PALEOPROTEROZOIC SUTURES: NE SIBERIA-SW LAURENTIA LINKS?

We present a refined reconstruction of a NE Siberia-SW Laurentia continent in which distinctive and correlative Archean and Paleoproterozoic orogenic belts and sutures are aligned. The restored belts are tightly cross-stitched by a1000 km-long Mesoproterozoic mafic dike swarm and overlapped by Mesoproterozoic successor basins. This restoration implies accretion, at ~ 2.0-1.9 Ga, between a large Archean terrane comprising the Olekma and Daldyn provinces of Siberia, and Nova and Slave provinces of Laurentia, and a second, somewhat disaggregated Archean belt, comprising the Batomga, Rae, and Hearne provinces. This produced the 4000-km long Aldan-Hapshan-North Alberta-Talston-Thelon belt, comprising both new Paleoproterozoic orogenic suites and remobilized Archean rocks. The Trans-Hudson orogen formed at ca. 1.9-1.8 Ga along the margin of this cratonal assemblage as it converged with the Superior Province. A craton containing the Archean Wyoming Province and Medicine Hat block accreted with the above assemblage at 1.72 Ga; its suture may trace from the Vulcan low in southern Alberta to SE Siberia. The Okhotsk and Ulkan regions of SE Siberia contain felsic igneous rocks and evidence of metamorphism at ~1.72-1.73 Ga, and the overlying Uchur Group has ~1.72 Ga detrital zircons (Khudoley et al., 2001). Archean to Paleoproterozic zircon ages from the Okhotsk region support its possible correlation with the Mojave Province of SW United States. The proposed 1.72 Ga suture zone appears to have undergone crustal extension during the Mesoproterozoic. Mafic dike swarms dated at 1.5-1.46 Ga and 1.38 Ga occur on both continents. A series of Mesoproterozoic grabens followed the suture, including the Siberian Udzha trough and blocks within the Belt-Purcell basin. These may have directed a fluvial system from Siberia toward the Belt-Purcell basin. The lower Belt-Purcell Supergroup was deposited from a point source that coincided with the Udzha trough in our restoration. Enigmatic detrital zircons dated at 1.575-1.600 Ga are found in both the lower Belt-Purcell Supergroup (Ross and Villeneuve, 1999) and the Mesoproterozoic Kerpyl Group of SE Siberia (Khudoley et al., 2001).