Multistage gold mineralization at the Lapa mine, Abitibi Subprovince: insights into auriferous hydrothermal and metasomatic processes in the Cadillac–Larder Lake Fault Zone

Compositional tomography of a gold‐bearing sample by Laser‐induced breakdown spectroscopy

“…The studied sample presents similarities and difference with the description of Simard et al () from the same geological unit. In that paper, the main end‐member of the amphibole series present in altered ultramafic schists is actinolite, whereas it is tremolite in our sample.…”

“…The studied sample was provided by the Lapa mine from the company Agnico Eagle (Val d’Or Canada). It is an altered ultramafic schist from the Piché Group, which is the main lithologic unit at the Lapa mine (Simard, Gaboury, Daigneault, & Mercier‐Langevin, ), and contains a vein with visible Au (Figure ). The same 2D area of the studied sample, which is also the first slice of the superposed images used to construct the 3D model by LIBS, was analysed for Al, Fe, Mg, Ca, Si, Au and Cu with both the SEM ‐SDD and the LIBS techniques.…”

Native antimony emplaced by methane‐rich hydrothermal fluid in an orogenic fault‐zone

“…Some tiny crystals of rounded ulmannite (NiSbS) are disseminated within the ultramafic talc schists (Figure a); A prograde greenschist–lower amphibolite facies peak metamorphic assemblage characterized by Mg‐hornblende and oligoclase in zones deeper than 1 km. The deposition of gold, in solid solution within finely disseminated arsenopyrite 1, occurs before the peak of metamorphism (Simard et al., ). It is coeval with potassic alteration and pervasive silicification, and is followed by local mobilization of the invisible gold outside arsenopyrite 1 during the crystallization of arsenopyrite 2 associated with peak metamorphism.…”

“…It is coeval with potassic alteration and pervasive silicification, and is followed by local mobilization of the invisible gold outside arsenopyrite 1 during the crystallization of arsenopyrite 2 associated with peak metamorphism. Early fine‐grained disseminated arsenopyrite is rich in Co (up to 4647 ppm), Ni (up to 5562 ppm), Sb (up to 3298 ppm) and Au (1825 ppm) (Simard et al., ). These elements likely occur in solid solution and correlate with each other; ulmannite, berthierite and arsenopyrite are associated and aligned along the foliation (Figure b); A lower greenschist facies retrograde assemblage of actinolite–albite–chlorite; A post‐foliation fissural stage with quartz ± dolomite‐calcite veins, arsenopyrite, gold, antimony minerals, pyrrhotite, pyrite, chalcopyrite and sphalerite (Figure c).…”

“…Antimony is abundant in the upper part of the deposit, above a depth of 1100 m (Simard, Gaboury, Daigneault, & Mercier-Langevin, 2013). The main mineralized zone of the Lapa deposit is hosted in subvertical mafic and ultramafic rocks of Pich e Group (2710 Ma, Pilote, Daigneault, David, & McNicoll, 2014), which are strongly deformed and altered, forming slivers within the CLLFZ (Simard et al, 2013) (Figure 2a). These rocks are in contact with the sedimentary Cadillac Group dated at 2687 Ma (Davis, 2002).…”