Geology Field Guide to Quesnel Terrane Rocks at Curlew, WA

Overview

This is a field guide to the geology of metamorphosed, ore-bearing rocks of the Quesnel terrane exposed in the Kettle River Valley north of Curlew, WA. In this post I revisit stops described in UW Emeritus Professor Eric Cheney's 2014 field guide, 'Stratigraphy, Structure, and Mineralization in the Quesnel Terrane north of Republic, Washington'. I add many new photos and a couple maps, clarify the complex geologic setting, and introduce a few additional stops.

Logistics

The town of Republic is the staging point for the trip. Gas, groceries, motels, a diner, and a great small town brewery are there. Seasoned RVers will camp at Curlew Lake State Park. Minimalists at the Ferry County Fairgrounds or nearby forests. The motels are good enough if you can get a room; miners fill most. Tugboat's Cafe in Curlew is a good stop for coffee and a breakfast burrito to go. There's not much in Danville except inquisitive border patrol agents and regret. Most of the stops are along Hwy 21, a curvy two-lane road with narrow shoulders and tidy gravel pullouts. Its not a busy road, but traffic moves fast. Running this trip with two vehicles is easy. With five its a real challenge. This is a trip for smaller groups and folks with sure feet. GPS coordinates are provided in UTM.

Kettle River Country. Accessible geology mixes with natural beauty and small town charm along this northern stretch of Hwy 21 through the Kettle River Valley from Republic to Curlew to Danville.

Geologic Summary

The Quesnel Terrane is a Permian-Triassic island arc that was accreted to the western edge of North America in the Jurassic. Rocks of the terrane are better understood north of the border by Canadians who named and described of its many formations. We're just seeing its southern tip here in Washington. Quesnel rocks exposed in the Curlew-Danville area include silty-sandy-cherty seafloor sediments, limestone, mafic dikes, felsic intrusives, and serpentinite (part of an ophiolite sequence). Everything has been tightly folded, faulted to one degree or another, metamorphosed to greenschist facies, and intruded by younger granites and andesitic dikes. Structurally, we are on the eastern shoulder of the Republic Graben, out of the Sanpoil Volcanic pile, and well above shear zone mylonites of the Kettle Core Complex. The rocks record an older history and a younger one. The older is pre-Jurassic, developed in an ancient island arc and on the adjacent seafloor. The younger began after accretion and includes Cretaceous compression (Sevier orogeny), Eocene extension (metamorphic core complexes), and Sanpoil volcanism.

What's a klippe? Let's begin by introducing ourselves to the structural framework of the Kettle River Valley, specifically the Chesaw Thrust sheet. The Chesaw Thrust is a regional structure that locally shoves Paleozoic rocks (yellow areas = 'Danville klippe') to the east over Mesozoic rocks (blue areas = 'Danville window') as indicated by the white arrows. The thrust is low angle, dipping ~20 degrees to the east, which is kind of weird. Typically, thrust faults dip in the direction opposite tectonic transport, but the Chesaw formed during accretion of the Quesnel terrane and was tilted after it formed. Visualize the yellow thrust sheet in the map above as a gently eastward-tilted panel that crosses the Kettle River Valley (diagram below). The blue area is an eroded window through the thrust sheet that exposes footwall rocks below. The German word for window is 'fenster', but I'm Welsh, so please use 'ffenestr'. The Skiffington Creek Fault (red line with teeth), also a thrust, lies above the Chesaw and parallels it. The Danville klippe is enclosed by a blue line with teeth pointing in both directions, a goofy cartographic convention. Remember: stuff moved east. The thrust faults' twisty map pattern has less to do with structural complexity and more to due with their interaction with topography. We will ignore the 'old footwall rocks' along the eastern edge of the map for now (green area); they're mostly phyllites. Map modified from Cheney (2014, Fig. 2.) by me.

Fresh new map. Linda Caron's and Eric Cheney's detailed mapping in the Curlew-Danville area highlights the Chesaw Thrust. Its fault zone is not only the most important structural feature in the area, but played a central role in mineralization at the Morning Star Mine. This map is a thing of beauty and a major contribution to NE Washington geology. It tips a cap to the Canadians' good work and goes a step further. It does precisely what great geologic maps should do: succinctly synthesize complicated geology so that industry can put the information to use. Their map prettied up by me.

