scholarly journals Geochemistry of Garga-Sarali intrusive granitoids (central domain of the central African fold belt in Cameroon): petrological implication

2020 ◽  
Vol 8 (1) ◽  
pp. 33
Author(s):  
Daama Isaac ◽  
Mbowou Gbambie Isaac Bertrand ◽  
Yamgouot Ngounouno Fadimatou ◽  
Ntoumbe Mama ◽  
Ngounouno Ismaïla
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
Fractional Crystallization ◽  
Coarse Grained ◽  
Geochemical Analysis ◽  
Fold Belt ◽  
Volcanic Arcs ◽  
Fine Grained ◽  
Incompatible Elements

The Garga-Sarali granitoids outcrop in form of large slabs and undistorted large blocks, into a schisto-gneissic basement. These rocks contain mainly muscovite and microcline, followed by K-feldspar, quartz, biotite, pyroxene, zircon and oxides, with coarse-grained to fine-grained textures. Geochemical analysis show that it belongs to differentiated rocks group (granodiorite-granite) with high SiO2 (up to 72 wt%) contents. Their genesis was made from a process of partial melting and fractional crystallization. These rocks are classified as belonging to I- and S-Type, meta-peraluminous, shoshonitic granites; belonging to the domain of volcanic arcs. The rare earth elements patterns suggest a source enriched of incompatible elements. The Nb-Ta and Ti negative anomalies from the multi-element patterns are characteristics of the subduction domains.  

Tetrad effect of rare earth elements caused by fractional crystallization in high-silica granites: An example from Central Tibet

Lithos ◽  
2021 ◽  
pp. 105968
Author(s):  
Xue Shuai ◽  
Shi-Min Li ◽  
Di-Cheng Zhu ◽  
Qing Wang ◽  
Liang-Liang Zhang ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Fractional Crystallization ◽  
Tetrad Effect ◽  
High Silica ◽  
Central Tibet

Petrogenesis of the Upper Cretaceous volcanism in the Kefken region, Western Pontides, NW Turkey

2021 ◽  
Author(s):  
Turgut Duzman ◽  
Ezgi Sağlam ◽  
Aral I. Okay
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
Upper Cretaceous ◽  
Volcanic Rocks ◽  
Early Eocene ◽  
Heavy Rare Earth ◽  
Heavy Rare Earth Elements ◽  
Cretaceous Volcanism ◽  
Oceanic Slab

<p>The Upper Cretaceous volcanic and volcaniclastic rocks crop out along the Black Sea coastline in Turkey. They are part of a magmatic arc that formed as a result of northward subduction of the Tethys ocean beneath the southern margin of Laurasia. The lower part of the Upper Cretaceous volcanism in the Kefken region, 100 km northeast of Istanbul, is represented by basaltic andesites, andesites, agglomerates and tuffs, which have yielded Late Cretaceous (Campanian, ca. 83 Ma) U-Pb zircon ages. The volcanic and volcanoclastic rocks are stratigraphically overlain by shallow to deep marine limestones, which range in age from Late Campanian to Early Eocene.  Geochemically, basaltic andesites and andesites display negative anomalies in Nb, Ta and Ti, enrichment in large ion lithophile elements (LILE) relative to high field strength elements (HFSE). Light rare earth elements (LREE) show slightly enrichment relative to heavy rare earth elements (La<sub>cn</sub>/Yb<sub>cn</sub> =2.51-3.63) and there are slight negative Eu anomalies (Eu/Eu* = 0.71-0.95) in basaltic andesite and andesite samples. The geochemical data indicate that Campanian volcanic rocks were derived from the partial melting of the mantle wedge induced by hydrous fluids released by dehydration of the subducted oceanic slab.</p><p>There is also a horizon of volcanic rocks, about 230 m thick, within the Late Campanian-Early Eocene limestone sequence.  This volcanic horizon, which consists of pillow basalts, porphyritic basalts,  andesites and dacites, is of Maastrichtian age based on paleontological data from the intra-pillow sediments and U-Pb zircon ages from the andesites and dacites (72-68 Ma).  The Maastrichtian andesites and dacites are geochemically distinct from the Campanian volcanic rocks. They show distinct adakite-like geochemical signatures with high ratios of Sr/Y (>85.5), high La<sub>cn</sub>/Yb<sub>cn </sub>(16.4-23.7) ratios, low content of Y (7.4-8.6 ppm) and low content of heavy rare-earth elements (HREE). The adakitic rocks most probably formed as a result of partial melting of the subducting oceanic slab under garnet and amphibole stable conditions.</p><p>The Upper Cretaceous arc sequence in the Kefken region shows a change from typical subduction-related magmas to adakitic ones, accompanied by decrease in the volcanism.</p><p> </p><p> </p>

