Petrology and Ni-Cu-Cr-PGE Mineralization of the Largest Mafic Pluton in Europe: The Early Proterozoic Burakovsky Layered Intrusion, Karelia, Russia

1995 ◽  
Vol 37 (6) ◽  
pp. 509-525 ◽  
Author(s):  
Evgenii V. Sharkov ◽  
O. A. Bogatikov ◽  
Tanya L. Grokhovskaya ◽  
A. V. Chistyakov ◽  
Vyacheslav A. Ganin ◽  
...  
Keyword(s):  
Layered Intrusion ◽  
Early Proterozoic ◽  
Pge Mineralization

scholarly journals Sr isotopes indicate millennial-scale formation of metal-rich layers by reactive melt percolation in an open-system layered intrusion

2020 ◽  
Author(s):  
J. Stephen Daly ◽  
Luke Hepworth ◽  
Brian O'Driscoll ◽  
Chris Johnson ◽  
Ralf Gertisser ◽  
...  
Keyword(s):  
Open Systems ◽  
Layered Intrusion ◽  
Chemical Zoning ◽  
Mafic Intrusions ◽  
Ionisation Mass Spectrometry ◽  
Pge Mineralization ◽  
Isotopic Analyses ◽  
Melt Percolation ◽  
Mineral Scale ◽  
Reactive Melt

<p>In order to test whether the crystal mushes that form layered mafic intrusions can behave as open systems, we investigated mineral-scale textural, chemical and Sr isotopic heterogeneity in the c. 60 Ma Rum intrusion, Scotland. Within Unit 10 of the Rum intrusion, intercumulus plagioclase and clinopyroxene crystals in peridotite 1-2 cm above and below millimetric Cr-spinel seams exhibit complex optical and chemical zoning (Hepworth et al. 2017). These Cr-spinel seams are closely associated with sulphide and platinum-group element (PGE) mineralization. High precision Sr isotopic analyses (undertaken by thermal ionisation mass spectrometry) of individual intracrystal zones (sampled by micromilling) in intercumulus plagioclase and clinopyroxene from within the PGE-enriched Cr-spinel seams have revealed significant intra-crystalline heterogeneity. <sup>87</sup>Sr/<sup>86</sup>Sr heterogeneity is present between plagioclase crystals, between clinopyroxene and plagioclase, and within plagioclase crystals, throughout the studied section. The preservation of Sr isotope heterogeneities at 10-100 µm length-scales implies cooling of the melts that formed the precious metal-rich layers at rates >1 °C per year, and cooling to diffusive closure within 10s-100s of years. The combined textural observations and intra-crystal plagioclase <sup>87</sup>Sr/<sup>86</sup>Sr data also highlight the importance of repeated cycles of dissolution and recrystallization within the crystal mush, and together with recent documentation of ‘out-of-sequence’ layers in other layered intrusions (Mungall et al. 2016; Wall et al. 2018), raise the prospect that basaltic magmatic systems may undergo repeated self-intrusion during solidification.</p><p>Hepworth, L.N., O’Driscoll, B., Gertisser, R., Daly, J.S. and Emeleus, H.C. 2017. Journal of Petrology 58, 137-166; Mungall, J. E., Kamo, S. L. & McQuade, S. 2016. Nature Communications 7, 13385; Wall, C. J., Scoates, J. S., Weis, D., Friedman, R. M., Amini, M. & Meurer, W. P. 2018. Journal of Petrology 59, 153–190.</p>

Low-sulfide PGE mineralization in layered intrusion ring, Vestfold Hills, Antarctica

2015 ◽  
Vol 57 (8) ◽  
pp. 657-673
Author(s):  
M. S. Egorov ◽  
V. S. Semenov ◽  
N. L. Alekseev
Keyword(s):  
Layered Intrusion ◽  
Pge Mineralization ◽  
Vestfold Hills

Metasomatic processes in the Lukkulaisvaara layered intrusion, Russia, and formation of low-sulfide PGE mineralization