Mining and Mineralization

Gold mining in the Republic Graben has been ongoing for the past 125 years. Early prospectors targeted old, deformed metasedimentary rocks intruded (and juiced) by younger plutons, veins, and dikes. Many small, sub-economic adits were driven into quartz veins along the shoulders of the graben before folks recognized the real money was hidden in the 'they-all-look-the-same' Sanpoil Volcanics. Today, the mines of Ferry County target rocks of the 50 million year old Sanpoil and Klondike Formations, specifically epithermal vein systems, dike contacts, unconformities, and breccias (Parker and Calkins, 1964; Fyles, 1990; Glover, 1994; Cheney and Rasmussen, 1996). The gold is microscopic, so exploration teams rely on near-mine drilling, assay data, predictive models, and a set of proxies to visually determine if gold is present. Field mapping, core logging, soil sampling, geophysical surveys, and 3D models are the tools used by exploration geologist. All mining in the district is done underground; there is no appetite for open pit operations in Washington State. The Morning Star Mine, located 7 miles north of Curlew (see map), was operated by local families for decades and produced gold, silver, copper, and nickel from serpentinite and felsic metavolcanic rocks along the Chesaw Thrust (Cheney et al., 1994; Cheney and Rasmussen, 1996; Cheney, 2014). In recent years, mining companies have shown a renewed interest in other replacement-type ore bodies in pre-Eocene rocks on the shoulders of the graben.

Terms

Quesnel - Pronounced 'Kuh-NELL' or 'QUIN-ell'. Either way, the 's' is silent.

Porphyry - Porphyritic volcanic rocks (i.e., andesites and dacites) formed in the upper crust above magma chambers where hydrothermal fluids circulate through fractured rock and precipitate minerals in stockwork vein networks. Many mines throughout the North American Cordillera target porphyry deposits.

Skarn - Hot fluids interacting with chemically-reactive rocks, often limestone, to precipitate minerals in sizable deposits.

VMS - Volcanogenic massive sulfide deposit. Strata-bound accumulations of sulfide minerals precipitated at the seafloor by volcanism.

Greenstone - Mafic volcanic rocks metamorphosed to greenschist facies. The term encompasses a variety of rocks.

Field Trip Guide

Start the trip by driving north from Republic, WA on Hwy 21 toward the town of Curlew. Just before Curlew, take the left turn onto Kettle River Road and regroup in the parking lot of Tugboat's Cafe. The field guide begins here (UTM: 382325, 5415270). If i've produced a .kml file containing locations for the stops mentioned here, a download link will follow.

Stop 1 - Elise Fm & Lexington with Scatter Creek

UTM: 388793, 5426743

Drive Hwy 21 north from Curlew for about 9 miles to MP........ and park on the right shoulder (east).

The Elise Fm is composed of mafic volcanics (augite-bearing flows and crystal tuffs), coarse volcaniclastics, and some andesite. Volcanic rocks were generated by the Quesnel arc and sediments were shed into the adjacent ocean basin around 200 million years ago. The Elise is part of the Early Jurassic Rossland Group whose type section is exposed near Nelson, BC (Hoy and Dunne, 2001). Far more of the Elise crops out in BC than in WA. We are in the footwall of the Chesaw Thrust. Greenschist facies metamorphism has turned these mafic volcanics green, so the term 'greenstone' fits.

Mineral deposits in economic quantities are widespread in rocks of the Rossland Group. In southern BC the Elise Fm hosts intrusion-related gold, copper, and molybdenum in veins, porphyries, and skarns. Near the charming mountain town of Rossland, a thrust fault places oceanic ultramafic rocks on top of the Elise. The whole package was later intruded by an Eocene batholith. The hunt for volcanic massive sulfide (VMS) deposits starts with volcanics and the Elise checks that box.

Stop 1. Locate this blocky outcrop or one that looks exactly like it. Milepost ........

Elise Fm. A photogenic 'greenstone' boulder conglomerate. Greenschist facies metamorphism replaces augite with green minerals such as chlorite, actinolite, and epidote. Looking past the metamorphic coloration, how does clast composition differ from the matrix? Can you estimate the dip on the formation?

