·- July 1983 Volume 11 Number 3 Washington Geologic Newsletter · . Lovitt mine, near Wenatchee, Chelan County, Washington, 1977. Photo by Jack Jansons BRIAN J . BOYLE COMMISSIONER OF PUBLIC LANDS ART STEARNS, Supervisor RAYMOND LASMANIS, State Geologist DEPARTMENT OF NATURAL RESOURCES DIVISION OF GEOLOGY AND EARTH RESOURCES Marlin Woy - To Porllond n Exit IOs·• [" GEOLOGY ANO /. t Roctl)11onl•t ... Solllh EARTH ~CES i..-<-....<....<c.L..'-'-! !! 0 I u Sound .. C 'Entrance- Moll Elf!H~~• · 0Poulsot\S. Mortin\ s,. : ••••• ,Porklno .....~ :....... ----. ........... .................... • • • • •• • • • • Coll•o• Z ·········o····· ... 4224 6th Ave. S.E., Lacey, Washington in Albortson• MAILING ADDRESS: Department of Natural Resources Division of Geology and Earth Resources Olympia, WA 98504 (206) 459-6372 Field office address: Department of Natural Resources Division of Geology and Earth Resources Spokane County Agricultural Center N. 222 Havana Spokane, WA 99202 ( 509) 458-2038 Lauta Btay, Editor The Washington Geologic Newsletter, a quarterly report of geologlc articles, Ts published by the Division of Geology and Earth Resources, Department of Natural Resources. The newsletter is free upon request. The division also publishes bulletins, information circulars, and geologic maps. A list of these publicatiOflS will be sent upon request. .. THE WENATCHEE GOLD RUSH by Bonnie Bunning* INTRODUCTION from the D ''reef" between 1949 and 1967. For a long time the ore was shipped directly to the Tacoma smelter On March 4, 19831 when Breakwater Resources LLd. where a substantial credit for the siliceous ores (used as and Asamera Minerals, Inc., made their exciting gold find flux in the smelter) helped make t he mine profitable. In public, companies and individuals from Canada and the 1961, Day Mines, Inc., and Lovitt Mining Co. became United States flocked to the area to lease private and partners in the renamed L-D mine and began construction state lands and to stake thousands of mining claims in of a cyanide mil l on the site. the Wenatchee National Forest. The possibility of While the L-0 mine was producing gold,-exploration ''getting a piece of the trend" led hopefuls to acquire to extend the ore body continued. Between 1950 and lands from Wenatchee Lake to the basalt-covered moun­ 1953, Anaconda Copper Co. explored the B "reef." tains 20 miles southeast uf Wenatchee, virtually blanket· Lovitt and Day Mines continued that work during the ing the Chiwaukum graben and its hypothetical extension. mid-l 960's with financial assistance from the federal Between March 7 and June 22, Chelan County recorded government. Underground and surface work successfully 3,733 claims and the Recorder's office is stil l crowded outlined new ore bodies in the 8 "reef" area, but the with people looking for available land . More than 50 depth and grade made the target sub-economic. From percent of the claims are staked in the Wenatchee area; 1975 to 1978, Cyprus Mines Corp_ explored all the known the remainder is distributed in neighboring mining dis­ "reefs" on the 5-mile-long trend, and successfully dis­ tricts. In April, the Department of Natural Resources covered the B West "reef" zone, which, along with the B logged over 150 mineral prospecting permit applications. "reef" is reported to contain 1.5 million tons of 0.16 At least half were obviously related to the Wenatchee oz/ton gold, proven and probable reserves_ find, while the remaining 50 percent boosted activity In 1981, Goldbelt Mines, Inc. (formerly known as dramatically in the adjacent Peshastin, Swauk, Entiat, 20th Century Energy Corporation and Gambier Explora­ and Leavenworth mining districts. tion Ltd.) joined with Asamera Minerals, Inc., to lease the land package formerly held by Cyprus. In order for THE WENATCHEE GOLD DISTRICT Goldbelt to maintain its equity in the project through the summer of 1982, financing was required. This was History provided by Breakwater Resources Ltd., giving Break­ water eventual control of Goldbelt. By the fall of 1982, In 1885, the Go lden King and MacBoth claims in Breakwater was a full participating partner with Asamera. Squilchuck Canyon were staked on gold-bearing quartz veins and silicified sandstone outcrops known as "reefs" Geology to the early miners. A small amount of gold was re­ covered with a stamp mill in 1894, but recovery of the Poorly consolldated Eocene shale, conglomerate, microfine go ld was poor and the mine didn't produce and arkosic sandstone of fluvial origin are the dominant again until 1910. Minor production is recorded for that rock types in the Wenatchee district (fig. 1). Organic year and again in the late 1930's and mid-l 940's. Lovitt material is abundant in thin horizons within the sequence, Mining Co . optioned the property in 1949, and within a and 1 to 2 percent pyrite is common. Sandstone in the month had begun producing ore from the Lovitt mine. mine area has traditionally been assigned to the Swauk Selective mining methods are credited with Lovitt's Formation, but recent mappers disagree over the name success in producing more than 1 million ounces of gold and age of the rocks. Tabor and others (1982) assign • Geologist with Division of Geology and Earth Resources field office in Spokane. ......