T. T. Alapieti

University of Oulu

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T. C. Devaraju

SRM University, Andhra Pradesh

J. J. Lahtinen

Outokumpu (Finland)

R. J. Kaukonen

University of Oulu

Rais Latypov

University of the Witwatersrand

A.Yu. Barkov

Cherepovets State University

K. Laajoki

University of Oulu

Sofya Chistyakova

University of the Witwatersrand

Tapio Halkoaho

Geological Survey of Finland

T. L. Sudhakara

Karnatak University

Robert F. Martin

Political Research Associates

Cooperative Institutions

University of Oulu

Geological Survey of Finland

Kola Science Centre

Geological Institute

McGill University

Universidad Complutense de Madrid

Karnatak University

Kuvempu University

Consejo Superior de Investigaciones Científicas

University of the Witwatersrand

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Petrology and Geochemistry of Mafic-Ultramafic Fragments from the Aguablanca Ni-Cu Ore Breccia, Southwest Spain

Economic Geology (2006)

Rubén Piña Rosario Lunar Hernández Lorena Ortega Menor Fernando Gervilla T. T. Alapieti

Aguablanca (southwest Spain) is the first economic Ni-Cu-(PGE) deposit found in southern Europe.Two features make it an unusual example of magmatic sulfide ore: it is related to the development of an Andean-type continental magmatic arc, and it is hosted by a subvertical magmatic breccia.The structural style and the geodynamic context of the deposit contrast with most plutonic Ni-Cu-PGE deposits elsewhere, which occur at specific levels of layered mafic intrusions in rift environments.The Ni-Cu deposit is hosted by the Aguablanca intrusion, a mafic body composed of gabbronorite and minor quartz-diorite, gabbro, and norite.Sulfides are concentrated in a gabbronorite matrix along a subvertical (dip of 70º-80º N), funnel-like magmatic breccia that contains barren or slightly mineralized ultramafic-mafic cu-mulate fragments.Modal compositions of the fragments reflect a wide variety of rock types, including peri-dotite (hornblende-rich werhlite, dunite, and hornblende-rich harzburgite), pyroxenite (ortho-and clinopyrox-enite), gabbro (gabbro, gabbronorite, and hornblende gabbro), and anorthosite.The primary silicate assemblage includes olivine (Fo91-Fo79), orthopyroxene (Mg no.0.85-0.73),clinopyroxene (Mg no.0.93-0.62),plagioclase (An99-An38), amphibole (Mg no.0.87-0.68)and phlogopite (Mg no.0.89-0.64).The wide range of rock types and the Fe-enrichment trends in the primary ferromagnesian silicates suggest magmatic differenti-ation processes from the parent melts, with the fragments representing different stages of cumulate formation.The ore-bearing breccia contains both semimassive and disseminated sulfides in the gabbronorite matrix.Textures vary between meso-and orthocumulate, and the rock-forming magmatic silicates are orthopyroxene (Mg no.0.83-0.74),clinopyroxene (Mg no.0.89-0.78),plagioclase (An50-An77), and intercumulus amphibole (Mg no.0.86-0.70),phlogopite (0.84-0.69) and minor quartz.The gabbronorite in the matrix of the breccia is petrographically and chemically very similar to that of the unmineralized parts of the main Aguablanca intru-sion and exhibits a similar differentiation trend, suggesting that the matrix of the ore-bearing breccia and the unmineralized rocks belong to a same magmatic suite.The local presence of mafic-ultramafic fragments in the barren Aguablanca intrusion supports this suggestion.The presence of highly Ni depleted olivine, whole-rock Cu/Zr ratios below 1, and the local occurrence of dis-seminations of magmatic sulfides in the peridotite fragments point to sulfide segregation before and/or during the formation of the peridotite cumulates.Mantlenormalized incompatible trace element patterns of the frag-ments along with published sulfur isotope data are consistent with crustal contamination, suggesting that addi-tion of crustal sulfur from pyrite-bearing black slates led to sulfide saturation.These results support a model in which sulfides segregated and settled during the differentiation of an unexposed mafic-ultramafic complex, now sampled as fragments in the breccia, whereas the overlying silicate magma, most probably fed by succes-sive fresh magma injections, underwent fractional crystallization, giving rise to this cumulate sequence.The emplacement of the ore breccia took place at temperatures above the (monosulfide solid solution (mss) solidus but below the olivine and pyroxene solidus, likely owing to the explosive injection of a new pulse of magma into the chamber, which mingled with the sulfide liquid and disrupted the overlying cumulate sequence.As a consequence, fragments reached their current position in the breccia, injected along with the sulfide and the sili-cate melts, which subsequently formed the sulfide-rich gabbronorite.

