Seafloor Volcanic and Hydrothermal Controls on Early Life Preserved in an Archean Greenstone Belt (Canada)
Figure 1. General geology of the Abitbi Greenstone Belt. Unit designations from Scott et al., 2002. Our fieldwork will be concentrated in the southwestern area of the map in the southern volcanic zone of the Abitibi Subprovince, on the mafic rocks (marked Volcanic cycle 3) in and around Rouyn-Noranda, Quebec and near Kirkland Lake, Ontario. (Figure modified from Scott et al., 2002.)
What: The Abitibi Greenstone Belt (AGB), and specifically the Blake River Group, affords us the relatively rare opportunity to study seafloor volcanic and hydrothermal processes in an area that is both accessible and has a significant thickness of exposed extrusive pile. We plan to study mafic volcanic rocks of the AGB that were erupted as part of an ancient Archean seafloor sequence. Our proposed detailed mapping, physical properties, geochemical, and petrographic studies will contribute to the geologic understanding of seafloor volcanic and hydrothermal processes within the context of modern ocean crustal processes and provide us with a better understanding of how hydrothermal fluid flow patterns may have operated early in Earth’s history.
When and Where: July 17-August 14, 2008. Students will arrive the Williams-Mystic campus in Mystic, CT by July 17, 2008. A few days will be spent in and around Mystic on field and laboratory methods and selecting projects. Students will live cooperatively in Williams-Mystic historic houses while in Mystic, and will have full access to the new Marine Science Center and Mystic Seaport. We will fly as a group to Rouyn, Quebec, and rent vehicles to drive to the nearby University of Quebec in Abitibi-Témiscamingue (UQAT), where we will stay in campus apartments. We will begin the field portion of the project with a two-day field trip to selected sites in the Blake River Group and several days of group reconnaissance, followed by fieldwork on projects. We will depart Rouyn, Quebec, and then spend another few days together in Mystic preparing samples, doing initial laboratory work or sending samples out to other analytic laboratories, and analyzing data. Departure from Mystic will be on/by August 14, 2008.
Who: Six students. Professor Lisa Gilbert (Williams) and Professor Neil Banerjee (U. of Western Ontario)
Project Description and Goals
Greenstone belts are useful for understanding ancient seafloor processes that we cannot access directly. When we study the ocean crust it is generally either just on the very surface of the seafloor, in a one-dimensional hole drilled into the crust, or by some remote method that prohibits detailed mapping. At the AGB, we will map and sample in several dimensions for studies of physical properties (including density, velocity, and porosity) and geochemistry to help constrain original setting, understand fluid flow and porosity of extrusive rocks, and explore the variety of compositions and relationships between volcanic facies preserved. We will put our results into context, using comparisons from other greenstone belts, ophiolites, and modern seafloor rocks.
We plan to use these results to better understand the importance of fluid flow to the distribution of microbial trace fossils that have been recently discovered in samples from the AGB. The microfossils occur in hyaloclastite samples and consist of micron-sized tubular structures mineralized by titanite. These structures are identical to microfossils described from 3.5 Ga greenstone belts from South Africa and Australia (e.g., Furnes et al., 2004; Banerjee et al., 2006; Banerjee et al., 2007). Based on their similarity to textures observed in recent glassy pillow basalts, these structures are interpreted to represent compelling evidence of ancient mineralized traces of microbial activity. Initial results from AGB samples lend evidence for microbial activity, but in order to further substantiate this interpretation we need to do more detailed sample collecting and mapping to place the samples in a volcanological and hydrothermal context, first at the outcrop scale and later in a more regional context. In addition to sample collection we will map out the distribution of originally glassy lithologies and make special note of primary alteration zones that may have acted as fluid flow zones within a hydrothermal context.
Listed below are potential student projects within our overall goal of assessing controls on the geologic and hydrothermal features of the Abitibi Greenstone Belt and the early microbial biosphere that thrived in the presence of hot circulating fluids in the Archean.
- Mapping and image analysis of the inter-pillow zones to estimate the original connected porosity and permeability of upper ocean crust, key controls on fluid flow, and thus on life in a Precambrian subseafloor (Figure 2).
- Characterization of the lava drain-back features and vesicles formed during emplacement.
- Paleoslope and depth of emplacement of the pillow lavas from 2-D and 3-D field measurements of pillow morphology and laboratory estimates of porosity.
