T25 Structural and Stratigraphic Architecture of Gold Deposits and Mining Districts

Monday, 26 October 2020
1:30 PM - 5:30 PM
Meeting Rooms

STRUCTURAL TRAPS ASSOCIATED WITH INTERMEDIATE TO FELSIC INTRUSIONS AT THE ODYSSEY PROJECT – EXTENDING THE CANADIAN MALARTIC GOLD SYSTEM, ABITIBI, CANADA

Paper number: T25-4
Program: Technical Sessions
Time: 2:05 PM – 2:20 PM

Authors

Abstract

Felsic-intermediate intrusive rocks are present in most orogenic and intrusion-related gold systems, and act as local structural or/and chemical traps for mineralizing fluids. This study aims at characterizing the gold-mineralized fracture network of the Odyssey project, a complex hydrothermal system mostly hosted by intrusive rocks and located 2 km east of the Canadian Malartic open pit gold mine (~26.2 Moz Au past-production, resources & reserves). Mineralized zones are developed within the Larder Lake-Cadillac fault zone, which is located between the Abitibi greenstone belt and supracrustal rocks of the Pontiac Group, in Quebec. The North and South zones (1.56 Moz indicated & inferred gold resources, Dec. 2018) are developed along the faulted contacts of a subalkaline to alkaline porphyritic quartz monzodiorite intrusion emplaced between the ultramafic rocks of the Piché Group and metasedimentary rocks of the Pontiac Group. These zones dip southward and are composed of quartz±calcite±pyrite±gold veins and disseminated pyrite±gold in the host intrusion. Westward, the North zone can be mapped into the Sladen fault, one of the main metallotects of the Canadian Malartic system. The Internal zones are spatially-associated with subalkaline mafic to felsic dikes crosscutting the main intrusion. These zones consist of quartz±calcite±pyrite±gold veins and hydraulic breccia that are associated with a N-S- to NNW-SSE-trending mineralized fracture cleavage. Most of the veins and breccias indicate a broad N-S trend and a steep dip (>60o), generally toward the west. Ore shoots are steeply-plunging and appear to be developed at the intersection between the N-S veins and dikes, thus suggesting that the dikes played a role in the formation of the shoots. The veins locally contain hydrothermal titanite that is paragenetically-associated with gold and yielded a U-Pb age of ~2661 Ma (ID-TIMS), which is comparable to the 2664 Ma Re-Os molybdenite age for mineralization, as determined in previous studies at the Canadian Malartic deposit. The continuity of the mineralized zones with ore-related structures of the Canadian Malartic deposit, and the new age for hydrothermal titanite at the Odyssey project, likely suggest that the extent of the Canadian Malartic system can be increased to >5 km along-strike.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359926

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