Geochemical evolution of the Chatham–Grenville stock, Quebec

1985 ◽  
Vol 22 (6) ◽  
pp. 872-880 ◽  
Author(s):  
Michael Denis Higgins
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Mass Balance ◽  
Major Element ◽  
Parental Magma ◽  
Alkali Feldspar ◽  
Geochemical Evolution ◽  
Wide Range ◽  
The Mean

The Chatham–Grenville stock is an anorogenic multiple intrusion that shows a complete gradation from early cumulate and noncumulate syenites to slightly peralkaline granites. It can be divided into four units. Unit 1, the first unit, is a noncumulate syenite with modal quartz less than 5%. Unit 2 has a wide range in composition from cumulate syenites (no modal quartz) to noncumulate syenites and quartz syenites (modal quartz = 20%). Units 3 and 4 are granites with modal quartz up to 25 and 30%, respectively. The parental magma of the whole complex was syenitic. Differentiation occurred as a result of crystal fractionation by filter pressing both at depth and in situ. Ba, Sr, Rb, and Eu abundances and major-element mass-balance calculations show that alkali feldspar, mafic minerals, and apatite were fractionated. At least 79% fractionation is necessary to transform the mean composition of the first unit (1) into the mean composition of the last unit (4). The rare-earth elements, Th, Ta, Hf, and Zr, did not behave in a residual fashion but may have been fractionated in minor accessory phases such as apatite, zircon, monazite, allanite, and xenotime.

scholarly journals Geochemical Characteristics and Tectonic Setting of Amphibolites in Ifewara Area, Ife-Ilesha Schist Belt, Southwestern Nigeria

2016 ◽  
Vol 6 (1) ◽  
pp. 43 ◽  
Author(s):  
Anthony Temidayo Bolarinwa ◽  
Adebimpe Atinuke Adepoju
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Major Element ◽  
Tectonic Setting ◽  
Crustal Contamination ◽  
Geochemical Evolution ◽  
Schist Belt ◽  
Southwestern Nigeria ◽  
Eu Anomaly ◽  
Ree Patterns

Trace and Rare Earth Elements (REEs) data are used to constrain the geochemical evolution of the amphibolites from Ifewara in the Ife-Ilesha schist belt of southwestern Nigeria. The amphibolites can be grouped into banded and sheared amphibolites. Major element data show SiO2 (48.34%), Fe2O3 (11.03-17.88%), MgO (5.76-9.90%), CaO (7.76-18.6%) and TiO2 (0.44-1.77%) contents which are similar to amphibolites in other schist belts in Nigeria. The Al2O3 (2.85-15.55%) content is varied, with the higher values suggesting alkali basalt protolith. Trace and rare earth elements composition reveal Sr (160-1077ppm), Rb (0.5-22.9ppm), Ni (4.7-10.2ppm), Co (12.2-50.9 ppm) and Cr (2-7ppm). Chondrite-normalized REE patterns show that the banded amphibolites have HREE depletion and both negative and positive Eu anomalies while the sheared variety showed slight LREE enrichment with no apparent Eu anomaly. The study amphibolites plot in the Mid Oceanic Ridge Basalts (MORB) and within plate basalt fields on the Zr/Y vs Zr discriminatory diagrams. They are further classified as volcanic arc basalt and E-type MORB on the Th- Hf/3- Ta and the Zr-Nb-Y diagrams. The amphibolites precursor is considered a tholeiitic suite that suffered crustal contamination, during emplacement in a rifted crust.

scholarly journals Heterogeneity in lunar anorthosite meteorites: implications for the lunar magma ocean model

2014 ◽  
Vol 372 (2024) ◽  
pp. 20130241 ◽  
Author(s):  
Sara S. Russell ◽  
Katherine H. Joy ◽  
Teresa E. Jeffries ◽  
Guy J. Consolmagno ◽  
Anton Kearsley
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Ocean Model ◽  
Magma Source ◽  
The Moon ◽  
Magma Ocean ◽  
Element Abundances ◽  
Wide Range ◽  
Lunar Meteorites

