Vertical Variation of Volcanic Glass Major Element Composition in a Volcanic Ash Layer.

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.

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

AMBIO ◽

10.1007/s13280-013-0487-2 ◽

2014 ◽

Vol 43 (7) ◽

pp. 878-890 ◽

Cited By ~ 5

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

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AMS 14C Dates and Major Element Composition of Glass Shards of Late Pleistocene Tephras on Tanegashima Island, Southern Japan

Radiocarbon ◽

10.1017/s0033822200047135 ◽

2012 ◽

Vol 54 (3-4) ◽

pp. 351-358 ◽

Cited By ~ 4

Author(s):

Mitsuru Okuno ◽

Masayuki Torii ◽

Hideto Naruo ◽

Yoko Saito-Kokubu ◽

Tetsuo Kobayashi

Keyword(s):

Late Pleistocene ◽

Major Element ◽

Volcanic Glass ◽

Archaeological Site ◽

Major Element Composition ◽

Ams Radiocarbon Dating ◽

Southern Japan ◽

Tephra Layers ◽

C 32 ◽

Glass Shards

Four late Pleistocene tephra layers—Tane I (Tn1), II (Tn2), III (Tn3), and IV (Tn4) in ascending order—are intercalated between widespread tephras, Kikai-Tozurahara (K-Tz: 95 ka) and Aira-Tn (AT: 30 cal kBP), on Tanegashima Island, in southern Japan. Paleolithic ruins such as the Yokomine C and Tatikiri archaeological sites were excavated from the loam layer between the Tn4 and Tn3 tephras. To refine the chronological framework on the island, we conducted accelerator mass spectrometry (AMS) radiocarbon dating for 2 paleosol and 6 charcoal samples related with the late Pleistocene tephras and the Yokomine C archaeological site. The obtained 14C dates are consistent with the stratigraphy in calendar years, 33 cal kBP for Tn4, 40 cal kBP for Tn3, and >50 cal kBP for Tn2 and Tn1. The charcoal dates from Yokomine C, 32–38 cal kBP, not only constrain the age of Tn4 and Tn3 ashes, but also serve as a possible date for the site. We also measured the major element compositions of volcanic glass shards with EDS-EPMA to characterize these tephras. Although we could not find a possible correlative for Tn3 and Tn4 ashes using major element oxides of the glass shards, i.e. 75–76 wt% in SiO2, the glass chemistry obtained in this study will be valuable in correlating these tephras with their source volcanoes in the near future.

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

Mineralogical Magazine ◽

10.1180/minmag.1983.047.344.03 ◽

1983 ◽

Vol 47 (344) ◽

pp. 291-300 ◽

Cited By ~ 37

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.

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

Clay Minerals ◽

10.1180/claymin.1991.026.3.04 ◽

1991 ◽

Vol 26 (3) ◽

pp. 343-358 ◽

Cited By ~ 24

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.

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Inference of parent rocks by means of zircon crystal morphology and major element composition of host rocks. An example of granitic mylonites within the Tanakura Shear Zone.

The Journal of the Geological Society of Japan ◽

10.5575/geosoc.100.495 ◽

1994 ◽

Vol 100 (7) ◽

pp. 495-504 ◽

Cited By ~ 2

Author(s):

Hiroto Ohira

Keyword(s):

Shear Zone ◽

Crystal Morphology ◽

Major Element ◽

Zircon Crystal ◽

Element Composition ◽

Major Element Composition ◽

Parent Rocks ◽

Host Rocks

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The Age of Glacier Peak Tephra in West-Central Montana

Quaternary Research ◽

10.1016/0033-5894(84)90087-5 ◽

1984 ◽

Vol 21 (1) ◽

pp. 36-41 ◽

Cited By ~ 51

Author(s):

Peter J. Mehringer ◽

John C. Sheppard ◽

Franklin F. Foit

Keyword(s):

Electron Microprobe ◽

Major Element ◽

Late Summer ◽

Volcanic Glass ◽

Late Glacial ◽

Major Element Chemistry ◽

West Central ◽

Ash Layer ◽

Central Montana ◽

Lake Deposits

At Sheep Mountain Bog, near Missoula, Montana, a late-glacial tephra, that probably fell in late summer, is preserved as an 8-mm-thick graded bed overlain by another 8 mm of redeposited ash mixed with lake deposits. Sediment surrounding the ash was 14C dated to about 11,200 yr B.P. Electron-microprobe analyses of the volcanic glass and hornblende phenocrysts from this ash layer indicate that they are similar in major-element chemistry to those of Glacier Peak layer G previously considered to be about 12,000 yr old or older.

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