Mica composition as a vector to gold mineralization: Deciphering hydrothermal and metamorphic effects in the Malartic district, Quebec

Gaillard, Nicolas; Williams‐Jones, Anthony E.; Clark, James R.; Lypaczewski, Philip; Salvi, Stefano; Piette-Lauzière, Nicolas; Linnen, Robert L.

doi:10.1016/j.oregeorev.2018.02.009

Cited by 50 publications

(37 citation statements)

References 95 publications

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“…Thus the absence of mica with PCG is consistent with the fluids being derived mainly from BIF elements ( Fig. 3f-g) (Gaillard et al, 2018). The association of PCG and apatite can be explained by hydroxyapatite and phyllosilicates co-precipitating from fluids.…”

Section: Co2 + Ch4→ 2c + 2h2osupporting

confidence: 77%

Widespread occurrences of variably crystalline 13C-depleted graphitic carbon in banded iron formations

Dodd

She

Manikyamba

et al. 2019

Earth and Planetary Science Letters

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Almost all evidence for the oldest traces of life on Earth rely on particles of graphitic carbon preserved in rocks of sedimentary protolith. Yet, the source of carbon in such ancient graphite is debated, as it could possibly be non-biological and/or non-indigenous in origin. Here we describe the co-occurrence of poorly crystalline and crystalline varieties of graphitic carbon with apatite in ten different and variably metamorphosed banded iron formations (BIF) ranging in age from 1,800 to >3,800 Myr. In Neoarchean to Palaeoproterozoic BIF subjected to low-grade metamorphism, 13 C-depleted graphitic carbon occurs as inclusions in apatite, and carbonate and arguably represents the remineralisation of syngenetic biomass. In BIF subjected to high-grade metamorphism, 13 C-depleted graphite co-occurs with poorly crystalline graphite (PCG), as well as apatite, carbonate, pyrite, amphibole and greenalite. Retrograde minerals such as greenalite, and veins cross-cutting magnetite layers contain PCG. Crystalline graphite can occur with apatite and orthopyroxene, and sometimes it has PCG coatings. Crystalline graphite is interpreted to represent the metamorphosed product of syngenetic organic carbon deposited in BIF, while poorly crystalline graphite was precipitated from CO -H fluids partially sourced from the syngenetic carbon, along with fluid-deposited apatite and carbonate. The isotopic signature of the graphitic carbon and the distribution of fluiddeposited graphite in highly metamorphosed BIF is consistent with carbon in the fluids being derived from the thermal cracking of syngenetic biomass deposited in BIF, but, extraneous sources of carbon cannot be ruled out as a source for PCG. The results here show that apatite + graphite is a common mineral assemblage in metamorphosed BIF. The mode of formation of this assemblage is, however, variable, which has important implications for the timing of life's emergence on Earth.

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Section: Co2 + Ch4→ 2c + 2h2osupporting

confidence: 77%

Widespread occurrences of variably crystalline 13C-depleted graphitic carbon in banded iron formations

Dodd

She

Manikyamba

et al. 2019

Earth and Planetary Science Letters

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“…Previous studies on biotite from other Au deposits have also reported variations in Mg-content. A study of the Canadian Malartic deposit documented higher X Mg values in the alteration zone proximal to the deposit, relative to the distal alteration zones [2], which is consistent with our data from Detour Lake. However, the X Mg values of the biotite within the mineralized zone at the Canadian Malartic fall within the phlogopite compositional field (0.72 < X Mg < 0.92 [2]).…”

Section: Chemical Variations In Biotitesupporting

confidence: 90%

“…Previous studies of orogenic Au deposits in the Archean Superior Province, including the Canadian Malartic deposit [1,2] and the Mouska deposit [3], have highlighted the importance of biotite as indicator minerals for Au mineralization and for constraining the paragenesis of mineralization. At the Detour Lake deposit, northeastern Ontario, a late, post-metamorphic biotite-bearing hydrothermal alteration mineral assemblage related to auriferous veins and broader mineralized zones, with disseminated Au, was identified [4].…”

Section: Introductionmentioning

confidence: 99%

Geochemical and Geochronological Discrimination of Biotite Types at the Detour Lake Gold Deposit, Canada

et al. 2019

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The Detour Lake deposit is at a faulted contact between mafic volcanic and siliciclastic to volcaniclastic rocks, differing from other orogenic Au deposits in the dominantly greenschist facies Abitibi region, by possessing amphibolite facies assemblages. Consequently, typical indicator minerals for mineralization, like secondary biotite, may not be useful for locating ore zone, due to the challenge of distinguishing hydrothermal versus metamorphic and magmatic phases. Herein, geochemical and 40Ar/39Ar geochronological data are presented for biotite from mineralized and barren (distal) magmatic rocks to characterize potential geochemical and geochronological variations between biotite types. Petrological observations reveal four biotite types: (1) Biotite hosted in mineralized, sulphidized quartz-calcite veins, (2) halo biotite at the margins of the aforementioned veins; (3) host rock biotite defining the foliation within the mafic volcanic rocks of the deposit; and (4) biotite defining the foliation within the barren meta-plutonic host rocks. Chemical analysis reveals a lower Ti- and higher Mg-content of mineralized biotite types, indicative of secondary hydrothermal processes. 40Ar/39Ar ages for all biotite types (2600–2390 Ma) post-date the main syn-deformation mineralization event at Detour Lake (≤2700 Ma). These results suggest chemical variations within biotite are due to a post-mineralization hydrothermal event, thus biotite should be used cautiously as a vector for gold mineralization in amphibolite facies terranes.

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“…The techniques described in this contribution consider whole-rock analyses. Hydrothermal systems can also be investigated with alternative technics, which rely on the chemistry of individual minerals used as tracers [83], while others focus on the nature of the fluid (using fluid inclusions [84]) or on its temperature (using stable isotopes-see for example [85,86]).…”

Section: Recommendations and Alternative Methodsmentioning

confidence: 99%

Quantifying Hydrothermal Alteration: A Review of Methods

Mathieu

2018

Geosciences

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Hydrothermal alteration is proximal to many base and precious metal deposits, and its products can provide insights into the characteristics of hydrothermal systems. To be useful to exploration geologists and researchers, however, alteration needs to be typified and quantified. Alteration type informs on mineralising style (e.g., have we found a porphyry or a volcanogenic massive sulphide deposit?), while quantification of its intensity helps position a sample within the system (e.g., how close are we to the main economic deposit?). Numerous methods-all having their specific advantages and disadvantages-are dedicated to the characterisation of alteration. As alteration is a process that induces chemical and mineralogical changes in rocks, it can be studied using petrological (e.g., mineral recognition in thin sections, mineral chemistry), mineralogical (e.g., alteration indices that use normative minerals), and chemical (e.g., mass balance calculations) approaches. This short review provides an overview of the methods useful to researchers and that are also applicable in an exploration context.

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Mica composition as a vector to gold mineralization: Deciphering hydrothermal and metamorphic effects in the Malartic district, Quebec

Cited by 50 publications

References 95 publications

Widespread occurrences of variably crystalline 13C-depleted graphitic carbon in banded iron formations

Widespread occurrences of variably crystalline 13C-depleted graphitic carbon in banded iron formations

Geochemical and Geochronological Discrimination of Biotite Types at the Detour Lake Gold Deposit, Canada

Quantifying Hydrothermal Alteration: A Review of Methods

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