Abstract

The Kamiskotia-Kidd Creek area comprises well-preserved granitoid-greenstone belt lithologies of the western-most Abitibi Subprovince, similar in composition and structural style to other Late Archean granitoid-greenstone terranes (e.g., Kalgoorlie-Norseman, Western Australia; Belingwe, Zimbabwe; Slave Province, Canada). It contains the Kidd Creek volcanogenic massive sulfide deposit and lesser deposits of the Kamiskotia district, and lode gold deposits associated with the Destor-Porcupine Fault Zone near the prolific Porcupine Gold District. The magmatic and tectonic history for the area is provided through detailed structural mapping and high-precision U-Pb geochronology. Field observations support the following sequence of magmatic and structural events in the Kamiskotia area: (1) formation of older mafic and intermediate volcanic rocks, followed by the emplacement of the Kamiskotia gabbroic complex (KGC) and cogenetic, massive sulfide-bearing bimodal volcanic rocks (KV); also accompanied by coeval intrusion of granitoid A into the crystallizing KGC; (2) regional, bulk rotation about a sub-horizontal axis of this stratigraphy to form a NE-facing monocline; (3) emplacement of three large granitoid intrusions, imparting their respective contact strain aureoles on the stratigraphy; (4) regional sub-horizontal, bulk north-south shortening that formed a non-penetrative east-west flattening fabric; with an element of (5) late dextral transpression, that formed high strain zones related to western Destor-Porcupine Fault Zone (DPFZ) within less competent volcanic units; and (6) emplacement of alkalic dikes associated with the late stages of transpressive deformation. U-Pb ages help substantiate this chronology and aid in the correlation of Kamiskotia lithologies across the southern Abitibi Subprovince. Zircon ages for the KGC and a Kamiskotia rhyolite are 2707 ± 2 Ma and 2705 ± 2 Ma, respectively. These ages are coeval with the Reid rhyolite, with a zircon age of 2706±2 Ma, but are significantly younger than the Kidd Creek rhyolite and the Prosser rhyolite, with zircon ages of 2717±2 Ma (data refined by the addition of an abraded, concordant analysis) and 2716+6/−3 Ma, respectively. Two of the granitoid intrusions have zircon ages of 2696± 1.5 and 2694±4 Ma. The older granitoid intrusion has a titanite population with a 207 Pb/ 206 Pb minimum age of 2692±5 Ma, which may represent a protracted cooling history or a metamorphic event after the setting of the zircon U-Pb system. Two zircon fractions from the younger granitoid intrusion exhibit inheritance, with 207 Pb/ 206 Pb minimum ages up to 2926 Ma, indicating the presence of significantly older crust in this region. Timing of north-south compression and late transpression may be constrained by a U-Pb garnet-titanite age on a late- to post-tectonic alkalic dike, at 2687±3 Ma.

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