**PODS Working Group (Petrology, Ore Deposits, Structure...)**

**S-4 Pre-Proposal**

**A linked 4-D study of deformation and paleogeohydrology at
Homestake/DUSEL**

-   **Science**

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-   Objectives

> Fundamental question: What are the respective roles of deformation and
> dynamothermal metamorphism in the production of fluids (magma and
> hydrothermal) and their flow-paths in compressional orogenic systems?
>
> The rocks of Homestake/DUSEL were highly deformed, metamorphosed, and
> mineralized by fluid flow during orogenic events in the last two
> billion years. The unique character of the giant ore deposit at
> Homestake makes it an exceptional place to study the links between the
> processes of deformation and paleogeohydrology. There is a continuum
> of deformation and mineralization events between 1750 Ma and 1715 Ma,
> from a period of deformation associated with dynamothermal
> metamorphism through hydrothermal mineralization and production and
> emplacement of S-type granites. A later phase of hydrothermal
> mineralization occurred during Tertiary magmatism (\~54 Ma). We
> propose a study utilizing of the exceptional three-dimensional access
> (by mine working, existing core, and new core) to the intricate
> geology within Homestake/DUSEL, and in the course of these studies
> adding the critical fourth dimension, time.
>
> The primary objective is to resolve the crustal processes that give
> rise to evolution of a giant hydrothermal system involving large-scale
> material transport within an orogenic system. This objective will be
> achieved by several lines of research involving characterization,
> modeling, and experimentation as outlined in the approach section
> below.

-   Why DUSEL?

> The combination of unique geology, extensive underground access, large
> core archive, and potential to acquire scientifically targeted core
> within and below Homestake/DUSEL provides an exceptional resource for
> addressing questions involving deformation, fluid flow, and
> mineralization. Additionally, many of the proposed research activities
> offer synergetic research opportunities with other working groups
> within the DUSEL process.

-   Why now?

> In consideration of mine/lab access issues, the proposed research is
> best initiated during the pre-construction and construction phases of
> the DUSEL facility. Access to unlined mine walls may be limited to
> this stage in some parts of the facility. Also, some proposed research
> activities support planning for construction and initial suites of
> experiments of other working groups (e.g., characterization of rock
> chemistry for modeling of background radiation to plan shielding for
> low background counting facility, collaboration with Dongming Mei,
> Univ. of South Dakota Physics). After the construction phase,
> continuation of research will involve participation in experiments of
> other working groups (e.g., Induced flow and transport group), and
> study of additional core generated by other working groups (e.g.,
> Ultra-deep biological observatory in the induced flow, transport and
> activity/induced rock deformation working group), as well as targeted
> core sampling specific to serving the objectives of this working
> group.

-   Approach

> Resolution of the interplay between the deformation, metamorphism, and
> paleogeohydrology will be addressed by:

-   Characterize 3-D geometries of **structures and fabrics and their
    timing** relationships in the Homestake mine, through lithologic
    mapping and chemostratigraphy, determination of intensity of strain
    and rheologic properties at the conditions of metamorphism.

-   **Model structural evolution** through comparison with existing
    kinematic and thermal-mechanical models to gain insight into
    processes of magma generation and flow-path development.

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-   Characterize in 3-D the **geometry and chronology of
    paleo-flowpaths**, manifested in multiple generations of quartz
    veins (Paleoproterozoic and early Tertiary), through additional
    mapping, mineralogical, geochemical, fluid inclusion and stable
    isotope studies.

-   Conduct experiments of **element mobilization and precipitation
    mechanisms** as models for formation of giant Paleoproterozoic
    ore-forming systems, as well as mineralization related to Tertiary
    magmatic-hydrothermal systems (Heater experiment -- collaboration
    with Induced Flow and Transport working group).

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-   Expected Results and their Significance

    -   **Structures and fabrics and their timing:** Previous research
        by working group member Michael Terry indicates a transition
        from horizontal flow to vertical flow during Proterozoic
        transpressive deformation of the rocks above the Yates unit of
        the Poorman Formation. Further detailed studies of structures
        and rock fabrics will reveal details of the timing and nature of
        this transition and allow consideration of mechanisms of
        deformation. Chemostratigraphy of the Yates unit of the Poorman
        Formation will facilitate characterization of strain in this
        rheologically contrasting (stronger) unit. Synthesis of these
        results will allow a determination of intensity of strain and
        rheologic properties at the conditions of metamorphism.

