Geochemistry and Mineralogy of Platinum Group Element Mineralization in the River Valley Intrusion, Ontario, Canada: A Model for Early-Stage Sulfur Saturation and Multistage Emplacement and the Implications for "Contact-Type" Ni-Cu-PGE Sulfide Mineralization

2014 ◽  
Vol 109 (3) ◽  
pp. 689-712 ◽  
Author(s):  
D. A. Holwell ◽  
R. R. Keays ◽  
E. A. Firth ◽  
J. Findlay
Keyword(s):  
Platinum Group Element ◽  
Early Stage ◽  
River Valley ◽  
Group Element ◽  
Sulfide Mineralization ◽  
Contact Type ◽  
Sulfur Saturation ◽  
Platinum Group

Controls on the Formation of Contact-Type Platinum-Group Element Mineralization in the East Bull Lake Intrusion

2001 ◽  
Vol 96 (3) ◽  
pp. 559-581 ◽  
Author(s):  
D. C. Peck ◽  
R. R. Keays ◽  
R. S. James ◽  
P. T. Chubb ◽  
S. J. Reeves
Keyword(s):  
Platinum Group Element ◽  
Group Element ◽  
Contact Type ◽  
Platinum Group

Variant Offset-Type Platinum Group Element Reef Mineralization in Basal Olivine Cumulates of the Kapalagulu Intrusion, Western Tanzania

2021 ◽  
Author(s):  
M. D. Prendergast
Keyword(s):  
Precious Metal ◽  
Platinum Group Element ◽  
Early Stage ◽  
Precious Metals ◽  
Parental Magma ◽  
Group Element ◽  
Metal Enrichment ◽  
Reef Development ◽  
Platinum Group ◽  
Olivine Cumulates

Abstract The Kapalagulu intrusion in eastern Tanzania hosts a major, 420-m-thick, stratiform/stratabound platinum group element (PGE)-bearing sulfide zone—the Lubalisi reef—within a prominent, chromititiferous, harzburgite unit close to its stratigraphic base. Several features of the vertical base and precious metal distributions (in a composite stratigraphic section based upon two deep exploration drill holes) display similarities to those of offset-type PGE reefs that formed under the overall control of Rayleigh fractionation: (1) composite layering (at several scales) defined by systematic vertical variations of sulfide and precious metal contents and intermetallic ratios, indicating repeated cycles of PGE enrichment and depletion in the order Pd-Pt-Au-Cu, and (2) in the lower part of the reef, stratigraphic offsets of the precious metal peaks below peak sulfide (Cu) content. The form and geochemistry of the reef are consistent with overturns of basal liquid layers within a liquid layering system (i.e., stable density-driven stratification of a magma chamber), plus at least two minor inputs of parental magma during which the resident magma was recharged with sulfur and metals, and the effective depletion of precious metals in the magma midway through reef development. The Lubalisi reef differs from classic offset-type PGE reefs, however, principally because individual Pd, Pt, and Au enrichment peaks are coincident, not offset. The reef is set apart from other offset-type PGE reefs in three additional ways: (1) its association with olivine cumulates that crystallized soon after initial magma emplacement and well below the first appearance of cumulus pyroxene or plagioclase (implying attainment of sulfide saturation and precious metal enrichment without prolonged concentration of sulfur and chalcophile metals by normal magma cooling and differentiation), (2) the probable role of chromite crystallization in not only triggering sulfide segregation during reef formation but also facilitating precious metal enrichment in the early stages of reef development, and (3) its great width. The early stage of fractionation may also help explain the coincident precious metal peaks through its effect on apparent precious metal partition coefficients.

