Rare-earth-element geochemistry of some Archean iron formations north of Lake Superior, Ontario

1988 ◽  
Vol 25 (4) ◽  
pp. 570-580 ◽  
Author(s):  
T. J. Barrett ◽  
P. W. Fralick ◽  
I. Jarvis
Keyword(s):  
Rare Earth ◽  
Red Sea ◽  
Rare Earth Element ◽  
Earth Element ◽  
Sea Water ◽  
Iron Formation ◽  
Submarine Fan ◽  
Eu Anomaly ◽  
Ree Patterns ◽  
Iron Formations

Rare-earth-element (REE) compositions of iron formation from two Archean terrains in western Ontario have been determined in order to assess the possible influence of hydrothermal activity on the REE patterns of chemical sediments. One terrain is characterized by sulfide-facies iron formation in association with volcanic flows and volcaniclastic sediments, whereas the other is dominated by oxide-facies iron formation intercalated within submarine-fan clastic sediments. Mineral separates of chert, magnetite, and pyrite from the iron formations have low ΣREE concentrations (< 20–30 ppm) and display moderate to strong positive Eu anomalies (relative to Archean shale). The positive anomalies (and lack of negative Ce anomalies) indicate that Archean sea water from which iron formation locally precipitated was reduced, although to varying degrees.The REE patterns of mineral separates from a given locality are almost identical, but the patterns for various localities differ in detail. A number of iron-formation samples interbedded within volcanics and at the volcanic–sediment interface show a distinct positive La anomaly and near-flat to slightly heavy-REE (HREE)-enriched patterns. The only modern environment where metalliferous sediments are accumulating with these combined characteristics is the Red Sea brine deeps. By contrast, limited data from iron formation interbedded within the clastic submarine fan suggest a fairly flat pattern with a moderate positive Eu anomaly and no La enrichment. We therefore suggest that the latter pattern typifies nonhydrothermal Archean seawater.Where seawater was influenced by a direct hydrothermal contribution, La enrichment and enhancement of the Eu anomaly could result. However, since periods of low-intensity discharge and (or) bottom-water mixing could eliminate the hydrothermal signal, not all samples from volcanic associations need show these features. By analogy with the Red Sea, preservation of a hydrothermal signal is most likely where circulation in the depositional basin is restricted and bottom waters are strongly reducing. Evidence for such conditions in the volcanic association is provided by the nature of the associated sediments (e.g., carbonaceous slates and unreworked distal turbidites).

Spatial variations in dissolved rare earth element concentrations in the East China Sea water column

2018 ◽  
Vol 205 ◽  
pp. 1-15 ◽  
Author(s):  
Le Duc Luong ◽  
Ryuichi Shinjo ◽  
Nguyen Hoang ◽  
Renat B. Shakirov ◽  
Nadezhda Syrbu
Keyword(s):  
Rare Earth ◽  
Water Column ◽  
East China Sea ◽  
Rare Earth Element ◽  
Earth Element ◽  
Sea Water ◽  
Spatial Variations ◽  
East China ◽  
The East China Sea ◽  
Element Concentrations

Rare earth element patterns of carbonado and yakutite: evidence for their crustal origin

1993 ◽  
Vol 57 (389) ◽  
pp. 607-611 ◽  
Author(s):  
Ken Shibata ◽  
Hikari Kamioka ◽  
Felix V. Kaminsky ◽  
Vassili I. Koptil ◽  
Darcy P. Svisero
Keyword(s):  
Trace Elements ◽  
Rare Earth ◽  
Neutron Activation ◽  
Rare Earth Element ◽  
Earth Element ◽  
Meteorite Impact ◽  
Abundance Patterns ◽  
Eu Anomaly ◽  
Crustal Origin ◽  
Monocrystalline Diamond

AbstractCarbonado and yakutite are both porous aggregates of polycrystalline micrometre-size diamond, with very different characters from those of monocrystalline diamond. The genesis of carbonado is very controversial, whereas yakutite is thought to have been formed by meteorite impact. Neutron activation analyses of trace elements in carbonado and yakutite indicate that their rare earth element (REE) abundance patterns have common characteristics: heavy REEs are not much depleted and a negative Eu anomaly is observed. These patterns are quite different from those of kimberlite and monocrystalline diamond and are similar to those of crustal materials such as shale, supporting the hypothesis of a crustal origin for carbonado and yakutite.

