Petrogenetic significance of chromian spinels from the Sudbury Ignecus Complex, Ontario, Canada

1997 ◽  
Vol 34 (10) ◽  
pp. 1405-1419 ◽  
Author(s):  
Mei-Fu Zhou ◽  
Reid R. Keays ◽  
Peter C. Lightfoot ◽  
Gordon G. Morrison ◽  
Michelle L. Moore
Keyword(s):  
Magma Mixing ◽  
Ore Deposits ◽  
Chromian Spinel ◽  
Triangular Diagram ◽  
Element Abundances ◽  
Sudbury Igneous Complex ◽  
Magmatic Sulfides ◽  
Sulfide Ore ◽  
Host Rocks ◽  
Chamber Floor

Chromian spinels occur in mafic–ultramafic inclusions in the Sublayer of the Sudbury Igneous Complex (SIC) as well as in mafic–ultramafic rocks in the immediate footwall of the Sublayer. The host rocks are pyroxenite and melanorite with minor dunite, harzburgite, and melatroctolite. As common accessory phases in these rocks, the chromian spinels display euhedral or subhedral forms and are included in olivine and orthopyroxene. Chromian spinel grains generally have ilmenite lamellae and contain abundant inclusions (zircon, olivine, diopside, plagioclase, biotite, and sulfide). All the chromian spinels have similar trace element abundances and are rich in TiO2 (0.5–15 wt.%). They have constant Cr# (100Cr/(Cr + Al)) (55–70) and exhibit a continuum in composition that traverses the normal fields of spinels in a Al–(Fe3+ + 2Ti)–Cr triangular diagram. This continuum extends to that of the composition of chromian magnetite in the host norite matrix to the mafic–ultramafic inclusions. This continuum in composition of the spinels suggests that the noritic matrix to the Sublayer formed from the same magma as the inclusions. A positive correlation between the Cr and Al contents of the spinels was probably produced by dilution of these elements by Fe3+ contributed, perhaps, by a plagioclase-saturated melt. Zircon inclusions in a chromian spinel grain reflect incorporation of crustal, felsic materials into the magma before crystallization of chromian spinel. The chemical characteristics and mineral inclusions of the spinels suggest that the Sublayer formed in response to magma mixing. It is suggested that subsequent to the formation of the crustal melt, mantle-derived high-Mg magmas mixed vigourously with this and generated the magmatic sulfides that eventually formed the Ni – Cu – platinum-group elements sulfide ore deposits. Some of the early crystallization products of the high-Mg magma settled to the chamber floor, where they partially mixed with the crustal melt and formed the mafic–ultramafic inclusions and footwall complexes.

Performance of low-fold scalar migration for downhole seismic imaging of massive sulfide ore deposits at Norman West, Sudbury, Canada

Geophysics ◽  
2012 ◽  
Vol 77 (5) ◽  
pp. WC3-WC13 ◽  
Author(s):  
Christof Mueller ◽  
Gilles Bellefleur ◽  
Erick Adam ◽  
Gervais Perron ◽  
Marko Mah ◽  
...  
Keyword(s):  
Seismic Data ◽  
Seismic Imaging ◽  
Signal To Noise Ratio ◽  
Massive Sulfide ◽  
Ore Deposits ◽  
Ore Deposit ◽  
Seismic Scattering ◽  
Vertical Seismic Profiling ◽  
Sudbury Igneous Complex ◽  
Sulfide Ore

The Downhole Seismic Imaging consortium conducted two consecutive vertical seismic profiling surveys in the Norman West mining camp (Sudbury, Canada) in 1998 and 1999. These were aimed toward imaging a massive sulfide ore deposit situated within the footwall of the Sudbury Igneous Complex (SIC). Three-component seismic data were acquired in four boreholes with variable signal-to-noise ratio and poor polarization quality. Consequently, the images suffered from strong azimuthal ambiguity. A strike filter, passing only reflections originating from within the SIC, was applied during migration to enhance interpretability of the images obtained. Migrated images showed structures correlating with the known position of an ore deposit located 1800 m away from one borehole (N40). Diffraction coherency migration enhanced the image of the deposit, and suggested strong seismic scattering from within the footwall of the SIC.