Multiple S Isotopes and S Isotope Heterogeneity at the East Eagle Ni-Cu-Platinum Group Element Deposit, Northern Michigan

2020 ◽  
Vol 115 (3) ◽  
pp. 527-541
Author(s):  
E.K. Benson ◽  
E.M. Ripley ◽  
C. Li ◽  
B.W. Underwood ◽  
R. Mahin
Keyword(s):  
Platinum Group Element ◽  
Group Element ◽  
Spatial Proximity ◽  
Small Scale ◽  
Sulfide Mineralization ◽  
Exchange Reactions ◽  
Wide Range ◽  
Platinum Group ◽  
Northern Michigan ◽  
S Isotope

Abstract The East Eagle Ni-Cu-platinum group element deposit is a conduit-type deposit located in northern Michigan, in close spatial proximity to the currently producing Eagle deposit. Massive and semimassive (net-textured) sulfide mineralization at East Eagle occurs approximately 800 m lower in the stratigraphic sequence than that at Eagle and only ~200 m above the contact between Proterozoic and Archean rocks. Although sulfide mineralogy and textural types are similar at the two occurrences, there are important differences in their S isotope systematics. Massive sulfide mineralization at East Eagle is characterized by a relatively narrow range of δ34S values from 1.5 to 3.2‰. Semimassive sulfides show a similar range from 2.1 to 3.8‰. In strong contrast to these values, those from disseminated sulfides that border the massive and semimassive mineralization define a much larger range from –4.3 to 22.8‰. The much more restricted range in δ34S values recorded in the massive and semimassive sulfide mineralization compared to that of the disseminated mineralization is thought to reflect isotopic exchange reactions in the conduit involving accumulated sulfide and pulses of magma containing S of mantle origin. The ∆33S values of all three major types of sulfide mineralization at East Eagle are near 0‰, with most values between –0.03 and 0.03‰. Unlike ∆33S values from semimassive sulfide mineralization at Eagle, the ∆33S values at East Eagle show no, or very limited, evidence for the involvement of S derived from Archean sedimentary rocks. The wide range in δ34S values recorded in the disseminated mineralization provides strong evidence that S from Proterozoic sedimentary host rocks was involved in the mineralization; in some cases, as much as 85% of the S may have been of external origin. In addition to the wide range in δ34S values, the disseminated mineralization is characterized by spatially heterogeneous δ34S values. Meter-scale S isotope variations, as well as variations in Pt and Pd tenor, are consistent with multiple inputs of magma, each characterized by distinct S isotope ratios. Heterogeneity of several per mill at the centimeter scale indicates that the degree of supercooling exceeded the S diffusivity, preserving small-scale S isotope variability inherited from the sedimentary country-rock source. Elongate, branching plagioclase grains in many of the gabbroic rocks that host the disseminated sulfide mineralization are consistent with a rapid second stage of cooling.

Sulfide saturation mechanisms in gabbroic intrusions in the Nipigon Embayment

2007 ◽  
Vol 44 (8) ◽  
pp. 1203-1214
Author(s):  
Stephen A Kissin ◽  
Geoffrey J Heggie ◽  
James M Franklin ◽  
Alireza Karimzadeh Somarin
Keyword(s):  
Platinum Group Element ◽  
Country Rock ◽  
Group Element ◽  
Isotopic Data ◽  
Sulfide Saturation ◽  
Copper Nickel ◽  
Northwestern Ontario ◽  
Reef Type ◽  
Sulfur Saturation ◽  
Platinum Group

The Seagull and Kitto intrusions in the Nipigon Embayment of northwestern Ontario were studied to gain an understanding of the processes involved in sulfur saturation of the mafic to ultramafic magmas leading to the formation of platinum group element (PGE) concentrations. Profiles of sulfur, copper, nickel, gold, palladium, and platinum concentrations as a function of depth revealed that sulfur saturation occurred at the base of the Seagull intrusion. A higher grade horizon occurs well above the base of the intrusion, suggesting that a reef-type of process was significant here and possibly in the Kitto intrusion, as well. Olivine compositions indicate that, in both cases, the parental magmas were undersaturated with respect to sulfur. Sulfur, neodymium–samarium, and rubidium–strontium isotopic data suggest that assimilation of country rock and sulfide played a role, especially in the formation of basal concentrations of PGEs.

PLATINUM GROUP ELEMENT (PGE) SYSTEMATICS OF ARC SULFIDES: A CASE STUDY FROM CUMULATES OF THE CHILAS COMPLEX, KOHISTAN ARC, PAKISTAN

2016 ◽  
Author(s):  
Ijaz Ahmad ◽  
◽  
Jeremy P. Richards ◽  
Jingao Liu ◽  
D. Graham Pearson ◽  
...  
Keyword(s):  
Platinum Group Element ◽  
Group Element ◽  
Platinum Group
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