The lunar magma ocean model is a well-established theory of the early evolution of the Moon. By this model, the Moon was initially largely molten and the anorthositic crust that now covers much of the lunar surface directly crystallized from this enormous magma source. We are undertaking a study of the geochemical characteristics of anorthosites from lunar meteorites to test this model. Rare earth and other element abundances have been measured in situ in relict anorthosite clasts from two feldspathic lunar meteorites: Dhofar 908 and Dhofar 081. The rare earth elements were present in abundances of approximately 0.1 to approximately 10× chondritic (CI) abundance. Every plagioclase exhibited a positive Eu-anomaly, with Eu abundances of up to approximately 20×CI. Calculations of the melt in equilibrium with anorthite show that it apparently crystallized from a magma that was unfractionated with respect to rare earth elements and ranged in abundance from 8 to 80×CI. Comparisons of our data with other lunar meteorites and Apollo samples suggest that there is notable heterogeneity in the trace element abundances of lunar anorthosites, suggesting these samples did not all crystallize from a common magma source. Compositional and isotopic data from other authors also suggest that lunar anorthosites are chemically heterogeneous and have a wide range of ages. These observations may support other models of crust formation on the Moon or suggest that there are complexities in the lunar magma ocean scenario to allow for multiple generations of anorthosite formation.

Synthetic zircon doped with hafnium and rare earth elements: A reference material for in situ hafnium isotope analysis

2011 ◽  
Vol 286 (1-2) ◽  
pp. 32-47 ◽  
Author(s):  
Christopher M. Fisher ◽  
John M. Hanchar ◽  
Scott D. Samson ◽  
Bruno Dhuime ◽  
Janne Blichert-Toft ◽  
...  
Keyword(s):  
Rare Earth ◽  
Reference Material ◽  
Rare Earth Elements ◽  
Isotope Analysis

scholarly journals Seasonal and annual mass balances of Mera and Pokalde glaciers (Nepal Himalaya) since 2007

2013 ◽  
Vol 7 (4) ◽  
pp. 3337-3378 ◽  
Author(s):  
P. Wagnon ◽  
C. Vincent ◽  
Y. Arnaud ◽  
E. Berthier ◽  
E. Vuillermoz ◽  
...  
Keyword(s):  
Mass Balance ◽  
Cross Sections ◽  
Mass Balances ◽  
Equilibrium Line Altitude ◽  
Nepal Himalaya ◽  
Limited Mass ◽  
In Situ Observations ◽  
The Mean ◽  
Southern Flank

Abstract. In the Everest region, Nepal, ground-based monitoring programs were started on the debris-free Mera Glacier (27.7° N, 86.9° E; 5.1 km2, 6420 to 4940 m a.s.l.) in 2007 and on the small Pokalde Glacier (27.9° N, 86.8° E; 0.1 km2, 5690 to 5430 m a.s.l., ∼ 25 km North of Mera Glacier) in 2009. These glaciers lie on the southern flank of the central Himalaya under the direct influence of the Indian monsoon and receive more than 80% of their annual precipitation in summer (June to September). Despite a large inter-annual variability with glacier-wide mass balances ranging from −0.77± 0.40 m w.e. in 2011–2012 (Equilibrium-line altitude (ELA) at ∼ 6055 m a.s.l.) to + 0.46 ± 0.40 m w.e. in 2010–2011 (ELA at ∼ 5340 m a.s.l.), Mera Glacier has been shrinking at a moderate mass balance rate of −0.10± 0.40 m w.e. yr−1 since 2007. Ice fluxes measured at two distinct transverse cross sections at ∼ 5350 m a.s.l. and ∼ 5520 m a.s.l. confirm that the mean state of this glacier over the last one or two decades corresponds to a limited mass loss, in agreement with remotely-sensed region-wide mass balances of the Everest area. Seasonal mass balance measurements show that ablation and accumulation are concomitant in summer which in turn is the key season controlling the annual glacier-wide mass balance. Unexpectedly, ablation occurs at all elevations in winter due to wind erosion and sublimation, with remobilized snow likely being sublimated in the atmosphere. Between 2009 and 2012, the small Pokalde Glacier lost mass more rapidly than Mera Glacier with respective mean glacier-wide mass balances of −0.72 and −0.26 ± 0.40 m w.e. yr−1. Low-elevation glaciers, such as Pokalde Glacier, have been usually preferred for in-situ observations in Nepal and more generally in the Himalayas, which may explain why compilations of ground-based mass balances are biased toward negative values compared with the regional mean under the present-day climate.