Nova-Bollinger Ni-Cu Sulfide Ore Deposits, Fraser Zone, Western Australia: Petrogenesis of the Host Intrusions

2021 ◽  
Author(s):  
Valentina Taranovic ◽  
Stephen J. Barnes ◽  
Steve Beresford ◽  
Morgan Williams ◽  
Colin MacRae ◽  
...  
Keyword(s):  
Western Australia ◽  
Regional Metamorphism ◽  
Parental Magma ◽  
Ore Deposits ◽  
Sulfide Deposit ◽  
Sulfide Liquid ◽  
Sulfide Ore ◽  
Primary Water ◽  
Magma Pulses ◽  
Host Rocks

Abstract The Nova-Bollinger Ni-Cu sulfide ore deposit is the first economic Ni-Cu-Co sulfide deposit to have been discovered in the Albany-Fraser orogen in Western Australia. The host rocks are mafic-ultramafic intrusive cumulates subdivided into two connected intrusions, designated Upper and Lower. The Upper Intrusion is bowl-shaped and modally layered with alternating peridotite and norite mesocumulate layers, with a Basal Series of dominantly orthocumulate mafic lithologies. The Lower Intrusion is a much thinner, semiconformable chonolith (flattened tube-shaped intrusion) consisting of mostly unlayered mafic to ultramafic orthocumulates. The Lower Intrusion hosts all the high-grade mineralization and most of the disseminated ores. A distinctive plagioclase-bearing lherzolite containing both orthopyroxene and olivine as cumulus phases is a characteristic of the Lower Intrusion and the Basal Series of the Upper. The intrusions differ slightly in olivine and spinel chemistry, the differences being largely attributable to the more orthocumulate character of the Lower Intrusion. Sector zoning in Cr content of pyroxenes is observed in the Lower Intrusion and in the lower marginal zone of the Upper and is attributed to crystallization under supercooled conditions. Symplectite pyroxene-spinel-amphibole coronas at olivine-plagioclase contacts are ubiquitous and are attributed to near-solidus peritectic reaction between olivine, plagioclase, and liquid during and after high-pressure emplacement, consistent with high Al contents in igneous pyroxenes and estimates of the peak regional metamorphism. Original cumulus olivines had compositions around Fo86 and were variably Ni depleted, interpreted as the result of preintrusion equilibration with sulfide liquid. The Upper and Lower Intrusion rocks represent cumulates from a similar parental magma, a high-Al tholeiite with MgO between 10 and 12%, low TiO2 (0.5–0.6%), and high Al2O3 (14–17%). Modeling using alphaMELTS indicates a primary water content of around 2 wt %. The cumulates of both intrusions were derived via multiple magma pulses of liquid-olivine-sulfide slurries with variable amounts of orthopyroxene, emplaced into the deep crust at pressures of around 0.7 GPa during the peak of regional metamorphism. The intrusions developed initially as a bifurcating sill, the lower arm developing into the ore-bearing Lower Intrusion chonolith and the upper arm inflating into the cyclically layered Upper Intrusion.

scholarly journals The Haidbach deposit in the Central Tauern Window, Eastern Alps, Austria: a metamorphosed orthomagmatic Ni-Cu-Co-PGE mineralization in the Polymetallic Ore District Venediger Nappe System – Hollersbach Complex

2021 ◽  
Vol 114 (1) ◽  
pp. 1-26
Author(s):  
Frank Melcher ◽  
Sonja Schwabl ◽  
Peter Onuk ◽  
Thomas Meisel ◽  
Thomas Aiglsperger ◽  
...  
Keyword(s):  
Precious Metal ◽  
Massive Sulfide ◽  
Eastern Alps ◽  
Chromian Spinel ◽  
Accessory Mineral ◽  
Tauern Window ◽  
Pge Mineralization ◽  
Sulfide Ore ◽  
Early Palaeozoic ◽  
Host Rocks

