Lost Zarembo Occurrence, Petersburg Mining District, Wrangell City and Bourough, Alaska, USAi

Regional Level Types
Lost Zarembo Occurrence	Occurrence
Petersburg Mining District	Mining District
Wrangell City and Bourough	Borough
Alaska	State
USA	Country

Location: This occurrence is well exposed on the north wall of a rock quarry adjacent to a logging road; the quarry is shown by symbol of the 1:63,360-scale topographic map in the NE1/4, section 27, T. 63 S., R. 80 E. It is at an elevation of about 600 feet about 4.0 mile southeast of the Zarembo Spring at the head of St. Johns Harbor.
Geology: Grybeck, Berg, and Karl (1984) describe this deposit as three, massive sulfide layers in orange-weathering, greenish-gray metarhyolite along the west wall of a quarry. The most prominent exposure of the sulfides is a 4-foot-thick layer that crops out for about 50 feet and is truncated at both ends by faults. Selected portions of the massive sulfide layers contain up to 30 percent sulfides, mainly sphalerite, accompanied by minor pyrite, chalcopyrite, and galena; the matrix is fine-grained silica and barite. Analyses of selected grab samples show up to 0.55 parts per million (ppm) gold, about 8 percent zinc, 0.25 percent lead, 0.39 percent copper, 30 ppm or less silver, and up to 5,000 ppm barium. The occurrence forms a wedge-shaped, fault-bounded outcrop about 30 by 100 feet in size that abuts steeply-dipping Tertiary basalt, diabase, and rhyolite dikes. The outcrop of the massive sulfide deposit is small and the quarry walls are dominated by the steeply dipping Tertiary dikes. The association of massive sulfides interbedded with metarhyolite indicates that this occurrence is part of the Duncan Canal-Zarembo belt of dismembered, Upper Triassic volcanogenic massive sulfide deposits described by Berg and Grybeck (1980) and Berg (1981). Karl and others (1999) map the rocks in this area as part of the Triassic Hyd Group which is the host for most of the other massive sulfide deposit along this mineralized belt. The occurrence was examined and sampled by Still and others (2002). Their samples across the sulfide layers contained 8.3 to 27.6 parts per million (ppm) silver, 966 to 3,781 ppm copper, 818 to 3,567 ppm lead, 1.9 to 4.6 percent zinc, and 1.53 to 10.10 percent barium.
Workings: Originally found by the USGS in the late 70's. Examined and sampled by Still and others (2002).
Age: As now known, this deposit marks the southern end of the Upper Triassic Duncan-Zarembo volcanogenic mineral belt defined by Berg and Grybeck (1980) and Berg (1981).
Alteration: Outcrop is iron-stained, probably from weathering of sulfides.

Commodities (Major) - Ag, Au, Ba, Cu, Pb, Zn
Development Status: No
Deposit Model: Kuroko volcanogenic massive-sulfide deposit (Cox and Singer, 1986; model 28a);

Other Databases

Link to USGS - Alaska:	PE062

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References