scholarly journals Thermobarometry of Diamond Inclusions: Evidence Mantle Evolution beneath Siberian Craton and Archean Cratons Worldwide.

2021 ◽  
Author(s):  
Igor Ashchepkov ◽  
Alla Logvinova ◽  
Zdislav Spetsius ◽  
Hilary Downes
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Middle Part ◽  
East European ◽  
Mantle Evolution ◽  
Mineral Inclusions ◽  
Amazonian Craton ◽  
Partial Melts ◽  
Continental Growth ◽  
Diamond Inclusions

Thermobarometric calculations for mineral inclusions in diamonds provide a systematic comparison of PTXFO2 conditions for different cratons worldwide, using a database of 4440 mineral EPMA analyses. Beneath all cratons, the cold branch of the mantle geotherm (35-32 mWm−2) relates to the sub-Ca garnets and rarely omphacitic diamond inclusions, referring to major continental growth events in Archean. High-temperature plume-related geotherms are common in Proterozoic kimberlites such as Premier, Mesozoic – Roberts Victor etc. and are common in Slave and Siberian cratons. In mobile belts: Limpopo, Magondi, Ural Ural, Khapchan belts and in the marginal parts of cratons like Kimberly Australia pyroxenitic and eclogitic pyroxenes and garnets prevail. The pyropes in the mobile belts are more Fe- and Ca-rich, in central parts of cratons, the peridotitic associations with sub- Ca pyropes prevail. The accretionary complexes like Khapchan and Magondi belts a thick eclogite-pyroxenite lens is highly diamondiferous. Comparison by minerals shows that the PT estimates for clinopyroxenes and orthopyroxene from peridotites and eclogites are representing mainly the middle part of the sub-lithospheric mantle while garnets gives more high-pressure estimates. refer to eclogites and reflect the processes of the differentiation during migration of partial melts. This produces the trends of joint decreasing Mg’ and pressures. The PT for the chromites reflect conditions just above the lithosphere-asthenosphere boundary and mainly were formed due to interaction with the hydrous plume protokimberlite melts. Archean diamond inclusions from Wawa province Canada are represented by Ca-enrich pyropes giving low-temperature conditions. Inclusions from younger kimberlites in Superior and Slave (and Siberian and East European ) cratons show complex high-temperature geotherms due to plumes influence. Peridotite garnets beneath the Amazonian craton indicate complex layering in the lithosphere base and a pyroxene layer in the middle part of SCLM. Diamond inclusions from the Kimberley craton of Australia show the greatest variations in the temperatures and composition.

Mantle evolution beneath Siberian and Archean cratons worldwide: evidence from thermobarometry of diamond inclusions

2021 ◽  
Author(s):  
Igor Ashchepkov ◽  
Alla Logvinova ◽  
Zdislav Spetsius ◽  
Hilary Downes
Keyword(s):  
High Temperature ◽  
Stability Field ◽  
Ministry Of Education ◽  
Magmatic System ◽  
The Urals ◽  
Mantle Evolution ◽  
Amazonian Craton ◽  
Superior Craton ◽  
Continental Growth ◽  
Diamond Inclusions

<p>Thermobarometric calculations for diamond inclusions allowed systematically compare the pressure-temperature, fO<sub>2</sub> conditions in the mantle beneath different cratons worldwide. Beneath Siberia, Kaapvaal, and other cratons, the cold geotherm branch, reconstructed using sub-Ca garnets and eclogitic diamond inclusions relates to a major event of continental growth. Colder geotherms (32 mWm<sup>-2</sup>) are related to early subduction. High-temperature plume-related geotherms are common for inclusions in Proterozoic kimberlites beneath Africa. In mobile belts such as Magondi, Ural and Limpopo belts, the amount of pyroxenitic and eclogitic garnets is greater than in the central cores of cratons where dunitic pyropes prevail. Beneath the Khapchan accretionary terrane in Siberia, eclogites are highly diamondiferous. In the mantle beneath Archean cratons, peridotite pyropes differ in CaO content. Depleted peridotitic and Fe-eclogitic diamond inclusions are abundant beneath the Zimbabwe craton, whereas beneath the Congo and West Africa, diamond inclusions yield higher temperatures. Beneath North American cratons, diamond-bearing eclogites are mainly Mg-type. In the Superior craton, Archean diamond inclusions from Wawa are Fe-, Ca-rich pyropes. The diamond inclusions of the Slave and Superior cratons give complex high-temperature plume-related geotherms. Beneath the Amazonian craton, peridotite garnets indicate complex layering at the base of the lithosphere and a pyroxene-rich layer in the middle. Fe-Mg eclogites from a high-temperature trend in which FeO increases with decreasing pressure. Diamond inclusions from the Kimberley craton of Australia show the greatest variations in temperature and composition. The  Eastern Europe craton and the Urals have greater amounts of eclogitic diamond inclusions and advective geotherms. Estimated pressure conditions lower than diamond stability field is due to exceeding pressures around magmatic system transferred by hydraulic forces from depth. </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.da049dd8a90069875421161/sdaolpUECMynit/12UGE&app=m&a=0&c=bc51032afd75e05d7c9ddb145ed4953a&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.f989a4f8a90062185421161/sdaolpUECMynit/12UGE&app=m&a=0&c=2d7358755816c2ee4f19e2586bb081b0&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.c8c08309a90067285421161/sdaolpUECMynit/12UGE&app=m&a=0&c=934f08823572f27e82297ebde537172f&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.d92e0d19a90063585421161/sdaolpUECMynit/12UGE&app=m&a=0&c=70ef014588742491519d2b3cd2ded5fc&ct=x&pn=gnp.elif&d=1" alt=""></p><p><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gnp.fc965d29a90069685421161/sdaolpUECMynit/12UGE&app=m&a=0&c=f4c5b7511a5379a41448d7bd48601f32&ct=x&pn=gnp.elif&d=1" alt=""></p>

