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Incompatible element

About: Incompatible element is a research topic. Over the lifetime, 2420 publications have been published within this topic receiving 154052 citations.


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TL;DR: The Tchircotchmonchiquites as discussed by the authors show a relatively restricted range of initial 87 Sr= 86 Sr ratio (0.70366- 0.70387), of "Nd values (þ2.5 to þ2.7), and rare earth element patterns similar to those of the least differentiated basalts of the Cameroon Line.
Abstract: Summary Dykes of Cenozoic age (37.5 � 2.3 Ma) crop out in the Tchircotcharea (Garoua rift, north Cameroon). They consist of a lamprophyric (monchiquite) series with diopside, subsilicic kaersutite and apatite phenocrysts, Ba-Ti-rich biotite microphenocrysts and Cr-diopside xenocrysts scattered in a matrix of analcitic composition containing oligoclase, albite and sanidine microlites and carbonate ocelli. Major and trace element distributions are interpreted in terms of crystal fractionation of olivine, clinopyroxene, amphibole and Fe-Ti oxides. The Tchircotchmonchiquites show a relatively restricted range of initial 87 Sr= 86 Sr ratio (0.70366-0.70387), of "Nd values (þ2.5 to þ2.7), and rare earth element patterns similar to those of the least differentiated basalts of the Cameroon Line. This supports a common magma source region. This mantle source is infra-lithospheric and is strongly enriched in incompatible elements (light REE, Zr, Sr, Ba) probably transported by volatile- and halogen-rich fluids. The monchiquites appear to be derived by low degrees of partial melting as attested by steep REE patterns and high contents of other incompatible elements, suggesting the presence of residual garnet in the source. Several lines of evidence support the occurrence of phlogopite in the source region of Tchircotchamprophyre magma.

13 citations

Journal ArticleDOI
TL;DR: In this paper, the authors compare field and petrological observations coupled with geochemical and isotopic analyses of samples from the off-axis diapir with those of the nearest on-axis dapir, with a particular focus on the Moho Transition Zone (MTZ), which is defined by the presence of steeply plunging lineations, but in the onaxis case, these lineations rotate gradually into parallelism with the horizontal magmatic lineations of the overlying crust.

13 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reported the PGE-geochemistry of mantle peridotites and Nd-isotope geochemistry of arc related mafic rocks from the Indus Suture Zone (ISZ), western Ladakh.
Abstract: Present study reports the PGE-geochemistry of mantle peridotites and Nd-isotope geochemistry of arc related mafic rocks from the Indus Suture Zone (ISZ), western Ladakh. The total PGE concentration of the Shergol and Suru Valley peridotites (∑PGE = 96–180 ppb) is much higher than that of the primitive mantle and global ophiolitic mantle peridotites. The studied peridotites show concave upward PGE-distribution patterns with higher palladium-group PGE/Iridium-group PGE ratios (i.e., 0.8–2.9) suggesting that the partial melting is not the sole factor responsible for the evolution of these peridotites. The observed PGE-distribution patterns are distinct from residual/refractory mantle peridotites, which have concave downward or flat PGE-distribution patterns. Relative enrichment of palladium-group PGE as well as other whole-rock incompatible elements (e.g., LILE and LREE) and higher Pd/Ir ratio (1.1–5.9) reflects that these peridotites have experienced fluid/melt interaction in a supra-subduction zone (SSZ) tectonic setting. Also, the Shergol mafic intrusives and Dras mafic volcanics, associated with the studied peridotites, have high 143Nd/144Nd ratios (i.e., 0.512908–0.513078 and 0.512901–0.512977, respectively) and positive eNd(t) (calculated for t = 140 Ma) values (i.e., +5.3 to +8.6 and + 5.1 to +6.6, respectively), indicating derivation from depleted mantle sources within an intra-oceanic arc setting, similar to Spongtang and Nidar ophiolites from other parts of Ladakh Himalaya. The transition from SSZ-type Shergol and Suru Valley peridotites to Early Cretaceous tholeiitic Shergol mafic intrusives followed by tholeiitic to calc-alkaline Dras mafic volcanics within the Neo-Tethys Ocean exhibit characteristics of subduction initiation mechanism analogous to the Izu-Bonin-Mariana arc system within western Pacific.