    -   **Modeling structural evolution:**

> Knowledge of the distribution of structures and their timing, strain
> intensity and type, and rheologic properties in the mine area will
> allow the development of kinematic and thermal-mechanical models
> designed to assess the role of changes in ductile flow in the
> initiation of processes including dome formation, S-type magmatism,
> and mineralization (element redistribution). The change from
> horizontal ductile flow to vertical flow during Proterozoic
> deformation, evident in the mine, is generally consistent with
> kinematic models for transpression. The timing of this change in
> ductile flow suggests a link to dome formation, S-type magmatism, and
> mineralization around \~1732-1715 Ma (Dahl et al., 2005). All of these
> processes are evident in the mine or in close proximity to the mine
> making it a unique volume of rock to evaluate the role in the change
> of ductile flow in initiating these processes. These models will give
> insights into understanding the initiation of such processes in
> ancient and modern transpressional orogenic belts worldwide. This
> Proterozoic (1750-1715 Ma) deformation observed the lab also controls
> the distribution of major rock types and thus variations rheologic
> properties in the lab which controls and/or influences paleo-fluid
> paths (Proterozoic and Tertiary) as well the present fractures and
> present-day groundwater flow.

-   **Geometry and chronology of paleo-flowpaths:** The Homestake Mining
    Company has studied Proterozoic-aged vein characteristics and
    geometries in order to assist their gold exploration (Caddey et al.,
    1991). Nuri Uzunlar (working group member) concluded that
    Tertiary-aged vein systems associated with magmas within the mine
    and surrounding area have a gradation in mineralogy and metals
    suggesting a source from a causative stock below the 8,000 foot
    level. Proposed studies will involve documentation of vein
    generations within both systems in key areas of the mine, in
    addition to archived drill core, to develop chrono-spatial models of
    fluid flow paths, with implications for fluid and element
    mobilization and concentration (collaboration with Ultra-deep
    Biological Observatory working group). Additional exposures
    resulting from the Ultradeep Biological Observatory drill holes will
    expand this model to current depths of at least 16,500 feet,
    equivalent to a 6 km deep exposure of the Tertiary hydrothermal
    system (3,500 feet of rock has been eroded since the Tertiary). Such
    an extent in a paleo-hydrothermal system is unique, and has
    implications for origin of Carlin-type gold deposits (similar to
    those in the northern Black Hills), currently the source of most of
    the US gold production.

-   **Element mobilization and precipitation mechanisms:** The flow
    paths established above together with stable isotope data on vein
    and replacement minerals will allow some constraints to be placed on
    the source regions of the fluids (magmas and aqueous). Conflicting
    theories for the Homestake-type deposits are (a) distal source
    external to the exposed mine rocks versus (b) redistribution of
    metals from the Homestake Formation that hosts the ore. The
    physicochemical conditions of element transport and mineral
    deposition established for both generations of hydrothermal systems
    through mineralogical, geochemical, fluid inclusion and stable
    isotope studies will be used to establish the temperature and
    composition conditions for the heater experiment to be conducted by
    the Induced Flow and Transport group.

-   Other results will be produced by synergistic activities with, and
    in support of, other working groups:

    1.  Baseline characterization: Proposed research activities include
        characterization of rock chemistry and mineralogy, and mapping
        of structural patterns and fabrics in the rocks. These
        activities contribute to the baseline characterization dataset
        for other experiments at DUSEL.

    2.  Ultra-deep biological observatory: the ultra-deep drilling
        proposed by this working group will produce core of great
        interest to our working group. Geologic characteristics
        (lithology, mineralogy, chemistry, and structure) of this core
        will contribute to evaluating the fundamental question posed in
        this proposal. Also, our working group offers the breadth of
        technical expertise in geology and local geologic knowledge
        necessary to contribute to the interpretation of these rocks,
        and to consult on rock units likely to be encountered in the
        course of ultra-deep drilling.

    3.  Induced flow and transport: collaboration of working group
        members in elements of the heater experiment as discussed above

    4.  Physics -- Low background counting facility: geochemical
        characterization of core in the planned laboratory construction
        areas will provide data on U, Th, and K abundance as well as
        other elements necessary to model shielding requirements for
        facility. Future collaboration with this group may also include
        sharing analytical facilities (e.g., ICP-MS and INAA, commonly
        used for trace-element geochemistry).

