scholarly journals Quantifying the Tetrad Effect, Shape Components, and Ce–Eu–Gd Anomalies in Rare Earth Element Patterns

2021 ◽  
Author(s):  
Michael Anenburg ◽  
Morgan J. Williams
Keyword(s):  
Rare Earth ◽  
Least Squares ◽  
Rare Earth Element ◽  
Earth Element ◽  
Quantitative Description ◽  
Tetrad Effect ◽  
Smooth Curves ◽  
Least Squares Fitting ◽  
Ree Patterns ◽  
Mathematical Derivation

AbstractPlots of chondrite-normalised rare earth element (REE) patterns often appear as smooth curves. These curves can be decomposed into orthogonal polynomial functions (shape components), each of which captures a feature of the total pattern. The coefficients of these components (known as the lambda coefficients—$$\lambda $$ λ ) can be derived using least-squares fitting, allowing quantitative description of REE patterns and dimension reduction of parameters required for this. The tetrad effect is similarly quantified using least-squares fitting of shape components to data, resulting in the tetrad coefficients ($$\tau $$ τ ). Our method allows fitting of all four tetrad coefficients together with tetrad-independent $$\lambda $$ λ curvature. We describe the mathematical derivation of the method and two tools to apply the method: the online interactive application BLambdaR, and the Python package pyrolite. We show several case studies that explore aspects of the method, its treatment of redox-anomalous REE, and possible pitfalls and considerations in its use.

Quantitative trace-element modelling of the crystallization history of the Kinojévis and Blake River groups, Abitibi Greenstone Belt, Ontario

1989 ◽  
Vol 26 (7) ◽  
pp. 1356-1367 ◽  
Author(s):  
A. D. Fowler ◽  
L. S. Jensen
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Fractional Crystallization ◽  
Earth Element ◽  
Calc Alkaline ◽  
Quantitative Modelling ◽  
Ti Oxides ◽  
History Of ◽  
High Level ◽  
Ree Patterns

The Archean tholeiitic Kinojévis suite is characterized by an iron-enrichment trend and abundant Fe–Ti oxides in its evolved basalts, andesites, and rhyolites. The rare-earth-element (REE) patterns of the suite remain flat from the basalts through to the rhyolites, with the development of small, negative Eu anomalies. Quantitative modelling of the trace elements from little-altered samples is consistent with the mineralogy, suggesting that the suite was produced through fractional crystallization of olivine, pyroxene, plagioclase, and Fe–Ti oxides. The evolved rhyolites are interpreted as having developed by greater than 90% fractional crystallization in a high-level magma chamber.The calc-alkaline Blake River Group conformably overlies the Kinojévis rocks and is characterized by enrichment in alkalis and silica. The REE patterns are light rare-earth-element (LREE) enriched, and the felsic rocks have prominent negative Eu anomalies. Geochemical modelling shows that the suite could have developed either through fractional crystallization dominated by plagioclase and clinopyroxene or by assimilation of tonalite, coupled with fractional crystallization.

The tonalite–trondhjemite–granodiorite (TTG) to granodiorite–granite (GG) transition in the late Archean plutonic rocks of the central Wyoming Province

2006 ◽  
Vol 43 (10) ◽  
pp. 1419-1444 ◽  
Author(s):  
Carol D Frost ◽  
B Ronald Frost ◽  
Robert Kirkwood ◽  
Kevin R Chamberlain
Keyword(s):  
Rare Earth ◽  
Continental Crust ◽  
Rare Earth Element ◽  
Earth Element ◽  
Gradual Transition ◽  
Heavy Rare Earth Element ◽  
Isotopic Compositions ◽  
Similar Range ◽  
Wyoming Province ◽  
Ree Patterns

