The 1501 Ma Kuonamka Large Igneous Province of northern Siberia : U-Pb geochronology, geochemistry, and links with coeval magmatism on other crustal blocks

Summary, in English

A new large igneous province (LIP), the 1501 ± 3 Ma Kuonamka LIP, extends across 700 km of northern Siberia and is linked with coeval dikes and sills in the formerly attached Sao Francisco craton (SFC)-Congo craton to yield a short-duration event 2000 km across. The age of the Kuonamka LIP can be summarized as 1501 ± 3 Ma (95% confidence), based on 7 U-Pb ID-TIMS ages (6 new herein) from dolerite dikes and sills across the Anabar shield and within western Riphean cover rocks for a distance of 270 km. An additional sill yielded a SIMS (CAMECA) age of 1483 ± 17 Ma and sill in the Olenek uplift several hundred kilometers farther east, a previous SIMS (SHRIMP) age of ca. 1473 Ma was obtained on a sill; both SIMS ages are within the age uncertainty of the ID-TIMS ages. Geochemical data indicate a tholeiitic basalt composition with low MgO (4-7 wt%) within-plate character based on trace element classification diagrams and source between E-MORB and OIB with only minor contamination from crust or metasomatized lithospheric mantle. Two subgroups are distinguished: Group 1 has gently sloping LREE ((La/Sm)_PM = 1.9) and HREE ((Gd/Yb)_PM = 1.8) patterns, slightly negative Sr and moderate TiO₂ (2.2 wt%), and Group 2 has steeper LREE ((La/Sm)_PM = 2.3) and HREE ((Gd/Yb)_PM = 2.3), strong negative Sr anomaly, is higher in TiO₂ (2.7 wt%), and is transitional from tholeiitic to weakly alkaline in composition. The slight differences in REE slopes are consistent with Group 2 on average melting at deeper levels. Proposed reconstructions of the Kuonamka LIP with 1500 Ma magmatism of the SFC-Congo craton are supported by a geochemical comparison. Specifically, the chemistry of the Chapada Diamantina and Curaga dikes of the SFC can be linked to that of Groups 1 and 2, respectively, of the Kuonamka LIP and are consistent with a common mantle source between EMORB and OIB and subsequent differentiation history. However, the coeval Humpata sills and dikes of the Angola block of the Congo craton represent a different magma batch.

• Author: R. E. Ernst; A. V. Okrugin; R. V. Veselovskiy; S. L. Kamo; Michael A. Hamilton; V. Pavlov; U. Soderlund; Kevin R. Chamberlain; Chad N Rogers
• Department/s: Department of Geology
• Publishing year: 2016-05-01
• Language: English
• Pages: 653-671
• Publication/Series: Russian Geology and Geophysics
• Volume: 57
• Issue: 5
• Links: http://dx.doi.org/10.1016/j.rgg.2016.01.015
• Document type: Journal article
• Publisher: Elsevier
• Topic: Geology
• Keywords: Dikes; Igneous province; Magmatism; Northern Siberia; Sills
• Status: Published
• ISBN/ISSN/Other: ISSN: 1068-7971