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-   Brief description of initial suite of experiments

    -   Geologic processes are understood by experimentation,
        observations in natural systems, and modeling (simulations). The
        kinds of geological research that we propose are mainly focused
        on the latter two of these approaches. However, members of our
        group (PODS) will participate in the heater experiment of the
        induced flow, transport and activity/induced rock deformation
        working group. The PODS participation in that experiment would
        be to trace fluids doped with various metals through
        thermally-driven flow through a variety of rock types
        encountered at depth at Homestake/DUSEL.

    -   Other research to be conducted in the initial suite of
        experiments, and in the construction phase leading up to this
        suite, [is discussed above in the *Approach* and *Anticipated
        Results and Significance* sections]{.underline}, with research
        foci in the following linked subject areas:

        -   Structures and fabrics and their timing

        -   Modeling structural evolution

        -   Geometry and chronology of paleo-flowpaths

        -   Element mobilization and precipitation mechanisms

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-   Development needs prior to conducting experiments at Homestake

    -   Infrastructure engineering and design

        -   Office and lab space with internet access at the surface
            (not underground).

        -   Access to internet-accessible 3D database.

        -   Onsite 3D visualization and analysis computer laboratory.

        -   Access to core archive, including archiving space for newly
            collected samples.

        -   Access to document archive (maps, cross sections, drill
            logs).

        -   Rock sample preparation and examination laboratory, assuming
            basic core laboratory equipment is available (binocular
            microscope, trim saw, slab saw, drill press, digital camera
            and accessories, petrographic microscope)

        -   Access to drilling rig (underground). Our need for new core
            is project-dependent. Examples of core that are of interest
            but appear to be scarce in the core archive include
            continuous core through **mineralized** zones (most core
            through these zones in our archive have been completely
            assayed or are already split-core sampled) and core from the
            Crook Mountain granite. We plan to hire DUSEL contracted
            drillers and would hope to obtain either HQ (63.5 mm
            diameter) or NX (54.7 mm diameter) core.

        -   Portable coring machine for collection of fresh samples
            (many orientated) in underground stopes and drifts.

        -   Roaming access to critical areas of the mine as prioritized
            through ongoing research. Table 7.1 identifies priority
            levels in which across-mine transects would be desirable to
            provide 3-D exposure for structural analysis and sampling.
            Access to other levels or areas will be identified and
            justified through on-going research.

> ![](media/image1.jpeg){width="5.270833333333333in"
> height="5.1194444444444445in"}
>
> Presently, a 3D database (Vulcan) of mine related information is not
> readily available to researchers wishing to plan and conduct research.
> Additionally, a functioning core archive and core-examination
> laboratory is likewise not yet available. The consensus of the Working
> Group is that it is extremely important that both of these
> "facility/infrastructure" components are available as soon as
> possible. In fact, the research action items developed by the Working
> Group are based on the premise that these two facility/infrastructure
> components of the Sanford Laboratory at Homestake will be available
> very soon.

-   Laboratory experiments, theoretical analyses

    -   None

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-   **Cost estimate**

    -   S-4 proposal cost (\~\$54k)

        -   Acquisition of core and underground samples for preliminary
            data collection, including sample preparation and
            petrographic and chemical analysis (\$5K)

        -   Principal investigators' time in establishing cost estimates
            (\$5K)

        -   College tuition fees for two principal investigators for
            course in Vulcan 3-D database management at SDSM&T (\$2K)

        -   Participation in DUSEL working group session at AGU (\$10K)

        -   Grant writing workshop for collaborators (\$30K)

    -   ISE Project cost (\~\$338k+)

> Note that some of the following would be needed by other working
> groups\*

-   Construct a permanent core facility in existing building (machine
    shop), core shelving and retrieval system, and staff\*. Includes 75
    bays of shelving (10 ft high x 9 ft x 4 ft, existing core would
    occupy 67, leaving 8 for new core -- unlikely to be enough) (\$55K);
    replacement and new core boxes (\$40-50K); scissor truck lift for
    handling (???)