scholarly journals SHRIMP U–Pb and REE data pertaining to the origins of xenotime in Belt Supergroup rocks: evidence for ages of deposition, hydrothermal alteration, and metamorphism

2015 ◽  
Vol 52 (9) ◽  
pp. 722-745 ◽  
Author(s):  
John N. Aleinikoff ◽  
Karen Lund ◽  
C. Mark Fanning
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Detrital Zircon ◽  
Earth Element ◽  
Greenschist Facies ◽  
Eastern United States ◽  
Burial Diagenesis ◽  
Heavy Rare Earth Element ◽  
Eu Anomaly ◽  
Belt Supergroup

The Belt–Purcell Supergroup, northern Idaho, western Montana, and southern British Columbia, is a thick succession of Mesoproterozoic sedimentary rocks with an age range of about 1470–1400 Ma. Stratigraphic layers within several sedimentary units were sampled to apply the new technique of U–Pb dating of xenotime that sometimes forms as rims on detrital zircon during burial diagenesis; xenotime also can form epitaxial overgrowths on zircon during hydrothermal and metamorphic events. Belt Supergroup units sampled are the Prichard and Revett Formations in the lower Belt, and the McNamara and Garnet Range Formations and Pilcher Quartzite in the upper Belt. Additionally, all samples that yielded xenotime were also processed for detrital zircon to provide maximum age constraints for the time of deposition and information about provenances; the sample of Prichard Formation yielded monazite that was also analyzed. Ten xenotime overgrowths from the Prichard Formation yielded a U–Pb age of 1458 ± 4 Ma. However, because scanning electron microscope – backscattered electrons (SEM–BSE) imagery suggests complications due to possible analysis of multiple age zones, we prefer a slightly older age of 1462 ± 6 Ma derived from the three oldest samples, within error of a previous U–Pb zircon age on the syn-sedimentary Plains sill. We interpret the Prichard xenotime as diagenetic in origin. Monazite from the Prichard Formation, originally thought to be detrital, yielded Cretaceous metamorphic ages. Xenotime from the McNamara and Garnet Range Formations and Pilcher Quartzite formed at about 1160–1050 Ma, several hundred million years after deposition, and probably also experienced Early Cretaceous growth. These xenotime overgrowths are interpreted as metamorphic–diagenetic in origin (i.e., derived during greenschist facies metamorphism elsewhere in the basin, but deposited in sub-greenschist facies rocks). Several xenotime grains are older detrital grains of igneous derivation. A previous study on the Revett Formation at the Spar Lake Ag–Cu deposit provides data for xenotime overgrowths in several ore zones formed by hydrothermal processes; herein, those results are compared with data from newly analyzed diagenetic, metamorphic, and magmatic xenotime overgrowths. The origin of a xenotime overgrowth is reflected in its rare-earth element (REE) pattern. Detrital (i.e., igneous) xenotime has a large negative Eu anomaly and is heavy rare-earth element (HREE)-enriched (similar to REE in igneous zircon). Diagenetic xenotime has a small negative Eu anomaly and flat HREE (Tb to Lu). Hydrothermal xenotime is depleted in light rare-earth element (LREE), has a small negative Eu anomaly, and decreasing HREE. Metamorphic xenotime is very LREE-depleted, has a very small negative Eu anomaly, and is strongly depleted in HREE (from Gd to Lu). Because these characteristics seem to be process related, they may be useful for interpretation of xenotime of unknown origin. The occurrence of 1.16–1.05 Ga metamorphic xenotime, in the apparent absence of pervasive deformation structures, suggests that the heating may be related to poorly understood regional heating due to broad regional underplating of mafic magma. These results may be additional evidence (together with published ages from metamorphic titanite, zircon, monazite, and garnet) for an enigmatic, Grenville-age metamorphic event that is more widely recognized in the southwestern and eastern United States.

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.

