scholarly journals Origin of Ru-Os Sulfides from the Verkh-Neivinsk Ophiolite Massif (Middle Urals, Russia): Compositional and S-Os Isotope Evidence

Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 329
Author(s):  
Kreshimir N. Malitch ◽  
Inna Yu. Badanina ◽  
Elena A. Belousova ◽  
Valery V. Murzin ◽  
Tatiana A. Velivetskaya
Keyword(s):  
Middle Urals ◽  
Crustal Component ◽  
Highly Siderophile Elements ◽  
Isotope Data ◽  
Enriched Mantle ◽  
Multi Stage ◽  
Placer Deposits ◽  
Isotope Evidence ◽  
Extraction Processes ◽  
Os Isotope

This study presents new compositional and S-Os isotope data for primary Ru-Os sulfides within a platinum-group mineral (PGM) assemblage from placer deposits associated with the Verkh-Neivinsk massif, which is part of the mantle ophiolite association of Middle Urals (Russia). The primary nature of Ru-Os sulfides represented by laurite (RuS2)–erlichmanite (OsS2) series is supported by occurrence of euhedral inclusions of high-Mg olivine (Fo92–94) that fall within the compositional range of mantle (primitive) olivine (Fo 88–93). The sulfur isotope signatures of Ru-Os sulfides reveal a range of δ34S values from 0.3 to 3.3‰, with a mean of 2.05‰ and a standard deviation of 0.86‰ (n = 18), implying that the sulfur derived from a subchondritic source. A range of sub-chondritic initial 187Os/188Os values defined for Ru-Os sulfides (0.1173–0.1278) are clearly indicative of derivation from a sub-chondritic source. Re-depletion (TRD) ages of the Verkh-Neivinsk Ru-Os sulfides are consistent with prolonged melt-extraction processes and likely multi-stage evolution of highly siderophile elements (HSE) within the upper mantle. A single radiogenic 187Os/188Os value of 0.13459 ± 0.00002 determined in the erlichmanite is indicative of a supra-chondritic source of HSE. This feature can be interpreted as evidence of a radiogenic crustal component associated with a subduction event or as an indication of an enriched mantle source. The mineralogical and Os-isotope data point to a high-temperature origin of the studied PGM and two contrasting sources for HSE in Ru-Os sulfides of the Verkh-Neivinsk massif.

Genesis of the mafic granophyre of the Vredefort impact structure (South Africa): Implications of new geochemical and Se and Re-Os isotope data

2021 ◽  
Author(s):  
Wolf Uwe Reimold ◽  
Toni Schulz ◽  
Stephan König ◽  
Christian Koeberl ◽  
Natalia Hauser ◽  
...  
Keyword(s):  
South Africa ◽  
Country Rock ◽  
Order Estimate ◽  
Impact Structure ◽  
Impact Melt ◽  
Highly Siderophile Elements ◽  
Isotope Data ◽  
Rock Types ◽  
Siderophile Elements ◽  
Os Isotope

ABSTRACT This contribution is concerned with the debated origin of the impact melt rock in the central uplift of the world’s largest confirmed impact structure—Vredefort (South Africa). New major- and trace-element abundances, including those of selected highly siderophile elements (HSEs), Re-Os isotope data, as well as the first Se isotope and Se-Te elemental systematics are presented for the felsic and mafic varieties of Vredefort impact melt rock known as “Vredefort Granophyre.” In addition to the long-recognized “normal” (i.e., felsic, >66 wt% SiO2) granophyre variety, a more mafic (<66 wt% SiO2) impact melt variety from Vredefort has been discussed for several years. The hypothesis that the mafic granophyre was formed from felsic granophyre through admixture (assimilation) of a mafic country rock component that then was melted and assimilated into the superheated impact melt has been pursued here by analysis of the two granophyre varieties, of the Dominion Group lava (actually metalava), and of epidiorite mafic country rock types. Chemical compositions, including high-precision isotope dilution–derived concentrations of selected highly siderophile elements (Re, Os, Ir, Pt, Se, Te), and Re-Os and Se isotope data support this hypothesis. A first-order estimate, based on these data, suggests that some mafic granophyre may have resulted from a significant admixture (assimilation) of epidiorite to felsic granophyre. This is in accordance with the findings of an earlier investigation using conventional isotope (Sr-Nd-Pb) data. Moreover, these outcomes are in contrast to a two-stage emplacement model for Vredefort Granophyre, whereby a mafic phase of impact melt, derived by differentiation of a crater-filling impact melt sheet, would have been emplaced into earlier-deposited felsic granophyre. Instead, all chemical and isotopic evidence so far favors formation of mafic granophyre by local assimilation of mafic country rock—most likely epidiorite—by a single intrusive impact melt phase, which is represented by the regionally homogeneous felsic granophyre.

