THE ROLE OF SALINE FLUIDS BASE-METAL AND GOLD MINERALIZATION AT THE COBALT HILL PROSPECT NORTHEAST OF THE SUDBURY IGNEOUS COMPLEX, ONTARIO: A FLUID-INCLUSION AND MINERALOGICAL STUDY

The Lac Panache (Nipissing) gabbro intrudes Huronian metasediments ca. 40 km southwest of the Sudbury Igneous Complex. The gabbro contains disseminated sulfides and is in contact with a chalcopyrite-rich quartz vein that crystallized from highly saline fluids (46.8 ± 3 equivalent wt.% NaCl) at a minimum temperature of 420 ± 27 °C. Chloride and carbonate inclusions in opened fluid inclusion cavities in the vein suggest that the brine contained dissolved metals (in addition to NaCl), such as Fe, Cu, Mn, and Co. The weakly altered quartz vein postdated regional metamorphism and was probably contemporaneous with the 1.7 Ga felsic magmatism and attendant albite alteration in the area. Cl-rich scapolite in the gabbro and highly saline fluid inclusions in the quartz vein suggest the existence of circulating hot brine throughout the tectonic evolution of the region. The 2.2 Ga old gabbro contains an abundance of Cl-rich scapolite intergrown with pyrrhotite and chalcopyrite that formed during the early hydrothermal (deuteric) alteration of the gabbro.

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Multiple fluid generations in the Sudbury igneous complex: fluid inclusion, Ar, O, H, Rb and Sr evidence

Chemical Geology ◽

10.1016/s0009-2541(98)00122-3 ◽

1999 ◽

Vol 154 (1-4) ◽

pp. 1-19 ◽

Cited By ~ 22

Author(s):

Dan Marshall ◽

David Watkinson ◽

Catharine Farrow ◽

Ferenc Molnár ◽

Anne-Marie Fouillac

Keyword(s):

Fluid Inclusion ◽

Igneous Complex ◽

Sudbury Igneous Complex ◽

Complex Fluid

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Geology, alteration, and the role of fluids in Cu-Ni-PGE mineralization of the footwall rocks to the Sudbury igneous complex, Levack and Morgan townships, Sudbury district, Ontario.

10.22215/etd/1995-02896 ◽

1995 ◽

Author(s):

Catharine Farrow

Keyword(s):

Igneous Complex ◽

Sudbury Igneous Complex ◽

Pge Mineralization

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High-Grade Magmatic Platinum Group Element-Cu(-Ni) Sulfide Mineralization Associated with the Rathbun Offset Dike of the Sudbury Igneous Complex (Ontario, Canada)

Economic Geology ◽

10.5382/econgeo.4717 ◽

2020 ◽

Vol 115 (3) ◽

pp. 505-525

Author(s):

Alexander Kawohl ◽

Wesley E. Whymark ◽

Andrejs Bite ◽

Hartwig E. Frimmel

Keyword(s):

Base Metal ◽

Precious Metal ◽

Quartz Diorite ◽

Metal Sulfides ◽

High Grade ◽

Igneous Complex ◽

Impact Melt ◽

Sudbury Igneous Complex ◽

Base Metal Sulfides ◽

Platinum Group

Abstract Quartz dioritic impact melt dikes around the 1.85 Ga Sudbury Igneous Complex, locally referred to as offset dikes, are well endowed with respect to Ni-Cu-platinum group elements (PGE). However, only those dikes proximal (<6 km) to the main mass of the Sudbury Complex are mineralized at an economic grade and, in places, host world-class deposits. We report on a new discovery of such heavily mineralized offset dike at Rathbun Lake, about 15 km east of the currently known extent of the Sudbury Igneous Complex. There, a segment of amphibole quartz diorite is exposed at the contact between Huronian metasedimentary rocks and gabbro of the 2.22 Ga Nipissing Suite, xenoliths of which are abundant throughout the diorite and record textural evidence of partial melting. The mafic inclusion-bearing quartz diorite is the host of the Rathbun Lake showing, a small but high-grade PGE-Cu(-Ni) sulfide occurrence of hitherto controversial origin. A detailed petrographic and mineralogical characterization of this occurrence revealed a two-stage mineralization history. Disseminated to semimassive (net-textured) chalcopyrite ± loop-textured pentlandite ± magnetite containing Pd-bismuthotellurides and, more rarely, sperrylite and native gold—all of which are closely associated with base metal sulfides—are interpreted as magmatic. The semimassive sulfide averages ~40 g/t Pd + Pt + Au at a Cu/(Cu + Ni) of >0.9 and a Pd/Ir of >100,000. Mineralogy, ore textures, and mantle-normalized PGE + Au patterns match a specific type of Cu-rich mineralization in the Sudbury Igneous Complex known as footwall mineralization. By analogy with these footwall deposits, the occurrence is interpreted as having formed by downward percolation of a highly fractionated sulfide melt toward the bottom of a now largely eroded offset dike. The magmatic paragenesis was hydrothermally overprinted at lower greenschist-facies conditions to pyrite-chalcopyrite-violarite ± covellite ± millerite. This involved also local remobilization into pyrite-chalcopyrite veinlets and the liberation of precious metal minerals from their sulfide hosts. In contrast to base metal sulfides, most precious metal minerals were resistant to hydrothermal alteration, although corrosion of some grains is noted as well as their truncation by chlorite and epidote. Micron-scale X-ray mapping revealed a progressive replacement of magmatic Pd-Bi-Te minerals, where in contact with hydrous silicates, by Sb- and Hg-bearing Pd minerals such as temagamite, Pd3HgTe3. The timing and nature of this hydrothermal overprint remains uncertain, but a connection to later regional metamorphism and faulting seems most plausible. Our finding of magmatic PGE-base metal sulfide at Rathbun Lake suggests a new subtype of distal offset dike-hosted mineralization in an area so far not known for offset dikes. It opens up new opportunities in the search for unconventional ore deposits around the Sudbury impact structure and improves our understanding on the distribution of impact melt-derived dikes around complex craters.

