under robust oxidation conditions, have important implications in understanding the mobility of neptunium in a range of engineered and natural environments.

scholarly journals Understanding Mineral Liberation during Crushing Using Grade-by-Size Analysis—A Case Study of the Penuota Sn-Ta Mineralization, Spain

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 164 ◽  
Author(s):  
Lorena Guldris Leon ◽  
K. Johan Hogmalm ◽  
Magnus Bengtsson
Keyword(s):  
Mechanical Test ◽  
Element Distribution ◽  
Size Analysis ◽  
Limiting Factor ◽  
Plant Design ◽  
Design And Optimization ◽  
Additional Information ◽  
Mineral Liberation ◽  
The Difference

Coarse comminution test-work and modeling are powerful tools in the design and optimization of mineral processing plants and provide information on energy consumption. Additional information on mineral liberation characteristics can be used for assessing the potential of pre-concentration stages or screens in the plant design. In ores of high-value metals (e.g., Ta, W), standard techniques—such as the mineralogical quantification of grain mounts by quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN) or chemical analysis by X-ray fluorescence (XRF) can be challenging, due to the low relative abundance of such valuable minerals. The cost of QEMSCAN is also a limiting factor, especially considering the large number of samples required for the optimization of coarse comminution. In this study, we present an extended analytical protocol to a well-established mechanical test of interparticle breakage to improve the assessment of coarse mineral liberation characteristics. The liberation of ore minerals is a function of the rock texture and the difference in size and mechanical properties of the valuable minerals relative to gangue minerals and they may fraction in certain grain sizes if they behave differently during comminution. By analyzing the bulk-chemistry of the different grain size fractions produced after compressional testing, and by generating element by size diagrams, it is possible to understand the liberation characteristics of an ore. We show, based on a case study performed on a tantalum ore deposit, that element distribution can be used to study the influence of mechanical parameters on mineral liberation. This information can direct further mineralogical investigation and test work.

Biotechnological Mineral Composites via Vaterite Precursors

2012 ◽  
Vol 1465 ◽  
Author(s):  
E. Weber ◽  
C. Guth ◽  
M. Eder ◽  
P. Bauer ◽  
E. Arzt ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Organic Molecules ◽  
Organic Matrix ◽  
Stable Form ◽  
Ambient Conditions ◽  
Calcium Carbonate Precipitation ◽  
Mineral Phases ◽  
Mineralization Processes ◽  
Co Precipitation

ABSTRACTVaterite is one of the thermodynamically less stable polymorphs of calcium carbonate. Under ambient conditions it transforms into calcite, the most stable form of calcium carbonate. Organisms are able to stabilize minerals such as vaterite by means of organic molecules. The exact mechanisms how biomineralization proteins interact with metastable mineral phases are, however, less well understood. Many in vitro studies were performed using calcite as a model system. A deeper understanding of the interaction of organic molecules with metastable mineral phases would make them useful as a tool to control mineralization processes in vitro. In this study, we report on the co-precipitation of a natively soluble histidine-tagged GFP (green fluorecent protein) with a metastable vaterite phase and the subsequent insolubility of the fluorescent organic matrix in a 30μl calcium carbonate precipitation assay. The intrinsic fluorescence of GFP is conserved during the interaction with the mineral phase, indicating proper folding even in the insoluble state. This experiment can be extended to obtain deeper insights into some mechanistic models of biomineralization proteins by tracking native and modified GFP proteins microscopically during various stages of mineral precipitation and dissolution.

scholarly journals Apatite Composition and U-Pb Geochronology from the Ptarmigan and Tom Deposits, NWT Canada; Implications for Petrogenesis

2021 ◽  
Author(s):  
Mark W. Richardson ◽  
Christopher R.M. McFarlane ◽  
David R. Lentz ◽  
Hendrik Falck
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Gold Deposits ◽  
Hydrothermal Fluids ◽  
Compositional Zoning ◽  
Eu Anomaly ◽  
Shaped Pattern ◽  
Flat Pattern

