The emerging Paleozoic gold district of central Newfoundland: new insights on structural controls and tectonic drivers of gold mineralization and preservation

Abstract

The formation and preservation of orogenic gold deposits are associated with a predictable set of magmatic, structural, and tectonic processes that have recurred throughout Earth's history. In world-class Archean gold districts, such as in the Superior Province of the Canadian Shield and the Yilgarn Craton of the West Australian Shield, the main gold-mineralized fault zones are characterized by early imbrication, lithospheric extension, synorogenic magmatism and sedimentation, thick-skinned re-imbrication, and late-stage strike-slip. Such an evolution results in the occurrence of gold-mineralized, upper crustal sequences of synorogenic magmatic and sedimentary rocks above terranes of granitoid rocks and/or older poly-deformed volcanic rocks. Targeted exploration for orogenic gold mineralization relies on remnant panels of synorogenic rocks (e.g. polymict conglomerate and bimodal magmatic rocks) as first-order field indicators of structurally controlled gold preservation along prospective crustal-scale fault zones. Paleozoic crustal-scale fault zones in central Newfoundland have been known to host significant gold mineralization and recent major discoveries (e.g. Valentine Lake gold deposit) and associated exploration suggest the emergence of a new district centred on the footwall rocks of the Victoria Lake shear zone. Fieldwork, combined with structural analysis and high-precision U-Pb geochronology throughout central Newfoundland, demonstrates that the structurally controlled Paleozoic gold district is remarkably similar to the much older Archean Abitibi gold district in scale, geological setting, structural architecture, synorogenic magmatism and sedimentation, style of mineralization, tectonic evolution, and process rates. In central Newfoundland, orogenic gold occurs within footwall blocks of an overall northwest-directed fault system that juxtaposed and deformed Neoproterozoic basement granitoid rocks and Late Silurian to Early Devonian synorogenic rocks during the Acadian Orogeny. Preliminary high-precision U-Pb zircon and rutile geochronology demonstrates that the key tectonic interval driving gold mineralization and synorogenic sedimentation and magmatism, including syenogranite and monzonite intrusions, occurred between 424 and 407 Ma, approximately the same relative time interval (15-20 million years) as the Abitibi greenstone belt. The similarities between the gold systems of central Newfoundland and the Abitibi imply that a common predictable set of structural and tectonic processes throughout Earth's history, and thus independent of time, have led to the deposition and preservation of orogenic gold mineralization.

Latest Silurian syntectonic sedimentation and magmatism and Early Devonian orogenic gold mineralization, central Newfoundland Appalachians, Canada: Setting, structure, lithogeochemistry, and high-precision U-Pb geochronology

“…et al, 2020); Late Silurian-Early Devonian plutonic rocks of the Mount Peyton Intrusive Suite (Strong, 1979;Blackwood, 1982;Dickson, 1993;Sandeman et al, 2017), and latest Silurian monzonite intrusions in the southern part of the Botwood basin (Fig. 2; Colman-Sadd et al, 1990;Rogers et al, 2005;Honsberger et al, 2020a). A critical unit of the Botwood Group is an ∼28 × 15 km felsic volcanic rock sequence (Stony Lake volcanic rocks) constrained by two independent U-Pb ages at ca.…”

“…5, B-B′), the Rogerson Lake Conglomerate and associated igneous rocks occur within two deformed structural blocks that are juxtaposed along the Wood Brook fault (Fig. 5B; Honsberger et al, 2020a), where the northeastern extension of the Valentine Lake Shear Zone places the Rogerson Lake Conglomerate against Neoproterozoic volcanic rocks. The southeastern boundary of the Rogerson Lake Conglomerate is truncated by a northwest-directed fault splay that uplifts Ordovician rocks of the Red Cross Group, micaceous metasedimentary rocks that are correlative with the Gander Zone, and a latest Silurian monzogranite at Wilding Lake that stitches the Dunnage-Gander Zone boundary (Fig.…”

“…Approximately 30 km northeast of the Valentine Lake deposit, high-grade gold-mineralized, locally tourmaline-bearing quartz veins of the Wilding Lake prospect cut the siderite-, ankerite-, and sericite-altered Rogerson Lake Conglomerate and associated felsic volcanic rocks (Fig. 5; Evans and Vatcher, 2016;Honsberger et al, 2019bHonsberger et al, , 2020a. Detailed mapping and structural analysis of two gold-bearing vein systems that are ∼1 km apart (Elm Zone and Alder Zone) indicate that the gold mineralization is associated with at least four generations of structurally controlled vein sets (Figs.…”

“…One such fault corridor that extends for more than 200 km southwest to northeast across central Newfoundland is remarkably similar to Archean orogenic gold-bearing fault systems with respect to geology, structure, and distinct geologic processes (Figs. 1 and 2; Tuach et al, 1988;Tuach, 1992;Evans, 1996;Dubé and Lauzière, 1997;Wardle, 2005;Lincoln et al, 2018;Honsberger et al, 2019aHonsberger et al, , 2020a. This fault corridor includes the Cape Ray Fault Zone in southwestern Newfoundland (Dubé et al, 1996;van Staal et al, 1996) and the Wood Brook fault and Victoria Lake Shear Zone in central Newfoundland (Figs.…”

U–Pb geochronology of Late Silurian (Wenlock to Pridoli) volcanic and sedimentary rocks, central Newfoundland Appalachians: targeting the timing of transient extension as a prelude to Devonian orogenic gold mineralization

“…The Rogerson Lake Conglomerate is imbricated with ca. 422 Ma felsic volcanic and volcaniclastic rocks, granitoid and gabbro bodies, and is locally cut by lower greenschist facies mafic dykes (Honsberger et al 2019(Honsberger et al , 2020. The Neoproterozoic to Late Silurian rocks in central Newfoundland are cut by orogenic gold-bearing quartz vein systems that define the main mineral resource of the central Newfoundland gold belt (Evans 1996;Honsberger et al 2022).…”