scholarly journals Kimberlite genesis from a common carbonate-rich primary melt modified by lithospheric mantle assimilation

2020 ◽  
Vol 6 (17) ◽  
pp. eaaz0424 ◽  
Author(s):  
Andrea Giuliani ◽  
D. Graham Pearson ◽  
Ashton Soltys ◽  
Hayden Dalton ◽  
David Phillips ◽  
...  
Keyword(s):  
Major Element ◽  
Element Composition ◽  
Major Element Composition ◽  
Compositional Evolution ◽  
Physical Conditions ◽  
Mantle Sources ◽  
Deep Earth ◽  
Abundant Evidence ◽  
Major Process ◽  
Primary Melt

Quantifying the compositional evolution of mantle-derived melts from source to surface is fundamental for constraining the nature of primary melts and deep Earth composition. Despite abundant evidence for interaction between carbonate-rich melts, including diamondiferous kimberlites, and mantle wall rocks en route to surface, the effects of this interaction on melt compositions are poorly constrained. Here, we demonstrate a robust linear correlation between the Mg/Si ratios of kimberlites and their entrained mantle components and between Mg/Fe ratios of mantle-derived olivine cores and magmatic olivine rims in kimberlites worldwide. Combined with numerical modeling, these findings indicate that kimberlite melts with highly variable composition were broadly similar before lithosphere assimilation. This implies that kimberlites worldwide originated by partial melting of compositionally similar convective mantle sources under comparable physical conditions. We conclude that mantle assimilation markedly alters the major element composition of carbonate-rich melts and is a major process in the evolution of mantle-derived magmas.

Provenance of basaltic tephra from Vatnajökull subglacial volcanoes, Iceland, as determined by major- and trace-element analyses

The Holocene ◽  
2011 ◽  
Vol 21 (7) ◽  
pp. 1037-1048 ◽  
Author(s):  
Bergrún Arna Óladóttir ◽  
Olgeir Sigmarsson ◽  
Gudrún Larsen ◽  
Jean-Luc Devidal
Keyword(s):  
Trace Element ◽  
Inductively Coupled Plasma ◽  
Major Element ◽  
Element Composition ◽  
Major Element Composition ◽  
Volcanic System ◽  
The Holocene ◽  
Inductively Coupled ◽  
Ice Cap ◽  
The North

The Holocene eruption history of subglacial volcanoes in Iceland is largely recorded by their tephra deposits. The numerous basaltic tephra offer the possibility to make the tephrochronology in the North Atlantic area more detailed and, therefore, more useful as a tool not only in volcanology but also in environmental and archaeological studies. The source of a tephra is established by mapping its distribution or inferred via compositional fingerprinting, mainly based on major-element analyses. In order to improve the provenance determinations for basaltic tephra produced at Grímsvötn, Bárdarbunga and Kverkfjöll volcanic systems in Iceland, 921 samples from soil profiles around the Vatnajökull ice-cap were analysed for major-element concentrations by electron probe microanalysis. These samples are shown to represent 747 primary tephra units. The tephra erupted within each of these volcanic system has similar chemical characteristics. The major-element results fall into three distinctive compositional groups, all of which show regular decrease of MgO with increasing K2O concentrations. The new analyses presented here considerably improve the compositional distinction between products of the three volcanic systems. Nevertheless, slight overlap of the compositional groups for each system still remains. In situ trace-element analyses by laser-ablation-inductively-coupled-plasma-mass-spectrometry were applied for better provenance identification for those tephra having similar major-element composition. Three trace-element ratios, Rb/Y, La/Yb and Sr/Th, proved particularly useful. Significantly higher La/Yb distinguishes the Grímsvötn basalts from those of Bárdarbunga and Rb/Y values differentiate the basalts of Grímsvötn and Kverkfjöll. Additionally, the products of Bárdarbunga, Grímsvötn and Kverkfjöll form distinct compositional fields on a Sr/Th versus Th plot. Taken together, the combined use of major- and trace-element analyses in delineating the provenance of basaltic tephra having similar major-element composition significantly improves the Holocene tephra record as well as the potential for correlations with tephra from outside Iceland.

scholarly journals Linking Cellulose Fiber Sediment Methyl Mercury Levels to Organic Matter Decay and Major Element Composition

AMBIO ◽  
2014 ◽  
Vol 43 (7) ◽  
pp. 878-890 ◽  
Author(s):  
Olof Regnell ◽  
Mark Elert ◽  
Lars Olof Höglund ◽  
Anna Helena Falk ◽  
Anders Svensson
Keyword(s):  
Organic Matter ◽  
Methyl Mercury ◽  
Major Element ◽  
Cellulose Fiber ◽  
Element Composition ◽  
Major Element Composition

The geochemistry of hydrothermal and pelagic sediments from the Galapagos Hydrothermal Mounds Field, D.S.D.P. Leg 70

1983 ◽  
Vol 47 (344) ◽  
pp. 291-300 ◽  
Author(s):  
S. A. Moorby ◽  
D.S. Cronan
Keyword(s):  
Major Element ◽  
Hydrothermal Solution ◽  
Element Composition ◽  
Pelagic Sediment ◽  
Solution Composition ◽  
Major Element Composition ◽  
Sediment Samples ◽  
Mn Oxide ◽  
Formation Conditions ◽  
Metal Ratios

