Rainbow; Aurora; Indian Prospects, Goodpaster Mining District, Southeast Fairbanks Census Area, Alaska, USAi

Regional Level Types
Rainbow; Aurora; Indian Prospects	Group of Prospects
Goodpaster Mining District	Mining District
Southeast Fairbanks Census Area	Census Area
Alaska	State
USA	Country

Location: This property consists of three blocks of State of Alaska claims-the Indian, Aurora, and Rainbow blocks - which are contiguous or close by; they cover much of sections 8-10, 16-17, 19-20, and 29-30 of T. 5 S., R. 14 E. The coordinates are at about the center of the largest claim block. The outlines of the claim boundaries are shown on figure 1 of Schaefer (2006). The claims are about 3 miles northwest of the Pogo Mine (BD033) and about 3 miles west of the junction of Indian Creek and the Goodpaster River. The location is accurate.
Geology: The Rainbow, Aurora, and Indian claim blocks were first located by three prospectors, beginning in 1999. In 2002, they were leased to the Anglo-Gold Corporation who did only limited work, mainly soil sampling on the ridges, as part of a larger effort in the area. In 2006, the claims were leased to Tonogold Resources Inc. (2008). The rocks in the area consists primarily of pre-Mississippian paragneiss and orthogneiss with lesser schist and quartzite; the metamorphic rocks are intruded by several Cretaceous granitic plutons (Werdon and others, 2004). The Aurora Block is underlain by paragneiss, schist, quartzite and minor orthogneiss that are cut by several Tertiary basaltic dikes. The Indian block is mainly underlain by orthogneiss similar to that at the nearby Pogo mine (BD033) with Cretaceous granodiorite of the Goodpaster Batholith to the north. The Rainbow Block is mainly paragneiss in contact with Cretaceous (96.6-99 Ma) tonalite; hornfels is developed at the contact. The Rainbow block also includes a small Cretaceous(?) granodiorite/quartz monzonite dike that is moderately altered to sericite and carbonate. The gneiss locally is moderately to strongly silicified with the development of sericite+/-carbonate. Airborne geophysical surveys (Burns and others, 2000 and 2005) show a marked magnetic anomaly over the hornfels adjacent to the Cretaceous tonalite at the Rainbow claims; a similar highly magnetic anomaly over the north half of the Aurora block suggests hornfels adjacent to a buried intrusive. Quartz veins with disseminated arsenopyrite have been found in float on the Rainbow claims near the contact between gneiss and the Cretaceous tonalite (Schaefer, 2006). Samples contain up to 2.4 grams of gold per ton with more than 10,000 parts per million (ppm) arsenic and anomalous bismuth. The scattered soil samples from the area are also anomalous in gold and arsenic and locally in bismuth and tellurium.
Workings: The Rainbow, Aurora, and Indian claim blocks were first located by three prospectors, beginning in 1999. In 2002, they were leased by the Anglo-Gold Corporation who did only limited work, mainly soil sampling on the ridges, as part of a larger effort in the area. In 2006, the claims were leased to Tonogold Resources Inc.
Age: Insufficient data; may be related to nearby Cretaceous plutons.
Alteration: At the Rainbow Block, the paragneiss at the contact with Cretaceous (96.6-99 Ma) tonalite is altered to hornfels. The Rainbow block also includes a small Cretaceous(?) granodiorite/quartz monzonite dike that is moderately altered to sericite and carbonate. The gneiss locally is moderately to strongly silicified with the development of sericite +/- carbonate.
Reserves: None.

Commodities (Major) - As, Au; (Minor) - Bi, Te
Development Status: None
Deposit Model: Arsenopyrite-gold-quartz veins.

Other Databases

Link to USGS - Alaska:	BD054

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References