The Ala-Penikka PGE reefs in the Penikat layered intrusion, Northern Finland

Halkoaho, Tapio; Alapieti, T. T.; Lahtinen, J. J.; Lerssi, J.

doi:10.1007/bf01162682

Cited by 27 publications

(33 citation statements)

References 14 publications

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“…They have so far not been exploited for PGE, although concentrations locally exceed 200 ppm (Halkoaho, 1994). They have so far not been exploited for PGE, although concentrations locally exceed 200 ppm (Halkoaho, 1994).…”

Section: Geologic Settingmentioning

confidence: 99%

Platinum-Group Element and Re-Os Isotope Variations of the High-Grade Kilvenjarvi Platinum-Group Element Deposit, Portimo Layered Igneous Complex, Finland

Thalhammer¹,

Schoenberg²

2006

Economic Geology

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The Kilvenjärvi deposit is a high-grade platinum-group element (PGE) deposit located in the basement below the Portimo Layered Igneous Complex, Finnish Lapland. It consists of a stockwork of massive Cu-Fe-Ni sulfide veins, up to a meter wide, which cut metamorphic banded gneiss, amphibolite, and granite. The veins are surrounded by intense sulfide disseminations that are accompanied by an alteration of the basement mineral assemblage to chlorite, calcite, orthoamphibole, monazite, and an unidentified hydrous ferroaluminous silicate. The veins locally carry in excess of 110 ppm PGE, and neighboring rocks in the basement that contain disseminated sulfides locally carry 25 ppm PGE. The PGE are hosted primarily by michenerite (PdBiTe) and sobolevskite (Pd[Bi,Te]), with only very few grains of merenskyite, sperrylite, vysotskite-braggite, paolovite, cooperite, and isomertieite.The massive sulfide veins host two distinct mineral assemblages that reflect an event of sulfur addition. The primary assemblage of chalcopyrite, pentlandite, and pyrrhotite is similar to that of common orthomagmatic sulfides and appears to represent the crystallization product from a sulfide melt. However, the primary minerals have been replaced extensively by a low-temperature secondary assemblage of chalcopyrite, pyrite, marcasite, Ni-bearing pyrite, violarite, and millerite. The disseminated sulfides in the basement lithologic units comprise only the secondary assemblage and are notably richer in chalcopyrite than the massive sulfide veins. The sulfides are associated with chlorite and calcite, indicating that they were likely introduced by carbon-rich (CO2 or CH4) hydrothermal fluids.The Kilvenjärvi deposit is extremely fractionated in PGE compared to unmineralized rocks and PGE occurrences within the Portimo Complex. Os and Ir concentrations are very low, and Pd/Ir ratios reach 2.5 × 10 5 . The massive and disseminated sulfides can be distinguished by their slightly different PGE patterns. Most notably, the massive sulfides are richest in Pd, and the disseminated sulfides are richest in Pt and Au. This fractionation appears to be consistent with an initial concentration in a magmatic sulfide melt followed by hydrothermal redistribution.The Re-Os isotopes have been significantly affected by Re mobility and cannot be used for dating. However, platinum-group mineral separates from the Kilvenjärvi deposit have nearly uniform isotopic compositions ( 187 Os/ 188 Os = 0.18-0.20) that are invariably higher than rocks from the Portimo Complex. Thus, it is evident that the Kilvenjärvi deposit had a significantly higher crustal contribution (possibly accounting for up to 18% of the Os) than parental magmas for the Layered series of the Portimo Complex. Contamination and fractional sulfide crystallization within the Portimo Marginal series may have been responsible for this isotopic signature.The deposit has some similarities to the various offsets associated with the Sudbury structure, Canada. A primary magmatic origin of the sulfides and PGE is evid...

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Section: Geologic Settingmentioning

confidence: 99%

Platinum-Group Element and Re-Os Isotope Variations of the High-Grade Kilvenjarvi Platinum-Group Element Deposit, Portimo Layered Igneous Complex, Finland

Thalhammer¹,

Schoenberg²

2006

Economic Geology

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“…Boudreau and McCallum (1992) referred the formation of the J − M reef in the Stillwater intrusion to the redeposition of magmatic sulfides resulting in the precipitation of ore mineral assemblages and hydrous silicates containing chlorine and high-salinity fluid inclusions (Ballhaus and Stumpfl, 1986). Iljina (1994) and Halkoaho (1994) came to the same conclusion with respect to the Penikat intrusion and Portimo igneous complex in Finland. They noted that the formation of PGM was not determined only by magma mixing.…”

Section: Introductionmentioning

confidence: 52%

“…A series of structural elements (Figs. 1b-1d) similar to those of the pot- (1) Medium-to coarse-grained gabbronorite, (2) coarse-grained gabbronorite, (3) medium-grained norite, (4) olivine gabbronorite, (5) melanocratic olivine norite, (6) coarse-grained norite, (7) fine-grained rocks overlapped by Quaternary sediments, (8) fine-grained norite, (9) fine-grained gabbronorite, (10) geophysical anomaly, (11) anorthosite, (12) quartz-bearing gabbro pegmatite, (13) Fe-Ni-Cu sulfide and PGM, (14) thin rhythmic layering, (15) geological boundaries, (16) geophysical boundaries, (17) faults, (18) hole type first described in the Merensky reef of the Bushveld Complex (Campbell et al, 1983;Kruger and Marsh, 1985) is abundant in the norite I and norite II zones. The rocks with high-grade sulfide and PGM are hosted in structural elements of this type.…”