AbstractOver 200 sediment samples taken from ten holes drilled in the Galapagos Hydrothermal Mounds Field during D.S.D.P. Leg 70 have been analysed for twenty-one elements. The three main sediment lithologies recognized are siliceous carbonate ooze, Mn-oxide crust, and an Fe-rich silicate (nontronite), the latter two being of hydrothermal origin. The major element composition of the hydrothermal deposits is similar in each mound hole, suggesting that formation conditions and hydrothermal solution composition have been constant both geographically and with time. The large variations which occur in the concentration of some trace elements in the Mn-oxide crusts and in transition metal ratios in the nontronite compared with the pelagic ooze suggests a hydrothermal supply to the mounds of Li, Mo, Pb, and Ba in addition to Mn, Fe, and silica.The data are compatible with suggestions that the nontronite formed at depth in the pelagic sediment blanket by replacement of biogenic ooze, whilst the Mn crusts formed at or near the sediment-water interface. Pelagic sediments in the mounds which have not been replaced are similar in composition to pelagic sediments from non-mounds holes.

A Kaolin-smectite interstratification sequence from a red and black complex

Clay Minerals ◽  
1991 ◽  
Vol 26 (3) ◽  
pp. 343-358 ◽  
Author(s):  
C. Bühmann ◽  
P. L. C. Grubb
Keyword(s):  
Major Element ◽  
Element Composition ◽  
Chemical Analyses ◽  
Sand Content ◽  
Major Element Composition ◽  
Genetic Link ◽  
Sequential Development ◽  
Mineral Compositions

AbstractThe sequential development of kaolin by progressive alteration of smectite, involving kaolin-smectite interstratifications as a genetic link is described from a red and black complex. Mineral compositions were studied using XRD, DTA and XRF techniques. The basalt-derived soils are situated along a 600 m transect and grade in colour from dark grey (10 YR 3/1) to red (5 YR 3/3). The kaolin proportions in the interstratification increase almost linearly with increasing reddening up to ∼80%. Whole-soil chemical analyses exhibit no significant variations in the major element composition, but dithionite extractable Fe increases along the transect from 1% to 4·16%. Hematite and goethite are the only secondary iron phases. Topographic differences are slight but sub-surface bedrock contours plus appreciable variations in sand content between red and black soils could be genetically significant.

The Major-Element Composition of Mercury's Surface from MESSENGER X-ray Spectrometry

Science ◽  
2011 ◽  
Vol 333 (6051) ◽  
pp. 1847-1850 ◽  
Author(s):  
L. R. Nittler ◽  
R. D. Starr ◽  
S. Z. Weider ◽  
T. J. McCoy ◽  
W. V. Boynton ◽  
...  
Keyword(s):  
Major Element ◽  
Element Composition ◽  
Major Element Composition ◽  
X Ray

Changes in major element composition of developing barley grain

1976 ◽  
Vol 86 (3) ◽  
pp. 627-632 ◽  
Author(s):  
Carol M. Duffus ◽  
Roberta Rosie
Keyword(s):  
Major Element ◽  
Barley Grain ◽  
Element Composition ◽  
Developmental Period ◽  
Major Element Composition ◽  
Nitrogen Phosphorus ◽  
Different Parts

SummaryChanges in the amounts of nitrogen, phosphorus, magnesium, calcium and sodium present in intact grain, endosperm, testa pericarp and embryo throughout the developmental period were recorded. While the overall pattern in intact grain was one of steady accumulation, considerable variation from this pattern was found within the different parts. The results are discussed in relation to the biochemical events accompanying maturation.

Episodic tourmaline growth and re-equilibration in mica pegmatite from the Bihar Mica Belt, India: major- and trace-element variations under pegmatitic and hydrothermal conditions

2016 ◽  
Vol 154 (1) ◽  
pp. 68-86 ◽  
Author(s):  
PRANJIT HAZARIKA ◽  
DEWASHISH UPADHYAY ◽  
KAMAL LOCHAN PRUSETH
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Major Element ◽  
Element Composition ◽  
Coarse Grained ◽  
Partial Replacement ◽  
Type I ◽  
Type Ii ◽  
Hydrothermal Conditions ◽  
Major Element Composition

AbstractMica pegmatites from the Bihar Mica Belt contain three distinct generations of tourmaline. The major-element composition, substitution vectors and trajectories within each group are different, which indicates that the three types of tourmalines are not a part of one evolutionary series. Rather, the differences in their chemistries as well their mutual microtextural relations, can be best explained by growth of tourmaline from pegmatitic melts followed by episodic re-equilibration during discrete geological events. The euhedral, coarse-grained brown type I tourmaline cores have relatively high Ca, Mg (XMgc. 0.37) and Al with correlated variation in Sr, Sc, Ti, Zr, Y, Cr, Pb and Rare Earth elements (REEs). They are inferred to have crystallized from pegmatitic melts. Monazites included within these tourmalines give chemical ages of 1290−1242 Ma interpreted to date the crystallization of the pegmatitic tourmaline. The bluish type II and greyish type III tourmalines with low Ca and Mg contents (XMg = 0.16−0.27) and high Zn, Sn, Nb, Ta and Na, formed by pseudomorphic partial replacement of the pegmatitic tourmaline via fluid-mediated coupled dissolution–reprecipitation, are ascribed to a hydrothermal origin. The ages obtained from monazites included in these tourmalines indicate two alteration events at c. 1100 Ma and c. 950 Ma. The correlated variation of Ca, Mg and Fe and the trace elements Sr, Sn, Sc, Zn and REE within the tourmalines indicates that the trace-element concentrations of tourmaline are controlled not only by the fluid chemistry but also by coupled substitutions with major-element ions.

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