- A comparative study of the microfossils preserved in different volcanic facies (i.e., pillow lavas, hyaloclastites, and volcanoclastic breccias; Figure 2). Field mapping of altered glass in these facies will be complimented by fine-scale sampling for possible microprobe work on thin sections.
- Detailed mapping of the glassy fragments in a continuous 1 km hyaloclastite layer and a geochemical comparison (carbon isotopes, trace elements, and oxygen isotopes) of hyaloclastite samples hosting microfossils.
- Spatial characterization of hydrothermal mineral assemblages around an Archean hydrothermal vent.
Students will live cooperatively and will be expected to participate in cooking and general community duties both at UQAT and at Williams-Mystic. No special gear is required: full kitchens and laundry are available at both sites, and students need only supply their own linens, clothes, and personal items.
Your general approach to scientific questions, work ethic, and interest in this project are more important than any specific courses taken. More important than any particular coursework, we are seeking students with a demonstrated ability to think creatively. Prior experience with field mapping (and/or field camp) would be helpful, but not required. Some coursework in one or more of the following fields might also be useful, but not necessary: mineralogy, oceanography, geophysics, structural geology, geochemistry, molecular biology, statistics, or computer science. Students without a valid passport should apply for one as soon as possible, preferably before May 1.
Interdisciplinary Studies in the Critical Zone, Boulder Creek Catchment, Front Range, Colorado
What: This project will join a large interdisciplinary study (Boulder Creek Critical Zone Observatory: Weathered profile development in a rocky environment and its influence on watershed hydrology and biogeochemistry—NSF 0724960) directed by Suzanne Anderson, University of Colorado and Institute for Arctic and Alpine Studies (INSTAAR). The “observatory” will consist of 3 small, instrumented sites in the Boulder Creek basin: (1) a steep alpine area in the Boulder watershed; (2) a forested, mid-elevation catchment developed in deeply weathered materials, and (3) a steep, lower-elevation basin where surficial deposits are of variable thickness.
When: July 16 – August 14, 2008
Who: 3 students and Professor David P. Dethier, Department of Geosciences, Williams College
Project Description and Goals
Fig. 1. Shaded relief and slope map of mountainous portion of Boulder Creek. Steepest slopes shaded red; shallowest slopes are blue. Study catchments include: A- Green Lakes Valley; B- Gordon Gulch and C- Betasso cutoff. Pleistocene glacial limits (white), and two existing USGS gauges are watershed shown. Boulder Falls is a knickpoint on N. Boulder Creek; similar knickzones are seen as steep-walled canyons.
The middle Boulder Creek catchment (Fig. 1) extends from the glaciated alpine zone of the Indian Peaks Wilderness Area east to the semi-arid western edge of the Great Plains. Deep, U-shaped valleys in the glaciated areas become shallower eastward through a zone of low relief and relatively low slopes, deepen into steep bedrock canyons as they pass knickzones, and flatten to lower channel slopes near the piedmont margin. Small glaciers and late-persisting snowfields dot the alpine zone, which exposes bedrock and relatively thin deposits related to the latest Pleistocene Pinedale glaciation. The thinly-forested zone of low relief exposes thick (characteristically 3 to 8 m) zones of grus, saprolite and oxidized bedrock. In the vicinity of the knickzone and downstream, slopes near channels are steep with shallow, fresh bedrock whereas more distant areas retain a deeply weathered mantle.
Project goals include: (1) education about the critical zone and methods used to characterize its development; (2) hands-on experience with field geophysical techniques and with field and laboratory methods for characterizing weathering and soils; (3) interaction with disciplinary investigators and their graduate students; and (4) contributing undergraduate topical studies to the overall critical zone project. Dethier has worked with his undergraduate students in the Boulder watershed and nearby areas on a variety of geomorphic studies for the past 9 years and with Matthias Leopold for the past 3 years.
Figure 2. View north from Niwot Ridge near the Mountain Research Station.
Niwot Ridge (Fig. 2), adjacent to the Mountain Research Station, is a long-term ecological research (LTER) site and the location for ecology and evolutionary biology research and for extensive studies about periglacial processes and landforms, snowmelt processes, and biogeochemical cycling. Keck project participants will be housed close to and will eat and recreate with students and graduate students doing research on Niwot Ridge and nearby areas. In past years these interactions have led to students helping each other on project “push” days and to some extraordinary cross-disciplinary education.