Use of element-mineral correlations to investigate fractionation of rare earth elements in fine-grained sediments

1994 ◽  
Vol 58 (393) ◽  
pp. 533-541 ◽  
Author(s):  
J. T. Temple ◽  
J. N. Walsh
Keyword(s):  
Rare Earth ◽  
Correlation Analysis ◽  
Rare Earth Elements ◽  
Partial Correlation ◽  
Correlation Coefficients ◽  
Partial Correlation Analysis ◽  
Middle Ordovician ◽  
Fine Grained ◽  
South Wales

AbstractRelative concentrations of elements in the minerals of fine-grained sediments can be inferred from element-mineral correlation coefficients. The technique is applied to the distribution of REE in Middle Ordovician shales from South Wales analysed by ICPAES, Leco C/S125 and XRD. Phosphate and chlorite show mid-REE enrichment; muscovite + biotite shows mid-REE depletion. The complementarity of the chlorite and muscovite + biotite patterns may be due to fractionation during diagenetic recrystallisation. Partial correlation analysis is used to infer the presence of zircon.

Petrology, age, and tectonic setting of the rapakivi-bearing Margaree pluton, Cape Breton Island, Canada: evidence for a Late Devonian posttectonic cryptic silicic-mafic magma chamber

2020 ◽  
Vol 57 (9) ◽  
pp. 1011-1029
Author(s):  
Gabriel Sombini dos Santos ◽  
Sandra M. Barr ◽  
Chris E. White ◽  
Deanne van Rooyen
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Magma Chamber ◽  
Magma Mixing ◽  
Tectonic Setting ◽  
Mafic Magma ◽  
Coarse Grained ◽  
Late Devonian ◽  
Cape Breton Island ◽  
Cape Breton

The Margaree pluton extends for >40 km along the axis of the Ganderian Aspy terrane of northern Cape Breton Island, Nova Scotia. The pluton consists mainly of coarse-grained megacrystic syenogranite, intruded by small bodies of medium-grained equigranular syenogranite and microgranite porphyry, all locally displaying rapakivi texture. The three rock types have similar U–Pb (zircon) ages of 363 ± 1.6, 364.8 ± 1.6, and 365.5 ± 3.3 Ma, respectively, consistent with field and petrological evidence that they are coeval and comagmatic. The rare earth elements display parallel trends characterized by enrichment in the light rare earth elements, flat heavy rare earth elements, moderate negative Eu anomalies, and, in some cases, positive Ce anomalies. The megacrystic and rapakivi textures are attributed to thermal perturbation in the magma chamber caused by the mixing of mafic and felsic magma, even though direct evidence of the mafic magma is mainly lacking at the current level of exposure. Magma evolution was controlled by fractionation of quartz, K-feldspar, and Na-rich plagioclase in molar proportions of 0.75:0.12:0.13. The chemical and isotopic (Sm–Nd) signature of the Margaree pluton is consistent with the melting of preexisting continental crust that was enriched in heat-producing elements, likely assisted by intrusion of mantle-derived mafic magma during Late Devonian regional extension. The proposed model involving magma mixing at shallow crustal levels in a cryptic silicic-mafic magma chamber during post-Acadian extension is consistent with models for other, better exposed occurrences of rapakivi granite in the northern Appalachian orogen.