The 2.95–2.82 Ga quartzofeldspathic gneisses and granitoids in the Bighorn, western Owl Creek, and northeastern Wind River uplifts in the central Wyoming Province include low-K tonalite–trondhjemite–granodiorite (TTG) and high-K granodiorite–granite (GG) rocks. Both types of granitoids were intruded contemporaneously, although TTGs are more abundant in the older gneisses. The TTG suite consists of calcic to marginally calc-alkalic rocks that straddle the boundaries between metaluminous and peraluminous and between ferroan and magnesian compositions. Rare-earth element (REE) patterns of these rocks may be highly fractionated with low heavy rare-earth element (HREE) contents and modest to absent Eu anomalies but may also be less strongly HREE depleted. These rocks do not represent first-generation continental crust: most have unradiogenic Nd and radiogenic 207Pb/204Pb isotopic compositions that require the incorporation of isotopically evolved sources. The GG suite has compositions that are transitional between Archean TTG and modern, continental margin calc-alkalic rocks. The GG suite is characterized by higher alkali contents relative to CaO than the TTG suite and higher K/Na ratios but exhibits a similar range in REE patterns. The Nd, Sr, and Pb isotopic compositions of the GG suite are slightly less variable but lie within the range of those of the TTG suite. We interpret them as having a source similar to that of the TTG, perhaps forming by partial melting of preexisting TTG. The shift from TTG-dominated to GG-dominated continental crust was a gradual transition that took place over several hundred million years. Clearly subduction-related calc-alkalic magmatism is not recognized in the Wyoming Province prior to 2.67 Ga.

scholarly journals Trace Element and Stable Isotope Geochemistry of Lwamondo and Zebediela Kaolins, Limpopo Province, South Africa: Implication for Paleoenvironmental Reconstruction

Minerals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 93
Author(s):  
Avhatakali Raphalalani ◽  
Georges-Ivo Ekosse ◽  
John Odiyo ◽  
Jason Ogola ◽  
Nenita Bukalo
Keyword(s):  
Trace Elements ◽  
Rare Earth ◽  
Stable Isotope ◽  
Trace Element ◽  
Continental Crust ◽  
Rare Earth Element ◽  
Earth Element ◽  
Paleoenvironmental Reconstruction ◽  
Δ18o And Δd ◽  
Ree Patterns

The aim of the present study was the paleoenvironmental reconstruction of the prevailing environment under which the Lwamondo and Zebediela kaolin deposits were formed. Hence, this study reports deuterium and oxygen stable isotope values and trace and rare earth element concentrations for two samples of kaolin. Upper continental crust-normalised trace-element patterns reveal that large ion lithophile elements and high-field-strength elements are generally depleted in Lwamondo and Zebediela kaolins, whereas transition trace elements are generally enriched in these kaolins. Upper continental crust-normalised rare earth element (REE) patterns show that there is a slight enrichment of heavy REEs (HREEs) compared to light REEs (LREEs) in these kaolins. The δ18O and δD stable isotope values for kaolinite from Lwamondo ranged from 17.4‰ to 19.1‰ and from −54‰ to 84‰, respectively, whereas those values for kaolinite from Zebediela varied from 15.6‰ to 17.7‰ and from −61‰ to –68‰ for δ18O and δD, respectively. The REE patterns and the content of other trace elements indicate ongoing kaolinitisation in the Lwamondo and Zebediela kaolins with minimum mineral sorting. The sources of the kaolins varied from basic to acidic and these were derived from an active margin tectonic setting. Lwamondo kaolin was deposited in an oxic environment whereas Zebediela kaolin was deposited under suboxic/anoxic conditions. Based on the δ18O and δD values of the kaolinite, they formed in a supergene environment at temperatures generally below 40 °C.

scholarly journals Rare Earth Element and Incompatible Trace Element Abundances in Emeralds Reveal Their Formation Environments

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 513
Author(s):  
Raquel Alonso-Perez ◽  
James M. D. Day
Keyword(s):  
Rare Earth ◽  
Trace Element ◽  
Rare Earth Element ◽  
Earth Element ◽  
Regional Metamorphism ◽  
Incompatible Trace Element ◽  
Plate Tectonic ◽  
Element Abundances ◽  
Type Ia ◽  
Ree Patterns

Emeralds require the unusual association of typically compatible elements (Cr, V), with incompatible Be to form, and occur in complex tectonic settings associated with sediments (type IIB; Colombia) or, more commonly, with magmatism and regional metamorphism (IA). Precise rare earth element (REE) and incompatible trace element abundances are reported for a global suite of emeralds, enabling the identification of the environments in which they formed. Type IIB emeralds have nearly flat continental crust normalized REE patterns (La/YbCC = ~2), consistent with a sedimentary source origin. Type IA emerald REE patterns have upturns in the heavy REE (La/YbCC = ~0.3), a feature also shared with South African emeralds occurring in Archaean host rocks. Modeling of type IA emerald compositions indicates that they form from magmatic fluids of sedimentary (S)-type granite melts interacting with Cr, V-rich mafic–ultramafic crustal protoliths. This geochemical signature links emerald formation with continental suture zones. Diamonds, rubies, and sapphires have been considered as ‘plate tectonic gemstones’ based on mineral inclusions within them, or associations with plate tectonic indicators. Emeralds are distinct plate tectonic gemstones, recording geochemical evidence for origin within their mineral structure, and indicating that plate tectonic processes have led to emerald deposit formation since at least the Archaean.

