ILSG - Houghton 2013

We are planning a whole bunch of great trips for the 2024 meeting. Although nothing is guaranteed yet, here is a list of what we have so far to whet your apetite

Pre-Meeting trips

1) Rift-filling Mesoproterozoic Strata and Native Copper Deposits of the Keweenaw Peninsula, Michigan

Leader: Ted Bornhorst (Michigan Tech)

Bedrock strata and native copper deposits of the Keweenaw Peninsula are part of the Mesoproterozoic Midcontinent Rift System. The elevated, central, bedrock “spine” of the Keweenaw Peninsula mostly consists of rift-filling, subaerial, basaltic lava flows with minor interflow, clastic, sedimentary rocks that make up the Portage Lake Volcanics (PLV). The PLV of the Keweenaw Peninsula hosts the world’s largest native copper mining district from which approximately 5 billion kg of refined copper was recovered. Rift-filling clastic sedimentary rocks overlie the PLV. The oldest of these is the Copper Harbor Formation that is mostly composed of volcanic-derived conglomerate but includes an informal member termed the Lake Shore Traps, which is composed of basaltic to andesitic lava flows. Younger rift-filling clastic sedimentary strata consist of the Nonesuch and Freda Formations. This one-day field excursion will traverse the Keweenaw Peninsula from South Range to Houghton/Hancock to Copper Harbor and will focus on lithologies of the PLV and Copper Harbor Formation and on the native copper hosted by the PLV.

2) Mining History and Geology of the Quincy Mine, Keweenaw Peninsula Native Copper District, Michigan

Leaders: Tom Wright (Quincy Mine Hoist Association), Jim DeGraff and others (Michigan Technological University)

The historic Quincy Mine was the fourth largest mine in the Keweenaw Peninsula native copper district. From 1851 to 1967, mining and processing of native copper ore produced ca. 488 million kg of refined copper via several shafts sunk along the top of the Pewabic basaltic lava flows. The Quincy Mine is interpreted and made accessible to the public by the Quincy Mine Hoist Association. The field excursion will include tours of: the largest steam-driven mine hoist in the world, the Quincy No. 2 shaft-rockhouse, geology of the 7th level (107 ft below surface), the Quincy smelter on the shore of Portage Lake, and two remote sites to discuss recovery of native copper from mined ore. Dress appropriately for the underground portion of the tour where the temperature averages 7°C (45°F). Walk-in is about 610 m on a wet surface and will access areas not normally visited by the public. Hard hats and lights will be provided.

3) Geoheritage of Buffalo Reef: Industrial Impact on Land, Culture, and Fish Sovereignty

Leaders: Erika Vye (Michigan Technological University)

Buffalo Reef is a geoheritage site with scientific, educational, cultural, and aesthetic value. This field trip explores the relationship between geology, mining waste, and culture of Buffalo Reef - a 2,200-acre natural cobble feature of Lake Superior’s lakebed southeast of the Keweenaw Peninsula and about 20 miles northeast of Houghton. Finely crushed waste rock (stamp sand) from copper ore milling operations at the community of Gay have been moved by currents along the shoreline of the Keweenaw Peninsula to Grand Traverse Bay, thus covering this highly productive spawning ground for lake trout and whitefish. This has negative implications for commercial fisheries, subsistence uses, and the cultural identity of tribal nations that identify as fishing people. This field trip begins at the waste rock pile of the Mohawk #4 mine in Mohawk, one source of rock in the Gay stamp sands. Participants will then travel to the town of Gay to explore the stamps sands and learn how Tribal, State, Federal, and Academic partnerships are collaborating to mitigate environmental damage and ultimately to restore Buffalo Reef to the ecological resource that has sustained both tribal and non-tribal communities for generations. From Gay we will travel to Big Traverse Bay to board Michigan Tech’s Research Vessel Agassiz to visit Buffalo Reef, comparing healthy parts with areas that have been covered by stamp sands. Dress in layers as it can be 20 o F colder on the water and wear good walking shoes. In the event of inclement weather prohibiting travel on water, you will be refunded a portion of the trip fee.