Simultaneous determination of Sm–Nd isotopes, trace-element compositions and U–Pb ages of titanite using a laser-ablation split-stream technique with the addition of water vapor

2021 ◽  
Author(s):  
Le Zhang ◽  
Jia-Lin Wu ◽  
Yanqiang Zhang ◽  
Ya-Nan Yang ◽  
Pengli He ◽  
...  
Keyword(s):  
Rare Earth ◽  
Water Vapor ◽  
Laser Ablation ◽  
Rare Earth Elements ◽  
Trace Element ◽  
Simultaneous Determination ◽  
Nd Isotopes ◽  
Trace Element Contents

Titanite is a widespread accessory nesosilicate with high trace-element contents including rare-earth elements, Th, and U, and is thus suitable for in situ isotopic and trace-element analyses and U–Pb dating....

Deformation-driven emplacement-differentiation in the Closepet pluton, Dharwar Craton, South India: an alternate view

2019 ◽  
Vol 489 (1) ◽  
pp. 261-274 ◽  
Author(s):  
Abhijit Bhattacharya
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
South India ◽  
Major Element ◽  
Volume Fraction ◽  
Dharwar Craton ◽  
The North ◽  
Magmatic Fabric ◽  
Melt Composition ◽  
Crystal Content

AbstractIn the Late Archean north-trending Closepet pluton, trains of euhedral K-feldspar phenocrysts and matrix-supported idiomorphic K-feldspar crystals in the central part of the pluton define oblique-to-pluton margin steep-dipping east/ENE-trending magmatic fabrics. The magmatic fabric is defined by phenocryst-rich and phenocryst-poor layers, with the euhedral porphyries continuous across the layers. The fabrics are near-orthogonal to the gently-dipping gneissic layers in the host gneisses. The fabrics curve adjacent to locally-developed north/NNE-trending melt-hosted dislocations parallel to the axial planes of horizontal/gently-plunging north-trending upright folds in the host gneisses. In the pluton interior, both fabrics in the intrusives formed at supra-solidus conditions, although the volume fraction of melts diminished drastically due to cooling/melt expulsion. At the pluton margin, the north-trending fabric is penetrative and post-dates magma solidification. Within the pluton, the major element oxides, rare earth elements, anorthite contents in plagioclase, and (Mg/Fe + Mg) ratios in biotite decrease with increasing SiO2 from phenocryst-rich (up to 75% by volume) granodiorite to phenocryst-poor (<15 vol%) granite that broadly correspond to minimum melt composition. The chemical-mineralogical variations in the pluton is attributed to deformation-driven ascent of magma with heterogeneous crystal content, ascending at variable velocities (highest in crystal-poor magma) along oblique-to-pluton margin east/ENE-trending extensional fractures induced by dextral shearing.

scholarly journals Allanite Geochemical Response to Hydrothermal Alteration by Alkaline, Low-Temperature Fluids

