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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

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

Gold mineralization at Sukhoi Log in eastern Siberia is hosted in a deformed Neoproterozoic organic-bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline. The deposit contains about 30 million ounces of gold at an average grade of 2.0 g/t Au and is one of the largest known undeveloped gold resources. The high-grade gold zone forms a gently dipping tabular body in the core of the anticline. The best gold grades occur in narrow, bedding-parallel pyrite-quartz veinlets that have been folded during the main deformation event. Lower grade gold is associated with disseminated pyrite developed in and around the high-grade core of the deposit. Detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments. The two earliest forms of pyrite, termed py1 and py2, are commonly developed in stratiform layers of micron-sized crystals, framboids and fine euhedra, which are interpreted as synsedimentary to early diagenetic in origin. Coarser grained, bedding-parallel aggregates of inclusion-rich pyrite, termed py3, contain inclusions of arsenopyrite, native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation. Coarse euhedral pyrite, py4, overgrows the earlier pyrite (py1, py2, and py3), and the slaty cleavage developed in the host rocks, indicating a syndeformation timing. Late- stage, inclusion-free pyrite, py5, overgrows and replaces earlier sulfides and is considered to be syn- to late deformation. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold, varying from 0.4 to 12.1 ppm, with a mean of 3.22 ppm Au, and 1,900 ppm As. Py1 is also enriched in a suite of trace elements (Mo, Sb, Ni, Co, Se, Te, Ag, Cu, Pb, Zn, Mn, Ba, Cr, U, V), which are similar to those concentra

In western Victoria, a widespread stratiform style of gold enrichment in Palaeozoic black mudstone and chert-clearly different from the classic mesothermal quartz vein deposits of the Victorian goldfields - has been confirmed by whole-rock geochemistry and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). This enrichment pre-dates compaction, deformation and low-grade metamorphism of the sedimentary host-rocks, and therefore possibly developed diagenetically during slow deposition of the thin carbonaceous black mudstone beds and the thinner layers of chert. These paired strata have been documented at many locations in three regional outcrop areas of chevronfolded Cambrian and Lower Ordovician metasediments in the Stawell and Bendigo Zones, where they are interbedded with quartz-rich turbidites. The layers were named 'indicators' by the early miners, who found locally rich nuggety gold deposits at intersections between these layers and mesothermal quartz veins. Gold is present in euhedral pyrite crystals in both black shale and chert. LA-ICPMS analysis of individual pyrite crystals in the indicator beds shows that pyrite is enriched in Au, As, Sb, Se, Te and Bi. The Au content of pyrite varies from 0.03 to 2.69 ppm with a mean of 0.58 ppm and shows a positive correlation with As, which varies from 1000 to 6000 ppm. Many pyrite crystals show enrichment of gold in their cores and depletion in their rims, confirming the likely syngenetic or syndiagenetic accumulation of gold during pyrite formation in the sediments. Prior to regional metamorphism, folding and faulting, the many indicator strata in the outcrop areas were parts of an extensive marine sequence of Late Cambrian and Early Ordovician age. The former primary source of this mineralisation is considered to have been one or more contemporaneously exhalative submarine hydrothermal systems. Thus, the older Palaeozoic sediments of the western Lachlan Fold Belt were significantly enriched in syn

Gold mineralization at Sukhoi Log in eastern Siberia is hosted in a deformed Neoproterozoic organic-bearing and pyritic black shale and siltstone sequence that is folded into a tight overturned anticline. The deposit contains about 30 million ounces of gold at an average grade of 2.0 g/t Au and is one of the largest known undeveloped gold resources. The high-grade gold zone forms a gently dipping tabular body in the core of the anticline. The best gold grades occur in narrow, bedding-parallel pyrite-quartz veinlets that have been folded during the main deformation event. Lower grade gold is associated with disseminated pyrite developed in and around the high-grade core of the deposit. Detailed paragenetic studies of the mineralization and host rocks have defined six stages of pyrite development in the carbonaceous sediments. The two earliest forms of pyrite, termed py1 and py2, are commonly developed in stratiform layers of micron-sized crystals, framboids and fine euhedra, which are interpreted as synsedimentary to early diagenetic in origin. Coarser grained, bedding-parallel aggregates of inclusion-rich pyrite, termed py3, contain inclusions of arsenopyrite, native gold and gold tellurides and are interpreted to form during late diagenesis and earliest deformation. Coarse euhedral pyrite, py4, overgrows the earlier pyrite (py1, py2, and py3), and the slaty cleavage developed in the host rocks, indicating a syndeformation timing. Late- stage, inclusion-free pyrite, py5, overgrows and replaces earlier sulfides and is considered to be syn- to late deformation. Laser-ablation inductively coupled plasma mass spectrometry (LA-ICPMS) analyses of the various pyrite types indicate that the synsedimentary py1 contains the highest levels of invisible gold, varying from 0.4 to 12.1 ppm, with a mean of 3.22 ppm Au, and 1,900 ppm As. Py1 is also enriched in a suite of trace elements (Mo, Sb, Ni, Co, Se, Te, Ag, Cu, Pb, Zn, Mn, Ba, Cr, U, V), which are similar to those concentra

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