Students and project faculty will make measurements and collect solid or liquid samples at field sites. We will work on laboratory preparation and initial sample analysis at MSR or at the extensive analytical facilities at INSTAAR in Boulder. I expect that participants will return to their home schools with field data, initial results of some laboratory measurements and samples ready for additional analysis. Data from geophysical (after post-processing) and geochemical analyses (as necessary) will probably return sometime in the fall semester. Analysis and interpretation of field and laboratory results at the home institution will be supervised by the student’s advisor and aided by the Project Director. Some potential student projects include:
- Characterizing the chemistry of shallow groundwater and meltwater near late-lying snowfields in the alpine zone and/or from baseflow in deeply weathered areas.
- Measurement of fracture spacing, width and orientation in surface and adjacent subsurface (mine portal or drill hole) exposures. Fracture density has a strong influence on long-term rates of weathering and erosion.
- Mapping the depth to bedrock and the structure of the shallow subsurface using seismic refraction and ground-penetrating radar techniques.
- Measuring variations in soil morphology and chemistry along a slope transect from ridge crest to channel.
- Constructing a detailed map of surficial deposits in one of the study catchments using field measurements and LIDAR imagery.
- Assessing the contribution of eolian material to soils in the Green Lakes (alpine) catchment.
- Measuring the degree of alteration of trace minerals (allanite, sphene, Ti-magnetite, zircon) on transects from fresh rock to soil.
Field Conditions and logistics
Students will fly into Denver, Colorado on 16 July and drive up to the University of Colorado’s Mountain Research Station (http://www.colorado.edu/mrs/), where project participants will live and eat at 9500 feet at the edge of the alpine part of the Boulder Creek catchment. Housing consists of rustic cabins and meals and lunch ingredients are served in a central lodge. The Station has laboratory, lecture, library and limited computer facilities, a local wireless network and provides regular weekday transportation to and from the CU campus.
We will spend part of the first week learning about local geology and research from investigators on the NSF grant, using a lecture and field trip format, and visiting each of the field locations and nearby Rocky Mountain National Park. Students and project faculty will all work with helping to pick locations for and to set up and run geophysical lines. Students will use this regional and site-specific background and consultation with project faculty to decide on their individual research topics (see examples below); projects will depend, in part, on the logistics of the individual sites. If a drill rig is working at one of the sites, for instance, logging and analysis of the cuttings and core might provide an ideal target for individual research. It is expected that students will work as a group on setting up some measurements and individually or as pairs at other times at local sites. Communication on-site will be by GPS/radio receivers. Project participants will return home from Denver on 14 August.
Important for the first year of this interdisciplinary project is a strong interest in surface and near-surface processes and in interdisciplinary science, a record of hard work and the ability to follow through. We would prefer gregarious, “can-do” students with a background in geology or physical geography and coursework in:
- Mineralogy and/or geochemistry
- Geomorphology or Quaternary geology or hydrology
- Sedimentology and/or soils (valuable)
- Structural geology, geophysics or field mapping (valuable)
- GIS or a strong background in supporting science (useful)
Quaternary Tectonic and Geomorphic Evolution of the Deluun Nuruu, Mongolian Altai, Western Mongolia
Figure 3. Oblique aerial view to NE across the Deluun Nuruu. The Tolbo Nuur Fault, which bounds the west side of the range, is in the foreground, while the Khovd Fault is in the background. The base camp location, denoted by the green tent symbol, is central to the individual project areas. Individual student project areas are outlined in blue boxes, with the number corresponding to the project designation (see text). The locations of Figures 4, 5, and 7 are shown. The image was generated from LandSat7 photography draped over an SRTM 90-m DEM and manipulated using NASA’s World Wind software.
What: In Central Asia, 2,500 km north of the India–Eurasia collision zone, a vast array of active intracontinental mountain belts are present. The Deluun Nuruu, a sub-range of the greater Mongolian Altai, is one of these. Paleozoic to Cenozoic sedimentary rocks crop out in the range and flanking hills, with minor amounts of late Paleozoic to Mesozoic intrusive rocks attesting to subduction, terrane collision and orogenesis during the Mesozoic when the Siberian and North China cratons collided (Tomurtogoo, 2003). Western Mongolia is host to many large active faults, including the Bulnay, Fu-yun, and Gobi Altai, which released three of the largest recorded intracontinental earthquakes in 1905 (Mw 8.1), 1931 (Mw 8), and 1957 (Mw 8.3), respectively (Baljinnyam et al., 1993).