Only the big questions. Clasts or phenos? Stretched or flattened? What's the average speed of an African swallow carrying a coconut?

Black spots. A black dot on a rock is a good thing. A black dot on a card handed to you by a pirate, very bad. I'm sure the cool black dots in unit Je5 of the Elise Fm indicate something important. Perhaps something geologic. However, a band of very small, very angry pirates cannot be ruled out.

Stop 2 - Serpentinite along Lone Ranch Creek Road

UTM: 388858, 5426175

Drive .............. for ......... miles. Exit Hwy 21 east onto Lone Ranch Creek Road at MP 189.2, cross the bridge, and drive 0.4 miles to a low roadcut on the right (east). Park on the shoulder and check it out. A second outcrop, shaped like a big boulder, lies a short distance up the road on the left. We are very near the Gray Eagle Fault, a steep, NW-trending structure that links segments of the shallowly-dipping Chesaw Thrust.

Roadcut on right - Hard, weakly-foliated, magnetic greenstone with deformed and undeformed quartz veins, black serpentinite on fractures, and some sulfides. Prior to accretion and regional metamorphism, the rock was probably basalt.

Boulder on left - Apple green to black serpentinite is soapy-slick and coats fractures in this metasedimentary rock with steeply dipping foliation.

Serpentinite. Rock that used to be oceanic crust - something like peridotite - was deformed and hydrated in a fault zone at around 300-400 degC. The black stuff is the antigorite polymorph of serpentinite. The apple green is lizardite. The tiny white veinlets might be listwanite (carbonized serp). The word listwanite should always be pronounced with a Dracula accent.

Stop 3 - Walk the Ferry County Rail Trail to outcrops

UTM: 388505, 5425910 (parking)

Turn around and backtrack a short distance down Lone Ranch Creek Road to the Ferry County Rail Trail. The path crosses the road just east of the bridge. Look for flat parking spots near the trailhead leading south. Many vehicles can be accommodated. Walk or bike the trail south along the Kettle River to outcrops listed below. Remain on the path. Lands to the right and left are private. The turn around point for the walk is ~1.5 miles from the car.

Cross footbridge and pass a sign that reads 'W' shortly after. A log home can be seen to the east next to a clearing.

Pass a cabin with a green roof on a bench to the east. The cabin sits near the Bradley Adit, the main entrance to the now inactive Morning Star Mine. Its owner is a local cattle rancher who has carefully preserved an archive of the mine's development. Adit entrances still exist and the underground workings were carefully mapped. Gold at Morning Star was mined from a sulfide-rich zone along the Chesaw Thrust which juxtaposed a thick body of black serpentinite over Triassic carbonates and Jurassic metavolcanics.

388455, 5425050 - Arrive at the first outcrops of dark gray-brown-black phyllitic rocks These were originally seafloor muds adjacent to the Quesnel island arc that were accreted and metamorphosed to greenschist facies. To the south, a talus slope with cliffs above on private land.

388436, 5424771 - Dark gray porphyritic andesite in the talus slope is same unit seen in roadcuts along Hwy 21 south of Little Goosmus Road (Stop 5 South). Cliffs above.

388418, 5424624 - Quartz cuts subhorizontally through dark metasedimentary rocks. Conspicuous rinds and coatings of calcium carbonate (CaCO3) on clasts and fractures surfaces appear below seeps.

388353, 5424532 - A band of quartz traces discontinuously across dark metapelitic rocks stained white, green, and red. The vein ends at an open adit. Brecciation is seen along the quartz band. Sheared rocks and many lineated surfaces in various orientations can be found.

388279, 5424452 - Sulfides abundant in a dark diorite. Thin, vertical microfractures are bleached. Cliffs above.

388993, 5424079 - Double-sided cut in dark metapelitic rocks.

388052, 5423943 - Metadiorite intrudes banded metasediments. Diorite contains abundant plagioclase. The phenos have fuzzy edges. Dark metasedimentary rocks with elongate 'vuggy' weathering features resemble the rusty, crenulated rocks of the Attwood Fm or Knob Hill Group that are widely exposed on BLM and State lands just to the east. A large glacial erratic of megacrystic syenite lies at south end of cut.

