Investigations of the Howland Reef of the Stillwater Complex, Minneapolis Adit area; stratigraphy, structure, and mineralization

Bow, C.; Wolfgram, D.; Turner, Alison; Barnes, Stephen J.; Evans, James P.; Zdepski, M.; Boudreau, A. E.

doi:10.2113/gsecongeo.77.6.1481

Cited by 32 publications

(11 citation statements)

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“…The PGE occur primarily in solid solution within disseminated base-metal sulfides (typically up to 5% volume, and locally in small bodies of massive sulfides in cores of discordant pegmatoids) and in a variety of discrete trace PGE-rich mineral phases (e.g. Bow et al, 1982;Barnes and Naldrett, 1985;Godel and Barnes, 2008;Turner et al 1985;Zientek et al 1985Zientek et al , 2002Corson et al, 2002). The J-M Reef has the largest average Pt + Pd grade of all known PGE deposits (∼18 ppm with an average Pd/Pt ratio of 3; Zientek et al, 2002).…”

Section: Olivine-bearing Zone I (Ob-i) and The J-m Reefmentioning

confidence: 99%

The Stillwater Complex, Montana – Overview and the significance of volatiles

Boudreau

2016

Mineral. mag.

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The geology of the 2.7 Ga Stillwater Complex in South-Central Montana is reviewed with a focus on the role of volatiles in locally modifying both the crystallization sequence of the evolving parent magma and the initially precipitated solid assemblages to favour olivine ± chromite. A secondary origin for these two minerals is particularly probable for the olivine-bearing rocks of the Banded series and, at a minimum, also increasing their modal abundance in the Peridotite zone of the Ultramafic series. Direct evidence for volatiles includes the presence of high-temperature fluid inclusions in pegmatoids and hydrous melt inclusions (now crystallized) in chromite and olivine from both the Ultramafic and the Banded series rocks. Indirect evidence includes the boninitic character of the parent magma, the presence of volatile-bearing minerals including high-temperature carbonates, rock textures, and Cl / F variations in apatite. Mechanisms which favour the formation of olivine (± chromite) over pyroxene include volatile phase boundary shifts induced by added H2O, incongruent melting of pyroxene by hydration of a partly-molten mush, and the near- to sub-solidus replacement of pyroxene by olivine and chromite by silica-undersaturated fluids. These mechanisms cast doubt that magmas with different liquid lines of descent were involved in the crystallization of the Stillwater Complex. A dry Stillwater magma would have been mineralogically and modally much less varied and lacking in high-grade platinum-group element and chromium deposits.

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Section: Olivine-bearing Zone I (Ob-i) and The J-m Reefmentioning

confidence: 99%

The Stillwater Complex, Montana – Overview and the significance of volatiles

Boudreau

2016

Mineral. mag.

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“…염기성-초염기성 페그마타이트는 화강암질 페그마타이 트에 비해 비교적 덜 알려져 있으나, 주로 염기성-초염 기성 화성암 복합체 내 불연속적인 암체로 발달하고 있 다. 대표적인 예로 부쉬벨트 복합체(Bushveld Complex) 에서 페그마타이트질 더나이트 파이프 (Cameron and Desborough, 1964;Scoon and Mitchell, 1994), 스캐어가 드 알카리 화성복합체 (McBirney and Sonnenthal, 1990;Irvine et al, 2001), 스틸워터(Stillwater) 복합체 (Raedeke and McCallum, 1984), 스마트빌 복합체 (Beard and Day, 1986) Scoon, 1985), 유체로 포화된 간극누적 Fe-부화 액상체의 여과 주입(filter-pressed) (Gabbro pegmatite in Duke Island, Irvine, 1974;Skaergaard Complex, McBirney and Noyes, 1979), 반려암질 모암의 subsolidus 교대작용 (Cameron and Desborough, 1964;Bow et al, 1982;Scoon et al, 2017) 등을 포함한다. 특히, 염기성-초염기성 페그 마타이트 중에서, 부쉬벨트 복합체 내 발달하는 Fe-부화 초염기성 페그마타이트는 Fe와 V의 주요 공급원으로 개 발되어 왔다 (Scoon et al, 2017).…”

Section: 휘석-인회석-저어콘 암석unclassified

A Preliminary Study on the Post-magmatic Activities Occurring at the Gonamsan Gabbroic Rocks in the Pocheon Area

Lee

Kim

Shin

2022

Econ. Environ. Geol.