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The role of evaporites in the genesis of base metal sulphide mineralisation in the Northern Platform of the Pan-African Damara Belt, Namibia: geochemical and fluid inclusion evidence from carbonate wall rock alteration

Mineralium Deposita ◽

10.1007/s001260050247 ◽

2000 ◽

Vol 35 (4) ◽

pp. 364-376 ◽

Cited By ~ 35

Author(s):

D. Chetty ◽

H. E. Frimmel

Keyword(s):

Fluid Inclusion ◽

Base Metal ◽

Wall Rock ◽

Base Metal Sulphide ◽

Metal Sulphide ◽

Pan African ◽

Wall Rock Alteration ◽

Sulphide Mineralisation ◽

Rock Alteration

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ALTERATION, VEIN TEXTURES AND FLUID INCLUSION PETROGRAPHY OF METAMORPHIC ROCK-HOSTED GOLD DEPOSIT AT ONZONKANBANI AREA, CENTRAL MYANMAR: IMPLICATION FOR ITS GENESIS

ASEAN Engineering Journal ◽

10.11113/aej.v8.15502 ◽

2018 ◽

Vol 8 (2) ◽

pp. 48-63

Author(s):

Aung Tay Zar ◽

I Wayan Warmada ◽

Lucas Donny Setijadji ◽

Koichiro Watanabe

Keyword(s):

Fluid Inclusion ◽

Base Metal ◽

Fluid Inclusions ◽

Gold Mineralization ◽

Homogenization Temperature ◽

Fluid Inclusion Study ◽

Small Scale ◽

Western Boundary ◽

Metamorphic Belt ◽

Neutral Ph

Gold and base metal mineralization of Onzon-Kabani area is located at the western part of Mogok Metamorphic Belt in central Myanmar, where the well-known Sagaing Fault serves as its western boundary. Artisanal and small-scale gold operations started here three decades ago on gold mineralization hosted in marble and gneiss. Mineralization occurs as fracture-filling veins of several types: gold-bearing quartz vein, base metal quartz-carbonate vein, and carbonate base metal sulfides vein. Three types of hydrothermal alteration zones develop from the proximal to distal zone of hydrothermal conduit: silicic, sericite-illite and propylitic alteration. Alteration mineral assemblages consist of quartz, calcite, sericite, adularia, epidote, chlorite, illite and smectite which are typical of neutral pH hydrothermal fluid. The presence of adularia and calcite within veins indicate boiling event of near-neutral pH condition. Common vein textures of quartz and calcite are banded, crustiform, bladed calcite, lattice, mosaic or jigsaw, cockade, comb and zonal. Boiling-related mineral textures (e.g. banded, bladed and lattice) and fluid inclusion characteristics of coexisting liquid-rich and vapor-rich fluid inclusions have been identified in mineralized samples. Common ore minerals are pyrite, sphalerite, galena, chalcopyrite and minor marcasite, electrum and native gold. Gold is mostly associated with quartz gangue, pyrite, sphalerite and galena. Fluid-inclusion study suggests the presence of liquid-rich and vapor-rich fluid inclusions which were trapped in boiling fluid at homogenization temperature of 159 to 315°C and moderate salinity of 0.88 to 12.51 wt.% NaCl equivalent. It is concluded that despite mesothermal gold system is more typical style of gold mineralization in the Mogok Metamorphic Belt, it is not the type of mineralization in the Onzon-Kanbani area. Instead, a low-sulfidation epithermal system is more characteristic to be present here. The knowledge generated from this study can serve as a guide in understanding new deposit type as well as mineral exploration in the region.

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