Section: Geology Of the Intrusionmentioning

confidence: 99%

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

et al. 2008

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The Nadezhda ore-controlling structure and related rocks of the Lukkulaisvaara layered intrusion from the Oulanka plutonic group have been studied. Tensile deformation arising at the cooling stage at interfaces of rocks dissimilar in composition with different compressibility coefficients controlled the intensity of secondary processes and the high concentration of sulfide and platinum group minerals (PGM) along the perimeter of the fine-grained gabbronorite body in contact zones with country rocks. These zones were specific geochemical barriers. Magmas of supplementary injections could have been one of the sources of fluid affecting the rocks. Fe-Ni-Cu sulfides and PGM crystallized within the temperature range T = 800-350° C. Regional metamorphism did not exceed conditions of greenschist facies. Results of modeling of metasomatic processes indicate that decompression played the leading role in formation of the major secondary mineral assemblages: Czo -An 10 -Chl-Tr(Act) and Qtz-An 70 -Amph-Bt. 1 The decreasing pressure under isothermal conditions resulted in a rise in solubility of metals in chloride solution and their transport into dilatable zones. The cooling model leading to the enrichment of rocks in potassium and then to its leaching is realized more seldom, resulting in a Qtz-Ms-Chl-Act-Czo mineral assemblage and eventually in Qtz-Chl veins. The change of P and T during pluton cooling resulted in changing of the direction of metasomatic processes and telescoping of different superimposed mineral assemblages: Amph( ± Act)-Bt ± Chl 1 ± Qtz as an early one and Qtz-Czo-Chl 2 -Ab-Ms as a late one. The model mineral assemblages that match natural counterparts are as follows: (1) QtzPl-Amph-Bt and Qtz-Pl-Chl-Bt(Ms) and (2) Tr(Act)-Chl-An 10 -Czo, Qtz-An 10 -Chl-Ms(Bt), and Qtz-CzoChl-An 10 -Ms. At the same time, the An 40-50 -Amph-Bt, Qtz-An 40-50 -Amph-Bt, Qtz-An 10 − 20 -Chl-Bt(Ms), An 30-40 -Chl-Tr(Act)-Bt, An 30 -Chl-Tr(Act), and An 30 -Tr ( Act ) -Bt assemblages are suggested to be intermediate and reflect the direction of metasomatic processes.

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“…1) is associated with the sulfide-poor Sompujärvi PGE reef. It is located near the interface between ultramafic and gabbroic cumulates, close to the contact with the country rocks at the northern end of the intrusion (Alapieti & Lahtinen 1986, Halkoaho et al 1990, Halkoaho 1993). This deposit locally contains unusually high concentrations of the PGE (possibly surpassing 0.5 kg/t total PGE, mainly Pd), observed in altered mafic-ultramafic rocks, predominantly pyroxenite which typically contains ≤200 ppm S and 0.1-3 wt.% Cr, and thus is nearly sulfide-free.…”

Section: Occurrence and Associated Mineralsmentioning

confidence: 97%

LAFLAMMEITE, Pd3Pb2S2, A NEW PLATINUM-GROUP MINERAL SPECIES FROM THE PENIKAT LAYERED COMPLEX, FINLAND

Barkov¹,

Martin²,

Halkoaho³

et al. 2002

The Canadian Mineralogist

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is a new parkerite-type sulfide discovered in the Penikat layered complex, Finland. It occurs in altered pyroxenite in the Kirakkajuppura deposit in association with actinolite and clinochlore, accessory chromite, various platinum-group minerals [vysotskite, zvyagintsevite, cuprorhodsite-(ferrorhodsite)-malanite, laurite-erlichmanite, irarsite, keithconnite, unusual Pb-(Pd)-rich thiospinels of Cu, Fe, Rh and Ir, unnamed Pd 9 PbO 10 and Rh(Ni,Fe,Cu) 2 S 3 ], Pd-rich gold, and minor base-metal sulfides (chalcopyrite, bornite and millerite). Laflammeite occurs as individual subhedral to euhedral crystals up to 0.3 mm in size, and in intergrowths with Pt-Ni-poor vysotskite. Laflammeite is opaque and cream-colored with a brownish tint in reflected light in air. The anisotropy is weak, from brownish gray to grayish brown. The bireflectance is weak; pleochroism was not observed. Reflectance percentages in air (and in oil) are,

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The Ala-Penikka PGE reefs in the Penikat layered intrusion, Northern Finland

Cited by 27 publications

References 14 publications

Platinum-Group Element and Re-Os Isotope Variations of the High-Grade Kilvenjarvi Platinum-Group Element Deposit, Portimo Layered Igneous Complex, Finland

Platinum-Group Element and Re-Os Isotope Variations of the High-Grade Kilvenjarvi Platinum-Group Element Deposit, Portimo Layered Igneous Complex, Finland

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

LAFLAMMEITE, Pd3Pb2S2, A NEW PLATINUM-GROUP MINERAL SPECIES FROM THE PENIKAT LAYERED COMPLEX, FINLAND

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