Post-meeting trips

4) Keweenaw Fault Geometry and Kinematics: Clues to Its Nature and Origin

Leaders: Jim DeGraff and others (Michigan Technological University)

From the beginning of native copper mining on the Keweenaw Peninsula in the mid-1800s, geologists have debated the nature of the contact between the Portage Lake Volcanics and Jacobsville Sandstone. Once considered by some to be a conformity between older sandstone and younger volcanics, since the late 1800s this contact has been recognized as the Keweenaw fault where Mesoproterozoic volcanics have been thrust southeastward over younger sandstone. Although the fault is portrayed as a single sinuous fault trace with some transverse offsets on published maps, recent mapping by Michigan Tech students reveals a system of fault segments with geometric motifs repeated along strike. The degree of dip slip and strike slip varies along the fault system and also among the segments. We will visit several classic localities, such as Hungarian and Houghton-Douglass Falls, as well as less-known sites that demonstrate key relationships among the fault segments and fault blocks in the region. Many sites will require walking off trail, so good field boots are highly recommended.

5) The Adventure Mine: Geology and History of a Native Copper Mine, Ontonagon County, Michigan

Leaders: Matt Portfleet (Adventure Mining Company), Ted Bornhorst (Michigan Tech)

The historic Adventure Mine in the Greenland-Mass subdistrict is located about 40 km southwest of the major copper deposits of the Keweenaw Peninsula native copper district. From 1851 to 1917, about 5 million kg of native copper were produced from several amygdaloidal tops of the Portage Lake Volcanics at the Adventure Mine. The character of mineralization at the Adventure Mine is similar to the major deposits of the Keweenaw Peninsula native copper mining district. The field excursion will include a walking tour of the 1st level and will focus on the geology and history of the Butler lode. The tour will provide an opportunity to collect native copper and associated mineral specimens in an underground stope that will be blasted and safety inspected prior to the tour. After the collecting opportunity, another blast will be conducted just before participants leave the mine. After the underground tour, participants will visit the Adventure Mining Company’s facility in Painesdale, about 40 km northeast, where specimens are prepared for sale to tourists and collectors. A short tour of the Champion No. 4 shaft-rockhouse adjacent to the workshop will be conducted. Dress appropriately for the underground tour walk-in, which is about 760 m on a wet surface. Underground temperatures are about 7°C (45°F). Hard hats and lights will be provided.

6) Southern Complex Granitoids, Gneisses and Migmatites: New Data, Discoveries, and Perspectives

Leaders: Chad Deering (Michigan Technological University)

The northern portion of the Southern Complex displays classic ‘dome-and-keel’ structures characterized by elongate domes of Archean basement surrounded by keels of Paleoproterozoic strata of the Marquette Range Supergroup. The Archean rocks include a complex assemblage of granitoids, gneisses, and migmatites intruded by numerous mafic dikes and/or sills. Recent research on rocks of the area has revealed new aspects of the igneous and metamorphic evolution that improve our understanding of the assembly of this large magmatic-metamorphic complex across the Archean-Proterozoic transition. The field excursion will explore a number of different terrains representative of the magmatic, metamorphic, and structural evolution of the Southern Complex; highlighting new discoveries while also providing an opportunity to investigate enigmatic elements of the region. The outcrops we will visit are largely along the roadside, but waterproof boots are recommended. We will eat lunch at a park along the way, so it is recommended that you pack a lunch. High-visibility vests and safety glasses will be provided and extra rock hammers will be available.

7) Landslides in the Glacial Lake Ontonagon Sediments

Leaders: Stan Vitton, Mohammad Sadeghi (Michigan Technological University)

In 2005, a massive landslide occurred on the East Branch of the Ontonagon River near US-45 in an area known as Military Hill. The Military Hill area is adjacent to a gap in the Portage Lake Volcanics Series at the confluence of the Ontonagon River's East, Middle, and West Branches. The Military Hill area has had a long history of slope instability caused mainly by a 20 to 25-m thick varved clay layer formed from Glacial Lake Ontonagon. The clay portion of the varved clay consists of highly plastic clay. We will visit the 2005 landslide, located approximately 500 m upstream from the roadside park on US-45 at the river crossing. While the area has had significant erosion and vegetation growth since 2005, liquefaction features from the underlying alluvial sand and portions of the varved clay escarpment still exist. The second stop will be along the east slope of US-45 in the section of varved clay that has continued to move since the initial excavation of the highway slopes. The final stop will be about 2 km south of the river at a recent excavation to improve the drainage along the east side of US-45. The slope was excavated at 2H:1V at the same angle as the road embankment's slope. While the road embankment was constructed from native clay, it was compacted and has remained stable over time. In contrast, the excavated slope to improve drainage was made in a natural clay slope, which has continued to fail every year since excavation six years ago. The main landslide site will require walking off trail, so good field boots are highly recommended.

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