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

Abstract

In the Val d'Or camp, Archean Abitibi greenstone belt, Canada, numerous gold-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 to those in the gold-hosting structures, and hence the CTZ could represent the main fluid conduit in the camp. The transcrustal CTZ at Orenada No. 2 contains structurally complex vein systems, with mineralized quartz-tourmaline veins related to both D2 oblique-reverse faulting and F3 dextral asymmetric folding, both of which have been overprinted by unmineralized subhorizontal and subvertical quartz veins. Quartz ± tourmaline veins within second- and third-order shear zones at Paramaque and Rivière Héva also formed during D2 deformation and have been, at least at Rivière Héva, deformed by F3 asymmetric folding. In contrast, mineralized quartz vein systems at Cartier Malartic are controlled by F3 folding and overprinted by late-stage D3 faults which host late quartz-tourmaline veins. Quartz vein textures are consistent with these timing relations, because D2-controlled veins contain deformed quartz grains, whereas quartz in D3-controlled veins is unstrained. The D2 and D3 timing of mineralized quartz veins in the transcrustal CTZ and in second- and third-order structures is consistent with the notion that the CTZ represents the main fluid conduit and that mineralization occurred in linked second- and third-order structures. The different timing of quartz-tourmaline veins in different shear zones indicates that the veins were probably hydraulically linked to the CTZ during at least two different episodes. The location of Cartier Malartic structurally below the CTZ indicates that fluids travelled either downward from the main conduit or that the shear zone was part of the CTZ.

The structural deformation characteristics and the control of gold mineralization of the upper Triassic flysch (Langjiexue Group) in Tibetan Plateau

“…It has been proved that the flow of large amounts of fluid in the region and the concentration of the gold and sulphur in the fluid are the key prerequisites for the formation of economic orogenic gold deposits (Loucks & Mavrogenes, ). The crustal structure is the principle channel for the migration of large scale of ore‐forming fluid, whereas the secondary or the third grade structures are the key place for gold aggregation and precipitation (Neumayr, Hagemann, & Couture, ). The structures experience times of activities and reactive history and are dominated by high‐angle reverse fracture system or thrust nappe shear zone.…”

Minéralisations et déformation à proximité de la faille de Davidson, Abitibi, Canada /

“…Dans ce cas, ces structures secondaires ont pu servir de conduits aux fluides minéralisateurs charriées par les structures majeures auxquelles elles sont connectées (Vearncombe, 1998et Neumayr et al, 2000. Si cette hypothèse venait à être vérifiée, ces structures constitueraient ainsi un critère de ciblage pour l'exploration des gisements orogéniques.…”

“…Néanmoins, dans le cas où ces générations de fluides sont responsables de la venue d'or, il apparaît peu probable que la variation de la composition des gaz majeurs et en traces n'influence pas la solubilité de l'or dans le fluide. En effet, le CO 2 est reconnu comme un élément critique dans l'équilibre des fluides hydrothermaux à potentiel aurifère (Benning et Seward, 1996) (Groves et al, 1998, Kerrich et Kyser, 1994, Neumayr et al, 2000, Pilote et al, 1990. • Le secteur d'étude se caractérise globalement par le passage de la zone à chlorite au Nord vers la zone à biotite au sud.…”

Contrôles structuraux de la minéralisation aurifère de la veine Consuelo, Pataz, La Libertad, Pérou /

“…L'acheminement des fluides de la source profonde jusqu'aux différents sites de dépôt est généralement induit par des structures de 1 er ordre comme des failles crustales majeures (Colvine et al 1988). Les veines sont typiquement encaissées dans des structures fragiles-ductiles de 2 e et 3 e ordre localisées près, et vraisemblablement connectées hydrauliquement (Beaudoin et al 2005;Neumayr et al 2000) à ces mêmes structures lithosphériques.…”