-   Rock sample preparation and examination laboratory, including rock
    saws (slab \$4.5K), trim \$2K), lab core drill (\$1.5K), thin
    section preparation equipment, two research petrographic microscopes
    (\$40K), cameras (microscope and underground) (\$3K), portable XRF
    analyzer (\$70K)

-   Underground drilling contract cost -- 2000 feet at \$50/foot
    (\$100K)

-   Portable coring machine for orientated samples (\$3.5K)

-   Onsite 3D visualization and analysis computer laboratory equipment\*
    (\$10K)

-   Office space on surface, with internet access, conference room,
    classroom, projection facilities, bathrooms, etc.\*

-   Visiting scientist/student accommodation\*

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-   Tasks required to refine cost estimate

    -   All of above items will need more detailed assessment of costs,
        based on listing of equipment and design plans for facilities

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-   **Schedule**

    -   Estimated time required and sequence of tasks; start with S-4
        activities

        -   Set up an informal gathering at a national conference (AGU)
            to identify further collaborators (Dec. 2008).

        -   Participate in the proposed AGU DUSEL Working Group meeting
            (Dec 2008).

        -   Use 3D database and document and core archives to plan sites
            for underground research tasks (Oct. -- Dec. 2008).

        -   Acquire safety training for those researchers needing
            underground access.

        -   Conduct underground visits to verify site selection, and
            conduct sampling for preliminary data collection and
            analyses (Oct. 2008 -- Feb. 2009).

        -   Conduct grant writing workshop for collaborators in Rapid
            City (Jan. 2009), including a visit to SUSEL/DUSEL facility
            and core archive.

        -   Submit S-5 proposal by May 2009.

-   **Facilities**

    -   Space, access, power, equipment, communications, services,
        special materials, etc. required to successfully conduct
        experiment

        -   Underground access to several levels. Highest priority
            levels are the 300, 2600 and 4100 L.

        -   Ventilation underground and access to water and hoses (to
            wash walls)

        -   Access to databases (Vulcan, map archives, logs) and the
            core archive

        -   Core lab for sample preparation of hand samples and core

        -   Contract drill rig and crew for drilling through areas
            identified in present and future research proposals

    -   Point of Contact for issues regarding facilities:

> Kelli McCormick (<Kelli.McCormick@state.sd.us>)

-   **Education & Outreach**

> Our proposed work lends itself well to education and outreach. The
> majority of our group is on faculty at either SDSM&T or USD where many
> of us interact with and advise students on a daily basis. We envision
> many opportunities to involve graduate students, undergraduate
> students, and science teachers in research projects and workshops or
> short courses that we develop.
>
> Through senior thesis and graduate degree research related to DUSEL,
> students will learn a number of important geologic and general science
> skills, including sample preparation and analytical analysis,
> petrography, mineral chemistry, geochemistry, analytical and numerical
> modeling, geologic mapping, scientific writing, and of course, how to
> carry out a research project. Examples of analytical tools that
> students may have an opportunity to use include the optical
> microscope, X-ray fluorescence spectrometer, inductively coupled
> plasma mass spectrometer, electron microprobe, scanning electron
> microscope, sensitive high-resolution ion microprobe, and X-ray
> diffractometer.
>
> SDSM&T has a strong field mapping component to its geology and
> geologic engineering programs. Thus, there is a strong impetus to
> involve graduate students in advanced underground mapping and conduct
> underground mapping camps for undergraduate geology students.
> Undergraduate field camps typically include students from universities
> across the country (and sometimes internationally), not just those
> students attending SDSM&T. We also hope to develop short courses in
> underground geologic mapping for industry personnel.
>
> Geoscience workshops could be set up for K-12 teachers and students at
> DUSEL in the summers. Several professional societies promote education
> and outreach. Our idea is to link up with programs through specific
> organizations to develop workshops for K-12 teachers and students.
> Examples of possible programs include the Geological Society of
> America's Teacher Advocacy Program and Sigma Xi's K-16 Education
> Programs.
>
> Opportunities also exists to set up short courses in conjunction with
> professional meetings, such as the Geological Society of America Rocky
> Mountain Section meeting, which is scheduled to be held in Rapid City
> in 2010. The American Institute of Professional Geologists is also
> considering holding a national meeting in Rapid City in 2010 or soon
> after.

