scispace - formally typeset
Search or ask a question
Topic

Incompatible element

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


Papers
More filters
Journal ArticleDOI
TL;DR: In this paper, the authors present new data on mineralogical, major and trace element compositions of lavas from the northernmost segment of the Kolbeinsey Ridge (NKR), showing evidence for mixing between different mantle sources and magma mixing.
Abstract: We present new data on mineralogical, major and trace element compositions of lavas from the northernmost segment of the Kolbeinsey Ridge (North Kolbeinsey Ridge, NKR). The incompatible element enriched North Kolbeinsey basalts lie on a crystal fractionation trend which differs from that of the other Kolbeinsey segments, most likely due to higher water contents (~0.2%) in the NKR basalts. The most evolved NKR magmas erupt close to the Jan Mayen Fracture Zone, implying increased cooling and fractionation of the ascending magmas. Mainly incompatible element-enriched basalts, as well as some slightly depleted lavas, erupt on the NKR. They show evidence for mixing between different mantle sources and magma mixing. North Kolbeinsey Ridge magmas probably formed by similar degrees of melting to other Kolbeinsey basalts, implying that no lateral variation in mantle potential temperature occurs on the spreading axis north of the Iceland plume and that the Jan Mayen Fracture Zone does not have a cooling effect on the mantle. Residual garnet from deep melting in garnet peridotite or from enriched garnet pyroxenite veins does not play a role. The incompatible element-enriched source has high Ba/La and Nb/Zr, but must be depleted in iron. The iron-depleted mantle is less dense than surrounding mantle and leads to the formation of the North Kolbeinsey segment and its shallow bathymetry. The enriched NKR source formed from a relatively refractory mantle, enriched by a small degree melt rather than by recycling of enriched basaltic crust. The depleted mantle source resembles the mantle of the Middle Kolbeinsey segment with a depletion in incompatible elements, but a fertile major element composition.

32 citations

Journal ArticleDOI
TL;DR: The mid-Tertiary lamprophyre dike swarm from Hermosillo (Sonora, NW Mexico) has calc-alkaline characteristics and includes NNW-striking, amphibole-phyric spessartite (~85% of the swarm) and NNE-striping, phlogopite-phyoric kersantite as mentioned in this paper.

32 citations

Journal ArticleDOI
TL;DR: It is hypothesized that rapid increases in mantle heterogeneity indicate the recycling of supracrustal materials back into Earth’s mantle via subduction, and new observations point to a ≥ 3.2 Ga onset of global subduction processes via plate tectonics.
Abstract: Progressive mantle melting during the Earth’s earliest evolution led to the formation of a depleted mantle and a continental crust enriched in highly incompatible elements. Re-enrichment of Earth’s mantle can occur when continental crustal materials begin to founder into the mantle by either subduction or, to a lesser degree, by delamination processes, profoundly affecting the mantle’s trace element and volatile compositions. Deciphering when mantle re-enrichment/refertilization became a global-scale process would reveal the onset of efficient mass transfer of crust to the mantle and potentially when plate tectonic processes became operative on a global-scale. Here we document the onset of mantle re-enrichment/refertilization by comparing the abundances of petrogenetically significant isotopic values and key ratios of highly incompatible elements compared to lithophile elements in Archean to Early-Proterozoic mantle-derived melts (i.e., basalts and komatiites). Basalts and komatiites both record a rapid-change in mantle chemistry around 3.2 billion years ago (Ga) signifying a fundamental change in Earth geodynamics. This rapid-change is recorded in Nd isotopes and in key trace element ratios that reflect a fundamental shift in the balance between fluid-mobile and incompatible elements (i.e., Ba/La, Ba/Nb, U/Nb, Pb/Nd and Pb/Ce) in basaltic and komatiitic rocks. These geochemical proxies display a significant increase in magnitude and variability after ~3.2 Ga. We hypothesize that rapid increases in mantle heterogeneity indicate the recycling of supracrustal materials back into Earth’s mantle via subduction. Our new observations thus point to a ≥ 3.2 Ga onset of global subduction processes via plate tectonics.