Ultramafic rock

Breccia

10.2113/gsecongeo.101.4.865

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Citations (58)

Editorial – Platinum-group element deposits in mafic and ultramafic rocks – a special issue in memoriam of Eugen F. Stumpfl

Mineralogy and Petrology (2007)

T. T. Alapieti Rais Latypov

Ultramafic rock

Platinum group

10.1007/s00710-007-0212-6

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Citations (1)

THE OCCURRENCE OF Pb Cl (OH) AND Pt Sn S COMPOUNDS IN THE MERENSKY REEF, BUSHVELD LAYERED COMPLEX, SOUTH AFRICA

The Canadian Mineralogist (2001)

A.Yu. Barkov Robert F. Martin R. J. Kaukonen T. T. Alapieti

An unusual phase rich in Cl (78.4 wt.% Pb, 19.2% Cl) and close in composition to penfieldite [Pb 2 Cl 3 (OH)] was found as a ~5 m inclusion in chalcopyrite, in a spatial association with platinum-group minerals, in a sulfide-poor (≤5 vol.% of base-metal sulfides) enstatite orthocumulate of the Merensky Reef, Bushveld layered complex, South Africa.This seems to be the first reported occurrence of a Pb-Cl-(OH) compound in mafic-ultramafic rocks.The associated platinum-group minerals are members of the braggite series, cooperite (which forms large intergrowths with braggite: up to 0.5 mm in the longest dimension), members of the rustenburgite-atokite and merenskyite-moncheite series, zoned laurite, and an unknown stannosulfide of Pt, the likely chemical formula of which is PtSnS.The stannosulfide probably formed at a hydrothermal stage from microvolumes of a latestage fluid or liquid.The Cl-rich phase precipitated from a late-stage solution rich in Cl, or formed as a result of replacement of a precursor mineral (probably galena) by an aqueous hydrochloric solution at a very low temperature, at the final stage of hydrothermal alteration.

Platinum group

10.2113/gscanmin.39.5.1397

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Citations (11)

Stratigraphy, petrology, and platinum-group element mineralization of the early Proterozoic Penikat layered intrusion, northern Finland

Economic Geology (1986)

T. T. Alapieti J. J. Lahtinen

The Penikat layered intrusion is part of an early Proterozoic belt of layered intrusions, 2,440 m.y. in age, which extends across northern Finland. The intrusion is located between late Archean granitoids and early Proterozoic supracrustal rocks. The Marginal series, with slightly contaminated chilled margin, separates the Penikat intrusion from the underlying basement complex. The Layered series is divided into five megacyclic units, I to V from bottom to top, each unit comprising an ultramafic lower part and a gabbroic upper part.Three major mineralized zones, enriched in platinum-group elements (PGE), the Sompujaervi (SJ), Ala-Penikka (AP), and Paasivaara (PV) mineralizations, have been delineated along almost 23 km of strike and occur in megacyclic unit IV. The Sompujaervi mineralization, about 1 m thick, is mostly associated with pyroxenitic rocks at the lower contact of the unit, whereas the Ala-Penikka zone (about 0.35 m thick) is associated with gabbronorite and poikilitic-textured anorthosite in the middle part and the Paasivaara zone (about 1 m thick) with leucogabbro and anorthosite very close to the upper contact.The ratios of platinum-group elements are relatively constant for each mineralization. The Paasivaara mineralization represents the most platinum-rich variety and the Ala-Penikka the most palladium-rich one, the ratio of Pd to Pt being typically about 2 for the sulfide-free type, and 1.5, 3.5, and 0.7 for the sulfide-bearing type for the Sompujaervi, Ala-Penikka, and Paasivaara mineralizations, respectively.The sulfur-free platinum-group minerals (PGM), sperrylite and isomertieite are the dominant species encountered in the Sompujaervi mineralization, whereas sulfur-bearing platinum-group minerals, together with sperrylite, dominate in the Ala-Penikka and Paasivaara mineralizations. These are represented by braggite and vysotskite in the Ala-Penikka one and by braggite and cooperite in the more platinum-rich Paasivaara mineralization.According to the new classification of platinum-group element deposits proposed by Cabri and Naldrett (1984), the typically sulfide-free Sompujaervi mineralization may be included in the oxide-silicate association as a possible new type, whereas the Ala-Penikka and Paasivaara mineralizations may be classified as Merensky reef-type of the sulfide associations.

Anorthosite

Platinum group

Layered intrusion

Ultramafic rock

Country rock

10.2113/gsecongeo.81.5.1126

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Citations (57)

Occurrence of Bismuth and Selenium in the Sulphide Ores of Ingaldhal and Kalyadi, Karnataka

Journal of the Geological Society of India (1997)

T. C. Devaraju T. T. Alapieti K. S. Ananthamurthy

Bismuth

10.17491/jgsi/1997/490616

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Citations (0)

First terrestrial occurrence of titanium-rich pyrrhotite, marcasite and pyrite in a fenitized xenolith from the Khibina alkaline complex, Russia

The Canadian Mineralogist (1997)

A.Yu. Barkov K. Laajoki Yuri P. Men’shikov T. T. Alapieti S. J. Sivonen

Marcasite

Xenolith

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Citations (10)

Cryptic variation of augite in the Penikat Layered Intrusion, Northern Finland, with reference to megacyclic units and PGE-enriched zones

Mineralogy and Petrology (1995)

T. T. Alapieti Tapio Halkoaho

Layered intrusion

Orogeny

10.1007/bf01162754

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Citations (11)

Osmian hollingworthite and rhodian cobaltite-gersdorffite from the Lukkulaisvaara layered intrusion, Russian Karelia

Mineralogical Magazine (1996)

A.Yu. Barkov T. T. Alapieti K. Laajoki Raija Peura

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Cobaltite

Layered intrusion

10.1180/minmag.1996.060.403.12

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Citations (8)

The marginal border group of the Porttivaara layered intrusion and related sulphide mineralization

Bulletin of the Geological Society of Finland (1977)

R. Piirainen T. T. Alapieti R. Hugg Olavi Kerkkonen

The marginal border group of the Porttivaara layered intrusion and related sulphide

Layered intrusion

10.17741/bgsf/49.2.006

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