Economic Geology Vol. 83, 1988, pp. 182-196 SCIENTIFIC COMMUNICATIONS GEOLOGY, GEOCHEMISTRY,AND TECTONIC SETTING OF THE KHAYYAM AND STUMBLE-ON MASSIVE SULFIDE DEPOSITS, PRINCE OF WALES ISLAND, ALASKA C. TUCKER BARItIE 'Department of Geology, University of Toronto, Toronto, Ontario, Canada M5S 1A1 AND J. RICHARDKYLE Department of Geological Sciences, University of Texas at Austin, Austin, Texas 78713 Introduction The Khayyamand Stumble-Ondeposits of the Ketchikan miningdistrictare two of at leastseven Cu-Zn-Au-Agvolcanic-hosted massive sulfidede- posits within the late Proterozoic(?) to Late Cam- brian Wales metamorphic suiteon Prince of Wales Island, Alaska. The deposits were mined for copper, gold, and silver from 1901 to 1907, during the most activeperiod in the districtwhich has seenonly intermittent activity since 1920 (Berg and Cobb, 1967). The Khayyam deposit remains the second largest copper producerin the Ketchikan district (Table 1). The earliest geologic investigation of the Ketchi- kan miningdistrictby Brooks (1902) presented a broadgeologic overview based on shoreline obser- vations and mine site descriptions. Wright and Wright (1908) compiled a morethorough descrip- tion of the regionalgeology and mineral produc- tion. A reasonably accurate stratigraphic column for Princeof WalesIsland was completed based on ex- tensivecompilation of mining reports and recon- naissance mapping by Buddington and Chapin (1929). Fosse (1946) reportedon the mine devel- opment, particularly the underground workings of the Khayyam andStumble-On mines, anddescribed the deposits assulfides intrudedalong shear planes in altered diorite. More recent studies include re- gional geologic and mineral depositdescriptions (Condon,1961; Eberlein and Churkin, 1970; Her- reid et al., 1978; Eberlein et al., 1983), a prelimi- nary description of the Klakas orogeny, a Silurian- Ordovician tectonic event that affected southern Prince of Wales Island (Gehrelset al., 1983), and a summary of the geology of southern Prince ofWales Island based on extensive field mapping, U-Pb geochronology and petrochemistry (Gehrelsand Saleeby,1987). The purpose of this study is to definethe nature andoriginof the massive sulfide deposits, including their tectonic setting within the Wales metamor- phic suite. The study is basedon reconnaissance mapping in the Walesmetamorphic suite of central Prince of Wales Island and on detailed mappingat scales of 1:5,000 in the vicinity of the deposits and 1:500 at the mine sites. The mapping concentrated on host-rock lithologies south of the deposits where there is excellent exposure. Underground workings at both mine sites were floodedat the time of map- ping and were not accessible. The petrology and geochemistry of the host rocks,including the un- usual wall-rock lithologies, havebeen studied using standard petrographic, microprobe, X-ray fluores- cence, and neutron activation techniques, and the ore mineralogy has been investigated using re- flectedlight microscopy, X-ray diffractometry, and the scanning electronmicroscope. RegionalSetting within the Craig Subterrane Prince of Wales Island lies entirely within the Craig subterrane, one of three subterranes that comprise the Alexander terrane(Fig. 1). The Craig subterrane is believed to have been accreted to the western edge of North America during the Late Cretaceous (Berg et al., 1978). A paleomagnetic study of Paleozoic rockswithin the Craig subter- rane by Van der Voo and Jones (1980) indicated that these rocks have undergone 15.5ø of north- ward displacement and 25ø of in situclockwise ro- tation since the Late Ordovician. It is unclear from the paleomagnetic data whether the original,pre- displacement position of these rocks was adjacent to North Americaat 40 ø N latitude (within the Paleo- zoiceugeosynclinal sequence of northern California and northwestNevada) or along the samelatitude but farther west with respect to North America. Formations in the Craig subterrane range in age from late Proterozoic(?) to Quaternary. Paleozoic rocks predominate and cover approximately 80 percentof Princeof WalesIsland. Volcanic rocks, mudstones, graywackes,and limestonesare the principal lithologies of the Paleozoic sequence and representa seriesof generallyupward-shoaling cycles within a volcanic-arc environment (Eberlein et al., 1983). 0361-0128/88/779/182-15$2.50 182