The Deluun Range is flanked on its western side by the Tolbo Nuur Fault, which exhibits evidence for both recent right-lateral strike-slip and thrust rupture, but has never been studied beyond a reconnaissance level (Baljinnyam et al., 1993). The Mongolian Altai is the largest glaciated area in Mongolia (Lehmkuhl, 1998), and the Deluun range supports retreating glaciers that provide runoff critical to local peoples and endemic species.
This project will examine the neotectonics, geomorphology, and paleoecology – climatology of this geologically fascinating area.
When: July 15 – August 10, 2008 (tentative)
Who: 8 students and 3 faculty – Professor Bob Carson, Department of Geology ,Whitman College; Karl Wegmann, Department of Earth and Environmental Sciences, Lehigh University; and Professor Amgalan (“Bayasaa”) Bayasgalan, GeoInformatics Center, Mongolian University of Science and Technology.
Project Description and Goals
Our motivations for the proposed research in western Mongolia are threefold: first, to provide constraints for models of active intracontinental faulting and orogenesis; second, to provide Late Quaternary paleoenvironmental proxy records of environmental change in this understudied portion of Central Asia; and third, to promote cross-cultural scientific exchange between U.S. and Mongolian geoscience students.
Student projects will be in 2 to 3 complimentary areas:
- neotectonic – tectonic geomorphology, fault characterization, and paleoseismology;
- glacial, periglacial, and fluvial geomorphology, and
- paleoclimatic proxies of Late Quaternary climate change.
Figure 5. Right-lateral displacement of drainages by the Tolbo Nuur Fault (TNF) at the northern end of the Deluun Nuruu, see Fig. 3 for location. A. A 90-m SRTM DEM showing present topography and drainage along the TNF. B. Approximately 750 m of restorative left-lateral displacement along the fault results in realignment of offset drainages. If the long-term slip rate for the TNF is 1 mm/yr, the amount of offset preserved by the drainages represents 750 ka of accumulated slip along the fault. If the slip rate is 3 mm/yr, the offsets would have accumulated in only 250 ka.
We have pre-identified nine individual projects (Fig. 3) and additional projects may be added based upon student-faculty sponsor interests and field opportunities.
- Projects 1-4: Tolbo Nuruu Fault: These projects will focus upon the geometry, kinematics, age and evolution of the Tolbo Nuruu Fault. Each project will cover ~25 km along strike that is characterized by differing geometry and apparent rupture behavior. Paleoseismic trenching is a possibility for each of these 4 projects. Projects 1 & 4 will focus upon the TNF near the ends of the Deluun Nuruu, where it is hypothesized that fault motion transitions from predominantly right-lateral strike-slip to a larger thrust component. Project 1 will utilize offset drainages to provide constraints on the amount of right-lateral slip (e.g. Fig. 5). Projects 2 and 3 will utilize alluvial fan relationships to characterize the style and amount of movement on the central part of the TNF (e.g. Walker et al., 2006).
- Project 5: Fluvial terraces: This project will focus upon mapping and dating fluvial terrace deposits above and within the upper few kilometers of the Buyant Gol gorge, straddling the trace of the TNF. The student will use geomorphic and sedimentologic evidence to develop a terrace chronostratigraphy, augmented by radiocarbon and/or cosmogenic age control. Terrace longitudinal profiles will be constructed in order to provide constraints on the kinematics of deformation along this portion of the TNF (e.g. Fig. 6). It is anticipated that this student will collaborate with the student working on the southern segment of the TNF (Project 4).
- Project 6: Pleistocene-holocene paleoclimatology: In sparsely populated western Mongolia, long-term climate measurements are rare. As a result paleo-records preserved in sedimentary or dendrochronologic archives may provide detailed information about past climate changes in this portion of central Asia. The focus of this project will be to retrieve proxy paleoclimatic records for the Holocene and possibly late Pleistocene. Examination of such records may reveal important climate forcing periodicities and potential driving mechanisms for climate change on various temporal scales. Predicative paleoclimate research is much needed in Mongolia, a dominantly agrarian society dependent upon dry-land grazing, especially in the face of warming temperatures during the 20th and 21st centuries. Paleoclimate records could be retrieved from Larix sibirica (Siberian larch) trees (e.g. Stratton et al., 2007; Jacoby et al., 1996), from sediment cores recovered small glacial lakes (e.g. Blyakharchuk et al., 2007), or from peat cores.
