Abstract Today we will be in the Early Proterozoic metavolcanic terrane between Prescott and Jerome, Arizona. This part of Arizona has been one of the major metal producers in the state, not only for base- and precious-metals from Proterozoic deposits, but also for metals from deposits of Laramide and Tertiary age. During the morning we will visit what was considered, until a few years ago, to be an atypical Early Proterozoic massive sulfide deposit at the Iron King mine, near Prescott. There, the regional geologic setting of the Prescott-Jerome are will be discussed, and specific details concerning alteration, mineralization, and metal concentrations of massive sulfide deposits in Arizona will be summarized. Hopefully, the outcome of this summary will be the recognition that, in Arizona, there are different types of massive sulfide deposits: 1) classic base-metal-rich deposits having massive and stringer ore and a well-defined chloritic alteration pipe (United Verde mine in the United Verde district; Bruce mine in the Old Dick district; 2) base-metal-poor deposits that lack stringer ore but that display chloritic alteration zones (Iron King mine in the Big Bug district; and 3) base-metal-poor deposits that lack massive ore and chloritic alteration pipes, but that are characterized by sericitic and aluminosilicate-type alteration (Copper Queen mine in the Agua Fria district; Zonia mine in the Zonia district; Bell Ranch and Huron-Montezuma prospects in the Agua Fria district). End members of the three types are not as common as deposits that share some characteristics of all three. The morning and afternoon

Abstract The Lavender open pit is approximately 80 mi (130 km) southeast of Tucson, Arizona, and can easily be reached by car from either Tombstone or Douglas on paved roads (Fig. 1). The overlook or observation site for the Lavender open pit copper mine is on U.S. 80 between Bisbee and Lowell. The topography and a few of the more famous landmarks—such as the Copper Queen mine, which was the first discovery, the Irish Mag mine, and Sacramento Hill (Ransome, 1904)—are shown on Figure 2. Unlike many of the porphyry copper deposits of the Lavender open pit mineralization is in a fluidized [intrusive] breccia pipe, not porphyry, and is Nevadan (130 Ma), Laramide, in age. The fluidized breccia is composed of exotic ments and boulders that have been transported from below in fine-grained or rock flour matrix of pulverized rock and ported sulfides. The transporting media was a circulating water slurry flowing along preexisting fractures. The ore actually mined in the Lavender pit were not in the porphyry rocks but were transported fragmental sulfides in the matrix mineralized fragments and boulders with later supergene chalcocite enrichment. The mineralization in the porphyrins limited to pyrite with a thin coat of chalcocite, and was very grade.

Abstract 0.0 Humboldt, Arizona. Proceed south on Arizona Highway 69 toward Mayer. For aspects of geology not covered by this road log, refer to the one by O'Hara and Armstrong (1986) and the paper on geology between the Iron King and Copper Queen mines (Anderson, 1986b). 0.1 Deep roadcut in fanglomerate. View at 12:00 is of small hill underlain by metarhyolite tuff and meta-andesite. Dump on the left is at the Lone Pine massive sulfide deposit (Anderson and Blacet, 1972b; Webb, 1979). On the skyline in the distance at 12:00 and 1:00 are Big Bug Mesa and Little Mesa, capped by basalt of the Hickey Formation. 0.4 Reatta Pass Steakhouse on the left. Hills on the left and ridges on the right are capped by fanglomerate of the Hickey Formation that obscures the Early Proterozoic metavolcanic rocks in this area. Straight ahead on the near horizon are dumps of the Victor-Swindler and Huron-Montezuma prospects (fig. 50). 0.7 Roadcut on the right in meta-andesite or chloritized metasedimentary rocks. 0.9 At 9:00 is the ridge underlain by metarhyolite at the Bell Ranch prospect that we will visit this afternoon. Roadcuts ahead in meta-andesite and chloritic metasedimentary rocks. 0.7 Roadcut on the right in meta-andesite or chloritized metasedimentary rocks. 0.9 At 9:00 is the ridge underlain by metarhyolite at the Bell Ranch prospect that we will visit this afternoon. Roadcuts ahead in meta-andesite and chloritic metasedimentary rocks. 1.1 Dumps on the right at 9:00, along the base of Spud Mountain, are on the Silver