The Saint-Honoré Carbonatite REE Zone, Québec, Canada: Combined Magmatic and Hydrothermal Processes

The Saint-Honoré carbonatite complex hosts a rare earth element (REE) deposit traditionally interpreted as being produced by late-stage hydrothermal fluids that leached REE from apatite or dolomite found in the early units and concentrated the REE in the late-stage units. New evidence from deeper units suggest that the Fe-carbonatite was mineralized by a combination of both magmatic and hydrothermal crystallization of rare earth minerals. The upper Fe-carbonatite has characteristics typical of hydrothermal mineralization—polycrystalline clusters hosting bastnäsite-(Ce), which crystallized radially from carbonate or barite crystals, as well as the presence of halite and silicification within strongly brecciated units. However, bastnäsite-(Ce) inclusions in primary magmatic barite crystals have also been identified deeper in the Fe-carbonatite (below 1000 m), suggesting that primary crystallization of rare earth minerals occurred prior to hydrothermal leaching. Based on the intensity of hydrothermal brecciation, Cl depletion at depth and greater abundance of secondary fluid inclusions in carbonates in the upper levels, it is interpreted that hydrothermal activity was weaker in this deepest portion, thereby preserving the original magmatic textures. This early magmatic crystallization of rare earth minerals could be a significant factor in generating high-volume REE deposits. Crystallization of primary barite could be an important guide for REE exploration.

Download Full-text

Fluid-rock interaction in the Kangankunde Carbonatite Complex, Malawi: SEM based evidence for late stage pervasive hydrothermal mineralisation

Open Geosciences ◽

10.2478/s13533-012-0192-x ◽

2014 ◽

Vol 6 (4) ◽

Cited By ~ 4

Author(s):

Raymond Duraiswami ◽

Tahira Shaikh

Keyword(s):

Rare Earth ◽

Late Stage ◽

Hydrothermal Activity ◽

Carbonatite Complex ◽

Alkali Chloride ◽

Rock Interaction ◽

The World ◽

Dissolution Corrosion ◽

Textural Evidence ◽

Rock Texture

AbstractThe Kangankunde Carbonatite Complex from the Cretaceous Chilwa Alkaline Province in southern Malawi contains ankeritic and siderite carbonatite that are affected by late stage remobilisation by a carbothermal or hydrothermal fluid. The coarse pegmatitic siderite carbonatite that hosts exotic minerals like monazite, synchysite, bastnasite, strontianite and apatite in vugs and cavities constitutes some of the richest rare earth deposits in the world. Besides these minerals, our studies reveal the presence of collinsite and aragonite from the siderite carbonatite. Fine drusy monazites are seen as overgrowths on thin veinlets of siderite within the rare earth mineralised zones. We present unambiguous SEM-based surface textural evidence such as presence of dissolution-corrosion features like etching along cleavage, solution channels, solution pits, sinstered scaly surface, etc. along with rare earth mineralisation that suggests the exotic minerals in the siderite carbonatite did not crystallise from carbonate magma and are a result of sub-solidus processes involving carbonatite-derived fluids. We believe that the monazite-synchysitebastnasite-strontianite-collinsite assemblages were formed by juvenile post magmatic hydrothermal alteration of pre-existing carbonatite by a complex CO2-rich and alkali chloride-carbonate-bearing fluid at ∼250 to 400°C in an open system. This late ‘magmatic’ to ‘hydrothermal’ activity was responsible for considerable changes in rock texture and mineralogy leading to mobility of rare earth elements during fluid-rock interaction. These aspects need to be properly understood and addressed before using trace and rare earth element (REE) geochemistry in interpreting carbonatite genesis.

