Jackson's Arm

The property is largely underlain by the Proterozoic Rattling Brook granite, previously informally named the French-Childs granodiorite by Tuach and French (1986), and the Apsy pluton by Saunders and Saunders & Tuach (1988). The granite is variable foliated coarse grained, K-feldspar porphyritic to unaltered lithology is dark in color and consists of grey quartz, nearly equal proportions of K-feldspar, and plagioclase, with 10 to 15 percent biotite and magnetite in the matrix. As a result of the latter, the granite is strongly magnetic.

The pluton outcrops over 90 km2 and is an inlier of the Grenville structural province that underlies the Great Northern Peninsula. The granite in the north is in fault contact with Lower Devonian Devil’s Room Granite.

The eastern margin of the granite has been strongly affected by deformation related to the Doucer’s Valley Fault System (DVFS), a north-northeast trending, dextral strike-slip structure associated with the Long-Range Fault system. The granite has undergone ductile strain, at least within the grid area, as evidenced by locally well-developed foliation, aligned K-feldspar augen and mylonite zones. These fabric elements are generally coplanar with the dominant regional trend (020˚); however, other prominent structural lineaments (e.g. 060˚) are present.

The DVFS is a prominent north-northeast trending structural lineament that juxtaposes the eastern margin of the Long-Range inlier, with eastward-lying Palaeozoic oceanic and continental, volcanic and sedimentary terranes (Kerr and Knight, 2004). Numerous accessory splays and faults occur along the DVFS, some of which were inferred to have been favorable environments for the passage of Au-enriched fluids and Au deposition (Sparks and MacDougall, 1991). This fault zone has a complex history of reactivation throughout the Paleozoic and therefore marks a major tectonostratigraphic break in the Appalachian Orogen (Tuach, 1987).

Lying immediately east of the Long-Range Inlier, is a thin, linear belt of deformed autohochthonous, Cambro-Ordovician, clastic and carbonate rocks belonging to the Labrador Group, which dip steeply to the east and show tight, isoclinal folding of both S and Z asymmetry. The eastern part of the area is dominated by the Silurian Aged Sops Arm Group. The rocks of the Sops Arm Group are mostly east dipping and east younging, suggesting that the oldest formations lie to the west and become progressively younger to the east. The Sops Arm Group is considered to have been deposited unconformably on the southern White Bay allochthon, but definitive contact relationships are observed only in one location, and typically the contacts are faulted (Kerr, 2006a). The present architecture of the Sops Arm Group is of Silurian to Devonian age, as the fossils preserved in the group indicate it is Silurian. These rocks are known to contain numerous gold occurrences (e.g., the Browning Mine), as well as stratabound lead mineralization occurring in brecciated dolostones (Saunders, 1991).