Pétrologie du granite peralcalin du lac Brisson, Labrador central, Nouveau-Québec. 1. Mode de mise en place et évolution chimique

1992 ◽  
Vol 29 (2) ◽  
pp. 353-372 ◽  
Author(s):  
D. Pillet ◽  
M. Chenevoy ◽  
M. Bélanger
Keyword(s):  
Fractional Crystallization ◽  
Fluid Phase ◽  
Major Elements ◽  
Magmatic Stage ◽  
Recent Phase ◽  
Element Enrichment ◽  
Magmatic Suite ◽  
End Members ◽  
Trace Element Enrichment ◽  
Middle Proterozoic

The Lake Brisson peralkaline granite in Labrador, which by way of its age of 1189 Ma is the most recent phase of the Gardar magmatic stage, was intruded in the Middle Proterozoic at the margin of a granulitic complex, retrograded to an amphibolite facies during Aphebian, and of an Elsonian adamellite pluton. It shows a petrographie zonation ("feldspathic" facies at the center, "quartzose" facies including early quartz at the edge) suggestive of a permissive multiphase intrusion, and is characterized by deuteritic alteration via metalliferous fluids (Zr, Y, Nb, Be; rare earths). All facies are Na-peralkaline, well evolved, and represent end-members of a differentiated magmatic suite of the designated A type. The relative behavior of the major elements indicates that the facies differentiation was controlled by fractional crystallization and was also greatly influenced by alkaline feldspath and by increase of f(O2) in the final stage of evolution. The trace elements contents, significantly higher than those reported for other peralkaline complexes, are a confirmation of the influence of fractional crystallization. The unsual trace element enrichment in an altered quartzose facies is the result of the effects of a final oxidizing fluid phase, rich in F; the relative depletion of Na and the enrichment in Sr and Ca of the fluid are explained by its having been contaminated by the wall rocks. [Journal Translation]

GEOGENIC TRACE ELEMENT ENRICHMENT IN THE NORTHERN DEVELI CLOSED BASIN (KAYSERI, TURKEY)

2017 ◽  
Author(s):  
Cigdem Yucel ◽  
◽  
Sebnem Arslan ◽  
Sebnem Arslan ◽  
Mehmet Celik ◽  
...  
Keyword(s):  
Trace Element ◽  
Closed Basin ◽  
Element Enrichment ◽  
Trace Element Enrichment

scholarly journals Origin of alkali-rich volcanic and alkali-poor intrusive carbonatites from a common parental magma

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ivan F. Chayka ◽  
Vadim S. Kamenetsky ◽  
Nikolay V. Vladykin ◽  
Alkiviadis Kontonikas-Charos ◽  
Ilya R. Prokopyev ◽  
...  
Keyword(s):  
Empirical Evidence ◽  
Fractional Crystallization ◽  
Melt Inclusions ◽  
Parental Magma ◽  
Progressive Increase ◽  
Topical Problem ◽  
Oldoinyo Lengai ◽  
Southern Siberia ◽  
Magmatic Stage ◽  
Common Parent

AbstractThe discrepancy between Na-rich compositions of modern carbonatitic lavas (Oldoinyo Lengai volcano) and alkali-poor ancient carbonatites remains a topical problem in petrology. Although both are supposedly considered to originate via fractional crystallization of a “common parent” alkali-bearing Ca-carbonatitic magma, there is a significant compositional gap between the Oldoinyo Lengai carbonatites and all other natural compositions reported (including melt inclusions in carbonatitic minerals). In an attempt to resolve this, we investigate the petrogenesis of Ca-carbonatites from two occurrences (Guli, Northern Siberia and Tagna, Southern Siberia), focusing on mineral textures and alkali-rich multiphase primary inclusions hosted within apatite and magnetite. Apatite-hosted inclusions are interpreted as trapped melts at an early magmatic stage, whereas inclusions in magnetite represent proxies for the intercumulus environment. Melts obtained by heating and quenching the inclusions, show a progressive increase in alkali concentrations transitioning from moderately alkaline Ca-carbonatites through to the “calcite CaCO3 + melt = nyerereite (Na,K)2Ca2(CO3)3” peritectic, and finally towards Oldoinyo Lengai lava compositions. These results give novel empirical evidence supporting the view that Na-carbonatitic melts, similar to those of the Oldoinyo Lengai, may form via fractionation of a moderately alkaline Ca-carbonatitic melt, and therefore provide the “missing piece” in the puzzle of the Na-carbonatite’s origin. In addition, we conclude that the compositions of the Guli and Tagna carbonatites had alkali-rich primary magmatic compositions, but were subsequently altered by replacement of alkaline assemblages by calcite and dolomite.