_ [;//)]Miocene basalt 8illoligocene Wenatchee Formation, sandstone - Altered Eocene sandstone "reefs" rn~ ~/}Eocene Swauk and(or) Chumstick Formations sandstone, shale, conglomerate -Eocene rhyodacite Eocene hornblende andesite FIGURE 1. - Geologic map of the Wenatchee gold district. Geology from Gresens (1983), Tabor and others (1982), and Patton and Chen~y (1971). them to the Chumstick Formation of middle to late higher silica conteRt and proximity to ore, the rhyodacite Eocene age. In contrast, Gresem (1983) placed the rocks is presumed to be the source of alteration and mineraliza­ in the Swauk(?) Formation of early Eocene age, On his tion. geologic map, the two units are shown to be in fault The Swauk/Chumstick sandstones were continu· contact in the mine area. The controversy is important ously folded during graben development and are uncon­ to gold exploration insofar as the latter interpretation forn,ably overlain by Oligocene sandstone of the Wenat­ allows the possibility that the Chumstlck Formation sand­ chee Formation. One deposit of clean silica sand in the stone was deposited after the Swauk Formation was min­ Wenatchee Formation is presently being mined at the eralized. On figure 1 of this report the Swauk(?Y and(or) head of Ory Gulch. Columbia River basalt of Miocene Churnstick rocks are shown with the same symbol. age covers the southeast extension of the graben, begin· Between 43 and 51 m.y.b.p. (million years before ning less than a mile south of the L-D mine. According to Patton and Cheney (1971), an oil and gas well drilled present) 1 the mine area rocks were intruded at shallow depths by flow-banded rhyodacite porphyry and perlite. in the area in 1934 (see ,rNorco drill hole" on fig. 1) penetrated basalt and encountered perlitic rhyolite During a second period of volcanism about 30 rn.y.b.p.1 the Eocene sandstone was intruded by hornblende ande­ between 715 and 815 feet, strongly suggesting that the site. Both intrusive units lie near siliclfled portlons of graben and favorab le rock types continue to the southeast sandstone along imbricate thrust faults. Because of its below basalt cover. 2 Mi neralized Trend included ln su lfide grains. Naumanite (Ag2Se} and agui larite (Ag2Se·Ag2S) have also been reported. Gangue At least 10 areas of silicified sandstone occur along is principal ly quartz with some calcite. All or part of the a northwest trend. The southernmost occurrence along pyrite (0 to 3 percent) found ln the ore zone may be the trend was found below basalt cover in the Norco test primary pyrite from the original sandstone. Arsenopyrite wel l. Shaly fault gouge from the dri ll cuttings assayed has also been reported. Trace element data are scarce on 0.697 oz/ton silver with no gold, while rhyo lile cuttings these deposits. An unpublished survey by the from several intervals below a depth of 900 feet assayed Washington Division of Mines and Geology (1964) docu­ 0.016 oz/ton to 0.048 oz/ton gold. Compton's Knob is mented an anomalous mercury halo over the Golden King the only known outcrop of silicified sandstone south of ore zone. Squilchuck Canyon, but no gold has been found there in According to an Asamera geologist, barite has been exploratory drilling. Most production to date has been noted In the L-D mine, but neither barite nor adularia from the D ''reef" (Golden King - Lovitt - L-D mine) has been identified to date in the Asamera ore bodies. with only 5,200 tons of 0.33 oz/ton gold mined from the All productive zones have been in sand stone. One B "reef." Years of exploration have developed significant sample of silica-flooded rhyodacite taken by the Washing­ reserves in the B and B West zones. In the past, minor ton Division of Geo logy and Earth Resources in 1983 near gold values were dri lled at E "reef," but underground B ' 4reef'' assayed only 43 ppb (parts per bil lion) go ld. exploration at the A, C, F, and G, "reefs" has found no gold. Ore Grades Alteration Historicall y, the Lovitt mi ne produced ore averaging 0.396 oz/ton gold and 0.6 oz/ton silver. During that time Patton and Cheney (1971) report studies showing a small amount of ore grading 0.33 oz/ton was mined at least three distinct episodes of silicification. First, from the B "reef." The average grade of Cyprus' 1976 pervasive silica flooded poorly consolidated sandstone. discovery (B West zone) is reportedly 0.16 oz/ton gold.