Minerals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 392 ◽  
Author(s):  
Katarzyna Gros ◽  
Ewa Słaby ◽  
Petras Jokubauskas ◽  
Jiří Sláma ◽  
Gabriela Kozub-Budzyń
Keyword(s):  
Rare Earth ◽  
Low Temperature ◽  
Rare Earth Elements ◽  
Geochemical Evolution ◽  
Additional Component ◽  
Second Stage ◽  
Ce Anomaly ◽  
Hydrothermal Processes ◽  
Fluid Infiltration ◽  
Two Stages

Allanite is one of the main rare earth elements (REE)-rich accessory minerals in composite dykes from the granitoid pluton of Karkonosze. These dykes differ in composition from the bulk of the pluton by elevated rare earth elements (REE), Y, Zr, and alkali contents, suggesting contribution of an additional component. Allanite exhibits complex alteration textures, which can be divided into two stages. The first stage is represented by allanite mantles, formed by fluid infiltration into previously crystallized magmatic allanite. These zones have low totals, are Ca-, Al-, Mg-, and light REE (LREE)-depleted, and Y-, heavy REE (HREE)-, Th-, Ti-, and alkali-enriched. The fractionation between LREE and HREE was caused by different mobility of complexes formed by these elements in aqueous fluids. The second stage includes recrystallized LREE-poor, Y-HREE-rich allanite with variable Ca, Al, Mg, and REE-fluorocarbonates. The alteration products from both stages demonstrate higher Fe3+/(Fe2+ + Fe3+) ratios and a negative Ce anomaly. These features point to the alkaline, low-temperature, and oxidized nature of the fluids. The differences in mobility and solubility of respective ligands show that the fluids from the first stage may have been dominated by Cl, whereas those of the second stage may have been dominated by F and CO2 (and PO4 in case of one sample). The inferred chemistry of the fluids resembles the overall geochemical signature of the composite dykes, indicating a major contribution of the hydrothermal processes to their geochemical evolution.

scholarly journals Petrography, geochemistry and age of Cerro Frontino Gabro

2015 ◽  
pp. 25-40
Author(s):  
Gabriel Rodríguez-García ◽  
Jose Gilberto Bermúdez-Cordero
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Alkali Feldspar ◽  
Silica Content ◽  
Magmatic Arc ◽  
Western Cordillera ◽  
Short Period ◽  
Heavy Rare Earth Elements ◽  
Light Rare Earth Elements ◽  
Northern Segment

The Gabro de Cerro Frontino was emplaced in the Cañasgordas Block, located in the Northern Segment of the Colombian Western Cordillera. It corresponds to a pluton composed of at least three magmatic pulses, emplaced during a short period of time. Gabbros and diorites are more common in the unit than clinopiroxenites, monzodiorites and monzonites. These rocks are composed of calcic to intermediate plagioclase, augite-egerine type clinopyroxene and biotite; olivine and flogopite may be present in some mafic rocks and alkali feldspar and quartz may be present in some felsic rocks. Sphene, magnetite and apatite are common accessory minerals. The silica content in the rocks varies between 37.08% and 54.4%, with constant values of MnO (0.1% 0.4%), impoverishment of Fe2O3, MgO, CaO, TiO2 and P2O5 as SiO2 increases, and enrichment of K2O, Na2O and Al2O3 as SiO2 increases. The basic and ultrabasic rocks fall in the sub-alkaline series, the rest of the samples fall in the medium to K-rich calc-alkaline series and in the shoshonitic series. The Gabro de Cerro Frontinocorresponds to magmas impoverished on heavy rare earth elements with respect to light rare earth elements, which suggests the contribution of a subduction component in the magma genesis. The LILE (Sr, K, Rb, Pb, Ba) are enriched with respect to the HFSE values that are relatively flat and impoverished; the unit also exhibits a negative anomaly of Nb with respect to Th and Ce, being a magmatic arc the environment of generation. The ages obtained in biotite using the Ar-Ar method fall between 9.87±0.18 Ma and 11.44±0.36 Ma, Middle to upper Miocene (Tortonian-Serravallian), similar to age of other plutons that are part of the Botón Arc.

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