Research theme: My research focuses on geochemistry (petrology) and assemblage tectonics of convergent margins, with an emphasis on the geodynamic and physical interactions between subducting slabs (lithosphere) and asthenosphere at slab "edge" conditions. Slab edges can be found bounding slab windows (side edges) or at nascent and post-collisional states of subduction (leading and trailing slab edges). Edge conditions are key to addressing some of the outstanding problems in the tectonic model for Mesozoic crustal growth by accretion in the Canadian Cordillera, the type-setting for accretionary-style convergent-margin tectonism. In particular, there are many outstanding questions regarding terrane affinity (cratonal vs. oceanic) and timing of amalgamation in the Cordillera. This is relevant to my broader interests in earth-material exchange between crustal and mantle reservoirs and crustal growth, and in the eludication of timescales for deep recycling of the crust. 

PhD project summary: This project bridges the petrologic, economic, and tectonic disciplines of study of convergent margins at the Mesozoic Canadian Cordillera type-setting for crustal growth by accretionary tectonism. The project objectives are threefold: 1) To advance the petrologic knowledge-base of subduction zone magmatism by examining possible linkages between slab dynamic and magma source at various stages of subduction; 2) to examine the role of convergent-margin magma sources with respect to metallogeny of temporally restrictive porphyry deposits along the arc; and 3) to test a subset of previously published tectonic hypotheses regarding the specific style and timing of assembly of inboard terranes of the southern Canadian Cordillera.  The petrogenetic working model envisages that changes in slab dynamic at the nascent convergence, steady-state subduction, and accretion/post-collision stages (i.e. leading and trailing slab edge conditions) of a subduction cycle and exert a strong control on available sources contributing to magmagenesis (supra-slab mantle wedge, subducted oceanic sediments, basaltic crust of the slab, and sub-slab asthenosphere). The major tool being applied is multi-system radiogenic (Sr, Nd, Pb, Hf) and stable (O) tracer isotopes, and high-resolution trace-element geochemistry. The new geochemical dataset comprises >70 samples representing 5 time-correlative suites or pulses of magmatism from Late Triassic (Norian and Rhaetian), Early Jurassic (Sinemurian and Pleinsbachian) and Middle Jurassic (Oxfordian) intrusions of the southern Quesnel terrane, and a smaller complementary dataset from the Stikine terrane. The project necessitated new U-Pb age determinations for 6 of the geochemical samples. The economic hypothesis assumes that examination and quantification of the role of subducted sediments source of the primary magma has potential to yield a new metallogenic model for Cordilleran Cu- and Au-bearing porphyry systems.  More generally, the project dataset has already begun to provide tools for the exploration community, through the provision of a “isotopic fingerprint” template by which to discriminate between Triassic alkalic Cu-Au±Ag mineralized porphyry intrusions of the Copper Mountain suite, calc-alkaline Cu±Mo±Au porphyry phases of the Guichon suite, and variably barren to Cu-bearing, alkalic and calc-alkaline pulses of Jurassic magmatism which followed.   The tectonic working model is based on the ability of tracer-isotope studies to provide a means to quantify crustal contamination in arc magmas.  This information, when coupled with the relatively robust existing U-Pb geochronological dataset for Mesozoic intrusions of the southern Quesnel terrane, will provide constraints on the affinity and structural relationship of the Quesnel arc stratigraphic package relative to underlying Precambrian, North American crust.  Preliminary indications that lateral slab-edge conditions may have played a role in Middle Mesozoic southern British Columbia include the presence of intrusive phases with adakitic characteristics amongst Early Jurassic intrusions of the Quesnel terrane. The apparent absence of Triassic Cu-Au and Cu-Mo porphyries in the southward extension of the Quesnel terrane into the United States (Olds Ferry terrane of WA & OR) is also intriguing if a 49-50°Lat slab-edge condition hypothesis can be supported for that timeframe. However, the conventional notion that equivalent porphyries are there buried beneath Cenozoic cover may remain as the more plausible rationale for non-identification of economically viable Mesozoic porphyries in the northern US Cordillera. 

PAPERS in prep:

Breitsprecher, K., Davis, W.J. [in prep]: New U-Pb (zircon) ages from the Okanagan composite batholith, southern Quesnel terrane, British Columbia, [for Geological Survey of Canada, Current Research]

Breitsprecher, K., Scoates, J.S., Weis, D., Anderson, R.G., [in prep]: High-precision Pb-isotopic systematics of the Mesozoic Quesnel arc intrusions: defining the geochemical fingerprint and identifying sources for Cu- and Au-bearing porphyry deposits in southern British Columbia [for Economic Geology]

Breitsprecher, K., Thorkelson, D.J., Villeneuve, M.E, Marshall, D.D., Thompson, B.I. [in prep.] Volcanic stratigraphy and geochemistry of the easternmost Kamloops Group - Enderby and Trinity Hills outliers: stratigraphic and geochemical characterization of the Eocene magmatic field in south-central British Columbia. [for Canadian Journal of Earth Sciences].

NON-REFEREED CONTRIBUTIONS:

Madsen, J.K., Breitsprecher, K. and Anderson, R.G. (compilers), 2006. CordMinAge 2006: Timing of significant metallogenic deposits of the Cordilleran province, British Columbia and Yukon, Canada. Database. Geological Survey of Canada Open-File 4969

Breitsprecher, K., and Mortensen, J.K., 2004. YukonAge 2004 - a database of isotopic age determinations for rock units from Yukon Territory: Yukon Geological Survey, Department of Energy, Mines and Resources, Government of Yukon, CD-ROM [released: July 2004] download

Breitsprecher, K. and Mortensen, J.K., 2004a. BCAge 2004A - a database of isotopic age determinations for rock units from British Columbia. British Columbia Ministry of Energy and Mines, Geological Survey, Open File 2004-3, 7763 records, 9.1 Mb. [released: Oct 2004] download

RECENT & UPCOMING CONFERENCE PARTICIPATION:

UPCOMING: Breitsprecher, K., Weis, D., Scoates, J.S., 2008. Variable role of crustal recycling relative to arc maturity for the Mesozoic Quesnellian convergent margin, Canadian Cordillera. GOLDSCHMIDT, July 13-19 2008, Vancouver, BC abstract

Breitsprecher, K., Weis, D., Scoates, J.S., Anderson, R.G., 2008. High-precision Pb-isotopic systematics of the Quesnel Arc: a potential exploration tool for distinguishing lower versus upper Nicola Group volcanic rocks. Mineral Exploration Roundup, Vancouver, B.C.

Breitsprecher, K., Weis, D., Scoates, J.S., Anderson, R.G., 2007. Lu-Hf, Pb-Pb, Sm-Nd and Rb-Sr isotope geochemistry of Mesozoic porphyry intrusions, Quesnel terrane, southern British Columbia. Ores & Orogenesis 2007 Dickinson Symposium, Arizona Geological Society, Tuscon, AZ

Breitsprecher, K., Thorkelson, D.J., 2007. Neogene Nazca-Antarctic-Phoenix slab windows as a framework for modern slab anatexis beneath Patagonia. Ores & Orogenesis 2007 Dickinson Symposium, Arizona Geological Society, Tuscon, AZ

Breitsprecher, K., Madsen, J.K., Ickert, R.B., Thorkelson, D.J., 2004. Geologic signature of Paleogene ridge subduction and slab window formation beneath the central North American Cordillera, GSA Cordilleran Section, Annual Meeting, Boise, Idaho., GSA Abstracts with Programs 36(4), p.7.