388095, 5423710 - Bouldery fan deposit and the tiny Skiffington Creek crossing. House above in trees. Turn around point.

Stop 4 - Brooklyn Limestone & Porphyritic Dikes

UTM: 387377, 5423678

Return to Hwy 21 and turn left (south). Park at a small pullout at MP 187.3 with room for 3 cars. Narrow shoulder at a bend in the road. Gather your group up on top of cut as much as possible. Chunks of rock lying in the ditch may be as helpful as what's in the outcrop itself.

A diminutive, beat up outcrop of rough-textured, gray limestone is cut by dikes and veinlets. Limestones in the area are clastic; this one contains chips of chert and other stuff. Cheney's description of the rock is good, "On weathered surfaces some of the sand-sized clasts of quartz or chert weather "up", giving the rock a sandpaper-like feel." A porphyritic dike of syenite some 3m wide has a dark gray groundmass and contains white plagioclase and pink kspar phenocrysts. Miners get excited when carbonate rocks are cut by magmatic dikes or cooked along the margins of plutons; it means a skarn-type ore body may be present. Skarn deposits at Buckhorn, Lamefoot, and elsewhere have supported economic mines.

Weathered Triassic limestone. Resistant bits 'weather up' as the limestone dissolves.

Clastic limestone. What lithologies can you identify in the mix? Also note the white veining. Quartz or calcite? In places the veins crosscut the clasts, in others they are offset by tiny faults. What does this tell you about its deformational history?

Porphyritic dike. Light colored phenocrysts in a dark gray groundmass. Two feldspars mean something about the chemistry of the melt, tectonic setting, age (around here anyway), and the nature of the rocks through which magma ascended. I just can't remember what. You must.

Kettle River Valley, WA.

Stop 5a - Brooklyn Fm 'Sharpstone' Conglomerate

UTM: 385415, 5420889

At MP 185.2, pull off Hwy 21 onto Little Goosmus Road and park at its wide entrance. Here we will look at a sedimentary breccia in the Triassic Brooklyn Fm. The term 'sharpstone' differentiates it from regular conglomerates with rounded clasts. I'd not heard this term before I moved to Baja Canada (Ferry County). Cheney's guide suggests you walk north, but the roadcuts to the south are also good. This is not a great stop for large groups due to the narrow road shoulder.

North Roadcut - Walk 0.2 miles north along highway to find pebble to boulder conglomerates interlayered with argillite. Slightly weathered surfaces show better than fresh ones. Climb around the outcrop a bit to find a few photogenic faces.

South Roadcut - Walk south along the shoulder to roadcuts near two road signs, 'Adopt-a-Highway' and 'MP 185'. A gray clastic unit is exposed north of Adopt-a-Highway sign and continues south to the 'MP 185' sign. Clast sizes remain mostly in the gravel range with a few boulder-sized chunks. We can be certain its sedimentary bedding rather than a metamorphic foliation because the clasts are so well preserved and only a little stretched. Black, fine grained beds may actually be interleaved mafic volcanics, but I doubt it. No phenos.

Two dark gray porphyritic dikes intrude roughly parallel to bedding and fractures (steep W-SW dips). The northern dike is narrow with a chilled margin some 6" wide. The contact is located directly across from the 'MP 185' sign. The southern dike is very thick, even-grained with a slight greenish cast. It exhibits a flow foliation that dips steeply SW. It comprises the entire south end of the cut. Its contact is exposed at road level about halfway between the '40 MPH' sign and 'MP 185' sign. Phenos within about a foot of the contact disappear and the dike becomes aphanitic and gray-green with rusty staining. Microfractures are also abundant here and some local shearing can be seen right along the contact. The clastic unit shows little to no contact halo.

Rip-rap boulders installed along the river bank beyond the guard rail are comprised of handsome megacrystic syenite quarried nearby. Kspar phenos are as big as your thumb. Its strongly foliated and pegmatitic in places with some slickensided faces. Careful - the boulders can be loose underfoot.

Sharpstone Conglomerate. Its a Canadian term for a pile of stony chunks with sharp corners. No one ever accused a Canadian of overthinking it.

