STATE OF WASHINGTON DEPARTMENT OF NATURAL RESOURCES BRIAN J. BOYLE, Commissioner of Public Lands ART STEARNS, Department Supervisor DIVISION OF GEOLOGY AND EARTH RESOURCES Raymond Lasmanis, State Geologist ANALYSES OF STREAM SEDIMENT SAMPLES IN WASHINGTON FOR COPPER, MOLYBDENUM, LEAD, ANO ZINC by Wayne S. Moen Washington Department of Natural Resources Division of Geology and Earth Resources Olympia, Washington 98504 Open- Fi 1e Report 69-2 1969 Revised October, 1989 ANALYSES OF STREAM SEDIMENT SAMPLES IN WASHINGTON FOR COPPER. MOLYBDENUM. LEAD. AND ZINC Geochemical prospecting is based on systematic measurement of one or more chemical properties of naturally occurring material. Commonly, trace amounts of metals are measured in rocks, soil, vegetation, water, or stream sediments. Such measurements sometimes reveal geochemical anomalies related to mineralization. The stream sediment geochemical prospecting method is based on the premise that metal deposits undergoing erosion become part of the surface drainage pattern and the liberated metals form dispersion patterns in drainage systems. Such dispersion patterns offer clues to the locations of ore deposits. Systematic sampling of the stream sediments in an upstream direction will often show an increase in the metal content of the sediments as one approaches the source of the metal. In some cases, metals from ore deposits are detectable in stream sediments as much as 30 miles from their source. As a geochemical exploration tool, stream sediment sampling allows large areas to be evaluated for metals in a minimum amount of time and at relatively low cost. Newly discovered areas of anomalous metal content can be followed up by a more detailed exploration program, and areas deficient in metals can be eliminated from irrvnediate exploration. It is not the purpose of this report to discuss geochemical prospecting methods. Numerous publications are available on this subject, and the reader is referred to the list of selected references that appears on page 3 of this report. The accompanying analyses are for stream sediment samples that were collected by Washington Division of Mines and Geology during the surrvner field seasons of 1965, 1966, 1967, and 1968. To date (1969), 1,916 samples have been collected from streams in parts of Whatcom, Skagit, Snohomish, King, Pierce, Lewis, Skamania, Yakima, Kittitas, Chelan, Okanogan, Ferry, Stevens, and Pend Oreille Counties. In addition to 115 samples collected by the Division of Mines and Geology in Pend Oreille County, the list contains 221 samples collected by geologists of the Northern Pacific Railway. The stream sediment sampling program undertaken by Washington Division of Mines and Geology has been confined to readily accessible streams--generally near road crossings. In several areas, major streams were sampled a few miles upstream from road crossings in order to include major tributaries. To date (1969), the main purpose of the sampling program has been to establish background readings for copper, molybdenum, lead, and zinc in stream sediments derived from different rock types. 1 Analyses of 1,916 samples show an average of 37 ppm (parts per million) copper, less than 5 ppm molybdenum, less than 25 ppm lead, and 82 ppm zinc. Stream sediments from areas of volcanic rocks show a background of 34 ppm copper, less than 2 ppm molybdenum, 13 ppm lead, and 72 ppm zinc. Sediments from areas of granitic rocks shov1 a background of 20 ppm copper, less than 5 ppm molybdenum, less than 25 ppm lead, and 55 ppm zinc. The background values for copper, molybdenum, lead, and zinc for different rock types [are] given in Table 1. By county, the frequency distribution of all samples collected to date (1969) is given in Table 2. The frequency distributions show that above average concentrations of copper occur in stream sediments from Whatcom, Skagit, Snohomish, King, Skamania, and Stevens Counties; above average concentrations of lead occur in the streams of Whatcom, Skagit, Snohomish, Skamania, Stevens, and Pend Oreille Counties; several streams in Whatcom, Skagit, Snohomish, King, Skamania, Stevens, and Pend Oreille Counties contain above average concentrations of zinc; anomalous concentrations of molybdenum occur in several streams in Hhatcom, Skagit, Snohomish, and King Counties. Most samples have been analyzed for copper, molybdenum, lead, and zinc. The