Download Full-text

Rare-earth mobility as a result of multiple phases of fluid activity in fenite around the Chilwa Island Carbonatite, Malawi

Mineralogical Magazine ◽

10.1180/minmag.2017.081.007 ◽

2017 ◽

Vol 81 (6) ◽

pp. 1367-1395 ◽

Cited By ~ 9

Author(s):

Emma Dowman ◽

Frances Wall ◽

Peter J. Treloar ◽

Andrew H. Rankin

Keyword(s):

Rare Earth ◽

Inductively Coupled Plasma ◽

Raw Materials ◽

Schematic Model ◽

Carbonatite Complex ◽

Inductively Coupled ◽

Rare Earth Minerals ◽

Plasma Mass Spectrometry ◽

Rare Earth Mineral ◽

The Rare Earth

AbstractCarbonatites are enriched in critical raw materials such as the rare-earth elements (REE), niobium, fluorspar and phosphate. A better understanding of their fluid regimes will improve our knowledge of how to target and exploit economic deposits. This study shows that multiple fluid phases penetrated the surrounding fenite aureole during carbonatite emplacement at Chilwa Island, Malawi. The first alkaline fluids formed the main fenite assemblage and later microscopic vein networks contain the minerals of potential economic interest such as pyrochlore in high-grade fenite and rare-earth minerals throughout the aureole. Seventeen samples of fenite rock from the metasomatic aureole around the Chilwa Island carbonatite complex were chosen for study. In addition to the main fenite assemblage of feldspar and aegirine ± arfvedsonite, riebeckite and richterite, the fenite contains micro-mineral assemblages including apatite, ilmenite, rutile, magnetite, zircon, rare-earth minerals and pyrochlore in vein networks. Petrography using a scanning electron microscope in energy-dispersive spectroscopy mode showed that the rare-earth minerals (monazite, bastnäsite and parisite) formed later than the fenite feldspar, aegirine and apatite and provide evidence ofREEmobility into all grades of fenite. Fenite apatite has a distinct negative Eu anomaly (determined by laser ablation inductively coupled plasma mass spectrometry) that is rare in carbonatite-associated rocks and interpreted as related to pre-crystallization of plagioclase and co-crystallization with K-feldspar in the fenite. The fenite minerals have consistently higher midREE/lightREEratios (La/Sm ≈ 1.3 monazite, ≈ 1.9 bastnäsite, ≈ 1.2 parisite) than their counterparts in the carbonatites (La/Sm ≈ 2.5 monazite, ≈ 4.2 bastnäsite, ≈ 3.4 parisite). Quartz in the low- and medium-grade fenite hosts fluid inclusions, typically a few micrometres in diameter, secondary and extremely heterogeneous. Single phase, 2- and 3-phase, single solid and multi solid-bearing examples are present, with 2-phase the most abundant. Calcite, nahcolite, burbankite and baryte were found in the inclusions. Decrepitation of inclusions occurred at ∼200°C before homogenization but melting-temperature data indicate that the inclusions contain relatively pure CO2. A minimum salinity of ∼24 wt.% NaCl equivalent was determined. Among the trace elements in whole-rock analyses, enrichment in Ba, Mo, Nb, Pb, Sr, Th and Y and depletion in Co, Hf and V are common to carbonatite and fenite but enrichment in carbonatitic type elements (Ba, Nb, Sr, Th, YandREE) generally increases towards the inner parts of the aureole. A schematic model contains multiple fluid events, related to first and second boiling of the magma, accompanying intrusion of the carbonatites at Chilwa Island, each contributing to the mineralogy and chemistry of the fenite. The presence of distinct rare-earth mineral microassemblages in fenite at some distance from carbonatite could be developed as an exploration indicator ofREEenrichment.

Download Full-text

REE Enrichment during Magmatic–Hydrothermal Processes in Carbonatite-Related REE Deposits: A Case Study of the Weishan REE Deposit, China

Minerals ◽

10.3390/min10010025 ◽

2019 ◽

Vol 10 (1) ◽

pp. 25 ◽

Cited By ~ 3

Author(s):

Yu-heng Jia ◽

Yan Liu

Keyword(s):