Abstract Cu-Ni-Co-PGE mineralization occurs at Haidbachgraben in the Early Palaeozoic, Subpenninic Hollersbach Complex of the Central Tauern Window, Austria. Massive sulfide ore formed from sulfide melt segregated from silicate melt during intrusion of pyroxenite into magmatic rocks formed in an MORB-type environment. Relics of magmatic minerals include chromian spinel and polyphase sulfide droplets composed of pyrrhotite, chalcopyrite and pentlandite preserved in recrystallized pyrite. Both ore and host rocks were multiply deformed and metamorphosed, leading to hornblendite carrying the ore, enveloped by chlorite-epidote schist. Conditions of – likely Variscan – amphibolite facies metamorphism are documented by relict pargasitic cores in hornblende and actinolite-tremolite, and by ternary sulfarsenide compositions in the Co-Ni-Fe solid solution series that are the most common accessory minerals found in the sulfide ore. Pyrrhotite, pentlandite, chalcopyrite and pyrite are the major sulfide minerals. Chalcopyrite is Cd-rich and retains a high-temperature magmatic signature. High Co/Sb and moderate Se/As ratios in pyrite also point to a magmatic environment of mineralization. The accessory mineral assemblage of small grain size (mostly <10 µm) comprises native Au-Ag alloy and petzite as Au-Ag minerals, sperrylite, a variety of Pd tellurides and bismuthotellurides with elevated Sb, irarsite, and Re sulfides such as tarkianite and a Pb-Re sulfide. In addition, minor molybdenite, bournonite, scheelite and selenides have been identified. Two precious metal assemblages are present in individual samples: (1) hessite associated with Pd tellurides, often accompanied by sphalerite and chalcopyrite; (2) tarkianite forming euhedral inclusions in pyrite. Sperrylite and Au-Ag native alloys are present throughout and were also detected in silicate matrix. Most of the precious metal-bearing phases must have formed during recrystallization of base metal sulfides after the magmatic, and probably during later metamorphic events terminating in the Neoalpine Tauern crystallization.

scholarly journals Magma Mixing Genesis of the Mafic Enclaves in the Qingshanbao Complex of Longshou Mountain, China: Evidence from Petrology, Geochemistry, and Zircon Chronology

Minerals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 195 ◽  
Author(s):  
Wenheng Liu ◽  
Xiaodong Liu ◽  
Jiayong Pan ◽  
Kaixing Wang ◽  
Gang Wang ◽  
...  
Keyword(s):  
Host Rock ◽  
Inductively Coupled Plasma ◽  
Magma Mixing ◽  
Coarse Grained ◽  
Calc Alkaline ◽  
Quartz Crystals ◽  
Alkaline Rocks ◽  
Mafic Enclaves ◽  
Normal Zoning ◽  
Host Rocks