2008 ◽  
Vol 50 (4) ◽  
pp. 249-274 ◽  
Author(s):  
S. V. Semenov ◽  
V. A. Glebovitsky ◽  
A. B. Kol’tsov ◽  
V. S. Semenov ◽  
S. I. Korneev ◽  
...  
Keyword(s):  
Layered Intrusion ◽  
Pge Mineralization

Petrology of the Early Proterozoic Burakovsky layered intrusion, southern Karelia, Russia: mineral and whole-rock major-element chemistry

1997 ◽  
Vol 34 (4) ◽  
pp. 390-406 ◽  
Author(s):  
S. J. Higgins ◽  
G. A. Snyder ◽  
J. N. Mitchell ◽  
L. A. Taylor ◽  
E. V. Sharkov ◽  
...  
Keyword(s):  
Partition Coefficient ◽  
Major Element ◽  
Layered Intrusion ◽  
Current Data ◽  
Rich Phase ◽  
Layered Series ◽  
Early Proterozoic ◽  
Major Element Chemistry ◽  
Entire Sequence ◽  
Southern Karelia

The Early Proterozoic (2449 ± 1.1 Ma) Burakovsky layered intrusion of southern Karelia, Russia, is the largest (700 km2) mafic pluton in the Fennoscandian Shield. The layered series contains two main parts: (i) an ultramafic series (85% dunite), and (ii) a mafic series (mostly gabbros). Mineral and whole-rock chemical variations in the ultramafic zone indicate little variation in chemistry over the entire sequence (e.g., in olivine, variations are from Fo89 to Fo87 over the upper 1600 m). In contrast, the Mg# in pyroxenes from the gabbronorite zone varies from 85 to 58 over an interval of 500 m. On the basis of the current data, there are no apparent reversals in chemistry in the ultramafic zone, whereas there is evidence for several in the gabbronorite zone. Furthermore, there is a distinctive reversal to more primitive compositions in mineral and whole-rock chemistry at the top of the ultramafic zone. These differences indicate that either (i) the gabbronorite zone crystallized from the residue left from formation of the ultramafic zone and the subsequent "flushing" of the more evolved portions to form the Early Proterozoic Karelian volcanic fields, or (ii) there were two separate magmas. Plagioclase crystals from the gabbronorite zone are chemically zoned, providing evidence of the local processes affecting crystallization of this sequence. Plagioclase crystals from near the base commonly display relatively Na-rich cores that are believed to result from either supersaturation at the onset of nucleation or the prior crystallization of some other, Ca-rich phase (e.g., clinopyroxene). Many plagioclase grains also contain reversely zoned rims, indicative of either (i) exchange between trapped liquid and the main magma during times of replenishment; or (ii) an increase in the CIPW-normative plagioclase–liquid partition coefficient for Ca, due to an increase in the augite component of the melt. The lack of evidence for abundant magma influxes in the ultramafic zone contrasts with the chemical reversals observed in the gabbronorite zone, suggesting that replenishment was a prevailing process only in the upper half of the intrusion.

The first data on possible Mezozoic magmatism within the Western slope of the Southern Urals

2018 ◽  
pp. 24-34
Author(s):  
A. O. Khotylev ◽  
N. B. Devisheva ◽  
Al. V. Tevelev ◽  
V. M. Moseichuk
Keyword(s):  
Southern Urals ◽  
Western Slope ◽  
Isotopic Age ◽  
The Southern Urals ◽  
Early Proterozoic ◽  
Carbonate Formations ◽  
Two Bodies

Within the Western slope of the Southern Urals, there are plenty of basite dyke complexes of Riphean to Vendian among Precambrian terrigenous-carbonate formations. In metamorphic formations of the Taratash complex (Archean to Early Proterozoic, the northern closure of the Bashkirian meganticlinorium) there was observed the andesitic dyke with isotopic age of 71±1 Ma (U-Pb SHRIMP II on zircons) and near Bakal two bodies of gabbroids with zircons of similar ages were found. These are the first evidence of possible Mezozoic magmatism in this region.

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