Structural setting, textures, and timing of hydrothermal vein systems in the Val d'Or camp, Abitibi, Canada: implications for the evolution of transcrustal, second- and third-order fault zones and gold mineralization
P. Neumayr et al., Structural setting, textures, and timing of hydrothermal vein systems in the Val d'Or camp, Abitibi, Canada: implications for the evolution of transcrustal, second- and third-order fault zones and gold mineralization, CAN J EARTH, 37(1), 2000, pp. 95-114
In the Val d'Or camp, Archean Abitibi greenstone belt, Canada, numerous gol
d-mineralized second- and third-order fault zones are spatially associated
with the transcrustal Cadillac Tectonic Zone (CTZ). This situation is used
to test whether fluid systems in the CTZ have a similar structural timing t
o those in the gold-hosting structures, and hence the CTZ could represent t
he main fluid conduit in the camp. The transcrustal CTZ at Orenada No. 2 co
ntains structurally complex vein systems, with mineralized quartz-tourmalin
e veins related to both D-2 oblique-reverse faulting and F-3 dextral asymme
tric folding, both of which have been overprinted by unmineralized subhoriz
ontal and subvertical quartz veins. Quartz +/- tourmaline veins within seco
nd- and third-order shear zones at Paramaque and Riviere Heva also formed d
uring D-2 deformation and have been, at least at Riviere Heva, deformed by
F-3 asymmetric folding. In contrast, mineralized quartz vein systems at Car
tier Malartic are controlled by F-3 folding and overprinted by late-stage D
-3 faults which host late quartz-tourmaline veins. Quartz vein textures are
consistent with these timing relations, because D-2-controlled veins conta
in deformed quartz grains, whereas quartz in D-3-controlled veins is unstra
ined. The D-2 and D-3 timing of mineralized quartz veins in the transcrusta
l CTZ and in second- and third-order structures is consistent with the noti
on that the CTZ represents the main fluid conduit and that mineralization o
ccurred in linked second- and third-order structures. The different timing
of quartz-tourmaline veins in different shear zones indicates that the vein
s were probably hydraulically linked to the CTZ during at least two differe
nt episodes. The location of Cartier Malartic structurally below the CTZ in
dicates that fluids travelled either downward from the main conduit or that
the shear zone was part of the CTZ.