PRECISE 1.59 GA AGE FOR WESTERN CHANNEL DIABASE, WOPMAY OROGEN: IMPLICATIONS FOR LAURENTIA APWP AND RECONSTRUCTIONS OF LAURENTIA, BALTICA AND GAWLER CRATON

U-Pb baddeleyite ages of 1592 ± 3 Ma and 1590 ± 4 Ma are reported for paleomagnetic sites in sheets and dykes of Western Channel Diabase (WCD) that intrude Proterozoic rocks of the flat-lying Hornby Bay Group and the deformed volcanic-plutonic Great Bear Magmatic Zone. A published WCD paleomagnetic pole has been interpreted as primary. It falls midway in time between the ages of 1740 Ma Cleaver dyke and 1460-1420 Ma Elsonian pluton paleopoles, filling an important gap in the Proterozoic apparent polar wander path (APWP) for Laurentia. The WCD pole can be compared with poles reported from similar-aged magmatic units on other cratons, in particular Baltica and Gawler craton (GC) of S Australia. A comparison of the Laurentian WCD pole with primary 1630 Ma and 1570 Ma Baltica poles, along with a comparison of precisely-dated 1270-1265 Ma poles for Laurentia and Baltica, suggests that the two cratonic blocks drifted as one entity with Baltica adjacent to eastern Greenland during the ca. 1600-1270 Ma interval. On the basis of less well-constrained ca. 1838-1827 Ma poles from Laurentia and Baltica, it is possible that this reconstruction existed as early as ca. 1830 Ma. WCD is identical in age with Wernecke breccias of the Wernecke and Ogilvie Mountains of NW Laurentia and with bimodal Gawler Range Volcanics (GRV) and related Olympic Dam breccias of GC. It has been suggested that GC lay adjacent to NW Laurentia at 1590 Ma, similar to its position in the SWEAT reconstruction hypothesized for later Rodinia time. The primary WCD pole provides an opportunity to test Laurentia-GC reconstructions at 1590 Ma. Although a pole has been reported for the GRV, its primary or secondary nature is controversial. If primary, or if acquired as an overprint during the later stages of 1600-1580 Ma Hiltaba-GRV magmatism, then a position for GC adjacent to NW Laurentia is permitted. A younger magnetic overprint is also possible, but we interpret published thermochronological data to suggest this occurred no later than 1400 Ma. Comparison of the GRV pole and primary poles for 1460-1420 Ma Elsonian plutons also permits a fit of GC adjacent to NW Laurentia. In the case of a 1590-1580 Ma reconstruction, the relative orientation of GC and Laurentia is similar to that in the SWEAT reconstruction, whereas for a 1460-1420 Ma fit, GC is rotated ~40° clockwise relative to Laurentia.