Rare Earth ◽

Late Stage ◽

Earth Element ◽

Low Grade ◽

Scattered Electron ◽

Ree Mineralization ◽

Hydrothermal Processes ◽

Informative Case ◽

Main Factors

The Weishan carbonatite-related rare earth element (REE) deposit in China contains both high- and low-grade REE mineralization and is an informative case study for the investigation of magmatic–hydrothermal REE enrichment processes in such deposits. The main REE-bearing mineral is bastnäsite, with lesser parisite and monazite. REE mineralization occurred at a late stage of hydrothermal evolution and was followed by a sulfide stage. Barite, calcite, and strontianite appear homogeneous in back-scattered electron images and have high REE contents of 103–217, 146–13,120, and 194–16,412 ppm in their mineral lattices, respectively. Two enrichment processes were necessary for the formation of the Weishan deposit: Production of mineralized carbonatite and subsequent enrichment by magmatic–hydrothermal processes. The geological setting and petrographic characteristics of the Weishan deposit indicate that two main factors facilitated REE enrichment: (1) fractures that facilitated circulation of ore-forming fluids and provided space for REE precipitation and (2) high ore fluorite and barite contents resulting in high F− and SO42− concentrations in the ore-forming fluids that promoted REE transport and deposition.

Download Full-text

Magmatic-Hydrothermal Processes Associated with Rare Earth Element Enrichment in the Kangankunde Carbonatite Complex, Malawi

Minerals ◽

10.3390/min9070442 ◽

2019 ◽

Vol 9 (7) ◽

pp. 442 ◽

Cited By ~ 3

Author(s):

Frances Chikanda ◽

Tsubasa Otake ◽

Yoko Ohtomo ◽

Akane Ito ◽

Takaomi D. Yokoyama ◽

...

Keyword(s):

Rare Earth ◽

Geochemical Data ◽

Carbonatite Complex ◽

Compositional Zoning ◽

Ree Mineralization ◽

Hydrothermal Processes ◽

Magmatic Stage ◽

Isotope Study ◽

Late Magmatic Stage ◽

Element Enrichment

Carbonatites undergo various magmatic-hydrothermal processes during their evolution that are important for the enrichment of rare earth elements (REE). This geochemical, petrographic, and multi-isotope study on the Kangankunde carbonatite, the largest light REE resource in the Chilwa Alkaline Province in Malawi, clarifies the critical stages of REE mineralization in this deposit. The δ56Fe values of most of the carbonatite lies within the magmatic field despite variations in the proportions of monazite, ankerite, and ferroan dolomite. Exsolution of a hydrothermal fluid from the carbonatite melts is evident based on the higher δ56Fe of the fenites, as well as the textural and compositional zoning in monazite. Field and petrographic observations, combined with geochemical data (REE patterns, and Fe, C, and O isotopes), suggest that the key stage of REE mineralization in the Kangankunde carbonatite was the late magmatic stage with an influence of carbothermal fluids i.e. magmatic–hydrothermal stage, when large (~200 µm), well-developed monazite crystals grew. The C and O isotope compositions of the carbonatite suggest a post-magmatic alteration by hydrothermal fluids, probably after the main REE mineralization stage, as the alteration occurs throughout the carbonatite but particularly in the dark carbonatites.

Download Full-text

Mineralogical and geochemical specificity of carbonaceous rocks from the area of Ust'-Kara astrobleme (Pay-Khoy)

Vestnik of Geosciences ◽

10.19110/geov.2021.11.1 ◽

2021 ◽

Vol 11 ◽

pp. 3-15

Author(s):

N. S. Kovalchuk ◽

◽

B. A. Makeev ◽

S. A. Svetov ◽

◽

...