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The Gonamsan gabbroic complex in the Pocheon area, northwestern region of South Korea consists of a variety types of gabbroic rocks and associated Fe-Ti oxide deposits caused by magmatic differentiation. Post-magmatic intrusions (i.e., gabbroic pegmatite and pyroxene-apatite-zircon rocks) partly intruded into the gabbroic rocks. The gabbroic pegmatite occurs in monzodiorite and oxide gabbro of the complex, intimately and spatially associated with high-grade lenticular Fe-Ti oxide mineralization. The pegmatite can be subdivided into plagioclase-amphibole and pyroxene-olivine pegmatite, in which the contact surface is sharp. The plagioclaseamphibole pegmatite comprises plagioclase and amphibole, with lesser amount of pyroxene, ilmenite, sphene, apatite, and biotite. The pegmatite shows plagioclase-amphibole intergranular texture, in which the open space formed by large plagioclase laths (An 2-26 Ab 72-98 Or 0-2 ) are infilled by amphibole. The pyroxene-olivine pegmatite is dark gray to black in color and also contains magnetite, ilmenite, spinel, apatite, and calcite as a minor component. The pyroxene (En 35-36 Fs 8-9 Wo 55 ) and olivine (Fo 84-85 Fa 15-16 ) partly show a poikilitic texture defined by smaller euhedral olivine enclosed by coarser clinopyroxene. Fe-Ti oxide minerals consist mainly of magnetite and ilmenite that are found interstitially to earlier formed silicates. Subsequently, they are encompassed by reaction rim (almost of amphibole and biotite) along the boundary with surrounding silicate minerals. Under the microscope, magnetite contains a lot of oxyexsolved ilmenite (trellis type) and spinel, and thereby is weakly enriched in magnetite-compatible elements such as Ti, Al, Mg, and V. The structure and textures at the contact zone as well as mineralogical disequilibrium between gabbroic pegmatite and the host gabbroic rocks suggest that the pegmatite may form as a result of accumulation from Fe-rich melt (or liquid) that occurred somewhere rather than in situ form from the host gabbroic rock during the magmatic differentiation. Consequently, the preliminary study suggests that further study on the post-magmatic activities can not only help us improve our understanding on magmatic fractionation but also provide critical information on Fe-Ti oxide mineralization in gabbroic rocks resulting from the magmatic differentiation.

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“…Also, geophysical surveys have proven that MK is stratified mafic and ultramafic rocks, encountered by sulphide mineralization within pyroxenite and gabbro horizon. MK from a structural point of view, is possibly analogue when comparing researches done on the Great Dyke in Zimbabwe (Wilson, 1982;Wilson, 1992;Wilson, 1996;Wilson et al, 2000), the Bushveld Igneous Complex in South Africa (Von et al, 1985;Mitchell,1990;Kruger, 1990;Ealesaand & Cawthornb, 1996), the Stillwater Igneous Complex in Montana (Bow et al, 1982;Raedeke & Mccallum, 1984;McCallum, 1996), and the Munni Munni Complex in Australia (Barnes & Hoatson, 1994). Each of these intrusions is a kind of assemblage of magmatic sediments forming stratified layers where sediment is represented by mineral grains from a gravitational fall in the magma.…”

Section: Structure Of Mount Kakoulimamentioning

confidence: 99%

Mount Kakoulima: An Overview and Analysis

Konaté¹,

Pan²

2013

ESR

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The interest generated by mafic-ultramafic rocks is justified by the fact that their structure and formational processes not only have scientific importance but also can lead to metal concentrations, making them economically viable. Located 50 km north-east of Conakry, Guinea's capital, Mount Kakoulima has long been one of the mafic-ultramafic rock areas of the world but has yet to be exploited; thus limited data have been published concerning it. The goal of this investigation is to describe the structure and formation process of Mount Kakoulima by means of geological field observations. The findings indicate that Mount Kakoulima is a stratified solid rock, formed with the result of some magma injections in some intrusive phases. With a Lithological sequence progressing from peridotite (dunite) to pyroxenite to extensive gabbro. The result will improve the understanding of geological processes on Mount Kakoulima to guide future surveys on mineral ores in the scientific and academic community for research and studies in the field of earth sciences.

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Investigations of the Howland Reef of the Stillwater Complex, Minneapolis Adit area; stratigraphy, structure, and mineralization

Cited by 32 publications

References 0 publications

The Stillwater Complex, Montana – Overview and the significance of volatiles

The Stillwater Complex, Montana – Overview and the significance of volatiles

A Preliminary Study on the Post-magmatic Activities Occurring at the Gonamsan Gabbroic Rocks in the Pocheon Area

Mount Kakoulima: An Overview and Analysis

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