scholarly journals Incompatible element ratios in oceanic basalts and komatiites: Tracking deep mantle sources and continental growth rates with time

2003 ◽  
Vol 4 (1) ◽  
pp. 1-28 ◽  
Author(s):  
Kent C. Condie
Keyword(s):  
Growth Rates ◽  
Incompatible Element ◽  
Element Ratios ◽  
Deep Mantle ◽  
Mantle Sources ◽  
Oceanic Basalts ◽  
Continental Growth

The occurrence of niobian zirconolite, pyrochlore and baddeleyite in the Kovdor carbonatite complex, Kola Peninsula, Russia

1996 ◽  
Vol 60 (401) ◽  
pp. 639-646 ◽  
Author(s):  
C. Terry Williams
Keyword(s):  
Kola Peninsula ◽  
Incompatible Element ◽  
Fluid Composition ◽  
Carbonatite Complex ◽  
Compositional Zoning ◽  
Accessory Minerals ◽  
Element Ratios ◽  
Backscattered Electron ◽  
Oxide Minerals ◽  
High Concentrations

AbstractThe compositions and textural relationships of the oxide minerals zirconolite, pyrochlore and baddeleyite are described. These occur as accessory minerals, often intergrown with each other, from a phoscorite rock associated with the Kovdor carbonatite complex. Both the zirconolite and baddeleyite have relatively high concentrations of Nb and Ta; the pyrochlore is rich in U and Ta. Backscattered electron images, coupled with detailed microprobe analyses, reveal complex compositional zoning in zirconolite and pyrochlore which reflect changes in the fluid composition during growth of these minerals. A comparison is made of incompatible element ratios Zr/Hf, Nb/Ta and Th/U between the three accessory minerals.

A preliminary assessment of the application of Sr, Nd, Pb, He and N isotope analysis to fluid inclusions in kimberlite olivine: A new approach to trace deep-mantle sources

2020 ◽  
Author(s):  
Andrea Giuliani ◽  
Janne M. Koornneef ◽  
Peter Barry ◽  
Patrizia Will ◽  
Henner Busemann ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Trace Element ◽  
Mass Spectrometer ◽  
Fluid Inclusions ◽  
Noble Gas ◽  
Isotope Analysis ◽  
Helium Isotope ◽  
New Approach ◽  
Deep Mantle ◽  
Mantle Sources