S-type granite formation in the Dalradian rocks of Connemara, W. Ireland

1990 ◽  
Vol 54 (374) ◽  
pp. 1-22 ◽  
Author(s):  
Y. Ahmed-Said ◽  
B. E. Leake
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
Fission Track ◽  
Sr Isotope ◽  
Crustal Rocks ◽  
Granite Formation ◽  
Type Granite ◽  
Gabbroic Intrusion ◽  
Detailed Picture

AbstractThe vicinity of the 490 Ma Cashel gabbroic intrusion experienced pressures of about 4.05 ± 0.2 kbar and temperatures in excess of 850 °C. These conditions caused intense hornfelsing and partial melting of the surrounding Dalradian metasediments. From the study of the progressively changed composition of the aureole hornfelses it is deduced that elements were fractionated into the melts as follows: Si>K>Na>Ca>Mn>Al>Fe>Mg and Rb>Ba>Sr>Ga>Cr,Ni,Co. This order of fractionation, which is the opposite to that in magmatic crystallization, provides a detailed picture of the mode of interaction between a mantle derived basic magma and mid-crustal rocks, illustrating how one type of S-type granite can be produced. The rare earth elements (REE) were both removed and fractionated but Eu largely remained in the crystal fractions giving increasing positive Eu anomalies with rising partial melting and these trends can be explained by the extraction of a granitic melt from the hornfelses. Fission track mapping of U is used to study the behaviour of U within the aureole and the metamorphic recrystallization of detrital brown zircon to pink new zircon. The S-type Cashel microgranite sill is shown to have been derived by anatexis from the Dalradian rocks, to have preserved the Sr isotope ratios of the metasediments at 490 Ma, and not to be of the same composition as the leucosomes in the metasediments.

INTERPHASE PARTITION OF RARE EARTH ELEMENTS DURING PARTIAL MELTING IN THE PERIDOTITE-CARBONATE-PHOSPHATE SYSTEM

1991 ◽  
Vol 33 (6) ◽  
pp. 565-573
Author(s):  
I. D. Ryabchikov ◽  
G. P. Orlova ◽  
V. G. Senin ◽  
N. V. Trubkin
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Partial Melting ◽  
Phosphate System

Paleoproterozoic carbonatitic ultrabasic volcanic rocks (meimechites?) of Cape Smith Belt, Quebec

2001 ◽  
Vol 38 (9) ◽  
pp. 1313-1334 ◽  
Author(s):  
W RA Baragar ◽  
U Mader ◽  
G M LeCheminant
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Hydrothermal Alteration ◽  
Regional Metamorphism ◽  
Volcanic Rocks ◽  
Light Rare Earth ◽  
Shallow Marine ◽  
Incompatible Elements ◽  
Thick Lens ◽  
Light Rare Earth Elements

A 500 m-thick lens of carbonatitic ultrabasic lapilli tuffs and lavas interbedded with platformal Povungnituk sediments in the foreland of the Cape Smith Belt is its earliest known magmatism and may relate to its initial rifting. The sequence comprises tuffs capped in part by effusives. Accretionary and cored lapilli in the tuffs and pillows in the lavas suggest emplacement in a shallow marine environment. Its current assemblage of antigorite, chlorite, talc, and (in part primary?) carbonate, magnetite, ilmenite, minor chromite, and phlogopite results from probable concurrent hydrothermal alteration and subsequent greenschist regional metamorphism. Surviving accessory minerals: apatite, monazite, zircon, rutile, and aeschenite(?) are widespread but scarce. Carbonate (mostly dolomite) is a major and integral component of the rock and interpreted as an original, albeit recrystallized, magmatic constituent. Magnetite is conspicuous in the tuffs: as lapilli and lapilli cores, locally as giant crystals, and as stringers. Except in subhedral groundmass crystals, its negligible TiO2 is evidence of its hydrothermal reconstitution. Compositions of chromite cores and rare relicts of phlogopite crystals are consistent with mantle derivation. Rock compositions are low in SiO2 (<35%) and Al2O3 (<3%), high in MgO (>25 wt.%) and alkaline. The immobile incompatible elements (e.g., Zr, average 260 ppm; Nb, average 130 ppm) and the light rare-earth elements are enriched. The rocks are compositionally similar to type Siberian meimechites and closely resemble the "meimechite"–carbonatite eruptives of Castignon Lake, Labrador Trough. Based on experimental evidence, Lac Leclair magmas are interpreted as originating by minor partial melting of carbonated mantle at ~100 km depths and reaching the surface via conduits opened by deep rifting that initiated the Cape Smith segment of the Trans-Hudson Orogen.