Keyword(s):

Hydrothermal Activity ◽

Rare Metal ◽

Impact Structure ◽

Hydrothermal Processes ◽

Upper Paleozoic ◽

Modern Methods ◽

Rare Earth Minerals ◽

Carbonaceous Shales ◽

Post Impact ◽

Carbonaceous Rocks

We studied Upper Paleozoic (P1pt-ng) carbonaceous shales and siltstones from the area of the Ust'-Kara astrobleme (PayKhoy). We analyzed mineralogical and geochemical features of carbonaceous rocks of the target in the vicinity of the Ust'-Kara astrobleme event using a complex of modern methods to identify possible mobilization, redeposition and concentration of ore substance under intensive post-impact hydrothermal activity. Geochemical features of carbon deposits, altered by post-impact hydrothermal processes in the vicinity of the Ust'-Kara impact structure, have been determined. We found anomalous contents of Ti, Mn, Cr, Zr, Ni, Li, Co, Sc and REE. Inherent rare metal and rare earth minerals (monazite, florensite), sulfides (pyrite, chalcopyrite, marcasite, sphalerite), apatite, barite, anatase, chrome spinels were diagnosed.

Download Full-text

REE -Sr-Ba minerals from the Khibina carbonatites, Kola Peninsula, Russia: their mineralogy, paragenesis and evolution

Mineralogical Magazine ◽

10.1180/002646198547594 ◽

1998 ◽

Vol 62 (2) ◽

pp. 225-250 ◽

Cited By ~ 67

Author(s):

Anatoly N. Zaitsev ◽

Frances Wall ◽

Michael J. Le Bas

Keyword(s):

Rare Earth ◽

Kola Peninsula ◽

Late Stage ◽

Light Rare Earth ◽

Heavy Rare Earth ◽

Excellent Opportunity ◽

Rare Earth Minerals ◽

Alkaline Massif ◽

The Rare Earth

AbstractCarbonatites from the Khibina Alkaline Massif (360–380 Ma), Kola Peninsula, Russia, contain one of the most diverse assemblages of REE minerals described thus far from carbonatites and provide an excellent opportunity to track the evolution of late-stage carbonatites and their sub-solidus (secondary) changes. Twelve rare earth minerals have been analysed in detail and compared with literature analyses. These minerals include some common to carbonatites (e.g. Ca-rare-earth fluocarbonates and ancylite-(Ce)) plus burbankite and carbocernaite and some very rare Ba,REE fluocarbonates.Overall the REE patterns change from light rare earth-enriched in the earliest carbonatites to heavy rare earth-enriched in the late carbonate-zeolite veins, an evolution which is thought to reflect the increasing ‘carbohydrothermal’ nature of the rock-forming fluid. Many of the carbonatites have been subject to sub-solidus metasomatic processes whose products include hexagonal prismatic pseudomorphs of ancylite-(Ce) or synchysite-(Ce), strontianite and baryte after burbankite and carbocernaite. The metasomatic processes cause little change in the rare earth patterns and it is thought that they took place soon after emplacement.

Download Full-text

Mineralogical and geochemical features of the black shales surrounding the Kara Astrobleme (Pay-Khoy)

LITOSFERA ◽

10.24930/1681-9004-2020-20-2-168-183 ◽

2020 ◽

Vol 20 (2) ◽

pp. 168-183

Author(s):

N. S. Kovalchuk ◽

T. G. Shumilova

Keyword(s):

Rare Earth ◽

Black Shale ◽

Black Shales ◽

Late Paleozoic ◽

Research Subject ◽

Impact Structure ◽

Hydrothermal Processes ◽

Rare Earth Minerals ◽

Post Impact ◽

Academy Of Sciences

Research subject. The Late Paleozoic (D3–P1) black shale strata surrounding the Kara Astrobleme (Pay-Khoy) were studied. Materials and methods. The rocks were sampled radially along the profile from the edge of the astrobleme (the at the contact zone with impactites) with access to black shales that were not affected by post-impact transformations. An analysis of the mineralogical and geochemical features of the black shales surrounding the Kara astrobleme was carried out using a complex of modern research methods (Geonauka Centre for Collective Use, IG FRC Komi Scientific Centre, Ural Branch of the Russian Academy of Sciences) in order to identify the possible mobilisation, re-deposition and concentration of ore matter under the conditions of intensive post-impact hydrothermal altering. Results and conclusions. The geochemical features of the black shale deposits altered by post-impact hydrothermal processes in the vicinity of the Kara impact structure were determined. The sharp abnormal contents of Mn, B, Zr, Sr, Ge, Cd, Hf, Se and Eu as well as the abnormal contents of Ti, Ba, Cr, Rb, Li, Ce, La, Ga, Sc, Co, Cs, Gd, Dy and W were revealed. The geochemical concentration specificity of components in different regions of the Kara astrobleme associated with the specialisation of target rocks was established. Raremetal and rare-earth minerals, sulphides and thymannite (HgSe) were diagnosed.