Matrix supported. Beds of clasts come and go throughout the unit. Here angular, cobble sized clasts dominate. In other places its pebbles. The unit is mostly matrix supported, which means Keanu Reeves sends in a check each Fall during the Fund Drive.

Just chill baby. Chilled margin of the northern dike is narrow, about 6" wide. The gravelly clastic unit above the contact shows remarkably little evidence of baking.

Flow foliation. Subtle compositional banding is seen in the thicker porphyritic dike at south end of the roadcut. Is the banding parallel or perpendicular to the dike's margins?

Countertop grade rip-rap. A prominent foliation enhances the visual appeal of this megacrystic syenite. Boulders of the stuff armor an outside bend in the Kettle River beyond the guardrail near Little Goosmus Road. Road crews in this neck of the woods are very selective about their rip-rap. Only the finest rocks are used in Ferry County.

Stop 5b - Farther up Little Goosmus Creek Road

UTM: 384415, 5421723

Drive up the dusty but quiet Little Goosmus Creek Road to a set of three outcrops on right (north). Park along the roadside.

Lower Roadcut - Dike of fine grained volcanic rock of intermediate composition (andesitic/dacitic) with biotites altered to green chlorite intrudes metaseds. Some 1/2" plagioclase phenos can be found in the dike. Narrow zones of breccia deform the metaseds. Many steep, N-S trending fractures. Small shear zones that parallel dikes contain serpentinite. Upper and Lower cuts are separated by ~50 yards.

Upper Roadcut - Serpentinite is seen on fracture surfaces, some basalt, 1m-wide porphyritic Scatter Creek dike dips steeply east, veining along contact for a few meters, intensely-veined metaseds, shearing along another SC dike 1.5m thick, fractures trend 160-170 dip NE.

Way, Way Up Roadcut - A thick slice of black serpentinite has many shiny slickenside faces oriented in various directions. Its margins are gradational with bedded argillite and bedding-parallel basalts. Look for a conspicuous zone of densely veined gray rocks (limestone?). Well-developed set of N-S fractures continues.

Stop 6 - Chesaw Thrust

UTM: 386272, 5422628

A very small pullout along Hwy 21 at MP 186.3 will accommodate 1 vehicle and pose a challenge for larger groups. The roadcut of interest is ~400 yards north of the pullout, not 0.2 miles as the Cheney guide indicates.

Two modest knobs of rock reveal an interesting package of foliated metasediments trending toward schist. We are in Jurassic sediments and the footwall of the Chesaw Thrust, but the presence of serpentinite indicates we're not far below it. Recall, the hanging wall consists of a thick body of serpentinite and the fault is not a line but a zone with some thickness. Complex folding is expressed here and there, including some nice boudins and elongate 'vuggy' weathering features. Slickensides are abundant, many dipping gently NE with some in serpentinite. Lots of curved fracture surfaces with green and red rusty staining throughout. Some low angle fracture-like surfaces look depositional. In places, breccia zones are found with angular clasts up to boulder size. Look for light-colored, quartz-rich and calcareous bedding as well as some ribbony black chert. What was the depositional environment? Is there any igneous melt here? Can you tell whether the section is right side up or overturned? The pink knobs to the north and west are porphyritic Scatter Creek intrusives, which I tend to ignore. Don't ask.

Look for the log deck and slash piles. The knobs just to the north are your target. Make sure you tromp around a bit and see rocks on all sides. An easy dozer trail leads up from the weedy roadside, seen in the photo at right.

Stop 7 - Rosetta Stone(?)

UTM:

Drive.................. This stop is not the Rosetta Stone, but it is important. You should pair Stop 7 with my Milepost 188 Stop to complete the picture of thrust-related mineralization.

A salt-and-pepper pophyry of diorite-monzonite (Scatter Creek intrusives) varies in appearance through the exposure. Hints of nearby faulting include microfracture networks, serpentinite on fracture faces, quartz and feldspar boudins, a slighly greener cast, and abundant east-dippping brittle fractures.

Optional: Stop 8 - Lamefoot Mine No Longer

UTM:

Drive................. Just south of the entrance to Curlew State Park exit Hwy 21 onto Wolf Camp Road (MP 168.6). The Lamefoot Mine plant and portal used to stand here. The ground has been reclaimed, though the job was "not great, Bob". Pull off where convenient.