copper, lead, and zinc contents were determined by atomic absorption, whereas molybdenum was determined color[i]metrically. The metal content of each sample is reported in ppm (parts per million). In addition to total copper, molybdenum, lead, and zinc, the cold extractable "heavy metals" content of each sample is reported. The "heavy metals" content was determined by the standard citrate-dithizone test and is reported in millimeters of 0.001 percent dithizone required to neutralize the solution (blue end point). Sample sites are designated by stream name, as well as a tovmship, range, and section designation based on an eight digit number system. As an example,--342416.56 designates township 34 north, range 24 east, section 16. The number 56 represents a subdivision of section 16 in which the section is subdivided into 100 parts as shown below; 56 indicates 5 squares right and 6 squares~· O> co '? I' ....... (0 .... ID -- ,. Secti on 16 ~ M N..... 0 ~ 0123456789 2 In Washington all townships are north of the Willamette Base Line, and all ranges are east of the Willamette Meridian. The locations of all stream sediment samples collected to date (1969) are plotted on a series of county maps (scale 1/2 inch equals 1 mile) that are on open file at the Division of Mines and Geology's [now Geology and Earth Resources] office in Olympia. SELECTED REFERENCES Andrew-Jones, D. A., 1968, The application of geochemical techniques to mineral exploration: Colorado School of Mines Mineral Industries Bulletin, Vol. 11, No. 6, November 1968. Hawkes, H. E•• 1957, Principles of geochemical prospecting: U.S. Geological Survey Bulletin 1000-F. MukherJee, N. R., and Anthony, L. M., 1957, Geochemical prospecting: University of Alaska School of Mines Bulletin 3. Robertson, F., 1956, Geochemical prospecting by soil analyses in Montana: Montana Bureau of Mines and Geology Bulletin 7. Stinson, M. C., and Putman, G. W., 1963, Geochemical prospecting: California Division of Mines and Geology Mineral Infonnation Service, Vol. 16, No. 5, May 1963. 3 TABLE 1. -Abundance of copper, molybdenum, lead, and zinc in stream sediments in Washington!/ Rock Type Copper Molybdenum Lead Zinc Andesite and basa It Lewis Co. 35Y 1 10 71 Skamania Co. (north ha If) 30 5 63 Skamania Co. (south ha If) 58 Jv 12 115 Ferry Co. 12 2 25 40 Granitic rocks King Co. 48 2 20 70 Whatcom Co. 25 1 18 65 Chelan Co. 8 ~ 25 45 Okanogan Co. 6 ~ 25 21 Pend Oreille Co. 12 £ 33 75 Gneiss 25 15 -5 - 30 Schist 25 30 15 -5 Limestone and marble 10 -2 30 50 Argi I lite and graywacke 45 -2 25 100 Arkose 25 40 10 -5 - Quartzite 8 -2 5 33 Phyllite (western Wash.) 28 2 18 112 Phyllite (eastern Wash.) 10 2 30 60 l/ Average metal content for specific rock type in nonmetallized areas. ~/ All values in parts per million. V ±_ equals less than 2. 4 TABLE 2. - Frequency distribution by county for copper, lead, zinc, and molybdenum in stream sediments* Meta I content Whatcom Skagit Snohomish King Pierce (ppm) 0 - 25 28 30 46 18 9 .... 26 - 50 28 34 41 29 23 ~ 51 - 75 23 11 12 11 4 a. 0 76 - 100 12 4 3 3 1 u 101 - 200 13 0 13 3 0 200+ 3 1 6 2 0 0 - 10 41 20 42 24 12 11 - 20 30 19 47 27 24 -0 25 1 0 0 0 0 0 21 - 30 15 13 16 8 1 ~ 31 - 50 7 18 10 6 0 51 - 100 8 8 2 1 0 100+ 5 2 4 0 0 0 - 50 4 16 32 15 4 51 - 100 45 48 57 33 31 u 101 - 150 25 11 21 12 1 C 151 - 200 13 3 1 N 3 4 201 - 250 9 0 1 3 0 250+ 11 2 6 0 0 49 55 68 24 15 E 2. ::> 2 - 4 50 21 48 36 22 C Q) .2 1 0 0 0 0 -0 _r, 5 0 0 1 3 0 >,. 6 - 10 3 2 2 1 0 -0 :E 10+ 4 2 2 2 0 Total number of samples 107 80 12 l 66 37 * Includes all samples to date (1969), 25 equals less than 25. 5 TABLE 2. - Frequency distribution by county for copper, lead, zinc, and molybdenum in stream sediments*-Continued Meta I content Lewis Skamania Yakima Kittitas Chelan (ppm) 0 - 25 45 113 71 64 145 '- 26 - 50 70 101 11 3 1 a..(I) a.. 51 - 75 9 32 1 0 1 u0 76 - 100 3 6 1 0 2 101 - 200 0 1 1 0 1 20o+ 0 1 2 0 0 0 - 10 97 194 2 0 1 11 - 20 18 32 4 0 1 -c, 25 0 66 141 0 0 65 ~ 21 - 30 11 6 9 0 2 31 - 50 0 16 4 1 2 51 - 100 1 6 1 0 0 lOo+ 0 0 2 0 3 0 - 50 26 67 15 29 109 51 - 100 98 147 52 36 33 u C 101 - 150 3 32 12 2 5 N 151-200 0 7 0 0 0 201 - 250 0 1 3 0 0 250+ 0 0 5 0 3 2 76 197 17 0 4 E :, 2 - 4 51 54 0 0 1 C (I) 5 0 0 64 65 143 -c, ..a 5 0 2 6 2 2 >,. 6 - 10 0 1 0 0 0 0 ::E lo+ 0 0 0 0 0 Tota I number 127 254 87 67 150 of samples * Includes all samples to date (1969), 25 equals less than 25.