Mineralogy, bulk and rare earth element geochemistry of massive sulphide-associated hydrothermal sediments of the Brunswick Horizon, Bathurst Mining Camp, New Brunswick

1996 ◽  
Vol 33 (2) ◽  
pp. 252-283 ◽  
Author(s):  
Jan M. Peter ◽  
Wayne D. Goodfellow
Keyword(s):  
Rare Earth ◽  
Sea Water ◽  
Sedimentary Rocks ◽  
Massive Sulphide ◽  
Hydrothermal Fluids ◽  
Iron Formation ◽  
Element Geochemistry ◽  
Bathurst Mining Camp ◽  
Felsic Volcanic ◽  
Ree Patterns

Massive sulphides are spatially and temporally associated with iron formation (IF) and other hydrothermal sedimentary rocks in the vicinity of the Brunswick No. 12, Brunswick No. 6, and Austin Brook deposits, Bathurst Mining Camp. Sulphide-, carbonate-, oxide-, and silicate-predominant IF is present. Carbonate-predominant IF is best developed in and around the Brunswick No. 12 deposit, whereas hematite-bearing IF is absent here but prominent in the Austin Brook–Brunswick No. 6 area. The IF is composed dominantly of Si, CO2, Fe, Mn, and Ca. Minor constituents include Mg, P, Ti, Al, and S. Statistically significant interelement correlations between Eu, Fe, Mn, Pb, Zn, Cd, Au, Ca, Sr, Ba, P, CO2, and S indicate that these elements were precipitated from hydrothermal fluids vented onto the seafloor. Positive interelement correlations between Si, Ti, Al, Mg, K, Zr, rare earth elements (REE's) except Eu, Se, V, Y, Yb, Co, Ni, and Cr reflect the presence of detrital clastic mafic and aluminosilicate minerals and hydrogenous sedimentary components. Felsic volcanic and pyroclastic rocks are considered to be the source for the detritus. REE patterns of IF at Brunswick No. 12 display similarities with those of modern high-temperature hydrothermal vent solutions, sea water, and host rhyolitic tuff and sedimentary rocks. These patterns are largely controlled by the relative proportions of hydrothermal and detrital components. The IF formed from reduced hydrothermal fluids vented into a stratified marine basin. The mineral precipitates were widely dispersed from the sites of venting and massive sulphide accumulation.

Eu anomaly- reliability of the proxy in inferring source composition of clastic Sedimentary rocks: A case study from western Dharwar craton, Karnataka, India

2020 ◽  
Author(s):  
Anirban Mitra ◽  
Sukanta Dey
Keyword(s):  
Rare Earth ◽  
Rare Earth Element ◽  
Earth Element ◽  
Sedimentary Rocks ◽  
Dharwar Craton ◽  
Source Rocks ◽  
Granitic Rocks ◽  
Negative Anomaly ◽  
Eu Anomaly ◽  
Ree Pattern

&lt;p&gt;Use of trace and rare earth element concentration of terrigenous sedimentary rocks to deduce the composition of their source rocks in the hinterland is a very common and efficient practice. The results of geochemical analysis of the metaquartzarenites located at the basal part of Bababudan and Sigegudda belt, late Archean greenstone sequences of western Dharwar craton show that the sediments were most possibly supplied from Paleo to Mesoarchean granitoids of western Dharwar Craton. Rare earth element patterns of these basal quartzites display fractionated REE pattern in variable degree (La&lt;sub&gt;N&lt;/sub&gt;/Yb&lt;sub&gt;N&lt;/sub&gt; =1.47-10.63) with moderate to highly fractionated LREE (La&lt;sub&gt;N&lt;/sub&gt;/Sm&lt;sub&gt;N&lt;/sub&gt;=2.67-8.93) and nearly flat to slighly elevated HREE (Gd&lt;sub&gt;N&lt;/sub&gt;/ Yb&lt;sub&gt;N&lt;/sub&gt;=0.62-1.29) and a significant Eu negative anomaly (avg. Eu/Eu*=0.67). In general, presence of negative Eu anomaly in clastic rocks reflect the widespread occurrence of granitic rocks in the source area, which possess negative Eu anomaly. On the other hand, mechanical enrichment of zircon (having negative Eu anomaly, high HREE concentration and low La&lt;sub&gt;N&lt;/sub&gt;/Yb&lt;sub&gt;N&lt;/sub&gt;), if present, will hamper the whole REE pattern of the sediments and necessarily, do not actually mimic the source composition. Here, in our study, the Th/Sc vs Zr/Sc diagram show mineral Zircon has been concentrated by mechanical concentration in the sedimentary rocks. Few quartzite samples which have high Zr content typically exhibit low La&lt;sub&gt;N&lt;/sub&gt;/Yb&lt;sub&gt;N&lt;/sub&gt; values, reflecting pivotal role of mineral zircon in controlling the REE pattern of the sediments. Hence, in this case, we should be cautious in interpreting of the Eu negative anomaly of the basal quartzites for meticulously identifying their source rock composition. More geochemical and other analytical approaches are required in this regard.&lt;/p&gt;

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