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

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.

Download Full-text

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

American Mineralogist ◽

10.2138/am-2020-7316 ◽

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.

Download Full-text

The Formation and Evolution of Cratonic Mantle Lithosphere – Evidence from Mantle Xenoliths

Treatise on Geochemistry ◽

10.1016/b978-0-08-095975-7.00205-9 ◽

2014 ◽

pp. 255-292 ◽

Cited By ~ 35

Author(s):

D.G. Pearson ◽

N. Wittig

Keyword(s):

Mantle Xenoliths ◽

Mantle Lithosphere ◽

Cratonic Mantle ◽

Formation And Evolution

Download Full-text

Phlogopite-pargasite coexistence in an oxygen reduced spinel-peridotite ambient

Scientific Reports ◽

10.1038/s41598-021-90844-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Costanza Bonadiman ◽

Valentina Brombin ◽

Giovanni B. Andreozzi ◽

Piera Benna ◽

Massimo Coltorti ◽

...

Keyword(s):

Oxygen Fugacity ◽

Upper Mantle ◽

Mantle Xenoliths ◽

Spinel Peridotite ◽

Simultaneous Formation ◽

Empirical Potentials ◽

Elastic Data ◽

Mineralogical Study ◽

Semi Empirical ◽

T Locus

AbstractThe occurrence of phlogopite and amphibole in mantle ultramafic rocks is widely accepted as the modal effect of metasomatism in the upper mantle. However, their simultaneous formation during metasomatic events and the related sub-solidus equilibrium with the peridotite has not been extensively studied. In this work, we discuss the geochemical conditions at which the pargasite-phlogopite assemblage becomes stable, through the investigation of two mantle xenoliths from Mount Leura (Victoria State, Australia) that bear phlogopite and the phlogopite + amphibole (pargasite) pair disseminated in a harzburgite matrix. Combining a mineralogical study and thermodynamic modelling, we predict that the P–T locus of the equilibrium reaction pargasite + forsterite = Na-phlogopite + 2 diopside + spinel, over the range 1.3–3.0 GPa/540–1500 K, yields a negative Clapeyron slope of -0.003 GPa K–1 (on average). The intersection of the P–T locus of supposed equilibrium with the new mantle geotherm calculated in this work allowed us to state that the Mount Leura xenoliths achieved equilibrium at 2.3 GPa /1190 K, that represents a plausible depth of ~ 70 km. Metasomatic K-Na-OH rich fluids stabilize hydrous phases. This has been modelled by the following equilibrium equation: 2 (K,Na)-phlogopite + forsterite = 7/2 enstatite + spinel + fluid (components: Na2O,K2O,H2O). Using quantum-mechanics, semi-empirical potentials, lattice dynamics and observed thermo-elastic data, we concluded that K-Na-OH rich fluids are not effective metasomatic agents to convey alkali species across the upper mantle, as the fluids are highly reactive with the ultramafic system and favour the rapid formation of phlogopite and amphibole. In addition, oxygen fugacity estimates of the Mount Leura mantle xenoliths [Δ(FMQ) = –1.97 ± 0.35; –1.83 ± 0.36] indicate a more reducing mantle environment than what is expected from the occurrence of phlogopite and amphibole in spinel-bearing peridotites. This is accounted for by our model of full molecular dissociation of the fluid and incorporation of the O-H-K-Na species into (OH)-K-Na-bearing mineral phases (phlogopite and amphibole), that leads to a peridotite metasomatized ambient characterized by reduced oxygen fugacity.

Download Full-text

Proterozoic lithosphere in Marie Byrd Land, West Antarctica: Re–Os systematics of spinel peridotite xenoliths

Chemical Geology ◽

10.1016/s0009-2541(02)00410-2 ◽

2003 ◽

Vol 196 (1-4) ◽

pp. 131-145 ◽

Cited By ~ 38

Author(s):

Monica R. Handler ◽

Richard J. Wysoczanski ◽

John A. Gamble

Keyword(s):

Spinel Peridotite ◽

West Antarctica ◽

Peridotite Xenoliths

Download Full-text

Depleted and enriched mantle processes under the Rio Grande rift: spinel peridotite xenoliths

Contributions to Mineralogy and Petrology ◽

10.1007/s00410-007-0183-y ◽

2007 ◽

Vol 154 (2) ◽

pp. 135-151 ◽

Cited By ~ 13

Author(s):

Y. Kil ◽

R. F. Wendlandt

Keyword(s):

Rio Grande ◽

Rio Grande Rift ◽

Spinel Peridotite ◽

Enriched Mantle ◽

Peridotite Xenoliths ◽

Mantle Processes

Download Full-text

Spinel-peridotite xenoliths from Kapfenstein (Graz Basin, Eastern Austria): A geochemical and petrological study

Mineralogy and Petrology ◽

10.1007/bf01161620 ◽

1996 ◽

Vol 57 (1-2) ◽

pp. 23-50 ◽

Cited By ~ 27

Author(s):

O. Vasellil ◽

H. Downes ◽

M. F. Thirlwall ◽

R. Vannucci ◽

N. Coradossi

Keyword(s):

Spinel Peridotite ◽

Peridotite Xenoliths ◽

Eastern Austria

Download Full-text

Minor elements in olivine from spinel lherzolite xenoliths: implications for thermobarometry

Mineralogical Magazine ◽

10.1180/minmag.1997.061.405.09 ◽

1997 ◽

Vol 61 (405) ◽

pp. 257-269 ◽

Cited By ~ 59

Author(s):

Suzanne Y. O'Reilly ◽

D. Chen ◽

W. L. Griffin ◽

C. G. Ryan

Keyword(s):

Trace Element ◽

Garnet Peridotite ◽

Spinel Peridotite ◽

Spinel Lherzolite ◽

Proton Microprobe ◽

Minor Elements ◽

Spinel Lherzolites ◽

Peridotite Xenoliths ◽

Trace Element Contents ◽

Element Contents

AbstractThe proton microprobe has been used to determine contents of Ca, Ti, Ni, Mn and Zn in the olivine of 54 spinel lherzolite xenoliths from Australian and Chinese basalts. These data are compared with proton-probe data for Ni, Mn and Zn in the olivine of 180 garnet peridotite xenoliths from African and Siberian kimberlites. Fe, Mn, Ni and Zn contents are well-correlated; because the spinel lherzolite olivines have higher mean Fe contents than garnet peridotite olivines (average Fo89.6vs. Fo90–92) they also have lower Ni and higher Mn contents. Zn and Fe are well-correlated in garnet peridotite olivine, but in spinel peridotites this relationship is perturbed by partitioning of Zn into spinel. None of these elements shows significant correlation with temperature. Consistent differences in trace-element contents of olivines in the two suites is interpreted as reflecting the greater degree of depletion of Archean garnet peridotites as compared to Phanerozoic spinel lherzolites. Ca and Ti contents of spinel-peridotite olivine are well correlated with one another, and with temperature as determined by several types of geothermometer. However, Ca contents are poorly correlated with pressure as determined by the Ca-in-olivine barometer of Köhler and Brey (1990). This reflects the strong T-dependence of this barometer: the uncertainty in pressure (calculated by this method) which is produced by the ±50°C uncertainty expected of any geothermometer is ca ± 8 kbar, corresponding to the entire width of the spinel-lherzolite field at 900–1200°C.

Download Full-text