Geology, lithogeochemistry, and significance of porphyry intrusions associated with gold mineralization within the Timmins–Porcupine gold camp, Canada

Abstract

The Timmins–Porcupine gold camp, Abitibi greenstone belt, is host >60 Moz of Au with many gold deposits spatially associated with porphyry intrusions and the Porcupine–Destor deformation zone (PDDZ). Porphyry intrusions form three suites. The Timmins porphyry suite (TIS) consists of high-Al tonalite–trondjhemite–granodiorite (TTG) with calc–alkalic affinities and high La/Yb ratios and formed during ∼2690 Ma D1-related crustal thickening and hydrous partial melting of mafic crust where garnet and hornblende were stable in the residue. The Carr Township porphyry intrusive suite (CIS) and the granodiorite intrusive suite (GIS) also have high-Al TTG, calc-alkalic affinities, but were generated 10–15 million years after the TIS; the CIS were generated at shallower depths (during postorogenic extension?) with no garnet in the crustal residue, whereas the GIS formed during D2 thrust-related crustal thickening and partial melting where garnet was stable in the residue. Gold mineralization is preferentially associated with the TIS, and to a lesser extent the GIS, proximal to the PDDZ. Intrusions near mineralization have abundant sericite, carbonate, and sulphide alteration. These intrusions exhibit low Na2O and Sr, and high Al2O3/Na2O, K2O, K2O/Na2O, Rb, and Cs, (i.e., potassic alteration); sulfide- and carbonate-altered porphyries have high (CaO + MgO + Fe2O3)/Al2O3 and LOI values. Although porphyries are not genetically related to gold mineralization, they are spatially related and are interpreted to reflect the emplacement of intrusions and subsequent Au-bearing fluids along the same crustal structures. The intrusive rocks also served as structural traps, where gold mineralization precipitated in dilatant structures along the margins of intrusions during regional (D3?) deformation.

Intrusion-Associated Gold Systems and Multistage Metallogenic Processes in the Neoarchean Abitibi Greenstone Belt

“…The giant McIntyre-Hollinger gold system ( Figure 2) is part of the Pearl Lake Cu-Mo-Au porphyry (Table 1) [41]. Pearl Lake and the porphyries of Bristol Township and Carr Township correspond to the largest intrusions of the Porcupine gold camp [41].…”

“…The giant McIntyre-Hollinger gold system ( Figure 2) is part of the Pearl Lake Cu-Mo-Au porphyry (Table 1) [41]. Pearl Lake and the porphyries of Bristol Township and Carr Township correspond to the largest intrusions of the Porcupine gold camp [41]. These intrusions are related to base metal mineralization associated with K-alteration (biotite) and breccia that are intersected by auriferous veins [41].…”

“…Pearl Lake and the porphyries of Bristol Township and Carr Township correspond to the largest intrusions of the Porcupine gold camp [41]. These intrusions are related to base metal mineralization associated with K-alteration (biotite) and breccia that are intersected by auriferous veins [41]. The McIntyre-Hollinger deposit has been interpreted as a porphyry system modified by subsequent deformation [42].…”

“…The intrusions described here are thus generally polyphase plutons that include C-rich phases (carbonatite and other alkaline magmas) or magmas having unusual chemistry (F-bearing sanukitoids). Most of these magmas may derive from a metasomatized mantle [41,58,59]. These are also oxidized magmas, as indicated by the lack of an Eu anomaly, the elevated Fe 2+ /Fe 3+ ratio, and the presence of magmatic magnetite, e.g., the East Sullivan intrusion [52].…”