scholarly journals Petrology and rare earth element geochemistry of clastic metasedimentary rocks from the Isua supracrustal belt, West Greenland

1983 ◽  
Vol 112 ◽  
pp. 23-33
Author(s):  
J.L Boak ◽  
R.F Dymek ◽  
L.P Gromet
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Thermal Gradients ◽  
Element Geochemistry ◽  
Metasedimentary Rocks ◽  
Sediment Types ◽  
Supracrustal Belt ◽  
Shallow Basin ◽  
Ree Patterns

An investigation of the petrology and rare-earth element (REE) geochemistry of clastic metasedimentary rocks from the ~ 3800 Ma Isua Supracrustal Belt has been carried out to provide constraints on the nature of early Archaean metamorphie regimes and on the sources of their sedimentary protolith. The assemblages garnet + staurolite + biotite and biotite + kyanite (both with qtz + muse + plag + Hm) characterize the Isua metasediments and represent types common in younger metamorphic belts. Secondary chlorite and sericite occur in most samples. Garnet-biotite geothermometry indicates T = 541 ± 43°C for prograde metamorphism and T = 464 ± 39°C for retrograde metamorphism. Suggested metamorphic conditions of T - 550°C and P - 5 Kb imply burial to at least 15 Km with metamorphic thermal gradients < 40°C/Km. These data argue against excessively steep early Archaean crustal thermal gradients. REE patterns for three museovite-biotite gneisses are strongly fractionated (CeN = 40-100; YbN = 2-8) with variable Eu-anomalies (Eu/Eu* = 0.48-0.95), not unlike patterns for Arehaean felsic voicanic rocks in other areas. Garnet-biotite sehists have less-fractionated light REE, and exhibit a slope reversal for the heavy REE (i.e., GdN< YbN. These most plausibly represent a mixed felsic-mafic (- ultramafic?) protolith. Both sediment types could be the erosion produets of a rapidly emergent voicanic structure shedding debris into a shallow basin.

Petrogenesis of mantle-derived, LILE-enriched Archean monzodiorites and trachyandesites (sanukitoids) in southwestern Superior Province

1989 ◽  
Vol 26 (9) ◽  
pp. 1688-1712 ◽  
Author(s):  
Richard A. Stern ◽  
Gilbert N. Hanson ◽  
Steven B. Shirey
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Mantle Source ◽  
Earth Element ◽  
Crustal Contamination ◽  
Mantle Peridotite ◽  
Superior Province ◽  
Source Regions ◽  
Enriched Mantle ◽  
Ree Patterns

In southwestern Superior Province, diorite, monzodiorite, and trachyandesite ("sanukitoids") occurring within syn- to post-tectonic intrusive complexes and within greenstone belts have the following chemical characteristics: 55–60 wt.% SiO2, MgO > 6 wt.%, Mg# > 0.60, Ni and Cr both > 100 ppm, Na2O + K2O = 6 wt.%, Sr and Ba both 600–1800 ppm, and rare-earth-element (REE) patterns that are strongly light rare-earth-element (LREE) enriched (Cen = 80–250, Ybn = 4 – 10) and show no Eu anomalies. Sanukitoids and their granodioritic derivatives constitute at least 5% of the exposed crust in the study area. The sanukitoids cannot be derived by melting, fractionation, or crustal contamination of basalts or lamprophyres that are coeval with the sanukitoids. Crustal contamination of komatiites fails to explain the high large-ion-lithophile-element (LILE) contents of the sanukitoids. Rather, we suggest that the sanukitoids were derived by hydrous melting of LILE-enriched mantle peridotite at pressures between 10 and 15 kbar. The sanukitoids with steepest REE patterns have the lowest FeO contents, indicating that the part of the mantle source with the highest Mg# had the most fractionated REE pattern prior to melting. Mantle source regions to the sanukitoids had different Mg#'s and were enriched in LILE's (metasomatized) to varying extents by fluids of crustal or mantle origin prior to melting.

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