Department of the Interior United States Geological Survey
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Department of the Interior To Accompany Map MF-1192-C United States Geological Survey MINERAL RESOURCE POTENTIAL OF THE SALMO-PRIEST WILDERNESS STUDY AREA PEND OREILLE COUNTY, WASHINGTON, AND BOUNDARY COUNTY, IDAHO SUMMARY REPORT By F. K. Miller1 , S. W. Schmauch2 , and E. A. Rodriguez1 STUDIES RELATED TO WILDERNESS Supergroup (Proterozoic Y), Windermere Group (Proterozoic Z and Proterozoic Z?), Gypsy Quartzite (Cambrian), Maitlen Under the provisions of the Wilderness Act (Public Law Phyllite (Cambrian), tonalite and tronhjemite (Mesozoic), 88-577, September 3, 1964) and the Joint Conference Report and glacial and alluvial deposits (Quaternary). on Senate Bill 1, 88th Congress, the U. S. Geological Survey and the U. S. Bureau of Mines have been conducting mineral Argillite, siltite, and quartzite of the Proterozoic Y surveys of wilderness and primitive areas. Areas officially Belt Supergroup crop out in the southeast corner of the designated as "wilderness," "wild," or "canoe" when the act study area. These rocks, here designated undivided Belt was passed were incorporated into the National Wilderness Supergroup, most closely resemble the Wallace Formation of Preservation System, and some of them are presently being the Belt Supergroup. Much of this part of the section, studied. The act provided that areas under consideration however, also resembles the Burke, St. Regis, and parts of for wilderness designation should be studied for suitability the Prichard Formations of the Belt Supergroup. The rocks for incorporation into the Wilderness System. The mineral consist of phylittic or schistose laminated argillite and surveys constitute one aspect of the suitability studied. siltite that locally have iron-oxide stained outcrop The act directs that the results of such surveys are to be surfaces and contain pyrite and pyrrhotite. made available to the public and be submitted to the President and the Congress. This report discusses the Rocks that propably are part of the Wallace Formation results of a mineral survey of the Salmo-Priest Wilderness overlie the undivided Belt unit. The lower part of the study area (RARE E6-981, A1-981), Kaniksu National Forest, Wallace Formation consists of carbonate rocks, dolomite, and Boundary County, Idaho, and Colville National Forest, Pend limy dolomite interbedded with lesser amount of phyllitic Oreille County, Washington. The area is being considered argillite. It forms a sinuous belt that underlies part of for inclusion in the wilderness system. the east edge of the study area. The upper part is made up chiefly of dark-gray argillite with sparse interbeds of SUMMARY carbonate rocks. None of the Belt Supergroup is known to contain significant mineralization in or nearby the study The geologic and geochemioal evaluation has pointed out area, except for the lead-silver deposit at the Continental no evidence to suggest a significant exploration target Mine 2.4 mi (H km) east of the study area. exists in the study area, with the possible exception of the areas of anomalous gold values. The Windermere Group consists of (ascending order) the Shedroof Conglomerate, Leola Volcanics, Monk Formation, and The mineral resource survey indicates that the area has Three Sisters Formation of Walker (1934). The Shedroof low potential for metallic and energy minerals, fossil Conglomerate of Proterozoic Z age crops out in a northeast- fuels, and geothermal resources. Nonmetallic potential, striking northwest-dipping homoclinal section in the eastern notably shale, is abundant, but adequate supplies are part of the study area. The Shedroof unconformably overlies adjacent to the Lehigh cement company plant in Metaline the Wallace Formation of the Belt Supergroup and gradation- Falls, Washington. ally underlies the Leola Volcanics. No mineral deposits or indications of significant mineralization are in or Introduction associated with the Shedroof Conglomerate within the study area. The Shedroof, like the Three Sisters Formation of The Salmo-Priest Wilderness study area is about 62 mi2 Walker (1931), however, is a Precambrian conglomerate and, (160 km2 ) and lies 85 mi (135 km) north of Spokane, Wash., as such, cannot be ruled out as a possible host to low-grade in the rugged mountains east of Metaline Falls, Wash. The large-tonnage gold deposits. area is bounded by the United States-Canadian border on the north (fig. 1). The Leola Volcanics of Proterozoic Z age is made up almost entirely of greenstone derived from basalt flows and To appraise the mineral resource potential of the tuffaceous and volcaniolastic rocks. The formation appears Salmo-Priest study area, geologic mapping and geochemical to grade downward into the Shedroof Conglomerate. No stream-sediment sampling of the area were done by the