A geochemical and Sr-Nd-O isotopic study of the Proterozoic Eriksfjord Basalts, Gardar Province, South Greenland: Reconstruction of an OIB signature in crustally contaminated rift-related basalts

2003 ◽  
Vol 67 (5) ◽  
pp. 831-853 ◽  
Author(s):  
R. Halama ◽  
T. Wenzel ◽  
B. G. J. Upton ◽  
W. Siebel ◽  
G. Markl
Keyword(s):  
Trace Element ◽  
Granulite Facies ◽  
Alkaline Basalt ◽  
Isotopic Study ◽  
Nd Isotope ◽  
Crustal Component ◽  
Isotope Data ◽  
Enriched Mantle ◽  
Mantle Sources ◽  
Lower Crustal

AbstractBasalts from the volcano-sedimentary Eriksfjord Formation (Gardar Province, South Greenland) were erupted at around 1.2 Ga into rift-related graben structures. The basalts have compositions transitional between tholeiite and alkaline basalt with MgO contents <7 wt.% and they display LREE-enrichment relative to a chondritic source. Most of the trace element and REE characteristics are similar to those of basalts derived from OIB-like mantle sources. Initial 87Sr/86Sr ratios of clinopyroxene separates range from 0.70278 to 0.70383 and initial ϵNd values vary from –3.2 to +2.1. The most unradiogenic samples overlap with the field defined by carbonatites of similar age and can be explained by mixing of isotopically depleted and enriched mantle components. Using AFC modelling equations, the Sr-Nd isotope data of the more radiogenic basalts can successfully be modelled by addition of <5% lower crustal granulite-facies gneisses as contaminants. δ18Ov-smow values of separated clinopyroxene range from +5.2 to +6.0% and fall within the range of typical mantle-derived rocks. However, up to 10% mixing with an average lower crustal component are permitted by the data.

Geochemistry of Ferrar Dolerite sills and dykes at Terra Cotta Mountain, south Victoria Land, Antarctica

1995 ◽  
Vol 7 (1) ◽  
pp. 73-85 ◽  
Author(s):  
A.D. Morrison ◽  
A. Reay
Keyword(s):  
Trace Element ◽  
Mantle Source ◽  
Source Region ◽  
Crustal Component ◽  
Enriched Mantle ◽  
Victoria Land ◽  
Trace Element Signature ◽  
Geochemical Variation ◽  
Element Enrichment ◽  
Taylor Glacier

At Terra Cotta Mountain, in the Taylor Glacier region of south Victoria Land, a 237 m thick Ferrar Dolerite sill is intruded along the unconformity between basement granitoids and overlying Beacon Supergroup sedimentary rocks. Numerous Ferrar Dolerite dykes intrude the Beacon Supergroup and represent later phases of intrusion. Major and trace element data indicate variation both within and between the separate intrusions. Crystal fractionation accounts for much of the geochemical variation between the intrusive events. However, poor correlations between many trace elements require the additional involvement of open system processes. Chromium is decoupled from highly incompatible elements consistent with behaviour predicted for a periodically replenished, tapped and fractionating magma chamber. Large ion lithophile element-enrichment and depletion in Nb, Sr, P and Ti suggests the addition of a crustal component or an enriched mantle source. The trace element characteristics of the Dolerites from Terra Cotta Mountain are similar to those of other Ferrar Group rocks from the central Transantarctic Mountains and north Victoria Land, as well as with the Tasmanian Dolerites. This supports current ideas that the trace element signature of the Ferrar Group is inherited from a uniformly enriched mantle source region.

scholarly journals Oxygen isotope composition of zircons from the Talnakh economic intrusion of the Noril’sk province: first data

2019 ◽  
Vol 489 (2) ◽  
pp. 170-173
Author(s):  
I. Yu. Badanina ◽  
E. A. Belousova ◽  
K. N. Malitch ◽  
S. F. Sluzhenikin
Keyword(s):  
Oxygen Isotope ◽  
Isotope Composition ◽  
Oxygen Isotope Composition ◽  
Primary Magma ◽  
Crustal Component ◽  
Layered Series ◽  
Isotope Data ◽  
Oxygen Isotope Data ◽  
First Results ◽  
Isotope Analyses