The Ptarmigan and Tom mesothermal gold deposits are located 10 km to the northeast of the city of Yellowknife, Northwest Territories in northern Canada. Both gold deposits comprise a series of en echelon veins that are hosted within upper greenschist to lower amphibolite facies ~2630 Ma (peak) rocks. Supracrustal units across the craton are intruded by the ca. 2610–2605-Ma granodiorite, tonalite, monzodiorite, quartz diorite, and affiliated rocks of the Concession Suite. Hydrothermal apatite is a common accessory mineral in both mineralized and non-mineralized quartz veins in the metasedimentary host rocks that constitute the Ptarmigan and Tom deposits. This study characterizes and compares turbidite-hosted hydrothermal apatite from the Ptarmigan and Tom deposits, non-mineralized veins adjacent to the ore body, and magmatic apatite from proximal LCT-pegmatites. Using electron probe microanalyses (EPMA), laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), micro-XRF, and cathodoluminescence (CL), the major, minor, and trace element abundances have been quantified and mapped. In addition to utilizing this data to determine if the chemistry of apatite can be used to constrain the source of hydrothermal fluids, the apparent age of the apatite is also evaluated utilizing in situ U-Pb dating. The distribution and abundance of major, minor, and trace elements from in situ recovered apatite were studied to characterize the nature of mineralizing fluids. Most apatite from mineralized and non-mineralized veins show different Mn, Sr, and Pb contents, as well as chondrite-normalized rare-earth element (REE) and Y abundance patterns. REEs display five unique chondrite-normalized patterns: (1) negative sloped pattern with slight negative Eu anomaly, (2) a flat pattern with a positive Eu anomaly, (3) a positive slope with a negative Eu anomaly, (iv) light rare earth element (LREE) depleted pattern with positive Eu anomaly, and (v) bell-shaped pattern with a negative Eu anomaly. The REE patterns reflect both the source of the auriferous hydrothermal fluids and, perhaps, co-precipitating mineral phases. Apatite from the Ptarmigan vein occurs with both: (1) a flat pattern with a positive Eu anomaly and (2) bell-shaped pattern with a negative Eu anomaly. The bell-shaped and flat patterns typify orogenic gold deposits. Vein-hosted apatite commonly displays compositional zoning with a characteristic yellow cathodoluminescence (CL) emission spectra with darker cores and brighter rims. The cores have lower REE, whereas the rims are notably higher in REE. It is thought that the darker cores in CL images reflect a transition from an early low REE hydrothermal fluid to one enriched in REE. The hydrothermal apatite age of 2585 ± 15 Ma is consistent with the intrusions of the 2605 and 2590 Ma two-mica granites of the Prosperous Suite and associated LCT pegmatites.

scholarly journals Carbon nanotube-layered double hydroxide nanocomposites

2014 ◽  
Vol 68 (5) ◽  
Author(s):  
Viktor Tóth ◽  
Mónika Sipiczki ◽  
Valéria Bugris ◽  
Ákos Kukovecz ◽  
Zoltán Kónya ◽  
...  
Keyword(s):  
Carbon Nanotube ◽  
Layered Double Hydroxide ◽  
Element Distribution ◽  
Layer By Layer ◽  
Multiwalled Carbon ◽  
X Ray ◽  
Electron Microscopies ◽  
Transmission Electron ◽  
Co Precipitation ◽  
Double Hydroxide

AbstractPreparation of multiwalled carbon nanotube-layered double hydroxide (MWCNT-LDH) nano-composites by (i) the co-precipitation of LDH components and pristine or surface-treated MWCNT or (ii) the delamination of LDH and application of the layer-by-layer technique has been attempted. For MWCNT, two types of surface treatment were used, either the surface was hydroxylated and deprotonated or wrapped in a tenside (dodecylbenzenesulfonate, DBS). LDH was delaminated by N,N-dimethylformamide. The obtained materials were characterized by X-ray diffractometry (XRD), and by scanning and transmission electron microscopies (SEM and TEM). Element distribution was mapped with help of the X-ray energy dispersive spectroscopy (XEDS) available as an extension of the scanning electron microscope. MWCNT could not be sandwiched between the layers of LDH by any of the methods employed; however, tenside-treated bundles of MWCNT could be wrapped in LDH thus forming a nanocomposite.

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