32 citations

Journal ArticleDOI
TL;DR: Basaltic lavas from the AMAR valley and the Narrowgate region of the FAMOUS Valley on the Mid-Atlantic Ridge (36° to 37° N) range in texture from aphyric to highly plagioclase phyric (>25% large plagiocase phenocrysts) as discussed by the authors.
Abstract: Basaltic lavas from the AMAR Valley and the Narrowgate region of the FAMOUS Valley on the Mid-Atlantic Ridge (36° to 37° N) range in texture from aphyric to highly plagioclase phyric (>25% large plagioclase phenocrysts). Based on 87Sr/86Sr and 143Nd/144Nd ratios, most of these lavas can be subdivided into two distinct, isotopically homogeneous, groups: Group I has lower 87Sr/86Sr (0.70288±1) and higher 143Nd/144Nd (0.51312±1) ratios; Group II has higher 87Sr/86Sr (0.70296±1) and lower 143Nd/144Nd (0.51309±2) ratios. Most Group II lavas are aphyric, whereas Group I lavas are primarily plagioclase phyric. Lavas from both groups show a wide range in incompatible element abundance ratios (e.g., Zr/Nb =6–29; (La/Sm)n=0.6–1.7). Aphyric lavas have relatively constant Sc (40±1.5 ppm) abundances and CaO/Al2O3 ratios (0.80±0.02). Group I lavas are confined primarily to the AMAR rift valley floor whereas Group II lavas are found along the east and west marginal highs. We interpret the isotopic differences between the two groups as reflecting a temporal change in the upwelling mantle beneath this region of the Mid-Atlantic Ridge which is south of the Azore Islands. For each group, a petrogenetic model consistent with the geochemical data is multi-stage decompression melting of an initially enriched, homogeneous, mantle source region. If the early derived, incompatible-element enriched, melt increments are not always pooled with subsequent increments, the erupted magma batches may have the major element characteristics of melts derived by 10 to 20% melting, but with incompatible element abundance ratios reflecting the change from an enriched to depleted source during the incremental melting process. In this process an initially homogeneous source can generate primary magmas with the required range in incompatible element abundance ratios shown by each group. The nearly constant CaO/Al2O3 ratios and Sc contents of the aphyric lavas with decreasing Mg ? reflects subsequent polybaric fractionation of clinopyroxene, plagioclase and olivine over the pressure interval 8–6 kbar (24–18 km), followed by rapid transport to the surface and eruption. There is no geochemical evidence for a crustal magma chamber beneath this section of the Mid-Atlantic Ridge.

32 citations

Journal ArticleDOI
TL;DR: The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus plagioclase (An53-86), and Fe-Ti oxides.
Abstract: Layered mafic intrusions (LMI) are sporadically distributed in the Early Permian Tarim large igneous province (LIP), NW China, and are crosscut by numerous contemporaneous dykes. The Xiaohaizi wehrlite intrusion is composed mainly of olivine (Fo69-75), clinopyroxene (Mg# = 75-84), intercumulus plagioclase (An53-86) and Fe-Ti oxides. Both petrography and mineral compositions suggest that olivine and clinopyroxene crystallized earlier than plagioclase and Fe-Ti oxides. The dykes are of alkali basalt to trachyandesite with low Mg# (35-39). The least-contaminated dykes display strong rare earth element (REE) fractionation, enrichment of Nb and Ta, and depletion of Pb relative to other similarly incompatible elements, bearing strong similarity to ocean island basalts (OIB). This, together with their positive epsilon Nd-i values (4.3-4.8), is consistent with derivation from an enriched asthenospheric mantle source. Clinopyroxenes in the wehrlites display convex-upward chondrite-normalized REE patterns. The melts in equilibrium with these clinopyroxenes have very similar trace element compositions to those of the crosscutting dykes, suggesting a similar mantle source shared by the Xiaohaizi wehrlite intrusion and dykes. The Xiaohaizi wehrlite intrusion is characterized by Sr-Nd isotopic disequilibrium between clinopyroxene and plagioclase separates: Sr-87/(86)Sri (0.7038-0.7041) and epsilon Nd-i (1.0-1.9) of clinopyroxene are lower and higher than the respective ratios of intercumulus plagioclase (Sr-87/Sr-86(i) = 0.7042-0.7043, epsilon Nd-i = 0.4-1.0). The Sr-87/(86)Sri and epsilon Nd-i of clinopyroxene separates correlate positively and negatively with Zr/ Nb, respectively, implying variable degrees of crustal contamination during the formation of the Xiaohaizi wehrlite intrusion. Sr-87/(86)Sri increases and epsilon Nd-i decreases with increasing Ca content of plagioclase, indicating that higher An plagioclases experienced higher degrees of contamination. This can be explained by assimilation of continental crust through a turbulent magma ascent (ATA) process. However, this ATA model fails to account for the positive correlation between the Mg# and epsilon Nd-i of clinopyroxene separates. The isotopic disequilibrium in the Xiaohaizi LMI is more probably generated during an assimilation and fractional crystallization process involving Archean-Neoproterozoic basement and carbonates as contaminants.

32 citations


Network Information
Related Topics (5)
Metamorphism
18.3K papers, 655.8K citations
94% related
Continental crust
11.1K papers, 677.5K citations
94% related
Basalt
18.6K papers, 805.1K citations
93% related
Mantle (geology)
26.1K papers, 1.3M citations
92% related
Zircon
23.7K papers, 786.6K citations
92% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20237
202216
202157
202056
201960
201851