<p>Kimberlites are the deepest melts that reach Earth’s surface and, therefore, can provide unique insights into the composition and evolution of the convective mantle through time. Application of isotope geochemistry to trace the composition of kimberlite sources has thus far been hindered by the ubiquitous alteration and incorporation of xenocrystic material in kimberlite rocks. Bulk-kimberlite analyses are typically considered reliable for Nd and Hf isotopes due to their overwhelmingly higher concentrations in kimberlite melts compared to common mantle and crustal contaminants. Conversely, Sr and Pb isotope compositions of bulk kimberlite samples are seldom considered representative of their parental melts thus requiring analysis of robust magmatic phases, primarily perovskite. Addressing the primary (i.e. magmatic) isotopic composition of volatile elements, such as N and noble gases, requires analyses of volatile-rich phases, and fluid inclusions in olivine represent a typical primary target in mantle-derived magmas. However, fluid inclusions in kimberlitic olivine are dominantly secondary in origin. Secondary inclusions can form at any time after crystallisation of their mineral host, which requires assessment of the origin of trapped fluids (i.e. pristine magmatic fluids, crustal fluids of external derivation, or combination thereof) before their isotopic composition can be used to make inferences about kimberlite mantle sources.</p><p>Here we present trace-element and Sr-Nd-Pb-He-N isotopic compositions of multiple olivine aliquots representing two different magmatic units of the ~88 Ma Wesselton kimberlite (Kimberley, South Africa). The Sr and Nd isotopic composition of olivine analysed by isotope-dilution (ID) TIMS are within the narrow range of perovskite <sup>87</sup>Sr/<sup>86</sup>Sr (0.7043-0.7046) and whole-rock <sup>143</sup>Nd/<sup>144</sup>Nd (eNd<sub>i</sub> = 0.4–2.2) for the Kimberley kimberlites. These results indicate that the secondary fluid inclusions, which dominate the incompatible trace-element budget of olivine separates, have a pristine magmatic origin devoid of crustal contribution.</p><p>Helium isotope compositions were measured by laser heating of 1.6 to 9.8 mg of olivine using an ultrahigh-sensitivity compressor-source noble gas mass spectrometer. <sup>3</sup>He/<sup>4</sup>He ratios are between 1.6 R<sub>A</sub> and 3.7 R<sub>A</sub> (where R<sub>A</sub> indicates the atmospheric <sup>3</sup>He/<sup>4</sup>He ratio), values more radiogenic than MORBs but comparable to HIMU OIBs. These results indicate a high time-integrated (U+Th)/He ratio in the source of the Kimberley kimberlites, which is consistent with the moderately high (i.e. HIMU-like) time-integrated U/Pb ratio implied by elevated initial <sup>206</sup>Pb/<sup>204</sup>Pb in Wesselton olivine (19.1-19.5), Kimberley kimberlites (up to 19.9) and megacrysts in southern African Cretaceous kimberlites (up to 20.5). The combination of low <sup>3</sup>He/<sup>4</sup>He, moderately radiogenic <sup>87</sup>Sr/<sup>86</sup>Sr, and negative d<sup>34</sup>S values (-2.6‰ to -5.7‰) require a contribution from subducted recycled material in the source of the Kimberley kimberlites. Conversely, a preliminary N isotope analysis of Wesselton olivine by in-vacuo crushing using a noble gas mass spectrometer returned a mantle-like d<sup>15</sup>N of -2.9‰, which might suggest limited recycling of surface N (d<sup>15</sup>N >0‰) in the source of these kimberlites. We conclude that the combination of Sr-Nd-Pb and He-N isotope tracing of fluid inclusions in olivine can provide a robust new approach to address the composition of kimberlite sources and, therefore, the evolution of the deep mantle through time.</p>

A comparative geochemical study of Mars and Earth basalt petrogenesis

2013 ◽  
Vol 50 (1) ◽  
pp. 78-93 ◽  
Author(s):  
John D. Greenough ◽  
Avee Ya’acoby
Keyword(s):  
Incompatible Element ◽  
A Priori ◽  
Correlation Coefficients ◽  
Small Sample ◽  
Geochemical Data ◽  
Data Set ◽  
Element Ratios ◽  
Highly Correlated ◽  
Small Sample Sizes ◽  
Priori Information

Geochemical data, from the Mars Meteorite Compendium web site, for 13 basaltic meteorites, possibly from only four localities on Mars, are used to study Martian petrogenetic processes. To achieve this goal, an exploratory data analysis technique, multidimensional scaling (MDS), is used to quantitatively assess the relative behavior (measured with correlation coefficients) of 160 incompatible element ratios involving 25 “trace” elements. The ratios behave as in Earth basalts, suggesting that relative element incompatibility is similar in both planets. Because mineralogy controls incompatibility, the mineralogy of Earth and Mars mantles appears similar. In addition, results suggest that ratios involving elements with highly different incompatibility (e.g., La/Yb) are dominantly controlled by % melting. Plots of SiO2 (pressure proxy; decreases with increasing pressure) versus La/Yb and Nb/Y (decrease as melting increases) imply that Mars basalts, like Earth tholeiites, reflect high percentages of melting, but opposite to Earth, % melting appears to increase with increasing pressure. The moderately correlated, positive, SiO2–La/Yb Mars relationship parallels highly correlated Lunar KREEP data and contrasts with Earth’s negative correlation. The positive relationships may reflect restricted mantle convection in some (Mars and the Moon are smaller) planetary bodies. Using similarly incompatible element ratios that are sensitive to source composition, to compare Mars and Earth with MDS, Mars sources most resemble depleted Earth mantle. Additionally, these ratios group Mars sources into enriched, depleted, and intermediate types. The groupings are the same as those suggested by isotopes, and we conclude that trace element data support the hypothesis that chemical variation in Mars may reflect crystallization of a Mars magma ocean. The natural patterns in ratios and samples revealed using MDS, which has no a priori information about relationships, support integrity of the geochemical data set, despite potential shortcomings such as small sample sizes, alteration, and weathering. However, whether the meteorites are representative of Mars as a whole is unknown.

