Graptolite-based evidence for a revised stratigraphic and structural setting of the Szechuan, Hunan and Xingchang antimony prospects, Exploits Subzone, central Newfoundland

• Published in: Atlantic Geology
• Main Authors: Williams, S. Henry, Tallman, Peter
• Format: Article in Journal/Newspaper
• Language: English
• Published: Atlantic Geoscience Society 1995
• Subjects: Nig; Newfoundland
• Online Access: https://journals.lib.unb.ca/index.php/ag/article/view/2100

Early Ordovician (late Arenig) graptolites are identified from strata near the Northwest Gander River of the Exploits Subzone which were previously considered to be of Silurian and/or middle Ordovician age. A second locality within a graphitic shale yields a Middle Ordovician (Caradoc) graptolite assemblage, suggesting that it is equivalent to the Lawrence Harbour Formation. The fossiliferous units are associated with antimony prospects and have fundamental implications regarding structural interpretation and age of mineralization. The early Ordovician occurrence is similar both in terms of age and biogeographic affinity to that from a fossiliferous greywacke unit which overlies ophiolites at Coy Pond to the south. This apparently confirms that early Ordovician rocks within the Exploits Subzone were formed in high latitudes along the southeast margin of Iapetus and suggests the possibility of widespread turbidite deposition at that time, possibly related to a major tectonic event. RÉSUMÉ On a repéré des graptolites de l'Ordovicien inférieur (Arénig tardif) dans des couches géologiques proches de la riviére Northwest Gander de la sous-zone d'Exploits, qui étaient auparavant considérées comme un secteur de la période du Silurien ou de l'Ordovicien moyen. Un deuxième emplacement à l'intérieur de schiste graphitique a donné une zone d'assemblage de graptolites de l'Ordovicien moyen (Caradoc), ce qui laisse supposer qu'clle équivaut à la Formation Lawrence Harbour. Les unites fossilifères sont associées à des zones d'intiret d'antimoine et elles ont des répercussions fondamentales en ce qui touche l'interprétation structurale et l'âge de la minéralisation. La venue de l'Ordovicien inférieur est semblable, tant du point de vue de l'âge que de l'afinité ...