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TitleGeochemistry, U-Pb geochronology, and genesis of granitoid clasts in transported volcanogenic massive sulfide ore deposits, Buchans, Newfoundland
AuthorWhalen, J B; Zagorevski, AORCID logo; McNicoll, V J; Rogers, N
SourceCanadian Journal of Earth Sciences vol. 50, no. 11, 2013 p. 1116-1133,
Alt SeriesEarth Sciences Sector, Contribution Series 20130171
PublisherCanadian Science Publishing
Mediapaper; on-line; digital
File formatpdf
ProvinceNewfoundland and Labrador
Lat/Long WENS-57.0000 -56.5000 49.0000 48.7500
Subjectsgeochemistry; geochronology; igneous and metamorphic petrology; uranium lead dating; uranium lead dates; radiometric dates; radiometric dating; major element geochemistry; trace element geochemistry; Buchans mining camp; Buchans Group; Buchans River Formation; Paleozoic; Ordovician
Illustrationslocation maps; plots; photomicrographs; Concordia diagrams; tables
ProgramTargeted Geoscience Initiative (TGI-4) Intrusion/Porphyry Ore Systems
Released2013 11 01
AbstractThe Buchans Group, central Newfoundland, represents an Ordovician continental bimodal calc-alkaline arc sequence that hosts numerous volcanogenic massive sulfide (VMS) occurrences, including both in situ and mechanically transported sulfide breccia - conglomerate orebodies. Diverse lithic clasts associated with transported deposits include rounded granitoid clasts. Earlier workers have suggested that Buchans Group VMS-hosting felsic extrusive units, small granodiorite intrusions (e.g., Wiley's Brook), and granitoid cobbles associated with transported ore represent co-genetic products of the same magmatic system. The granitoid cobbles and small granodiorite intrusions are geochemically similar and closely resemble Buchans Group felsic volcanic units. U - Pb zircon age determinations show a (i) 466.7 ± 0.5 Ma crystallization age for the Wiley's Brook granodiorite (WBG), (ii) 464 ± 4 Ma crystallization age for a granitoid cobble, and (iii) 466 ± 4 Ma maximum deposition age for a conglomerate - sandstone sequence associated with transported ore. Thus, Buchans Group felsic plutonic rocks are within experimental error of felsic volcanism and VMS deposition. Furthermore, ENd (T) (T, time of crystallization) values of four granitoid cobbles ( -1.95 to - 4.0) overlap values obtained from Buchans Group felsic volcanic units. Our results are compatible with plutonic and volcanic rocks being related through fractional crystallization or partial melting processes but do not support a petrogenetic link between VMS deposition and exposed felsic plutons. Comparisons to modern arc analogues favour exhumation of plutonic rocks by extension along caldera or rift walls and (or) subaerial erosion. Enigmatic rounding of Buchans granitoid clasts was likely accomplished in a subaerial or shallow marine environment, and the clasts transported into a VMS-active basin by mass flows.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This manuscript concerns the origin of granite cobbles that are contained within sedimentary debris flows that also contain Pb-Zn-Cu sedimentary ore deposits at Buchans in central Newfoundland.

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