This study presents the first results of oxygen isotope analyses (18O) collected on zircons from the Talnakh economic intrusion within the Norilsk province. Zircons from gabbro-diorite, gabbroic rocks of the layered series and plagioclase-bearing wehrlite have similar mantle-like mean 18O values (5,39 0,49; 5,64 0,48 and of 5,28 0,34, respectively), which differ from 18O in zircons from sulfide-bearing melanocratic troctolite with a taxitic texture in the lower part of the intrusion (mean 18O = 6,50 0,98). These new oxygen isotope data support (i) the mantle-derived origin of the primary magma(s), parental to the Talnakh intrusion, and (ii) possible involvement of a crustal component during the formation of sulfide-bearing taxitic-textured rocks.

Cosmogenic 3He in detrital Pt-alloy grains: tracing the accumulation of critical metals

2021 ◽  
Author(s):  
Olga Yakubovich ◽  
Finlay Stuart ◽  
Alexander Mochalov ◽  
Roman Palamarchuk
Keyword(s):  
Source Rock ◽  
Total Duration ◽  
River System ◽  
Placer Deposit ◽  
Middle Urals ◽  
The Urals ◽  
Critical Metals ◽  
Pt Alloy ◽  
Placer Deposits ◽  
Exposure Ages

&lt;p&gt;The application of cosmogenic noble gases (&lt;sup&gt;3&lt;/sup&gt;He and &lt;sup&gt;21&lt;/sup&gt;Ne) in detrital grains to quantify sediment transport rates and storage timescales is largely undeveloped. We have previously shown that cosmogenic He can be measured in single grains (Yakubovich et al. 2019). The low He diffusion rate and the chemical and/or physical robustness of metal alloys (eg Au, Ag, Cu, Pt, Fe) means the technique has potential to determine how critical metals accumulate at the Earth surface. &amp;#160;In an effort to determine how long detrital Pt-alloy grains spend travelling to placer deposits we have measured cosmogenic&lt;sup&gt;3&lt;/sup&gt;He concentrations in 60 (0.5&amp;#8211;7 mg) grains of isoferroplatinum (Pt&lt;sub&gt;3&lt;/sub&gt;Fe) from the world largest alluvial Pt placer deposits in the Kondyor-Uorgalan rivers in Khabarovsk region, and the Is-Turinsk and Nyas&amp;#8217;ma river systems in Middle Urals, Russia.&lt;/p&gt;&lt;p&gt;In both systems, there are no significant cosmogenic &lt;sup&gt;3&lt;/sup&gt;He in the grains from the low order streams that drain the source rock. &lt;sup&gt;3&lt;/sup&gt;He&lt;sub&gt;cos&lt;/sub&gt;concentrations in Pt grains from distant placers (30 km) varies in order of magnitude from 0.3 to 30 x 10&lt;sup&gt;7&lt;/sup&gt;at g&lt;sup&gt;-1&lt;/sup&gt;in grains in Uorgalan river, 5 to 40 x 10&lt;sup&gt;7&lt;/sup&gt;at g&lt;sup&gt;-1&lt;/sup&gt;in Glubokinskoe placer deposit (Is river) and 20 to 70 x 10&lt;sup&gt;7&lt;/sup&gt;at g&lt;sup&gt;-1&lt;/sup&gt;in the Generalka deposit (Nyas&amp;#8217;ma river). Converting this to surface residence times (P = 25 at g y&lt;sup&gt;-1&lt;/sup&gt;, Yakubovich et al., 2019) yields model exposure durations of0.1&amp;#173;&amp;#8211;10, 3&amp;#8211;20 and 13&amp;#8211;38 Myr for grains from the Uorgalan, Glubokinskoe and Generalka deposits respectively. Assuming that all grains were extracted from shielded locations this exposure ages indicate the total time of transport and residence of the grains on river bed surface prior to final deposition.&lt;/p&gt;&lt;p&gt;Pt grains are added to the river system constantly. If we assume that the average transport conditions are essentially identical for all grains, then the difference between the maximum and minimum exposure ages within the same location indicates the total duration of placer supply from the source rock. For the Urals it is equal for 17&amp;#8211;25 Myr, while for Kondyor-Uorgalan placer it is 10 Myr. This is in a good agreement with geological observations. Within Kondyor-Uorgalan placer deposit the age of the alluvium varies from Neogene to Quaternary, while in the Urals Pt-bearing Jurassic, Neogene and Quaternary fluvial sediments are distinguished within the placers.&lt;/p&gt;&lt;p&gt;Paleo peneplain surfaces are established nearby the Kondyor massif and pre-date the most productive platinum sands. Several stages of peneplenisation are evident in the Urals from thick weathering crusts. The exposure ages indicate10&amp;#8217;s million-year scale of transport/deposition histories of detrital Pt alloys, which might result of multiple redeposition of material during long term accumulation of cosmogenic &lt;sup&gt;3&lt;/sup&gt;He during peneplenisation. &amp;#160;&lt;/p&gt;&lt;p&gt;Yakubovich O., Stuart F.M., Nesterenok A. and Carracedo A. (2019). Chem. Geol. 517, 22-33.&lt;/p&gt;

