scholarly journals Deciphering the composition and structure of Wyoming craton mantle lithosphere: insights from peridotite xenoliths

2019 ◽  
Keyword(s):  
Mantle Lithosphere ◽  
Wyoming Craton ◽  
Peridotite Xenoliths ◽  
Composition And Structure

Geothermobarometry of spinel peridotites from southern British Columbia: implications for the thermal conditions in the upper mantle

2013 ◽  
Vol 50 (10) ◽  
pp. 1019-1032 ◽  
Author(s):  
A.M.R. Greenfield ◽  
E.D. Ghent ◽  
J.K. Russell
Keyword(s):  
British Columbia ◽  
Microprobe Analysis ◽  
Thermal Conditions ◽  
Spinel Lherzolite ◽  
Mantle Lithosphere ◽  
Exchange Reactions ◽  
Alkali Basalts ◽  
South Central ◽  
Peridotite Xenoliths ◽  
Mineral Pair

Spinel lherzolite xenoliths within alkali basalts exposed at Rayfield River and Big Timothy Mountain, south-central British Columbia, represent samples of the underlying lithospheric mantle. Electron microprobe analysis shows that most xenoliths comprise compositionally homogeneous grains of olivine, orthopyroxene, clinopyroxene, and spinel. We applied the following mineral-pair geothermometers to these rocks: orthopyroxene–clinopyroxene, spinel–orthopyroxene, and spinel–olivine. Temperatures calculated using the Brey and Köhler calibration of two-pyroxene thermometry were constrained in pressure by being required to lie on a model geotherm we develop for this region of B.C. The model geotherm is constrained to produce a temperature at the Moho (33 km) of 825 ± 25 °C to match the lowest temperature peridotite xenoliths recovered in this study. Although the overall effect of pressure on the temperature calculations is negligible (∼2 °C for 0.1 GPa), the simultaneous solution of the model geotherm and the pressure-dependent Brey–Köhler two-pyroxene thermometry removes the need for adopting an arbitrary pressure. We take these temperatures to represent peak mantle lithosphere temperatures. Fourteen Rayfield River xenoliths return two-pyroxene temperatures between 841 and 962 °C corresponding to depths of 34–42 km. Orthopyroxene–spinel and olivine–spinel results are 889 ± 60 and 825 ± 88 °C, respectively. Five Big Timothy xenoliths have two-pyroxene temperatures spanning 840–1058 °C and corresponding to depths of 34–48 km. Mean orthopyroxene–spinel and olivine–spinel temperatures are 844 ± 63 and 896 ± 232 °C, respectively. We argue that the differences in ranges of temperature do not represent closure temperatures imposed during cooling either in the mantle or during transport by the magma. Rather, these differences reflect differences in the original calibrations of the geothermometers or different degrees of equilibration in exchange reactions in dry rocks. Isochemical phase diagrams (pseudosections) constrain the pressure–temperature (P–T) field in which spinel is stable. These diagrams suggest that the spinel-bearing peridotites equilibrated at pressures ranging from ∼9.6 to 14 kbar (10 kbar = 1 GPa).

Varieties of eclogites and their positions in the cratonic mantle lithosphere revealed by Jd-Di thermobarometry and trace element geochemistry

2021 ◽  
Author(s):  
Igor Ashchepkov ◽  
Alla Logvinova ◽  
Zdislav Spetsius ◽  
Theodoros Ntaflos ◽  
Hilary Downes ◽  
...  
Keyword(s):  
Trace Element ◽  
Lithospheric Mantle ◽  
Middle Part ◽  
Trace Element Geochemistry ◽  
Mantle Lithosphere ◽  
Ministry Of Education ◽  
Element Geochemistry ◽  
Wyoming Craton ◽  
Partial Melts ◽  
Diamond Inclusions