scholarly journals Pyrrhotite–silicate melt partitioning of rhenium and the deep rhenium cycle in subduction zone

Geology ◽  
2021 ◽  
Author(s):  
Shuo Xue ◽  
Yuan Li
Keyword(s):  
Partition Coefficients ◽  
Laboratory Experiments ◽  
Silicate Melt ◽  
Primitive Mantle ◽  
Total Iron Content ◽  
Slab Melting ◽  
Deep Mantle ◽  
Depleted Mantle ◽  
Oceanic Basalts ◽  
Increasing Temperature

The Re-Os isotopic system serves as an important tracer of recycled crust in Earth’s deep mantle because of the large Re/Os ratios and time-integrated enrichment of radiogenic Os in Earth’s crust. However, the Re distribution in Earth’s known reservoirs is mass imbalanced, and the behavior of Re during subduction remains little understood. We performed laboratory experiments to determine the partition coefficients of Re between pyrrhotite and silicate melt (DRepo/sm) at 950–1080 °C, 1–3 GPa, and oxygen fugacities (in log units relative to the fayalite-magnetite-quartz [FMQ] buffer) of FMQ –1.3 to FMQ +2. The obtained DRepo/sm values are 200–25,000, which increase with decreasing oxygen fugacity and the total iron content (FeOtot) of silicate melt but decrease with increasing temperature or decreasing pressure. Applying DRepo/sm to constrain the behavior of Re during slab melting demonstrates that slab melts contribute minimal Re to the sub-arc mantle, with most Re dissolved in sulfides subducted into Earth’s deep mantle. Deep storage of recycled oceanic basalts and sediments can explain the mass imbalance of Re in Earth’s primitive mantle, depleted mantle, and crust.

Petrological and geochemical constraints on the genesis of Mesozoic–Cenozoic magmatism of King George Island, South Shetland Islands, Antarctica

1991 ◽  
Vol 3 (3) ◽  
pp. 293-308 ◽  
Author(s):  
K. Birkenmajer ◽  
L. Francalanci ◽  
A. Peccerillo
Keyword(s):  
Incompatible Element ◽  
South Shetland Islands ◽  
Geochemical Data ◽  
King George Island ◽  
Island Arcs ◽  
Calc Alkaline ◽  
Constant Composition ◽  
Shetland Islands ◽  
Element Ratios ◽  
Incompatible Trace Elements

Petrological and geochemical data are reported for a series of Late Cretaceous-Middle Miocene volcanic, hypabyssal and intrusive rocks from King George Island (KGI) and from nearby Ridley Island, South Shetland Islands. Major element data indicate a calc-alkaline, basic to intermediate composition for the analysed samples. Although emplaced on a continental margin, the KGI rocks generally display low abundances of incompatible trace elements, close to those typically observed in calc-alkaline suites erupted in intraoceanic island arcs. A few samples have a significant negative Ce anomaly. Many incompatible elements define smooth positive trends on interelemental variation diagrams which suggests that magmas erupted at different times on KGI maintained a rather constant composition in terms of incompatible element ratios. Geochemical modelling, based on Sr isotope ratios and incompatible element ratios, suggests that the primary calc-alkaline magmas of KGI were all generated in an upper mantle modified by addition of small amounts of pelagic sediments dragged down by subduction processes.