Pb-isotope evidence on the origin of the West Shropsh orefield, England

1996 ◽  
Vol 133 (5) ◽  
pp. 611-617 ◽  
Author(s):  
R. Haggerty ◽  
B. M. Rohl ◽  
P. D. Budd ◽  
N. H. Gale
Keyword(s):  
Sea Water ◽  
Multiple Sources ◽  
Pb Isotope ◽  
The West ◽  
Minor Variation ◽  
Isotope Data ◽  
Water Origin ◽  
Isotope Evidence ◽  
Significant Spread ◽  
Isotope Variation

AbstractPb-isotope data on ore galenas from the West Shropshire orefield show a significant spread of 20pb/204pb values, with minor variation in 207Pb/204Pb and 208Pb/204Pb ratios. These indicate that lead was derived from multiple sources, some of them uranium-enriched and incompletely mixed prior to ore deposition. Four possible mineralizing agents are considered: circulating sea-water, metamorphic waters, basinal brines and convecting formation waters. Pb-isotope data exclude a circulating sea-water origin for the mineralization, and best support a convecting formation water mineralizing agent. A model involving a single fluid tapping multiple lead sources is proposed to explain the observed Pb-isotope variation.

Fractionation of highly siderophile elements in refertilized mantle: Implications for the Os isotope composition of basalts

2014 ◽  
Vol 400 ◽  
pp. 33-44 ◽  
Author(s):  
Claudio Marchesi ◽  
Christopher W. Dale ◽  
Carlos J. Garrido ◽  
D. Graham Pearson ◽  
Delphine Bosch ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Highly Siderophile Elements ◽  
Siderophile Elements ◽  
Os Isotope

Geology, geochronology, and geochemistry of basaltic flows of the Cat Hills, Cat Mesa, Wind Mesa, Cerro Verde, and Mesita Negra, central New Mexico

2006 ◽  
Vol 43 (9) ◽  
pp. 1251-1268 ◽  
Author(s):  
Florian Maldonado ◽  
James R Budahn ◽  
Lisa Peters ◽  
Daniel M Unruh
Keyword(s):  
New Mexico ◽  
Trace Element Composition ◽  
Rio Grande Rift ◽  
Magma Source ◽  
Temporal Shift ◽  
Crustal Component ◽  
Isotopic Compositions ◽  
Source Regions ◽  
Enriched Mantle ◽  
Lower Crustal

The geochronology, geochemistry, and isotopic compositions of basaltic flows erupted from the Cat Hills, Cat Mesa, Wind Mesa, Cerro Verde, and Mesita Negra volcanic centres in central New Mexico indicate that each of these lavas had unique origins and that the predominant mantle involved in their production was an ocean-island basalt type. The basalts from Cat Hills (0.11 Ma) and Cat Mesa (3.0 Ma) are similar in major and trace element composition, but differences in MgO contents and Pb isotopic values are attributed to a small involvement of a lower crustal component in the genesis of the Cat Mesa rocks. The Cerro Verde rock is comparable in age (0.32 Ma) to the Cat Hills lavas, but it is more radiogenic in Sr and Nd, has higher MgO contents, and has a lower La/Yb ratio. This composition is explained by the melting of an enriched mantle source, but the involvement of another crustal component cannot be disregarded. The Wind Mesa rock is characterized by similar age (4.01 Ma) and MgO contents, but it has enriched rare-earth element contents compared with the Cat Mesa samples. These are attributed to a difference in the degree of partial melting of the Cat Mesa source. The Mesita Negra rock (8.11 Ma) has distinctive geochemical and isotopic compositions that suggest a different enriched mantle and that large amounts of a crustal component were involved in generating this magma. These data imply a temporal shift in magma source regions and crustal involvement, and have been previously proposed for Rio Grande rift lavas.

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