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Reconnaissance U-Pb geochronology of Precambrian crystalline rocks from the northern Black Hills, South Dakota: Implications for regional thermotectonic history

Ghosh, Amiya Kumar
http://rave.ohiolink.edu/etdc/view?acc_num=kent1240007954

Abstract Details

2009, MS, Kent State University, College of Arts and Sciences / Department of Earth Sciences.
Th/U-bearing accessory minerals monazite, zircon, and titanite occurring in selected metamorphic and igneous rocks from the northern Black Hills (NBH), South Dakota, were analyzed by standard U-Pb radiometric methods to unravel the Precambrian thermotectonic events that affected the area. Four metapelites from the Crook Mountain borehole contain metamorphic monazites for which EMP spot-analysis yielded total-Pb dates ranging from ~2680-1600 Ma but mostly between ~1790-1650 Ma. Individual spot-dates obtained for the metapelites were grouped according to compositional domains, as revealed by X-ray imagery, whereupon the resultant domain ages resolved into four discrete age clusters of ~1780 ± 3 Ma (32% of the dates), ~1751 ± 3 Ma (44%), ~1718 ± 14 Ma (7%), and ~1650 ± 9 Ma (16%, all dates reported at 95% confidence). These dates correspond to thermotectonic and magmatic events previously recognized at these times in the southern Black Hills, and the timing of Homestake gold mineralization is constrained between ~1740 -1718 Ma. Spot-analysis of zircon grains extracted from a Crook Mountain granite pegmatite yielded 207Pb/206Pb upper- and lower-intercept ages of 1718 ± 22 Ma and 51 ± 17 Ma, which are interpreted as intrusive and uplift ages, respectively. Detrital zircons of magmatic origin from two Black Hills metapelites have also been spot-dated. Five 207Pb/206Pb age populations are recognized at: ~3830 ± 8, ~3365 ± 5, ~3425 ± 7, ~3240 ± 4, and ~2970 ± 11 Ma. These ages indicate zircon provenance from the ~3550-2550 Ma Wyoming craton rather than from the ~2900-2600 Ma Superior craton. Thus, the Black Hills appears to have been part of the Wyoming craton as of 2015-1880 Ma shale deposition.
Peter Dahl, PhD (Advisor)
Abdul Shakoor, PhD (Committee Member)
Daniel Holm, PhD (Committee Member)
131 p.
Geochemistry; Geology
Black Hills; Crook Mountain granite; Homestake gold mine; gold mineralization; magmatism; metamorphism; metapelite; g monazite; zircon; titanite; geochronology; thermotectonism

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Citations

  • Ghosh, A. K. (2009). Reconnaissance U-Pb geochronology of Precambrian crystalline rocks from the northern Black Hills, South Dakota: Implications for regional thermotectonic history [Master's thesis, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1240007954

    APA Style (7th edition)

  • Ghosh, Amiya. Reconnaissance U-Pb geochronology of Precambrian crystalline rocks from the northern Black Hills, South Dakota: Implications for regional thermotectonic history. 2009. Kent State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1240007954.

    MLA Style (8th edition)

  • Ghosh, Amiya. "Reconnaissance U-Pb geochronology of Precambrian crystalline rocks from the northern Black Hills, South Dakota: Implications for regional thermotectonic history." Master's thesis, Kent State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1240007954

    Chicago Manual of Style (17th edition)

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© 2009, all rights reserved.
This open access ETD is published by Kent State University and OhioLINK.