Isotopic study of basaltic dikes in the Nain Plutonic Suite: evidence for enriched mantle sources

1993 ◽  
Vol 30 (6) ◽  
pp. 1141-1146 ◽  
Author(s):  
R. W. Carlson ◽  
R. A. Wiebe ◽  
R. I. Kalamarides
Keyword(s):  
Mantle Source ◽  
Incompatible Element ◽  
Isotopic Study ◽  
Major Element Composition ◽  
Enriched Mantle ◽  
Mantle Sources ◽  
Mineral Isochron ◽  
Lithospheric Mantle Source ◽  
Nain Plutonic Suite ◽  
Alkalic Basalts

Basaltic dikes cutting the Nain Plutonic Suite (NPS) of Labrador include two chemically distinct groups. One is a high-Fe tholeiitic to transitional alkalic composition similar to some of the magmas involved in the formation of the NPS. The other, distinguished by high phosphorus and incompatible element contents, is similar in major element composition to intraplate oceanic alkalic basalts. A Rb–Sr mineral isochron for one high-P2O5 sample defines an age of 1276 ± 23 Ma indicating that it is similar in age to, or only slightly younger than, the circa 1305 Ma anorthosites.Compositional and isotopic characteristics of the high- and low-P2O5 dikes show that the gross features of their initial isotopic characteristics (i.e., low 87Sr/86Sr, negative εNd, nonradiogenic Pb) probably derive from a distinct lithospheric mantle source with similar characteristics. To have developed these isotopic characteristics by the time of dike emplacement, their mantle source must have formed and separated from oceanic-type upper mantle well prior to Nain anorthosite genesis, possibly between 2.0 and 2.6 Ga.

Low recycling efficiency of boron into the deep mantle

2020 ◽  
Author(s):  
Horst Marschall ◽  
Matthew Jackson
Keyword(s):  
Melt Inclusions ◽  
Mobile Elements ◽  
Primitive Mantle ◽  
Arc Magmas ◽  
Ocean Island Basalts ◽  
Deep Mantle ◽  
Mantle Sources ◽  
Source Mantle ◽  
Geochemical Tracer ◽  
Morb Source

<p>Boron is a distinctly crustal element in that it is strongly enriched in the surface reservoirs, such as continental crust, seawater, sediments, serpentinites and altered oceanic crust, relative to the mantle. These B-enriched reservoirs are also isotopically very distinct from the regular depleted upper mantle (d<sup>11</sup>B = -7.1 ±0.9 ‰ [10.1016/j.gca.2017.03.028]). This has encouraged the idea that boron could be an ideal tracer for subducted surface materials in the deep mantle in the form of isotopically anomalous recycled components in ocean island basalts (OIB) and enriched MORB. Yet, the potential of a geochemical tracer of this type is weakened by its extraction from the slab at the onset of subduction by dewatering and metamorphic dehydration, because this process depletes the recycled components in fluid-mobile elements. As such, this “subduction barrier” diminishes the deep recycling efficiency of incompatible, fluid-mobile tracers like B.</p><p>This study focuses on the B abundances and B isotopic compositions of glasses and melt inclusions that show low Cl/K ratios and are thought to represent the uncontaminated mantle signal from the HIMU (Tuvalu and Mangaia), EM1 (Pitcairn) and EM2 (Samoa) sources. Strikingly, all samples are depleted in boron by a factor of approximately 1.5 to 4 relative to non-fluid-mobile elements of similar incompatibility (e.g. LREE, P, Be). This negative boron anomaly is ubiquitous in OIB and is consistent with the results of previous studies [10.1016/0016-7037(95)00402-5; 10.1016/j.epsl.2018.12.005]. It also mirrors their characteristic negative Pb anomaly. These anomalies show that the mantle sources of OIB are depleted in B (and Pb) relative to non-fluid-mobile elements of similar incompatibility and relative to the MORB-source mantle. This is best explained by the presence in the OIB sources of recycled components that are enriched in all incompatible elements except for the fluid-mobile B (and Pb). The fluid mobile elements must have been preferentially extracted in the subduction barrier and returned to the surface on the short path via arc magmas. Arc magmas consistently show a general enrichment in isotopically heavy boron [10.1007/978-3-319-64666-4_9] with positive B anomalies.</p><p>Despite of the low recycling efficiency of boron into the convecting mantle, OIB still have B isotope signatures that are distinct from those of MORB. Previous studies have reported OIB signatures slightly lighter than MORB and the primitive mantle [10.1016/j.epsl.2018.12.005]. However, our study exclusively finds isotopically heavy B with a range in d<sup>11</sup>B from MORB-like values (-8.6 ±2.0 ‰) up to -2.5 ±1.5‰ for EM1 and HIMU lavas. The total OIB range is small but significant, and is consistent with the deep recycling of material that is strongly depleted in boron, but isotopically distinct (with isotopically heavy B in the case of our EM1 and HIMU samples). The B depletion combined with the B isotopic anomaly in OIB shows that B is efficiently (but not quantitatively) removed from the slab during subduction, and that isotopically distinct mantle domains are thus produced. The subduction barrier for boron increases its strength as a tracer in arcs, but it diminishes its potential as a tracer of deep mantle recycling.</p>