Articles by Cheney (2014, Fig. 4) and Mussig (1962) describe the ore body developed in limestone cut by quartz veins along a contact with felsic volcaniclastic rocks. Cheney notes, "most of the gold came from quartz veinlets crosscutting massive magnetite and pyrrhotite, or interbanded magnetite, jasper, and quartz plus carbonate...[and]...1-20cm wide veinlets of quartz-pyrite-chalcopyrite-pyrrhotite-arsenopyite-gold in the adjacent felsic (sericitic) volcaniclastic rocks to the east."

Stop 9 - Greenstone and Chesaw Thrust

UTM:

...more to come...

Pug Loop Pullout -

UTM: 385320, 5419929

Drive................ Pullout is located ~300 yards south of the 'Pug Loop' signed private road and accommodates 4-5 vehicles.

Limestone and minor phyllite exposed here are in the footwall of the Chesaw Thrust. In fact, all limestones along this stretch of the valley are in the footwall. Here, the bedded, light gray to black limestone dips steeply west. Which way is up? Should we call it 'foliation' or is 'bedding' okay? A breccia exposed near south end of cut contains rounded, blocky, and lath-shaped clasts in pebble to boulder sizes. Deformation is partitioned differently along the roadcut based on subtle changes in lithology. For example, thin phyllitic zones show twisting and shearing, while the blocky limestone resists change. Note the prominent NE dipping fracture set and many slickensided surfaces that assume various orientations. The carbonate is cut by an intrusion of Mesozoic Shasket Creek(?). The intrusive contact trends NW and lies 20' north of powerpole in a dirty ramp beneath forked fir tree. Look along its right side for a green phyllite in contact with Shasket. Examination with a hand lens reveals the intrusive rock is 'juiced' with quartz.

Looks like bedding. Thin muds separate steeply dipping beds of limestone, making them easier to see. Bedding or foliation? Debate.

Worms Roxanne worms. Conglomerate riven with white fractures filled with either quartz or calcite. I didn't check. You should. This stuff may be an ophicalcite, a mix of serpentinite and calcite formed in a fault zone.

Fractal geology. Small scale fracture patterns in outcrops are often mimicked by larger fault systems. Can you tell from the angle of the diagonal fractures which direction the bounding fractures moved? Is the sense of shear sinistral or dextral? What's a good term for these things - transfer structures, step-overs, structural bridges?

Milepost 188 Pullout - Abundant Sulfides in Sheared Limestone w/ Quartz Porphyry(?)

UTM: 385324, 5419929

A small pullout a short distance north of MP 188 accommodates .......... vehicles.

Milepost 188. This is the place. Grab your hand lens.

"What you're smelling is food and that thing is a burger". That's simple, clear messaging from my childhood heroes Bob and Doug McKenzie. To wit, the gray stuff is limestone. Its been deformed and juiced.

Limestone above, sheared mix below. If ophiolitic rocks are going to host gold, they demand a list of about six requirements be met. One of which is abundant carbon. Limestone is made of calcium + carbon + ate (CaCO3). Now go look for sulfides.

Low angle shears cut by steep faults. Elongate clasts of black chert(?) are also smeared out.

Hasty sketch. Abundant sulfides occur in shattered rock mostly above the limestone.

Milepost 188 Pullout - Glacial Deposits

From the same pullout, walk the road shoulder south toward the big bend and the bluff of white sediment. Outcrops of well-cemented foreset cobble gravels emerge before you reach the cliff of white glaciolacustrine stuff. Jump the concrete barrier or guard rail for safer walking.

Foreset bedding. Foresets of cobble gravel that crop out along Hwy 21 at MP 188 are cemented by CaCO3 and presumably of Pleistocene age.

Firmly cemented. Mixed lithology gravel appears to be a steep, high energy alluvial fan deposit, similar to what is seen in the Eocene O'Brien Creek Fm. But that formation was deposited during graben subsidence when topography was changing rapidly. This was deposited by an unusually energetic outwash stream or a down-valley flood, possibly release from a glacial lake somewhere to the north.

Bigger clasts below. Glacially striated rocks underlie the foresets.