<p>The PT conditions and position of different groups of eclogites in the subcratonic lithospheric mantle (SCLM) worldwide has been established using clinopyroxene Jd-Di thermobarometry for different cratons and kimberlite localities. Beneath Siberia, Fe-eclogites found within the 3.0-4.0 GPa  and  were probably formed in Early Archean times forming the base of the lithosphere. In the Middle and Late Archean, eclogites were melted during subduction creating restite and cumulates from partial melts traced ascending channels.</p><p>High-Mg eclogites (partial melts or arc cumulates) are related to low-T geotherms. Melt-metasomatized eclogites trace a high-T geotherm and are often close to the middle part of the mantle lithosphere. Abundant eclogitic diamond inclusions from Siberia also mostly belong to the middle part of the lithosphere. </p><p>Ca-rich eclogites from Precambrian kimberlites of India are located in the middle lithospheric mantle whereas those entrained in Phanerozoic magmas are derived from the lithosphere base. In the Wyoming craton, kimberlites carry eclogite xenoliths captured from the 4.0-2.5 GPa interval.  In mantle lithosphere sampled by Proterozoic kimberlites, Ca-rich eclogites and grospydites occur in the 4.0-5.0 GPa interval. South Africa HT eclogite and diamond inclusions from the Proterozoic Premier kimberlites are derived from the deeper part of the mantle lithosphere and trace a high-T geotherm at depths of 7.0-4.0 GPa showing an increase in Fe upwards in the mantle section. Similar trends are common beneath the Catoca cluster kimberlites in Angola.</p><p>Mantle eclogites have clinopyroxenes and garnet trace element patterns with opposite inclinations determined by KDs with melts. Flatter and bell-like REE patterns with Eu anomalies? HFSE troughs and U, Pb peaks are common for MORB-type basaltic eclogites. High-Mg eclogites show less fractionated incompatible element patterns.  LILE-enrichments and HFSE troughs are typical for kyanite-bearing eclogites. Clinopyroxenes from diamond-bearing eclogites show lower REE and troughs in Nb and Zr, peaks in Pb and U concentrations compared to barren eclogites with round smooth trace element patterns and small depressions in Pb and Ba.</p><p>Support: RFBR 19-05-00788,  Russian Ministry of Education and Science</p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.2c9ebbff3c0067455141161/sdaolpUECMynit/12UGE&app=m&a=0&c=4b235af5b7a8029fc48da92cba3afd9d&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.d13207104c0065755141161/sdaolpUECMynit/12UGE&app=m&a=0&c=d8f9503af82277872a4263e84ff9e0cf&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.6b7fb9204c0063955141161/sdaolpUECMynit/12UGE&app=m&a=0&c=6b87575d150326ed00a773ccd740ef07&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.d6683a304c0060165141161/sdaolpUECMynit/12UGE&app=m&a=0&c=d034421517782917a447efa1c07c6281&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.336759404c0065265141161/sdaolpUECMynit/12UGE&app=m&a=0&c=b4a9255ae696984c788c9868caf7be97&ct=x&pn=gnp.elif&d=1" alt=""></p>

Wyoming Craton Mantle Lithosphere: Reconstructions Based on Xenocrysts from Sloan and Kelsey Lake Kimberlites

2013 ◽  
pp. 13-27 ◽  
Author(s):  
I. V. Ashchepkov ◽  
H. Downes ◽  
R. Mitchell ◽  
N. V. Vladykin ◽  
H. Coopersmith ◽  
...  
Keyword(s):  
Mantle Lithosphere ◽  
Wyoming Craton

scholarly journals Composition of the mantle lithosphere beneath south-central Laurentia: Evidence from peridotite xenoliths, Knippa, Texas

Geosphere ◽  
2011 ◽  
Vol 7 (3) ◽  
pp. 710-723 ◽  
Author(s):  
Urmidola Raye ◽  
Elizabeth Y. Anthony ◽  
Robert J. Stern ◽  
Jun-Ichi Kimura ◽  
Minghua Ren ◽  
...  
Keyword(s):  
Mantle Lithosphere ◽  
South Central ◽  
Peridotite Xenoliths

Characterization of hydration in the mantle lithosphere: Peridotite xenoliths from the Ontong Java Plateau as an example

Lithos ◽  
2015 ◽  
Vol 212-215 ◽  
pp. 189-201 ◽  
Author(s):  
Sylvie Demouchy ◽  
Akira Ishikawa ◽  
Andréa Tommasi ◽  
Olivier Alard ◽  
Shantanu Keshav
Keyword(s):  
Mantle Lithosphere ◽  
Ontong Java Plateau ◽  
Peridotite Xenoliths
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