The Qingshanbao complex, part of the uranium metallogenic belt of the Longshou-Qilian mountains, is located in the center of the Longshou Mountain next to the Jiling complex that hosts a number of U deposits. However, little research has been conducted in this area. In order to investigate the origin and formation of mafic enclaves observed in the Qingshanbao body and the implications for magmatic-tectonic dynamics, we systematically studied the mineralogy, petrography, and geochemistry of these enclaves. Our results showed that the enclaves contain plagioclase enwrapped by early dark minerals. These enclaves also showed round quartz crystals and acicular apatite in association with the plagioclase. Electron probe analyses showed that the plagioclase in the host rocks (such as K-feldspar granite, adamellite, granodiorite, etc.) show normal zoning, while the plagioclase in the mafic enclaves has a discontinuous rim composition and shows instances of reverse zoning. Major elemental geochemistry revealed that the mafic enclaves belong to the calc-alkaline rocks that are rich in titanium, iron, aluminum, and depleted in silica, while the host rocks are calc-alkaline to alkaline rocks with enrichment in silica. On Harker diagrams, SiO2 contents are negatively correlated with all major oxides but K2O. Both the mafic enclaves and host rock are rich in large ion lithophile elements such as Rb and K, as well as elements such as La, Nd, and Sm, and relatively poor in high field strength elements such as Nb, Ta, P, Ti, and U. Element ratios of Nb/La, Rb/Sr, and Nb/Ta indicate that the mafic enclaves were formed by the mixing of mafic and felsic magma. In terms of rare earth elements, both the mafic enclaves and the host rock show right-inclined trends with similar weak to medium degrees of negative Eu anomaly and with no obvious Ce anomaly. Zircon LA-ICP-MS (Laser ablation inductively coupled plasma mass spectrometry) U-Pb concordant ages of the mafic enclaves and host rock were determined to be 431.8 5.2 Ma (MSWD (mean standard weighted deviation)= 1.5, n = 14) and 432.8 4.2 Ma (MSWD = 1.7, n = 16), respectively, consistent with that for the zircon U-Pb ages of the granite and medium-coarse grained K-feldspar granites of the Qingshanbao complex. The estimated ages coincide with the timing of the late Caledonian collision of the Alashan Block. This comprehensive analysis allowed us to conclude that the mafic enclaves in the Qingshanbao complex were formed by the mixing of crust-mantle magma with mantle-derived magma due to underplating, which caused partial melting of the ancient basement crust during the collisional orogenesis between the Alashan Block and Qilian rock mass in the early Silurian Period.

scholarly journals Magmatic Sulfide Ore Deposits

Elements ◽  
2017 ◽  
Vol 13 (2) ◽  
pp. 89-95 ◽  
Author(s):  
Stephen J. Barnes ◽  
David A. Holwell ◽  
Margaux Le Vaillant
Keyword(s):  
Ore Deposits ◽  
Sulfide Ore ◽  
Magmatic Sulfide

scholarly journals Introduction to the special issue on the Flatreef PGE-Ni-Cu deposit, northern limb of the Bushveld Igneous Complex

2020 ◽  
Author(s):  
Wolfgang D. Maier ◽  
Marina Yudovskaya ◽  
Pedro Jugo
Keyword(s):  
Ore Deposits ◽  
Special Issue ◽  
Ore Formation ◽  
Igneous Complex ◽  
Northern Limb ◽  
Pge Mineralization ◽  
World Class ◽  
Bushveld Igneous Complex ◽  
Mine Development ◽  
Host Rocks

AbstractMore than 30 years ago, Cox and Singer (1986) suggested that magmatic platinum-group element (PGE)-Ni-Cu deposits are amongst the best understood of ore deposits, yet the origin of PGE mineralization in the Bushveld Igneous Complex (BIC) remains controversial after a century of study. In the northern limb of the BIC, the unravelling of ore formation proved particularly difficult due to relatively poor outcrop, which is typically affected by contamination of the intruding magmas with the host rocks and expressed in the form of abundant xenoliths, footwall rafts and disturbance of magmatic stratigraphy. In this thematic issue, we present contributions on the Flatreef, a recently discovered world-class PGE-Ni-Cu deposit constituting a downdip extension of the mineralized unit of the Platreef of the northern limb. Two deep shafts are currently being sunk, making the Flatreef one of the most significant new mine development on the Bushveld in several decades.

scholarly journals Ore Formation During Jurassic Subduction of the Tethys Along the Eurasian Margin: Constraints from the Kapan District, Lesser Caucasus, Southern Armenia