13 citations

Journal ArticleDOI
TL;DR: In this paper, the authors presented a new petrological-geochemical data set for the Monte Capio and Alpe Cevia mafic-ultramafic sequences, which are exposed in the deepest levels of the Ivrea-Verbano Zone.
Abstract: This study presents a new petrological–geochemical data set for the Monte Capio and Alpe Cevia mafic–ultramafic sequences, which are exposed in the deepest levels of the Ivrea–Verbano Zone. These sequences are composed of a peridotite core, with dunite in the center, mantled by minor orthopyroxene-dominated pyroxenites and subordinate hornblende gabbronorites. Amphibole is ubiquitous in the peridotites and the pyroxenites (≤ 15 vol % and 10–40 vol %, respectively), and the peridotite–pyroxenite associations are frequently crosscut by amphibole-rich (45–90 vol %) veins/dykes showing sinuous-to-sharp planar boundaries towards host rocks. The whole-rock Mg# [100 × Mg/(Mg + Fetot2+)] decreases from the peridotites to the pyroxenites and the crosscutting amphibole-rich dykes (84–81, 80–77, and 73–66, respectively), consistently with the Mg# variations shown by included orthopyroxene, clinopyroxene, and amphibole. Olivine has relatively low forsterite and NiO amounts (84–78 mol % and ≤ 0.14 wt%), and spinel is characterized by low Cr# [100 × Cr/(Cr + Al)] of 7–24. The anorthite content of plagioclase varies from 91 to 88 mol% in plagioclase-bearing pyroxenites to 91–75 mol% in amphibole-rich dykes. The chondrite-normalized REE patterns of amphibole from peridotites and pyroxenites show nearly flat MREE–HREE, no evident Eu anomaly, and LREE that are slightly depleted to slightly enriched with respect to MREE. Amphibole from the amphibole-rich veins/dykes exhibits slight LREE depletion. Whole-rock and amphibole separates show substantial variations in initial Nd–Sr isotopic compositions (e.g., whole-rock eNd calculated at 290 Ma ranges from − 0.3 to − 4.7), irrespective of the rock-type and of incompatible element amphibole compositions. We propose that the Monte Capio–Alpe Cevia dunites formed by cooling of magma lenses that intruded the lowermost continental crust of the Ivrea–Verbano Zone. The chemically evolved signature of the dunites documents earlier crystallization of chemically primitive dunites at lower levels, or olivine fractionation within the dunites during melt ascent. Associated pyroxene-bearing peridotites show a magmatic evolution ruled by reaction of a melt-poor crystal mush with migrating melts relatively rich in SiO2 and H2O, which developed orthopyroxene and amphibole at the expenses of olivine ± clinopyroxene. These migrating melts may be reconciled with those feeding the crosscutting amphibole-rich veins/dykes, whose compositions suggest formation by chemically evolved H2O-rich basalts with an arc-type incompatible trace-element fingerprint. Unraveling the origin of the Monte Capio–Alpe Cevia pyroxenites is hampered by the complex open-system magmatic evolution, which also included assimilation of material released by basement metasediments and/or involvement of primary melt batches with different compositions.

13 citations

Journal Article
TL;DR: In this paper, the major and trace element whole-rock analyses for eight spinel peridotite nodules and their host basalt from Quaternary volcanoes in Vestspitsbergen are presented.
Abstract: Mineral compositions and major and trace element whole-rock analyses for eight spinel peridotite nodules and their host basalt from Quaternary volcanoes in Vestspitsbergen are presented. Modally the nodules range from harzburgite, lherzolite (dominant) and olivine websterite, and they are consid­ ered to represent mantle material. The olivines range in composition from Fo 88.1 to 92.0, the ortho­ pyroxenes have 100 Mg /(Mg + Fe') ratios between 88.9 to 92.3. The clinopyroxenes are chrome­ diopside and the oxide phase is Alor Cr-spinel. The compatible trace elements of the nodules correlate with their modal composition. Thus Se corre­ late positively with clinopyroxene, whereas Ni and Co correlate positively with olivine. La, Ta, Th, U and K show highest concentrations in some of the most refractory nodules, and their REE patterns are very variable. The refractory nature of some of the nodules is thought to relate to an earlier basalt extraction from the mantle. This 'refractory' mantle was subsequently enriched in the highly incompatible elements, probably by the veining or the metasomatism by alkali basalt. The host basalt can be modelled, in terms of RE elements, to represent a partial melt (around 3% batch melting) of a composite source, represented by the spinel peridotites nodules.

13 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20237
202216
202157
202056
201960
201851