Abstract
Gold deposits are not uniformly distributed along major faults due to complex (and long-debated) interactions between seismicity, hydrothermalism, and structural heterogeneities. Here, we use static stress modelling (SSM) to quantitatively investigate these interactions, by exploring the role of Cadillac-Larder Lake Fault (CLLF) Archean seismicity in the genesis of the regional goldfields. Various rheological factors are evaluated for optimizing the models’ ability to reproduce known gold occurrences, regarded as the fossil primary markers of synkinematic hydrothermal systems. We propose that the marked structural heterogeneities of the CLLF induced persistent seismic segmentation and recurrent ruptures of the same fault windows that arrested on robust node points. These ruptures favour repeated occurrences of seismically triggered hydrothermalism along long-existing fluid pathways having an enhanced permeability and iterative ore formation into supracrustal discharge zones by means of episodic drops and build-ups of pressure. Two-dimensional SSM permits the predictive mapping of these high-potential zones. These modelled zones correlate positively with the actual observed gold distribution. We demonstrate that(1)the ruptures along the Joannes Segment arresting on the Davidson Fault and Lapa’s bend can explain the occurrence and location of the Rouyn and Malartic goldfields;(2)the models’ validity is improved by implementing regional geological constraints; and(3)the distant gold occurrences from the CLLF, including the Bourlamaque field, can be explained by doublet seismic events along the Rivière-Héva and Lapause subsidiary faults. Our results provide new perspectives from a fundamental standpoint and for exploration purposes.
Highlights
Mesothermal gold deposits are developed by the discrete circulation of mineralized fluid flows that are controlled by structural frameworks (e.g., [1,2,3,4,5])
This study aims to identify the role of Archean seismicity along the Cadillac-Larder Lake Fault (CLLF) on gold deposition in the Abitibi greenstone belt, Quebec, Canada
Static stress change mapping around the CLLF was done by the testing of seven models (Table 1 and Figure 2)
Summary
Mesothermal gold deposits are developed by the discrete circulation of mineralized fluid flows that are controlled by structural frameworks (e.g., [1,2,3,4,5]). The complex distribution of gold deposits along regionalscale faults has long been a major focus for understanding the controls on mesothermal gold mineralization processes [11,12,13]. The segments are separated from each other by bending step-overs, hard links, or gaps [17] These large fault segments play a critical role in seismic behaviour, displacement, and failure propagation. Segmentation has been a major focus of seismology for understanding seismic hazards around existing active fault zones. This has produced the aftershocks theory; this idea involves the geomechanical modelling of static stress changes around a ruptured segment for predictive mapping of coseismic activity and aftershock triggering zones. The zones are generally referred to as coseismic damage zones
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