Reactive trace element enrichment in a highly modified, tidally inundated acid sulfate soil wetland: East Trinity, Australia

2010 ◽  
Vol 60 (4) ◽  
pp. 620-626 ◽  
Author(s):  
Annabelle F. Keene ◽  
Scott G. Johnston ◽  
Richard T. Bush ◽  
Edward D. Burton ◽  
Leigh A. Sullivan
Keyword(s):  
Trace Element ◽  
Acid Sulfate Soil ◽  
Acid Sulfate ◽  
Element Enrichment ◽  
Trace Element Enrichment

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

Minerals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 442 ◽  
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.

scholarly journals The Formation of Barite and Celestite through the Replacement of Gypsum

Minerals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 189 ◽  
Author(s):  
Pablo Forjanes ◽  
José Astilleros ◽  
Lurdes Fernández-Díaz
Keyword(s):  
Solid Solution ◽  
Fluid Phase ◽  
Secondary Phase ◽  
Crystal Habit ◽  
Replacement Reaction ◽  
Random Orientation ◽  
End Members ◽  
Kinetics Of ◽  
Oriented Layer ◽  
Orientational Relationship

Barite (BaSO4) and celestite (SrSO4) are the end-members of a nearly ideal solid solution. Most of the exploitable deposits of celestite occur associated with evaporitic sediments which consist of gypsum (CaSO4·2H2O) or anhydrite (CaSO4). Barite, despite having a broader geological distribution is rarely present in these deposits. In this work, we present an experimental study of the interaction between gypsum crystals and aqueous solutions that bear Sr or Ba. This interaction leads to the development of dissolution-crystallization reactions that result in the pseudomorphic replacement of the gypsum crystals by aggregates of celestite or barite, respectively. The monitoring of both replacement reactions shows that they take place at very different rates. Millimeter-sized gypsum crystals in contact with a 0.5 M SrCl2 solution are completely replaced by celestite aggregates in less than 1 day. In contrast, only a thin barite rim replaces gypsum after seven days of interaction of the latter with a 0.5 M BaCl2 solution. We interpret that this marked difference in the kinetics of the two replacement reactions relates the different orientational relationship that exists between the crystals of the two replacing phases and the gypsum substrate. This influence is further modulated by the specific crystal habit of each secondary phase. Thus, the formation of a thin oriented layer of platy barite crystals effectively armors the gypsum surface and prevents its interaction with the Ba-bearing solution, thereby strongly hindering the progress of the replacement reaction. In contrast, the random orientation of celestite crystals with respect to gypsum guarantees that a significant volume of porosity contained in the celestite layer is interconnected, facilitating the continuous communication between the gypsum surface and the fluid phase and guaranteeing the progress of the gypsum-by-celestite replacement.

Origin of anomalous iron meteorites

1979 ◽  
Vol 43 (327) ◽  
pp. 415-421 ◽  
Author(s):  
Edward R. D. Scott
Keyword(s):  
Fractional Crystallization ◽  
Genetic Relationships ◽  
Bulk Composition ◽  
Iron Meteorites ◽  
End Members ◽  
Chemical Groups ◽  
Chemical Trends

SummaryAnomalous iron meteorites are those which do not have Ni, Ga, and Ge contents appropriate to one of the twelve chemical groups; they account for 14% of all irons. The chemistry of irons in the twelve groups can be largely understood in terms of primary fractionation in the nebula, which established the bulk composition of the groups, and secondary fractionation in the parent bodies (probably fractional crystallization), which produced the chemical trends within groups. Logarithmic element-Ga graphs containing data for groups and anomalous irons reveal that anomalous irons experienced the same primary and secondary fractionations as affected the groups.The uniformity of chemical trends within groups allows possible genetic relationships between anomalous irons and groups and among anomalous irons to be tested. It is concluded that the sixty-nine anomalous irons are samples from fifty-odd additional groups, which had similar histories to the twelve groups. Less than five of the anomalous irons could be compositional end- members or reprocessed irons from the groups.Because ‘anomalous’ means abnormal, some other term for the irons which do not belong to the twelve groups would be a useful reminder that these irons formed in a similar way to irons in the major groups. They could be called members of minor groups or grouplets.

scholarly journals Correction: Lead isotope evidence for young trace element enrichment in the oceanic upper mantle

Nature ◽  
1993 ◽  
Vol 362 (6416) ◽  
pp. 184-184 ◽  
Author(s):  
Alex N. Halliday ◽  
Gareth R. Davies ◽  
Der-Chuen Lee ◽  
Simone Tommasini ◽  
Cassi R. Paslick ◽  
...  
Keyword(s):  
Trace Element ◽  
Upper Mantle ◽  
Lead Isotope ◽  
Isotope Evidence ◽  
Element Enrichment ◽  
Trace Element Enrichment
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