New insights for the mantle source components of the most primitive recent basaltic rocks from central and western Anatolia: Evidences for the involvement of pyroxenite and the peridotite source domains

2020 ◽  
Author(s):  
Biltan Kurkcuoglu ◽  
Tekin Yurur
Keyword(s):  
Mantle Source ◽  
Incompatible Element ◽  
Central Anatolia ◽  
Spinel Peridotite ◽  
Western Anatolia ◽  
The West ◽  
Cinder Cones ◽  
Basaltic Rocks ◽  
Mantle Sources ◽  
Source Component

<div> <p>Basaltic activities  developed  extensively in central and western Anatolia since middle –Miocene to quaternary time, the most primitive lavas are  situated at  the eastern end of  central Anatolia, (southern Sivas) and the most recent ones  are situtated in central (basaltic cinder cones at south of Hasandağ) and also in western Anatolia (Kula region),  Among those  primitive recent  lavas, mantle sources that are responsible for the generation of basaltic rocks is  still a matter of a debate.          </p> <p>Previous studies suggested  that  spinel peridotite source   is the dominant source  component  for many of the basaltic rocks which are situated in several different locations in central Anatolia, including, Erciyes and Hasandağ stratovolcanoes,  Erkilet, Develidağ, Karapınar vents and Salanda fissure eruptions while Sivas fissure basalts in the east,  Gediz and Kula  basalts in the west, were  derived  mostly  from  the  garnet peridotite sources, but , the  specific  incompatible element ratios  and the melting model based on Rare Earth Elements obviously  indicate that  these basaltic rocks could not be solely generated  from  the garnet- spinel transition zone,   instead another mantle source component need to be involved  in the generation of the basaltic rocks.</p> <p>Tb/Yb(N) and Zn/Fe  ratios provide significant values   in order to constraint for the magmas  generated from the asthenosphere.  Tb/Yb(N) ratio seperates  garnet – spinel transition [1]  and Zn/Fe  ratio  displays separation between the peridotite-derived (Zn/Fe <12, [2,3]) and pyroxenite-derived (13-20 [2,3]) melts.  Zn/Fe, as well as  the  Tb/Yb(N) ratios and the melting model display  that single spinel  source   component  is not solely   responsible for  the generation of  the basaltic rocks,   pyroxenite  source domain  should    also  be involved in   during  the genesis of these rocks as well, besides, the  contributions from  the both of the  mantle source domains also explain the  depleted  magma nature that is observed  in some of recent basaltic rocks ( e.g, Salanda  and  Hasandağ  volcanic  systems) which is diffrent  from the dominated alkaline character,  generally observed  as  the   final products  of central Anatolian  magmatism   </p> <p><em>1.Wang et al., 2002, J.Geophys.Res.vol:107,ECV 5 1-21</em></p> <p><em>2 .Le Roux, et al.,2011,EPSL, vol:307, 395-408</em></p> </div><p><em>3. Ducea, et al.,2013, GEOLOGY, Vol:41, 413-417</em></p><p><em>This study   is financially supported by Hacettepe University, BAB project no: FHD-2018-17283</em></p>

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