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>

scholarly journals Olivine in komatiite records origin and travel from the deep upper mantle

Geology ◽  
2021 ◽  
Author(s):  
Allan Wilson ◽  
Robert Bolhar
Keyword(s):  
High Pressure ◽  
Upper Mantle ◽  
Direct Evidence ◽  
Core Mantle Boundary ◽  
Mantle Evolution ◽  
Mineral Inclusions ◽  
Naturally Occurring ◽  
Deep Mantle ◽  
Earth’S Early Mantle ◽  
Insight Into

The deep upper mantle is the main source of high-temperature magmatism, but the only known naturally occurring samples of high-pressure mantle constituents are mineral inclusions in diamonds. Trace elements in olivine crystals from the 3.33 Ga Commondale Greenstone Belt in South Africa reveal that these crystals formed in the deep upper mantle as high-pressure phenocrysts, and some perhaps even formed in the mantle transition zone (410–600 km) where they began as wadsleyite. The crystals were entrained within ascending komatiite magma and conveyed to the surface. The olivine crystals have the highest contents of Al2O3 (0.3 wt%) recorded in any terrestrial olivine, which is indicative of formation at high pressure. The deep mantle gave rise to Archean komatiites, extraordinarily hot magmas (up to 1700 °C), which provide insight into Earth’s early mantle evolution and the formation of most ancient continental and oceanic crust. In spite of extensive research since their discovery over 50 years ago, the origins of komatiites have remained contentious. Plumes—thermochemical instabilities originating at the core-mantle boundary—are the most likely source, but no direct evidence of a deep mantle origin of komatiite has yet been recognized.

Microstructural Study of Diamond Deformed Under High Pressure and Temperature

1985 ◽  
Vol 43 ◽  
pp. 230-231
Author(s):  
E. F. Koch
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Lattice Structure ◽  
Diamond Particle ◽  
Polycrystalline Diamond ◽  
Sintering Process ◽  
Ion Milling ◽  
Sintered Compact ◽  
Transmission Electron ◽  
High Pressure Sintering

Because of the extremely rigid lattice structure of diamond, generating new dislocations or moving existing dislocations in diamond by applying mechanical stress at ambient temperature is very difficult. Analysis of portions of diamonds deformed under bending stress at elevated temperature has shown that diamond deforms plastically under suitable conditions and that its primary slip systems are on the ﹛111﹜ planes. Plastic deformation in diamond is more commonly observed during the high temperature - high pressure sintering process used to make diamond compacts. The pressure and temperature conditions in the sintering presses are sufficiently high that many diamond grains in the sintered compact show deformed microtructures.In this report commercially available polycrystalline diamond discs for rock cutting applications were analyzed to study the deformation substructures in the diamond grains using transmission electron microscopy. An individual diamond particle can be plastically deformed in a high pressure apparatus at high temperature, but it is nearly impossible to prepare such a particle for TEM observation, since any medium in which the diamond is mounted wears away faster than the diamond during ion milling and the diamond is lost.

YSS YXM4

Alloy Digest ◽  
2019 ◽  
Vol 68 (11) ◽  
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Physical Properties ◽  
Tool Steel ◽  
High Speed ◽  
Temperature Performance

Abstract YSS YXM4 is a cobalt-alloyed molybdenum high-speed tool steel with resistance to abrasion, seizure, and deformation under high pressure. This datasheet provides information on composition, physical properties, and hardness. It also includes information on high temperature performance. Filing Code: TS-780. Producer or source: Hitachi Metals America, Ltd.

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