Geologic mapping in the study area identified several new areas of hydrothermal alteration and has shown the known areas of high-sulfidation alteration to be of much greater size than formerly realized (Hughes, 1987). Consequently, we think that the mineral resource potential has been underestimated as well. Much of the strongly altered rock in this area, as well as that in the rest of the Carolina slate belt, has been evaluated only in a reconnaissance manner and deserves a more thorough examination. The abundance of large areas of high-sulfidation type hydrothermal alteration within arc volcanic rocks is an important characteristic shared by the Snow Camp-Saxapahaw area and many regions bearing important gold deposits. The study area has potential for additional pyrophyllite-andalusite deposits and possibly some potential for silver, copper, and molybdenum.
Anomalous amounts of molybdenum were found in soils and in float boulders in an area south of Saxapahaw, but with neither outcrops nor drill-hole data, it is not possible to assign a potential for an economic deposit. Soil sample data provide the largest database, but we lack more information on the probable local behavior of the molybdenum during soil weathering.
Gold Potential of Area
Our reconnaissance evaluation of the gold potential depended largely on results of sampling the sediments of many streams (D'Agostino and Schmidt, 1986), on the analyses of sulfide-bearing rock from shear zones, on the mining history of the area, and on comparisons with districts with similar geology. The two-stage mineralization model proposed for the Snow Camp-Saxapahaw area by Payás and others (1988) is adapted here as a best-fit interpretation of the gold mineralization history. Multiple hydrothermal events such as those we think took place here are generally considered to be positive features in evaluating the mineral potential of an area. Our conclusions regarding the potential for economically extractable gold deposits are summarized in figure 5.
We think that the gold was introduced during the early high-sulfidation alteration, perhaps as wide disseminations in the altered rock, and was later concentrated in veins, fracture zones, and more localized disseminations. Fracture zones and fault breccias near the highly altered siliceous core zones and places associated with major shear zones would have provided favorable sites. We think that the gold-bearing sulfide gossan (sample 6277, fig. 3, sector G; table 10), associated with an unmetamorphosed porphyry stock (Cg), was formed during the intrusion of that stock, probably by remobilization.
Nineteenth-century gold mining and significant prospecting were located largely on major shear zones in the South Fork fault system, with a lesser amount on the sides of major core zones at the eastern end of Major Hill and on the northern slope of the Central Highland (D'Agostino and Schmidt, 1986). The lack of production data makes evaluation more difficult. Gold production in the area, using mining practices profitable for relatively small deposits of high-grade ores, probably ceased near the end of the 19th century. Only very limited private exploration designed to evaluate the area for much larger, albeit lower grade deposits suitable for modern exploitation, has been carried out in the area in recent years.
The best primary gold mineralization was probably in the uppermost parts of the original high-sulfidation alteration systems, the part that was eroded to different degrees before a new episode of volcanism. We regard the remaining uppermost parts of the original systems as good exploration targets.
No former mining activity is known between the Lindley Farms Quartz Monzonite and the Zachary gold mines (fig. 2 and fig. 5, sectors J and K), but two samples were collected there close to a probable fault strand. A sample of sheared sulfide-bearing rock (CA25), from a site northwest of Highway 1340 and near the county boundary (fig. 3, sector J, exact location uncertain), contained 0.9 ppm gold, and sample CA26A (also sector J) contained 0.095 ppm gold. Pyrite-rich zones in the same area were described to us, but we were not able to visit them. The abundance of shearing and brecciation and of quartz-sericite alteration near the Lindley Farms Quartz Monzonite and the pyrophyllite-bearing float and andalusite in stream sediments near the Zachary Farms alteration zone further suggest that this area deserves more evaluation.
Small amounts of gold were detected in stream-sediment samples taken from both the northern and southern slopes of the Central Highland alteration zone (sectors C and G) by the panned-concentrate survey (D'Agostino and Schmidt, 1986) and in panned soil samples from the northern slope. A former mine working or workings, no longer visible on the northern slope, was described to us by local residents.
We collected 11 samples from the extensive quartz granofels breccias of the Snow Camp-Saxapahaw area, but found only a trace of gold in one of them (0.115 ppm, sample CA84, table 8; fig. 3, sector N).
Pyrophyllite and Andalusite Mineral Potential of Area
The study area, as well as many other high-sulfidation alteration areas in the Carolina slate belt, has been a major producer of aluminum silicate minerals for ceramics and refractory purposes in past decades. The association of the pyrophyllite-andalusite bodies with hill-forming silica core zones was recognized early in the industry and used as a prospecting guide (Broadhurst and Councill, 1953; Stuckey, 1967; and Schmidt, 1982); but where the tops of core zones are barely exposed without forming prominent hills, the potential for aluminosilicate deposits may remain untested. This study has greatly increased the known areas of high-sulfidation alteration within which these deposits have been found and has identified several additional places where core-zone minerals are present, such as the alteration zone southwest of the Zachary mines, that has pyrophyllite in float and andalusite grains in panned stream sediments, as well as in core zones west, northwest, and southeast of Sheeprock (fig. 2, sector N), indicated only by exposures or float of quartz granofels.