scholarly journals Petrografia, Geoquímica, Análises Isotópicas (Sr, Nd) e Geocronologia Ar-Ar dos Basaltos de Tapirapuã (Tangará da Serra, Mato Grosso, Brasil)

2006 ◽  
Vol 33 (2) ◽  
pp. 71 ◽  
Author(s):  
MÁRCIA APARECIDA DE SANT’ANA BARROS ◽  
ANA MARIA MIZUSAKI ◽  
RICARDO WESKA ◽  
ANDRÉ DE BORBA ◽  
FARID CHEMALE JR ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
North Atlantic ◽  
Volcanic Event ◽  
Mato Grosso ◽  
Fine Grained ◽  
The North ◽  
Tectonic Environment ◽  
Heavy Rare Earth Elements ◽  
Light Rare Earth Elements

 The basaltic flows from Tapirapuã Formation are exposed at Tangará da Serra region, 250 km from Cuiabá (MT) and the thickness can reach 310 meters. The basalts range from massive dark gray, with colunar disjunctions at the base to purple amygdaloidal at the top. They are generally fine-grained, however gabroics portions have been identified. In thin section the Tapirapuã basalts show subophitic texture. Chemical analyses in these rocks suggest tholeiitic compositions, within continental tectonic environment. There is an enrichment of light rare earth elements when compared to heavy rare earth elements. The studied samples have low contents of TiO2 and P2O5 being similar to low P2O5 and TiO2 group from Serra Geral Formation (Paraná Basin). Analyses of Sr and Nd isotopes show the following results: 87Sr/86Sr between 0.703 and 0.707, ∈Nd from –0.01 to + 2.32 and model ages (TDM)= (931 to 1.267 Ma). 40Ar / 39Ar geochronology of plagioclase crystals from Tapirapuã basalts presented a plateau age of 206 ± 6 Ma, in agreement with previous ages obtained from Anari and Tapirapuã sub-provinces. This result places the volcanic event at the limit of the Triassic-Jurassic periods, related to the opening of the North Atlantic.

scholarly journals Geochemistry of garnet megacrysts from the Mir kimberlite pipe (Yakutia) and the nature of prothokimberlite melt

2019 ◽  
Vol 486 (5) ◽  
pp. 583-587
Author(s):  
A. M. Agashev
Keyword(s):  
Trace Elements ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Negative Correlation ◽  
Kimberlite Pipe ◽  
Major And Trace Elements ◽  
Major Elements ◽  
Incompatible Elements ◽  
Composition Study ◽  
Melt Composition

The paper presents the results of major and trace elements composition study of garnet megacrysts from Mir kimberlite pipe. On the major elements composition those garnets classified as low Cr and high Ti pyropes. Concentrations of TiO2 show a negative correlation with MgO и Cr2O3 contents in megacrysts composition. Fractional crystallization modeling indicates that the most appropriate melt to reproduce the garnet trace elements signatures is the melt of picritic composition. Composition of garnets crystallized from kimberlite melt do not correspond to observed natural garnets composition. Kimberlites contain less of Ti, Zr, Y and heavy REE (rare earth elements) but more of very incompatible elements such as light REE, Th, U, Nb, Ba then the model melt composition that necessary for garnet crystallization.

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