scholarly journals Geochemistry of the Cheremkhovo and Lower Prisayan Formations from the Jurassic Irkutsk Coal-Bearing Basin: Evidence for Provenance and Climate Change in Pliensbachian–Toarcian

Minerals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 357
Author(s):  
Ekaterina A. Mikheeva ◽  
Elena I. Demonterova ◽  
Alexei V. Ivanov
Keyword(s):  
Volcanic Ash ◽  
Geochemical Data ◽  
Eastern Siberia ◽  
Climate Conditions ◽  
X Ray ◽  
Rock Types ◽  
Irkutsk Basin ◽  
Ash Layer ◽  
Major Oxide ◽  
Geochemical Studies

The Cheremkhovo formation (Pliensbachian) is the primary coal-bearing formation of the Irkutsk basin, Eastern Siberia. Still, few geochemical studies of the Jurassic sediments of the Irkutsk coal-bearing basin have been conducted, and there are no data on the geochemistry of the coal-bearing formation itself. This study presents geochemical data for 68 samples from the Cheremkhovo formation and the overlying Lower Prisayan formation. The age of the former has been estimated by U-Pb dating of zircon from a tonstein (altered volcanic ash) layer as Pliensbachian, whereas the age of the latter is estimated as Pliensbachian–Toarcian according to regional stratigraphy. Major oxide and trace element concentrations were obtained using X-ray fluorescence spectrometry. Geochemical indicators showed diversity between the two studied formations. The indicators used show the change in climate conditions, from warm and humid in the Cheremkhovo formation, to hot and arid during the deposition of the lower Prisayan formation. The provenance of the Irkutsk coal-bearing basin was mainly influenced by the source composition, not recycling, and sediments were mainly derived from felsic to intermediate igneous rocks with a mixture of other rock types.

scholarly journals Identification and correlation of distal tephra layers in deep-sea sediment cores, Scotia Sea, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 285-289 ◽  
Author(s):  
S. G. Moreton ◽  
J. L. Smellie
Keyword(s):  
Deep Sea ◽  
Volcanic Ash ◽  
Sediment Cores ◽  
Quaternary Deposits ◽  
Deep Sea Sediment ◽  
Scotia Sea ◽  
Ash Layer ◽  
Tephra Layers ◽  
Major Oxide ◽  
Water Depths

Quaternary deposits in six sediment cores from the Scotia Sea, Antarctica, were examined for the presence of volcanic ash layers. The cores were recovered from water depths of 3369-4025 m. Altogether, 23 ash layers were found, 18 of which have been investigated by electron-probe microanalysis. Deception Island is identified as the source of all the ash layers analyzed. The upper ash layer in each core can be correlated across all six cores, over a distance of -100 km, on the basis of its unusual bimodal composition, major oxide geochemistry and stratigraphie position. Two other ash layers can also be correlated between several of the cores.

scholarly journals Volcanic ash layer depth: Processes and mechanisms

2015 ◽  
Vol 42 (2) ◽  
pp. 637-645 ◽  
Author(s):  
H. F. Dacre ◽  
A. L. M. Grant ◽  
N. J. Harvey ◽  
D. J. Thomson ◽  
H. N. Webster ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Layer Depth ◽  
Ash Layer

Geochemistry of halloysite-7Å formation from plagioclase in trachyandesite rocks from Limnos Island, Greece

Clay Minerals ◽  
2014 ◽  
Vol 49 (1) ◽  
pp. 75-89 ◽  
Author(s):  
D. Papoulis ◽  
S. Komarneni ◽  
D. Panagiotaras
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Chemical Analysis ◽  
Geochemical Data ◽  
X Ray Diffraction ◽  
Polarizing Microscopy ◽  
X Ray ◽  
Geochemical Evaluation ◽  
Scanning Electron ◽  
Southwest Part

AbstractTrachyandesite rocks, occurring over an area of about 1 km2in the southwest part of Limnos Island, Greece, are altered mainly to halloysite. The samples were collected and analysed by polarizing microscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical analysis. The alteration of plagioclase to halloysite follows seven discrete stages that are described in detail. The geochemical evaluation of the data shows enrichment of the lightREE(LREE) over heavyREE(HREE) as expressed by the (La/Yb)n ratio. TheΣLREErange from 206.44 to 272.30, while the sum ofHREEvaries from 11.01 to 26.26. The (La/Yb)n ratio ranges from 9.72 to 27.64. Fractionation amongLREEexpressed as (La/Sm)n and between middleREE(MREE) andHREEis shown as (Tb/Yb)n ratios. The most altered rocks close to the fault zone have high (Tb/Yb)n ratios and low (La/Sm)n and Eu/Eu* ratios. Although mineralogy and clay mineral textures indicate hydrothermal genesis of halloysite, the geochemical data are not conclusive due to a secondary weathering effect.

scholarly journals A Study on Appling the Expert System for Correlating Volcanic Ash Layer

1987 ◽  
Vol 1987 (12) ◽  
pp. 105-110
Author(s):  
Kaichiro YAMAMOTO ◽  
Younosuke NAKAGAWA
Keyword(s):  
Expert System ◽  
Volcanic Ash ◽  
Ash Layer

scholarly journals Evidence of mingling between contrasting magmas in a deep plutonic environment: the example of Várzea Alegre, in the Ribeira Mobile Belt, Espírito Santo, Brazil

