Segregation of magmatic fluids and their potential in the mobilization of platinum-group elements in the South Kawishiwi Intrusion, Duluth Complex, Minnesota — Evidence from petrography, apatite geochemistry and coexisting fluid and melt inclusions

Gál, Benedek; Molnár, Ferenc; Guzmics, Tibor; Mogessie, Aberra; Szabó, Csaba; Peterson, Dean M

doi:10.1016/j.oregeorev.2013.03.001

Cited by 25 publications

(20 citation statements)

References 81 publications

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“…The total homogenization temperature observations from the Type 1 fluid inclusions, which homogenized into a vapor phase, are challenging due to the optical properties of the host mineral. An attempt was made to re-check the temperatures by continuous monitoring of the Raman spectrum during heating (e.g., Gál et al, 2013). However, this was unsuccessful due to the strong OH-group spectra from host tourmaline, which masked the spectrum of the water in the fluid inclusions.…”

Section: Results Of Raman Spectroscopymentioning

confidence: 99%

Epigenetic gold occurrence in a Paleoproterozoic meta-evaporitic sequence in the Rompas-Rajapalot Au system, Peräpohja belt, northern Finland

Ranta¹,

Molnár²,

Hanski³

et al. 2018

Bull Geol Soc Finland

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The Rompas-Rajapalot gold prospect is located in the northern part of the Paleoproterozoic Peräpohja belt. It covers an area of at least 10 x 10 km and comprises various styles of gold mineralization ranging from localized high-grade Au pockets in uraniniteand pyrobitumen-bearing calcsilicate-carbonate-quartz veins in mafic metavolcanic rocks (Rompas area) to disseminated gold grains in Fe-Mg-rich metasediments and quartz-tourmaline-sulfide-native gold veins (Palokas area). This study deals with the petrography and mineral chemistry of the gold mineralization at Palokas, which occurs in the eastern part of the Rompas-Rajapalot prospect. Major and trace element data and fluid inclusion characteristics of tourmaline are used to evaluate the origin and the pressure-temperature-fluid composition parameters of hydrothermal fluids. Whole-rock geochemical analyses are utilized to evaluate the nature of the protolith of the host rocks. Gold occurs in a native form in at least two different textural settings: 1) single, relatively coarse grains disseminated among the rock-forming silicates in cordierite-orthoamphibole rocks and 2) smaller grains occurring in fractures of tourmaline in quartz-sulfide-tourmaline breccias and in fractures of chloritized cordierite-orthoamphibole rocks adjacent to the tourmaline-rich breccias. Fracture-related gold is associated with Bi-Se-S-bearing tellurides, native Bi, molybdenite, chalcopyrite, and pyrrhotite. Coarser-grained disseminated gold were not found to be clearly associated with sulfides nor any fractures. Statistical correlations show that the Au concentration correlates strongly with Te, Cu, Co, Se, Bi, Mo, and Ag (ρ = 0.730-0.619) whereas Au correlates moderately with As, Fe, W (ρ = 0.523-0.511) and to a lesser extent with U, Pb, and Ni (ρ = 0.492-0.407). Gold has the strongest negative correlations with Sr and Ca. The chondrite-normalized REE patterns of tourmaline from the Au-mineralized rocks (both vein type and host-rock tourmaline) and the late-to post-orogenic granite partly overlap and show similar LREE-enriched trends, with the enrichment being lower in tourmaline from the granite. Fluid inclusion studies from tourmaline in gold-bearing

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Section: Results Of Raman Spectroscopymentioning

confidence: 99%

Epigenetic gold occurrence in a Paleoproterozoic meta-evaporitic sequence in the Rompas-Rajapalot Au system, Peräpohja belt, northern Finland

Ranta¹,

Molnár²,

Hanski³

et al. 2018

Bull Geol Soc Finland

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“…Previous studies reported the characteristics of fluid inclusions hosted in the late‐stage igneous minerals such as quartz (Jin et al, ). These fluid inclusions are considered to be the reservoir of the primary hydrothermal fluids and were considered to represent the fluids that transferred various metals and halogens from the evolving magmas (Audétat & Pettke, ; Webster, ; Gál et al, ; Vaughn & Ridley, ; Yardley & Bodnar, ; Howarth et al, ; Luo et al, ). Change of chemical composition of the host magma following the release of hydrothermal fluids would influence the nature of minerals crystallizing from the magma.…”

Section: Discussionmentioning

confidence: 99%

Occurrence and Chemical Compositions of Amphiboles in Altered Dioritic Rocks of Laiwu Skarn‐Type Iron Deposit in West Shandong Area, China

et al. 2018

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The Laiwu Fe deposit is the largest skarn-type deposit in West Shandong in China, with an estimated reserve of 290 Mt of iron ore. Here, we investigate the occurrence and chemical composition of amphiboles in altered dioritic rocks of this deposit. Three generations of amphibole group minerals were identified in these rocks. The first type (Type 1) is a hornblende with a generally euhedral crystal shape, 150-500 μm in size, and dominantly occurs in the host monzonite. The second type (Type 2) of hornblende occurs as fine grains (<100 μm) or concentric rims, less than 50 μm in thickness, around the Type 1 hornblende. The third type (Type 3) of amphibole is anhedral actinolite occurring along the boundary or the cracks of the Type 1 or 2 hornblende grains. The Type 1 hornblende has higher FeO (12.5-15.6 wt.%) and lower MgO contents (11.2-14.6 wt.%) than the Type 2 hornblende, which has an FeO content ranging from 8.8 to 10.5 wt.% and MgO content ranging from 14.2 to 17.1 wt.%. The Type 3 actinolite shows the lowest FeO (4.6-6.4 wt.%) and highest .2 wt.%) contents. We infer that the Type 2 hornblende formed from Fe-rich hydrothermal fluids released during rapid upwelling of the crystallizing magma. The fluids were relatively reduced and enriched in Fe. The Type 3 actinolite formed by coupled dissolution and reprecipitation, and its formation is one of the features denoting Fe-enrichment events. Our study of these types of amphibole provides insights into the ore formation process.

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“…Magmatic Ni-Cu deposits occur at the base of two of the intrusions (Fig. 1), the Partridge River (see description below) and the South Kawishiwi (recent studies of Cu-Ni-PGE mineralization in Gál et al, 2013;Benkó et al, 2015a, b;Raic et al, 2015).…”

Section: Geological Contextmentioning

confidence: 98%

A laser ablation inductively coupled plasma mass spectrometry study of the distribution of chalcophile elements among sulfide phases in sedimentary and magmatic rocks of the Duluth Complex, Minnesota, USA

Samalens

Barnes

Sawyer

2017

Ore Geology Reviews

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Segregation of magmatic fluids and their potential in the mobilization of platinum-group elements in the South Kawishiwi Intrusion, Duluth Complex, Minnesota — Evidence from petrography, apatite geochemistry and coexisting fluid and melt inclusions

Cited by 25 publications

References 81 publications

Epigenetic gold occurrence in a Paleoproterozoic meta-evaporitic sequence in the Rompas-Rajapalot Au system, Peräpohja belt, northern Finland

Epigenetic gold occurrence in a Paleoproterozoic meta-evaporitic sequence in the Rompas-Rajapalot Au system, Peräpohja belt, northern Finland

Occurrence and Chemical Compositions of Amphiboles in Altered Dioritic Rocks of Laiwu Skarn‐Type Iron Deposit in West Shandong Area, China

A laser ablation inductively coupled plasma mass spectrometry study of the distribution of chalcophile elements among sulfide phases in sedimentary and magmatic rocks of the Duluth Complex, Minnesota, USA

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