Relative europium concentration in a mineral is either enriched or depleted
The europium anomaly is the phenomenon whereby the europium (Eu) concentration in a mineral is either enriched or depleted relative to some standard, commonly a chondrite or mid-ocean ridge basalt (MORB). In geochemistry a europium anomaly is said to be "positive" if the Eu concentration in the mineral is enriched relative to the other rare-earth elements (REEs), and is said to be "negative" if Eu is depleted relative to the other REEs.
While all lanthanides form relatively large trivalent (3+) ions, Eu and cerium (Ce) have additional valences, europium forms 2+ ions, and Ce forms 4+ ions, leading to chemical reaction differences in how these ions can partition versus the 3+ REEs. In the case of Eu, its reduced divalent (2+) cations are similar in size and carry the same charge as Ca2+, an ion found in plagioclase and other minerals. While Eu is an incompatible element in its trivalent form (Eu3+) in an oxidizing magma, it is preferentially incorporated into plagioclase in its divalent form (Eu2+) in a reducing magma, where it substitutes for calcium (Ca2+).[2]
Enrichment or depletion is generally attributed to europium's tendency to be incorporated into plagioclase preferentially over other minerals. If a magma crystallizes stable plagioclase, most of the Eu will be incorporated into this mineral, causing a higher than expected concentration of Eu in the mineral versus other REE in that mineral (a positive anomaly). The rest of the magma will then be relatively depleted in Eu with a concentration of Eu lower than expected versus the concentrations of other REEs in that magma. If the Eu-depleted magma is then separated from its plagioclase crystals and subsequently solidifies, its chemical composition will display a negative Eu anomaly (because the Eu is locked up in the plagioclase left in the magma chamber). Conversely, if a magma accumulates plagioclase crystals before solidification, its rock composition will display a relatively positive Eu anomaly.[3][4]
A well-known example of the Eu anomaly is seen on the Moon. REE analyses of the Moon's light-colored lunar highlands show a large positive Eu anomaly due to the plagioclase-rich anorthosite comprising the highlands. The darker lunar mare, consisting mainly of basalt, shows a large negative Eu anomaly. This has led geologists to speculate as to the genetic relationship between the lunar highlands and mare. It is possible that much of the Moon's Eu was incorporated into the earlier, plagioclase-rich highlands, leaving the later basaltic mare strongly depleted in Eu.[5]
^McLeod, Claire L.; Krekeler, Mark. P. S. (August 2017). "Sources of Extraterrestrial Rare Earth Elements: To the Moon and Beyond". Resources. 6 (3). MDPI: 40. Bibcode:2017Resou...6...40M. doi:10.3390/resources6030040.
^Sinha, Shyama P.; Scientific Affairs Division, North Atlantic Treaty Organization (1983). "The Europium anomaly". Systematics and the properties of the lanthanides. pp. 550–553. ISBN 978-90-277-1613-2.
^Weill, D. F.; Drake, M. J. (1973). "Europium Anomaly in Plagioclase Feldspar: Experimental Results and Semiquantitative Model". Science. 180 (4090): 1059–1060. Bibcode:1973Sci...180.1059W. doi:10.1126/science.180.4090.1059. PMID 17806582.
^Bau, M. (1991). "Rare-earth element mobility during hydrothermal and metamorphic fluid-rock interaction and the significance of the oxidation state of europium". Chemical Geology. 93 (3–4): 219–230. Bibcode:1991ChGeo..93..219B. doi:10.1016/0009-2541(91)90115-8.
^Mcsween, Jr., Harry Y.; Huss, Gary R. (30 June 2010). "Composition of the Lunar Mantle and Core". Cosmochemistry. pp. 456–460. ISBN 978-0-521-87862-3.
The europiumanomaly is the phenomenon whereby the europium (Eu) concentration in a mineral is either enriched or depleted relative to some standard,...
europiumanomaly than does monazite, and hence is the major source of europium today. The development of easy methods to separate divalent europium from...
the relative abundance of europium compared to the other REE is often markedly higher or lower, and called the europiumanomaly. It arises because Eu2+...
important differences; for example, mare basalts show a large negative europiumanomaly. The type location is Mare Crisium sampled by Luna 24. KREEP Basalts...
results in a positive Ce-anomaly. Cerium EuropiumEuropiumanomaly Lanthanides Rare-earth elements Stratigraphic trends in cerium anomaly in authigenic marine...
Lunar Magma Ocean explains the Moon's largely anorthositic crust, europiumanomaly, and KREEP material. The Lunar Magma Ocean was initially proposed by...
primarily in the Archean. These older BIFs tend to show a positive europiumanomaly consistent with a hydrothermal source of iron. By contrast, Lake Superior-type...
The light rare earth elements LREE are also elevated but without a europiumanomaly. Another source gives: Estimates from petrographic observation of average...
values between 1.4 and 6.1. A positive europiumanomaly is very weakly expressed and in more felsic appinites the anomaly turns slightly negative (0.96-0.70)...
mendelevium is more easily reduced to the +2 state than thulium or even europium (the lanthanide with the most stable +2 state, on account of its half-filled...
magnitude of +3.67. The spectrum displays abundance anomalies of the elements strontium, chromium, and europium. It was first classified as an Am star in 1965...
by the impact that formed the Chicxulub crater. Similarly, an iridium anomaly in core samples from the Pacific Ocean suggested the Eltanin impact of...
contrast agents are either paramagnetic (e.g.: gadolinium, manganese, europium), and are used to shorten T1 in the tissue they accumulate in, or super-paramagnetic...
Mutsuo; Toriyama, Motohiro; Niihara, Koichi (March 1998). "Curie temperature Anomaly in Lead Zirconate Titanate/Silver Composites". Journal of the American...
placed in group 2. These tend to relate to kainosymmetry and the first-row anomaly: the first orbital of any type is unusually small, since unlike its higher...
proposed measuring the systematics of the nuclear properties of a series of europium isotopes to test the universality of the rule (Z. Phys. 1997). Researchers...
containing traces of europium-151, europium-153 and cobalt-59, which neutron absorption transforms into radioactive europium-152, europium-154 and cobalt-60...
of a nuclear quadrupole moment in order to explain anomalies in the hyperfine structure of Europium, Cassiopium(older name for Lutetium), Indium, Antimony...
ion Li+. Lithium may increase the risk of developing Ebstein's cardiac anomaly in infants born to women who take lithium during the first trimester of...
Vandemeulebrouck, J.; Poussielgue, N.; Tabbagh, J.; Punongbayan, R. (2003). "Radon anomaly in the soil of Taal volcano, the Philippines: A likely precursor of the...
dominant +5 oxidation state, with the other group 5 elements, with a few anomalies due to relativistic effects. A limited investigation of dubnium chemistry...
shell has only one electron (the final electron is in a lower shell). This anomaly is observed in the neighboring metals niobium (41), molybdenum (42), and...
example, the 4d elements have the greatest concentration of Madelung anomalies, because the 4d–5s gap is larger than the 3d–4s and 5d–6s gaps. For the...
Janet's left-step table. Arguments for this often rest on the first-row anomaly trend (s >> p > d > f), which states that the first element of each group...
matching an F-type main-sequence star with abundance anomalies of strontium, chromium, and europium in the spectrum. It is a variable star of type Alpha2...
A7VpSrCrEu, where the suffix notation indicates abundance anomalies of strontium, chromium, and europium. The star is 437 million years old with 2.3 times the...
classification of ApSrEuCr, displaying strong abundance anomalies of the elements strontium, europium, and chromium. Abt and Morrell (1995) found a class...