- Figure 6. Longitudinal profile of channel elevation as a function of distance for the Buyant Gol from its headwaters in the NW Deluun Nuruu to just past Khovd (near its terminus in Khar-Us Nuur). Note the prominent knickpoint and steepening of the profile that occurs at the range front, where the river crosses the trace of the Tolbo Nuur Fault and enters into a ~30-km-long gorge. River terraces preserved at the head of the gorge might provide insights into the type and rate of deformation of the Tolbo Nuur Fault.
- Projects 7 & 8: Glacial and periglacial geomorphology: These projects will focus upon the number, extent, age, and climatic significance of glaciations in the Deluun Nuruu region. Of importance is the validation (invalidation) that the OIS 2 glaciers extended further downvalley than previous glacial advances. Because several of the larger valley glacier systems exited onto the piedmont, there is the opportunity to constrain the rate of offset on the TNF by dating offset glacial features (moraines and outwash terraces). It is anticipated that the students working on Projects 7 & 8 will collaborate with those working on segments 2 & 3 of the TNF projects (Fig. 3). Additionally, Holocene and modern glacial and periglacial processes could be incorporated into these projects.
Figure 7. Oblique aerial view to NE of piedmont debris flow deposit. Sapping of a small moraine-dammed lake may have generated the debris flow. In addition the headward-retreating valley may capture the lake and upstream drainage in the near future. Dating of the debris deposit could constrain the rate of faulting along this portion of the Tolbo Nuur Fault.
Project 9: Mass wasting deposit and incipient drainage capture: A conspicuous debris flow deposit is observable overlying Holocene alluvial fans (Figs. 3, 7). The deposit was derived from a deeply incised valley exiting the mountain front along the TNF, and may be cut by the fault. The head of this valley may be sapping a small glacial lake in a drainage exiting the east side of the range, and thus may be in the process of generating a near-future drainage capture. This student would collaborate with students on projects 3, 7, and 8.
We will have two or three projects in each of the following subject areas: (1) neotectonics, (2) geomorphology, and (3) paleoecology – climatology. Students will be selected to fill these slots. A general requirement is a course in field methods or field camp. Those interested in geomorphology should have a course in geomorphology or Quaternary geology. Those interested in neotectonics should have courses in structure and geomorphology.
Identifying tectonic assembly in high-grade gneiss terranes: Case study in the Adirondack Lowlands, New York.
What: This project will be an integrated structural and metamorphic study that will focus on two high-grade fault zones in the Adirondack portion of the Grenville Province, with a focus on dating deformation, determining shearing conditions within the zone, and identifying discontinuities across the boundaries.
When: July 12 to August 9, 2008
Where: Adirondacks and Colgate University
Who: 9 students. William Peck, Associate Professor, Colgate University; Bruce Selleck, Harold Orville Whitnall Professor of Geology, Colgate University; and Martin Wong, Assistant Professor, Colgate University.
Project Description and Goals
This project will focus on the Carthage Colton Shear zone (CCSZ) and Black Lake shear zone (BLSZ) in the Adirondacks. Two weeks will be spent mapping and collecting samples in the field, after an introductory field trip examining Adirondack geology. The final two weeks of the project will be spent at Colgate preparing samples for analytical work at Colgate and elsewhere. We will make use of SEM, XRF, XRD, stable isotope and fluid inclusion instrumentation at Colgate, tailoring analytical strategies to either be completed before departure or finished at student home institutions.
Possible projects include deformation studies of fault rocks and syntectonic intrusive rocks, metamorphic petrology and carbon isotope thermometry of marbles across the faults, geothermobarometry of pelites in the fault zone, fluid inclusion and stable isotope study of syntectonic high-temperature veins, whole-rock chemistry of aluminous rocks from the BLSZ to determine protoliths of the enigmatic tectonized lithologies. These projects will probably be synthesized into topical papers about the BLSZ and CCSZ discussing metamorphic petrology, intrusion history, and structures.
We will be housed in cabins in the Adirondacks and dorms at Colgate. The closeness of the field sites to Colgate (2-3 hrs) will allow return trips to the field near the end of the project if preliminary work shows the need to make new measurements or collect additional samples. Field work in this part of the Adirondacks is fairly straightforward; access is good, the locals are friendly, and the localities are close enough to each other that the students will have a good idea of the scope of all the projects.
Igneous & Metamorphic Petrology or Structural geology, Field camp (or similar field experience) recommended.