GRAPTOLITE-BASED EVIDENCE FOR A REVISED STRATIGRAPHIC AND STRUCTURAL SETTING OF THE SZECHUAN, HUNAN AND XINGCHANG ANTIMONY PROSPECTS, EXPLOITS SUBZONE, CENTRAL NEWFOUNDLAND

Early Ordovician (late Arenig) graptolites are identified from strata near the Northwest Gander River of the Exploits Subzone which were pre viously considered to be of Silurian and/or middle Ordovician age. A s econd locality within a graphitic shale yields a Middle Ordovician (Ca radoc) graptolite assemblage, suggesting that it is equivalent to the Lawrence Harbour Formation. The fossiliferous units are associated wit h antimony prospects and have fundamental implications regarding struc tural interpretation and age of mineralization. The early Ordovician o ccurrence is similar both in terms of age and biogeographic affinity t o that from a fossiliferous greywacke unit which overlies ophiolites a t Coy Pond to the south. This apparently confirms that early Ordovicia n rocks within the Exploits Subzone were formed in high latitudes alon g the southeast margin of Iapetus and suggests the possibility of wide spread turbidite deposition at that time, possibly related to a major tectonic event.