U. S. mineral deposits or indications of significant mineraliza Geological Survey in 1978 (Miller, 1982). The U. S. Bureau tion in or associated with the Leola Volcanics have been of Mines searched for all known mining claims within the found within study area. study area and took rock samples for prospects or mine workings in 1976 and 1978. These studies were supplemented The Monk Formation of Proterozoic Z age is a hetero by aeromagnetic, airborne gamma-ray spectrometry, and geneous unit that consists chiefly of argillite, but con reconnaissance gravity surveys by the U. S. Geological tains substantial amounts of dolomite, conglomerate, and Survey (Pitkin and Duval, 1980). quartzite. The Monk rests in apparent unconformity on the Leola Volcanics and appears to grade upward conformably into the Three Sisters Formation of Walker (1934). Other than a small talc prospect in metamorphosed dolomite about 0.6 mi Rocks in the study area range in age from Proterozoic (1 km) outside the proposed wilderness area, no mineral to Cenozoic. They include (ascending order) the Belt deposits have been identified in the Monk Formation. U. S. Geological Survey. U. S. Bureau of Mines. O I CO C"I 3 O a: o (i) 3 3"03 O 3 ^ OQ W O. H- oa oa0> o CT c 3 s: O. H- P h-1 T O. ^ CD O 3 O (D C 03 3 03 -t^ COn- c M O. 31 O Jr UJ l\) -« CD Vf T n H 0 mow tr 0 X ^ H* > "< O o g 0) c-TJ T O TD f 04 P) I » (D i-1 ta (0 *o (D 3 < Q. *^0 tsc>I> P> P> ^ a 1-5(0 3 0. (D ^ (D CD ^ o 0 CO g' ZO P- CO 3 0 C o Z (D t-3 (D o M O. g M p> o C P- (B O 3 o CO o PC O Z 0. -* 3- cr rf P> 0 o cr -* q g 0 M cf 0> CO O (D 3 o 0. (D Z O P. O l\) rt- 3 CO Cfl The Three Sisters Formation of Walker (1934) is The rocks below the Shedroof Conglomerate in the probably Proterozoic Z in age. In the study area, it is eastern part of the study area may be cut by one or more made up of conglomerate, conglomeratic quartzite (grit), faults of large displacement. The Newport fault zone quartzite and argillite. Although no known mineralization (Miller, 1974; Miller and Engles, 1975) may project into the is in or associated with this formation in the study area, Upper Priest River valley from Upper Priest Lake, although the unit is a Precambrian conglomerate, a rock type that is no evidence of the fault has been found north of the upper host to low-grade large-tonnage gold deposits in other parts lake. of the world. The more massive, competent units, such as the Gypsy The Gypsy Quartzite of Early Cambrian age unconformably Quartzite and the Three Sisters Formation of Walker (1934), overlies the Hindermere Group and gradationally underlies show very little internal deformation such as minor folds, the Maitlen Phyllite. The Gypsy forms a relatively unde- cleavage or shearing. This is in sharp contrast to the formed belt through the western part of the study area. The other formations, especially the Maitlen Phyllite, which rock is predominantly medium- to fine-grained quartzite nearly everywhere shows internal deformation. Argillite in containing lesser amounts of conglomeratic quartzite and the Monk Formation is so highly cleaved that it crops out phyllitic argillite. No known mineral deposits or minerali rarely, and almost all tuffaceous rock or fine-grained flow zation are associated with the Gypsy Quartzite in the study rock in the Leola Volcanics is highly phyllitic and area. sheared. The Shedroof Conglomerate has irregular slip planes pervasively developed throughout the rock, along The Maitlen Phyllite of Early Cambrian age consists of which stretched clasts have been reoriented at moderate interbedded phyllite, quartzite, argillitic carbonate rocks, angles to bedding planes. and carbonate rocks. No known mineral deposits or minerali zation occurs in the lower part of the Maitlen Phyllite Results of Geochemical Sampling within the study area, although barren quartz veins and veinlets are common throughout the formation. West of the The collection and analysis of geochemical stream- study area, near Metaline Falls, are numerous mines and sediment and heavy-mineral-concentrate samples permit the prospect pits in the uppermost carbonate-bearing part of the area of a stream drainage above a given sample locality to Maitlen Phyllite and in the lower part of the overlying be tested for mineralization. Sample localities were chosen Metaline Limestone. These deposits appear to be associated along streams and tributaries at selected intervals to with the carbonate-rich part of the Maitlen, which does not maximize areal coverage (see map). All samples are occur within the study area. composites of several samples collected from several sites along a small area of a stream; composite samples were taken The tonalite of the Continental Mountain pluton of to reduce the variance in sample results due to stream Mesozoic age forms two lobes Joined along the west margins; sorting or channel configuration.