Plume impingement on the Siberian SCLM: Evidence from Re–Os isotope systematics

摘要: Abstract We report Re–Os and platinum group element (PGE) systematics for a suite of 16 mantle peridotites from the Udachnaya (360 Ma) Obnazhennaya (160 Ma) kimberlite pipes, Siberia. Xenoliths these pipes bracket thermal climax Siberian plume, which is represented by emplacement ~ 250 Ma Flood Basalts (SFBs). Thus, xenoliths represent snapshots sub-continental lithospheric (SCLM) before after plume modification. Pre-plume peridotite generally display unradiogenic Os-isotopes with respect to CI-chondrite (expressed γOs, percentage difference between Os-isotope composition sample average chondrite composition; 187Os/188Os — 0.127), coupled low [Pd/Ir]N, both whole-rock olivine mineral-fraction analyses. Such signatures are typical an ancient depleted cratonic that underwent melt extraction. The preservation compositions (γOs − 5 − 14), (  0.1292), overlap convecting range. At first glance, observations in agreement garnet chemistry data, indicate high-degrees silicate-melt percolated through lithosphere during SFB. However, mineral-separates ‘depleted’ (> Fo 92 [Pd/Ir]N), consistent ‘pristine’ residues. suggest ‘newly formed’ residues associated partial melts extracted impinging on SCLM. During impingement, thermo-chemical erosion thought be important process, acting remove original material. In space created, new refractory may able infill this void; i.e., plume-subcretion. Importantly, two very − 9 − 10) indicating preserved Overall, we impingement not ubiquitous within SCLM, leaving characterized its newly formed, related addition, samples one Udachnaya, contain highly radiogenic ratios (γOs > + 85). values cannot accounted kimberlitic or plume-related metasomatism. Instead, reflect metasomatism fluids derived source long-term high 187Re/188Os, such as recycled subducted material (i.e., oceanic crust sediments). These lithologies were introduced into SCLM craton growth events ~ 1.8 3.0 Ga. identification reflects metasomatic suites reveal complex evolution lithosphere, birth Archean, followed major depletion Proterozoic, ending tectonothermal perturbation plume.