Download Full-text

Mineralogy of Dolomite Carbonatites of Sevathur Complex, Tamil Nadu, India

Minerals ◽

10.3390/min11040355 ◽

2021 ◽

Vol 11 (4) ◽

pp. 355

Author(s):

Maria Rampilova ◽

Anna Doroshkevich ◽

Shrinivas Viladkar ◽

Elizaveta Zubakova

Keyword(s):

Tamil Nadu ◽

Minor Amount ◽

Carbonatite Complex ◽

Accessory Minerals ◽

Main Mass ◽

Fault Systems ◽

Hydrothermal Processes ◽

Lree Enrichment ◽

Primary Minerals

The main mass of the Sevathur carbonatite complex (Tamil Nadu, India) consists of dolomite carbonatite with a small number of ankerite carbonatite dikes. Calcite carbonatite occurs in a very minor amount as thin veins within the dolomite carbonatite. The age (207Pb/204Pb) of the Sevathur carbonatites is 801 ± 11 Ma, they are emplaced within the Precambrian granulite terrains along NE–SW trending fault systems. Minor minerals in dolomite carbonatite are fluorapatite, phlogopite (with a kinoshitalite component), amphibole and magnetite. Pyrochlore (rich in UO2), monazite-Ce, and barite are accessory minerals. Dolomite carbonatite at the Sevathur complex contains norsethite, calcioburbankite, and benstonite as inclusions in primary calcite and are interpreted as primary minerals. They are indicative of Na, Sr, Mg, Ba, and LREE enrichment in their parental carbonatitic magma. Norsethite, calcioburbankite, and benstonite have not been previously known at Sevathur. The hydrothermal processes at the Sevathur carbonatites lead to alteration of pyrochlore into hydropyrochlore, and Ba-enrichment. Also, it leads to formation of monazite-(Ce) and barite-II.

Download Full-text

Prepare a catalyst consist of rare earth minerals to denitrate via NH3-SCR

Green Processing and Synthesis ◽

10.1515/gps-2020-0020 ◽

2020 ◽

Vol 9 (1) ◽

pp. 191-202

Author(s):

Jian Wang ◽

Chao Zhu ◽

Baowei Li ◽

Zhijun Gong ◽

Zhaolei Meng ◽

...

Keyword(s):

Rare Earth ◽

Active Sites ◽

Nh3 Scr ◽

Composite Oxides ◽

Rare Earth Minerals ◽

Denitrification Activity ◽

Denitrification Reactor ◽

Surface Active ◽

Rare Earth Tailings ◽

Treatment Step

AbstractTo research the roles of rare earth minerals in denitrification via the NH3-SCR, a mixture was made by certain ratio of rare earth concentrates and rare earth tailings, then treated by microwave roasting, and acids and bases to form a denitrification catalyst. The mineral phase structure and surface morphology of the catalyst were characterized by XRD, BET, SEM and EDS. The surface properties of the catalyst were tested by TPD and XPS methods, and the denitrification activity of the catalyst was evaluated in a denitrification reactor. The results showed that the denitrification efficiency increased up to 82% with complete processing. XRD, BET, SEM, and EDS spectrum analysis stated that the treated minerals contained cerium oxides and Fe−Ce composite oxides. The surface of the modified minerals became rough and porous, the surface area increased, and the surface-active sites were exposed. The results of NH3-TPD and NO-TPD showed that the catalyst surface could gradually adsorb more NH3 and NO after each step. XPS analysis indicated that there were more Ce3+, Fe2+, and lattice oxygen in rare earth minerals catalyst after each treatment step.

Download Full-text