Detrital Zircon Provenance of the Mesoproterozoic Midcontinent Rift, Lake Superior Region, USA

作者：Craddock John P^*; Konstantinou Alex; Vervoort Jeffrey D; Wirth Karl R; Davidson Cam; Finley Blasi Lee; Juda Natalie A; Walker Erin

来源：Journal of Geology, 2013, 121(1): 57-73.

DOI：10.1086/668635

We report the ages of detrital zircons (Pb-207/Pb-206 LA-ICPMS; n = 1188) from 12 clastic units that are representative of the Mesoproterozoic Midcontinent Rift System (MRS) of North America. Magmatism of the MRS spanned 1115-1085 Ma. The Puckwunge, Nopeming, and Bessemer basal sandstones and the Oronto and Bayfield Group sandstones received a predominance of Keweenaw Rift-Grenville (1.3-1.0 Ga) zircons but also contributions of Wolf River (1.45 Ga), Yavapai (1.75 Ga), Penokean (1.8 Ga), and Archean(2.6-3.6 Ga) ages. Interflow sedimentary rocks in the North Shore Volcanic Group received only rift-aged zircons. The maximum depositional ages derived from detrital zircons also better constrain the age-stratigraphic relationship of the unfossiliferous rift section, in comparison to the overlying fossiliferous Franconia (n = 99 zircons), Mt. Simon (n = 116), and Munising (n = 110) late Cambrian transgressive sands. We also report the date of a granite xenolith (similar to 1 km(3)) in the Beaver Bay Complex, which has a rift age (1091 Ma; n = 19) and is therefore not a rafted inclusion of Archean basement as previously suspected.

• 出版日期2013-1