2001 ◽  
Vol 73 (1) ◽  
pp. 99-119 ◽  
Author(s):  
SILVIA R. MEDEIROS ◽  
CRISTINA M. WIEDEMANN-LEONARDOS ◽  
SIMON VRIEND
Keyword(s):  
Partial Melting ◽  
Granitic Magma ◽  
Geochemical Data ◽  
Mobile Belt ◽  
Tholeiitic Magma ◽  
Rock Types ◽  
Upper Proterozoic ◽  
Incompatible Elements ◽  
Wide Range ◽  
Intermediate Rock

At the end of the geotectonic cycle that shaped the northern segment of the Ribeira Mobile Belt (Upper Proterozoic to Paleozoic age), a late to post-collisional set of plutonic complexes, consisting of a wide range of lithotypes, intruded all metamorphic units. The Várzea Alegre Intrusive Complex is a post-collisional complex. The younger intrusion consists of an inversely zoned multistage structure envolved by a large early emplaced ring of megaporphyritic charnoenderbitic rocks. The combination of field, petrographic and geochemical data reveals the presence of at least two different series of igneous rocks. The first originated from the partial melting of the mantle. This was previously enriched in incompatible elements, low and intermediate REE and some HFS-elements. A second enrichment in LREE and incompatible elements in this series was due to the mingling with a crustal granitic magma. This mingling process changed the composition of the original tholeiitic magma towards a medium-K calc-alkalic magma to produce a suite of basic to intermediate rock types. The granitic magma from the second high-K, calc-alkalic suite originated from the partial melting of the continental crust, but with strong influence of mantle-derived melts.

scholarly journals Quantifying uncertainties in marine volcanic ash layer records from ocean drilling cores

2014 ◽  
Vol 357 ◽  
pp. 218-224 ◽  
Author(s):  
Sue H. Mahony ◽  
R.S.J. Sparks ◽  
Nick H. Barnard
Keyword(s):  
Volcanic Ash ◽  
Ocean Drilling ◽  
Ash Layer

scholarly journals Люминесценция кристаллов BaBrI, активированных ионами Ce-=SUP=-3+-=/SUP=-

2019 ◽  
Vol 61 (5) ◽  
pp. 930
Author(s):  
Р.Ю. Шендрик ◽  
И.И. Ковалев ◽  
А.И. Русаков ◽  
Ю.В. Сокольникова ◽  
А.А. Шалаев
Keyword(s):  
Luminescence Spectra ◽  
Russian Science ◽  
Scientific Center ◽  
X Ray ◽  
Trivalent Lanthanides ◽  
Scientific Equipment ◽  
The Government ◽  
Geochemical Studies ◽  
Transfer Mechanisms

The optical properties of BaBrI crystals doped with cerium ions were studied. The possible types of cerium-containing luminescence centers are established. Based on the experimental data obtained for trivalent lanthanides, a Dorenbos diagram was constructed. According to the results of the study of the luminescence spectra measured under X-ray excitation, possible energy transfer mechanisms are assumed. This work was supported by the Russian Science Foundation, a grant of the Russian Science Foundation 17-72-10084: spectroscopy of cerium and cerium-oxygen centers, determination of cerium concentration in crystals, analysis of the results obtained. Some of the crystals investigated in the article were grown as part of the government assignment 0350-2016-0024. The data in the work were obtained using the scientific equipment of the Collective Scientific Center "Isotope-geochemical studies" of the IHP SB RAS.

scholarly journals Granulometry, heavy mineral and geochemical studies of stream sediments around Bula, Dass District, Northeast Nigeria

2020 ◽  
Vol 18 ◽  
pp. 63-73
Author(s):  
C. I. Adamu ◽  
E.E. Okon ◽  
D.O. Inyang
Keyword(s):  
Trace Elements ◽  
Stream Sediments ◽  
Stream Sediment ◽  
Heavy Mineral ◽  
Geochemical Data ◽  
Provenance Analysis ◽  
Sediment Samples ◽  
Granulometric Analysis ◽  
Elemental Analyses ◽  
Geochemical Studies

Active stream sediments generally consist of broken-down fragments of pre-existing rocks by the action of river (stream) flow. This makes them target materials for routine geochemical surveys and provenance analysis. Fifteen (15) stream sediment samples were collected in some parts of Bula and its environs, northeastern Nigeria, in order to determine their textural characteristics, heavy mineral and elemental composition. The sediments were subjected to granulometric, heavy mineral and elemental analyses. The result of granulometric analysis show that the streamsediments are poorly to moderately well sorted, very platykurtic to leptokurtic, fine to medium grained and positively skewed. Zircon, rutile and tourmaline are the dominant heavy mineral species occurring in the sediments. The computed Zircon-Tourmaline-Rutile (ZTR) index values for the samples range from 59.18 - 83.53, indicating mineralogical maturity. The geochemical data of the stream sediment samples show that the mean contents of the trace elements [Ti (0.73 ± 0.74%), Fe (0.39±0.19%), Cr (816±639ppm), Ni (258±108ppm), Pb (48±12.37ppm) and Zn (502±126ppm)] were higher than their respective average crustal values except for Fe. Computed threshold values indicate possible mineralization containing Fe and Ti. The elements have variable spatial distribution. The study shows that the trace elements composition of the stream sediments is majorly lithogenic. Because mineralization in rocks and sediments are often characterized by considerable variation in their trace elements contents, the metal concentrations in these sediments are large enough for Ilmenite and Rutile mineralization to be suspected within the study area.

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