A petrochronological approach for the detrital record: Tracking mm-sized eclogite clasts in the northern Canadian Cordillera

作者：Kellett Dawn A^*; Weller Owen M; Zagorevski Alex; Regis Daniele

来源：Earth and Planetary Science Letters, 2018, 494: 23-31.

DOI：10.1016/j.epsl.2018.04.036

• eclogite
• petrochronology
• rutile U-Pb
• thermobarometry
• detrital record
• Canadian Cordillera

Sutures recording the accretion history of the Canadian Cordillera terranes are poorly preserved. The Whitehorse trough syn-orogenic basin formed during early Mesozoic terrane accretion at the western margin of Laurentia and contains a similar to 300 m thick horizon that includes eclogite clasts possibly sourced from a suture zone. By applying petrochronological micro-analytical techniques to the mm-diameter eclogite clasts, including thermobarometry and in situ rutile thermochronology, as well as detrital zircon geochronology and thermal diffusion modeling, we constrain a source-to-sink path for the clasts. The eclogite clasts likely reached peak metamorphic conditions of 2.2-2.9 GPa and >= 800 degrees C, cooled through Pb closure in rutile during Early Jurassic at >= 610 degrees C and were deposited into the basin by latest Pliensbachian/earliest Toarcian. This history implies minimum mean cooling and exhumation rates on the order of similar to 38 degrees C/myr and similar to 4.1 km/myr, respectively, consistent with rates reported for subduction-related eclogite worldwide. We suggest the most likely source for the clasts is the suture between the Yukon-Tanana and Stikinia terranes, involving a latest Triassic collision, followed by rapid Early Jurassic exhumation of the lower plate Yukon-Tanana terrane, either by buoyant extrusion or in a plate boundary zone metamorphic core complex. Our study demonstrates that micro-analytical techniques used for petrochronology can be applied to very small lithic clasts in the sedimentary record towards the tectonic reconstruction of accretionary orogens.

• 出版日期2018-7-15