-   **Risk identification and management**

    -   Potential problems that could affect successful outcome

        -   Lack of access to critical areas of the mine because of
            tunnel instability, flooding, or ventilation issues

        -   Lack of access to necessary existing resources, such as
            databases and archives

    -   Potential problems that could affect other experiments or
        facility

        -   Lack of access underground will delay our ability to
            characterize rock chemistry and mineralogy and map
            structural patterns and fabrics in the rocks and thereby
            potentially affect scientists who rely on existing data to
            plan their experiments (e.g., anyone relying on baseline
            characterization data)

-   **Interested principals and collaborators**

> Active participants in the working group are as follows:

-   Colin J. Paterson, Professor, working group leader, Department of
    Geology and Geological Engineering, South Dakota School of Mines and
    Technology

-   Michael P. Terry, Assistant Professor, Department of Geology and
    Geological Engineering, South Dakota School of Mines and Technology

-   Brennan T. Jordan, Assistant Professor, Department of Earth
    Science/Physics, University of South Dakota

-   Kelli A. McCormick, Senior Geologist, South Dakota Geological Survey

-   Nuri Uzunlar, Associate Professor, Department of Geology and
    Geological Engineering, South Dakota School of Mines and Technology

-   Maribeth H. Price, Chair and Associate Professor, Department of
    Geology and Geological Engineering, South Dakota School of Mines and
    Technology

-   Alvis L. Lisenbee, Professor Emeritus, South Dakota School of Mines
    and Technology

-   Derric L. Iles, South Dakota State Geologist

> In addition to the Working Group participants listed above, there are
> more than 20 other geoscientists who have participated in submitting
> Letters of Interest on topics relevant to the PODS Working Group since
> February 2006. Many of the research interests represented by these
> scientists are aligned with the research proposed by the PODS Working
> Group. We will actively seek their collaboration as the planning for
> underground science continues. Additional LOIs and scientists include:
>
> **Precambrian Geology**

-   Partitioning of CO2, H2O, gold and trace metals between synformal
    and antiformal fold hinges: *Diane Wolfgram, Christopher H. Gammons
    and Colleen Elliott (Montana Tech)*

-   \*Geochronology and geochemistry of orogenic gold deposits, Black
    Hills, South Dakota: *Ryan Morelli (<rmorelli@ualberta.ca>, Univ.
    Alberta)*

-   \*The age and source of gold mineralization at the Homestake gold
    deposit: *David L Huston (<David.Huston@ga.gov.au>, Geoscience
    Australia, Canberra) and Richard Goldfarb (<Goldfarb@usgs.gov>,
    USGS, Denver)*

-   \*3D Structural Permeability Revealed by Gold Mineralization in the
    Homestake Mine: *Richard H. Sibson
    (rick.sibson@stonebow.otago.ac.nz) and David Craw
    (<Dave.Craw@stonebow.otago.ac.nz>, University of Otago, New
    Zealand)*

-   \*Source of gold in the Homestake Mine: *Ross Large
    (Ross.Large@utas.edu.au) and Leonid Danyshevsky (CODES, Univ of
    Tasmania, Australia):*

> **Tertiary Mineralization**

-   Breccia evolution associated with degassing of Tertiary veins and
    dikes at Homestake: *Alvis Lisenbee, Nuri Uzunlar, (SDSM&T); Scott
    Cooper, (Sandia National Lab )*

-   Crustal assimilation and volatile evolution in rhyolite and
    phonolite dikes: isotopic and geochemical variations along 8000-ft
    exposure: *Genet Duke, Alvis Lisenbee (SDSM&T), Scott Cooper (Sandia
    National Lab), Carol D. Frost (U. Wyoming)*

-   Thermal History of Homestake Mine, Lead, South Dakota: *Nuri
    Uzunlar, Alvis L. Lisenbee, Colin J. Paterson, Edward F. Duke
    (SDSM&T), Shari Kelley (New Mexico State University)*

> **Geological Database**

-   Develop An Internet-Accessible Database of 3D Geologic and
    Engineering data for Homestake: *Maribeth Price (SDSM&T), Jason Love
    RE/SPEC, Derric Iles (SD Geol. Survey), and Gail Postrollo
    (Homestake-Adams Research Center)*

-   Development of a Geological 3D model of the Homestake Mine: *Dean
    Peterson (U Minnesota-Duluth)*