Rhythmites anyone? Structureless sand beds alternate with thinner silty-clayey lacustrine intervals along Hwy 21. Together they form a stack of ~20 beds with characteristics closely resembling cyclic lake bottom and flood deposits of Glacial Lake Columbia (Lake Roosevelt). Deposits that build on the story developed here are also exposed near Curlew along Boulder Creek Road and Kettle River Road. It appears a large lake resided here for a time and was inundated by floods that repeatedly dumped large loads of sediment. This photo shows strata at the bottom of the exposed pile. They unconformably overlie the cemented foresets. I know of no reports on these deposits.

Thick sands. Massive white sand beds up to several meters thick are separated from one another by thin beds of laminated lake bottom sediment. The lake bottom intervals are the thin lines running across the outcrop. These thick beds lie atop a package of thinner beds shown in previous photo. Holes are from birds, not a machine gun.

Sketches made while you wait. My take on what's going on at this roadcut after 3-5 minutes of looking.

Big Goosmus Creek Road Serpentinite and Dikes

UTM: 384415, 5421723

Turn west off Hwy 21 just south of MP 186 onto Big Goosmus Creek Road and continue uphill for ......... Pull to the side of the road near outcrops.

Okanogan Highlands. The topography of upland areas is glacially subdued with an aspect-controlled grass-tree mosaic. Valleys contain flights of glacial terraces, some till, and inset fans. Its a stair-stepped landscape formed by tectonics and ice.

Core Complex Mylonites Exposed West of Curlew

UTM:

Park along the shoulder isn't great...

From the four-way intersection at Tugboat's Cafe, drive the Kettle River Road 4.2 miles west past the entrance to Kinross Gold's reactivated K2 mine. At MP....., a large roadcut exposes west-dipping mylonitic rocks in the shear zone of the Kettle Metamorphic Core Complex. The dark layers were probably basalts prior to extension unroofing, but its not entirely clear. The light colored stuff is granitic melt. Look for crosscutting relationships between sheared rocks and melts that would indicate that sliding and intrusion were coeval. These are footwall rocks of the core complex. Everything we've seen so far has been hanging wall. The detachment is cut by steep normal faults of the Republic Graben (and Toroda Creek Graben) and likely lies beneath the graben and its fill (O'Brien Creek Fm, Sanpoil Volcanics, Klondike Fm).

Glacial Rhythmites West of Curlew

UTM:

Drive ..... miles west from Tugboat's on Kettle River Road to a pullout...

Energetic rhythmites. Sediments exposed in this roadcut are comparable with those at MP 188 along Hwy 21. Bouldery gravel beds here correlate with sand beds there (flood deposits). Sand beds here correlate with silt-clay intervals there (lake bottom deposits).

Boulder Creek Road

UTM:

From the four-way intersection at Tugboat's Cafe, take the Boulder Creek Road east for ...... miles. Park in wide pullout at MP.....

Basalt dike. A 3m-thick basalt dike, likely part of the Klondike Fm, cuts a diorite pluton. To the right of the dike, the diorite is strongly sheared. The zone of shattered diorite is about a meter wide. Did the dike overprint a fault or did a fault follow the dike?

Day Creek Road Tour

UTM:

Turn north off Boulder Creek Road onto Day Creek Road at MP..... Wind through the forest for several miles, eventually looping back to Lone Ranch Creek Road, then Hwy 21.

Examine roadside outcrops of monzodiorite, serpentinite, hard black micrograined unit, and metaseds in the uplands east of the Kettle River Valley.

References

Beattie

Berger et al., 1991

Caron, 2002 unpublished geologic map and report

Caron and Glover, 2005 unpublished geologic map

Cheney et al., 1994

Cheney 2010 unpublished report on Morning Star Mine

Cheney, 2014, Northwest Geology, v. 43, p. 177-188 (TRGS Guidebook to the Republic area)

Cheney and Rasmussen, 1996, Regional geology of the Republic Area, Washington Geology, v. 24, p. 3-7

Church, 1972 Handwritten notes

Church, 1992

Fyles, 1990

Glover, 1994

Hoy and Dunne, 2001

Little

Lowe and Larson, 1996

Massey....Lexington porphyry

Mussig

Pearson, 1977

Parker and Calkins, 1964

Rasmussen, 1993 Dissertation on Overlook Mine