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TitleU-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
AuthorHonsberger, I WORCID logo; Bleeker, WORCID logo; Kamo, S L; Sutcliffe, C N; Sandeman, H A I
SourceAtlantic Geology 2022 p. 2015-237,
Alt SeriesNatural Resources Canada, Contribution Series 20220005
PublisherAtlantic Geoscience Society
Mediapaper; digital; on-line
RelatedNRCan photo(s) in this publication
File formatpdf
ProvinceNewfoundland and Labrador
Lat/Long WENS -60.3928 -52.4114 51.8822 46.3836
Subjectseconomic geology; general geology; mineralogy; Nature and Environment; Science and Technology; uranium lead dating; volcanic rocks; sedimentary rocks; orogenies; gold; Silurian; Devonian
Illustrationslocation maps; diagrams; photographs; photomicrographs; graphs
ProgramTargeted Geoscience Initiative (TGI-6) Ore systems
Released2022 06 10
AbstractBimodal igneous suites and associated immature clastic sedimentary rocks are diagnostic of orogenic gold-mineralized, crustal-scale fault zones. In the central Newfoundland Appalachians, the Rogerson Lake Conglomerate belt and Botwood basin are Late Silurian, fault-controlled, magmatic suites and sedimentary rock sequences closely associated with orogenic gold mineralization; however, the spatio-temporal evolution of faulting and associated magmatism and sedimentation are not fully resolved. U-Pb zircon geochronological results were obtained by using an integrated approach employing both LA-ICPMS (laser ablation-inductively coupled plasma mass spectrometry) and CA-ID-TIMS (chemical abrasion-isotope dilution-thermal ionization mass spectrometry) on the same detrital samples. Using this approach, a maximum depositional age for the Rogerson Lake Conglomerate sequence is 421.9 ± 1.0 Ma, which confirms that it is younger than, and stratigraphically overlies, ca. 422-420 Ma igneous rocks exposed along the central Newfoundland gold belt. Towards the stratigraphic middle of the Botwood basin in north-central Newfoundland, a tuffite layer intercalated with graded siltstone produced a maximum depositional age of 427.9 ± 3.1 Ma. The age of emplacement of an autobrecciated, flow-banded rhyolite dome of the Charles Lake volcanic belt along the northwestern Botwood basin is 429.3 ± 0.7 Ma. Detrital zircon age distributions for sedimentary rocks of the Rogerson Lake Conglomerate belt and Botwood basin are interpreted to represent a mixed Laurentian-Gondwanan provenance, whereas high-precision CA-ID-TIMS zircon data establish a clear link between Late Silurian magmatism and sedimentation throughout central Newfoundland. Furthermore, these geochronological results are consistent with a structural model involving the southeastward advancement of a transient, intra-terrane, extensional fault system across strike of the Exploits Subzone between ca. 429 and 418 Ma, with propagation along strike to the southwest (Rogerson Lake Conglomerate belt) at ca. 422 Ma. Extensional faulting may have contributed to Late Silurian basin formation, subsidence, and exhumation of pre-Late Silurian rocks of the Exploits Subzone. Time-transgressive, extension-related magmatism and clastic sedimentation are compatible with Salinic slab rollback and break-off prior to compressional Acadian overprint; therefore, extension appears to mark the transition between the Salinic and Acadian orogenic cycles along the central Newfoundland gold belt. Transient lithospheric extension may have been important for increasing heat and fluid flow in the crust as a prelude to Acadian crustal thickening and Devonian orogenic gold mineralization.
Summary(Plain Language Summary, not published)
This research constrains the timing and evolution of tectonic processes associated with the formation of igneous and sedimentary rocks that contain gold deposits in central Newfoundland. This work contributes to the understanding of how and where gold deposits form.

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