scholarly journals Metasomatism in cratonic mantle root: insight from geochemistry of deformed peridotite xenoliths of Udachnaya pipe

2019 ◽  
Keyword(s):  
Udachnaya Pipe ◽  
Peridotite Xenoliths ◽  
Cratonic Mantle

Decoupled water and iron enrichments in the cratonic mantle: A study on peridotite xenoliths from Tok, SE Siberian Craton

2020 ◽  
Vol 105 (6) ◽  
pp. 803-819
Author(s):  
Luc S. Doucet ◽  
Yongjiang Xu ◽  
Delphine Klaessens ◽  
Hejiu Hui ◽  
Dmitri A. Ionov ◽  
...  
Keyword(s):  
Water Content ◽  
Siberian Craton ◽  
Lithospheric Mantle ◽  
Large Scale ◽  
Basaltic Magma ◽  
Mantle Xenoliths ◽  
Spinel Peridotite ◽  
Peridotite Xenoliths ◽  
Cratonic Mantle ◽  
Water Contents

Abstract Water and iron are believed to be key constituents controlling the strength and density of the lithosphere and, therefore, play a crucial role in the long-term stability of cratons. On the other hand, metasomatism can modify the water and iron abundances in the mantle and possibly triggers thermo-mechanical erosion of cratonic keels. Whether local or large scale processes control water distribution in cratonic mantle remains unclear, calling for further investigation. Spinel peridotite xenoliths in alkali basalts of the Cenozoic Tok volcanic field sampled the lithospheric mantle beneath the southeastern margin of the Siberian Craton. The absence of garnet-bearing peridotite among the xenoliths, together with voluminous eruptions of basaltic magma, suggests that the craton margin, in contrast to the central part, lost its deep keel. The Tok peridotites experienced extensive and complex metasomatic reworking by evolved, Ca-Fe-rich liquids that transformed refractory harzburgite to lherzolite and wehrlite. We used polarized Fourier transform infrared spectroscopy (FTIR) to obtain water content in olivine, orthopyroxene (Opx), and clinopyroxene (Cpx) of 14 Tok xenoliths. Olivine, with a water content of 0–3 ppm H2O, was severely degassed, probably during emplacement and cooling of the host lava flow. Orthopyroxene (49–106 ppm H2O) and clinopyroxene (97–300 ppm H2O) are in equilibrium. The cores of the pyroxene grains, unlike olivine, experienced no water loss due to dehydration or addition attributable to interaction with the host magma. The water contents of Opx and Cpx are similar to those from the Kaapvaal, Tanzania, and North China cratons, but the Tok Opx has less water than previously studied Opx from the central Siberian craton (Udachnaya, 28–301 ppm; average 138 ppm). Melting models suggest that the water contents of Tok peridotites are higher than in melting residues, and argue for a post-melting (metasomatic) origin. Moreover, the water contents in Opx and Cpx of Tok peridotites are decoupled from iron enrichments or other indicators of melt metasomatism (e.g., CaO and P2O5). Such decoupling is not seen in the Udachnaya and Kaapvaal peridotites but is similar to observations on Tanzanian peridotites. Our data suggest that iron enrichments in the southeastern Siberian craton mantle preceded water enrichment. Pervasive and large-scale, iron enrichment in the lithospheric mantle may strongly increase its density and initiate a thermo-magmatic erosion. By contrast, the distribution of water in xenoliths is relatively “recent” and was controlled by local metasomatic processes that operate shortly before the volcanic eruption. Hence, water abundances in minerals of Tok mantle xenoliths appear to represent a snapshot of water in the vicinity of the xenolith source regions.

Composition of the Siberian cratonic mantle: evidence from Udachnaya peridotite xenoliths

1997 ◽  
Vol 128 (2-3) ◽  
pp. 228-246 ◽  
Author(s):  
F. R. Boyd ◽  
N. P. Pokhilenko ◽  
D. G. Pearson ◽  
S. A. Mertzman ◽  
N. V. Sobolev ◽  
...  
Keyword(s):  
Peridotite Xenoliths ◽  
Cratonic Mantle

scholarly journals High water contents in the Siberian cratonic mantle linked to metasomatism: An FTIR study of Udachnaya peridotite xenoliths

2014 ◽  
Vol 137 ◽  
pp. 159-187 ◽  
Author(s):  
Luc S. Doucet ◽  
Anne H. Peslier ◽  
Dmitri A. Ionov ◽  
Alan D. Brandon ◽  
Alexander V. Golovin ◽  
...  
Keyword(s):  
High Water ◽  
Ftir Study ◽  
Peridotite Xenoliths ◽  
Cratonic Mantle ◽  
Water Contents

scholarly journals Evolution of Deformation Fabrics Related to Petrogenesis of Upper Mantle Xenoliths Beneath the Baekdusan Volcano

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 831 ◽  
Author(s):  
Munjae Park ◽  
Youngwoo Kil ◽  
Haemyeong Jung
Keyword(s):  
High Stress ◽  
Equilibrium Temperature ◽  
Mantle Xenoliths ◽  
Spinel Peridotite ◽  
Localized Deformation ◽  
Peridotite Xenoliths ◽  
Dry Conditions ◽  
Cratonic Mantle ◽  
Formation And Evolution ◽  
High Degree

Knowledge of the formation and evolution of cratonic subcontinental lithospheric mantle is critical to our understanding of the processes responsible for continental development. Here, we report the deformation microstructures and lattice preferred orientations (LPOs) of olivine and pyroxenes alongside petrological data from spinel peridotite xenoliths beneath the Baekdusan volcano. We have used these datasets to constrain the evolution of deformation fabrics related to petrogenesis from the Baekdusan peridotites. Based on petrographic features and deformation microstructures, we have identified two textural categories for these peridotites: coarse- and fine-granular harzburgites (CG and FG Hzb). We found that mineral composition, equilibrium temperature, olivine LPO, stress, and extraction depth vary considerably with the texture. We suggest that the A-type olivine LPO in the CG Hzb may be related to the preexisting Archean cratonic mantle fabric (i.e., old frozen LPO) formed under high-temperature, low-stress, and dry conditions. Conversely, we suggest that the D-type olivine LPOs in the FG Hzb samples likely originated from later localized deformation events under low-temperature, high-stress, and dry conditions after a high degree of partial melting. Moreover, we consider the Baekdusan peridotite xenoliths to have been derived from a compositionally and texturally heterogeneous vertical mantle section beneath the Baekdusan volcano.

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