2019 ◽  
Vol 114 (7) ◽  
pp. 1251-1284 ◽  
Author(s):  
Johannes Mederer ◽  
Robert Moritz ◽  
Massimo Chiaradia ◽  
Richard Spikings ◽  
Jorge E. Spangenberg ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Late Jurassic ◽  
Ore Deposits ◽  
Sulfide Deposit ◽  
Short Time Interval ◽  
Ore Formation ◽  
Magmatic Arc ◽  
Argillic Alteration ◽  
Lesser Caucasus ◽  
Host Rocks

Abstract The Kapan mining district in the southernmost Lesser Caucasus is one of the few locations along the central Tethyan metallogenic belt where ore-forming processes were associated with magmatic arc growth during Jurassic Tethys subduction along the Eurasian margin. Three ore deposits of the Kapan district were investigated in this study: Centralni West, Centralni East, and Shahumyan. The ore deposits are hosted by Middle Jurassic andesitic to dacitic volcanic and volcaniclastic rocks of tholeiitic to transitional affinities below a late Oxfordian unconformity, which is covered by calc-alkaline to transitional Late Jurassic-Early Cretaceous volcanic rocks interlayered with sedimentary rocks. The mineralization consists of veins, subsidiary stockwork, and partial matrix replacement of breccia host rocks, with chalcopyrite, pyrite, tennantite-tetrahedrite, sphalerite, and galena as the main ore minerals. Centralni West is a dominantly Cu deposit, and its host rocks are altered to chlorite, carbonate, epidote, and sericite. At Centralni East, Au is associated with Cu, and the Shahumyan deposit is enriched in Pb and Zn as well as precious metals. Both deposits contain high-sulfidation mineral assemblages with enargite and luzonite. Dickite, sericite, and diaspore prevail in altered host rocks in the Centralni East deposit. At the Shahumyan deposit, phyllic to argillic alteration with sericite, quartz, pyrite, and dickite is dominant with polymetallic veins, and advanced argillic alteration with quartz-alunite ± kaolinite and dickite is locally developed. The lead isotope composition of sulfides and alunite (206Pb/204Pb = 18.17–18.32, 207Pb/204Pb = 15.57–15.61, 208Pb/204Pb = 38.17–38.41) indicates a common metal source for the three deposits and suggests that metals were derived from magmatic fluids that were exsolved upon crystallization of Middle Jurassic intrusive rocks or leached from Middle Jurassic country rocks. The δ18O values of hydrothermal quartz (8.3–16.4‰) and the δ34S values of sulfides (2.0–6.5‰) reveal a dominantly magmatic source at all three deposits. Combined oxygen, carbon, and strontium isotope compositions of hydrothermal calcite (δ18O = 7.7–15.4‰, δ13C = −3.4−+0.7‰, 87Sr/86Sr = 0.70537–0.70586) support mixing of magmatic-derived fluids with seawater during the last stages of ore formation at Shahumyan and Centralni West. 40Ar/39Ar dating of hydrothermal muscovite at Centralni West and of magmatic-hydrothermal alunite at Shahumyan yield, respectively, a robust plateau age of 161.78 ± 0.79 Ma and a disturbed plateau age of 156.14 ± 0.79 Ma. Re-Os dating of pyrite from the Centralni East deposit yields an isochron age of 144.7 ± 4.2 Ma and a weighted average age of the model dates of 146.2 ± 3.4 Ma, which are younger than the age of the immediate host rocks. Two different models are offered, depending on the reliability attributed to the disturbed 40Ar/39Ar alunite age and the young Re-Os age. The preferred interpretation is that the Centralni West Cu deposit is a volcanogenic massive sulfide deposit and the Shahumyan and Centralni East deposits are parts of porphyryepithermal systems, with the three deposits being broadly coeval or formed within a short time interval in a nascent magmatic arc setting, before the late Oxfordian. Alternatively, but less likely, the three deposits could represent different mineralization styles successively emplaced during evolution and growth of a magmatic arc during a longer time frame between the Middle and Late Jurassic.

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