Age and pyrite Pb-isotopic composition of the giant Sukhoi Log sediment-hosted gold deposit, Russia
Meffre, S and Large, RR and Scott, RJ and Woodhead, JD and Chang, Z and Gilbert, SE and Danyushevsky, LV and Maslennikov, VV and Hergt, J (2008) Age and pyrite Pb-isotopic composition of the giant Sukhoi Log sediment-hosted gold deposit, Russia. Geochimica Et Cosmochimica Acta, 72 . pp. 2377-2391.
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Official URL: http://dx.doi.org/10.1016/j.gca.2008.03.005
Sukhoi Log is one of the largest gold deposits in Russia (1100 t Au at 2.45 g/t). Like many other sediment-hosted gold
deposits throughout the world, Sukhoi Log preserves textural, structural and geochemical evidence for multiple generations
of Au enrichment and pyrite growth.
The deposit is located in the Lena gold province of Siberia, on the edge of the Siberian Craton and occurs in the core of a
recumbent anticline in a Neoproterozoic black shale and quartz-rich siltstone–sandstone turbidite succession. Temporal constraints
on pyrite paragenesis at the deposit have been determined using laser ablation inductively coupled mass spectrometry
(LA-ICPMS) measurements of U, Th and Pb isotopes in pyrite, monazite and zircon. LA-ICPMS age determinations on
detrital zircons indicate the host rocks were deposited after 600 ± 10 Ma and derived from a mixture of Palaeoproterozoic
and Neoproterozoic sources. The U, Th and Pb isotopic systematics indicate the cores of large monazite crystals, which predate
obvious tectonic fabric development in the host rocks, began growing at 573 ± 12 Ma. The rims of the same monazite
crystals formed at 516 ± 10 Ma, during peak metamorphism and deformation. Small monazite crystals also grew in the sedimentary
rocks during the Devonian (374 ± 20 Ma) and the Carboniferous or Early Permian (288 ± 22 Ma), possibly in
response to fluid movements triggered by synchronous granite intrusion in the area. Multi-collector and quadrupole LAICPMS
Pb isotopic determination on pyrite, combined with overprinting criteria, show that the earliest (stratiform) Pb
and Au-bearing pyrite formed prior to metamorphism—possibly during sedimentation or early diagenesis (575–600 Ma).
Small Au-rich pyrite nodules preserved as cores to folded bedding-parallel pyrite–quartz veins probably grew during late diagenesis
or early metamorphism. Large pyrite euhedra, which overgrow the strong axial planar cleavage in the host rocks, have
more radiogenic Pb-isotopic compositions and formed either late during or after deformation. Framboidal pyrite that is overgrown
by both the late diagenetic–early metamorphic and syn- to post-metamorphic pyrite has the most radiogenic Pb-isotopic
composition suggesting exchange with radiogenic Pb in the matrix may have continued until late in the history of the
The dating and Pb isotopes support a multistage origin for the gold deposit with Au first introduced during or prior to
growth of the earliest stratiform pyrite and progressively re-concentrated (with or without addition of further gold) during
later metamorphic events.
|Keywords:||Sedex gold, Syngenetic gold, Orogenic gold, Ore geochronology, Sukhoi Log, La-ICPMS, Pb Isotopes, Lead Isotopes, Proterozoic|
|Deposited By:||Mrs Hlaing Nilar|
|Deposited On:||30 Apr 2008 13:08|
|Last Modified:||15 Oct 2013 10:07|
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