Diamonds and their mineral inclusions from the Renard kimberlites in Quebec

Babushkina²,

Mevedev³

et al. 2021

Preprint

In the subcratonic mantle beneath Leningrad pipe, West Ukukit field, Yakutia garnet thermoba-rometry give division to 7 horizons (paleosubduction slabs). Cr-bearing amphiboles >500 reveal a broad range changing from Cr- pargasitic hornblendes to pargasites, edinites, kataforites, К-richterites with increasing pressure determined with new amphibole thermobarometer. Cr-hornblendes compiles the high-temperature branch from 3.5 GPa to Moho for basaltic melt. Amphiboles in the middle eddinites and high-pressure interval reveal different PT ranges from 35 to 40 mw/m2. Richterites near the lithosphere base both trace low –T and convective branches. The amphiboles reveal the 9 geochemical groups. The low-temperature varieties reveal Eu minima and U, Ba, Sr peaks high LILE, Sr, Rb and troughs in Nb, Pb. While high –T varieties have no Eu dips and reveal higher HFSE. Clinopyroxenes and garnets show variable trace ele-ment patterns and divisions in groups eth the plume and subduction signs. The contrasting be-haviour of Ta and Nb is regulated by the rutile partition coefficients likely for primary eclogites. Subduction and Na and K (siliceous) types of fluids percolated through the mantle with abun-dant eclogites causing amphibolization at the different levels of the mantle column. The plume melts produced hybridism and more smooth trace element patterns in reacted minerals, clino-pyroxene. monomineral thermobarometry.

Section: Model Of the Mantle Evolution Of The Sclm Beneath The Ukukit Field And The Role Of The Subductionmentioning

confidence: 56%

Unique Amphibole Bearing Mantle Column Beneath the Leningrad Kimberlite Pipe, West Ukukit Field, NE Yakutia

Babushkina²,

Mevedev³

et al. 2021

Preprint

“…It was determined with the new version of the amphibole thermobarometry [51] (see appendix) calibrate using the experimental data [120][121][122][123][124][125][126][127][128][129][130][131][132][133][134]. It supported by the presence of amphiboles in diamond inclusions [135] and deepest metasomatites [128,136,137]. And as we can see from the Leningrad kimberlite xenocrysts they form continuous series in the thick lithoapheric mantle beneath Sibeian [138] and possibly other cratons.…”

Section: Model Of the Mantle Evolution Of The Sclm Beneath The Ukukit...mentioning

confidence: 99%

Unique Amphibole Bearing Mantle Column Beneath the Lenin-Grad Kimberlite Pipe, West Ukukit field, NE Yakutia.

Babushkina²,

Mevedev³

et al. 2022

Preprint

In the subcratonic lithospheric mantle (SCLM) beneath Leningrad pipe (West Ukukit field), Yakutia garnet thermobarometry allows us to identify seven horizons (paleo subduction slab). Microprobe data for Cr-bearing amphiboles >500 grains from mantle xenoliths and concentrates reveal a broad range of compositions changing from Cr- pargasitic hornblendes to pargasites, edinites, kataforites, К-richterites with increasing pressure determined with new amphibole ther-mobarometer constructed by the first author The low pressure (LP) Cr-hornblendes and pargasites compiles the high-temperature branch (90-60 mw/m2) from 3.5 GPa to Moho traced by basaltic cumulates. In the middle part of SCLM edinites mark 35 to 40 mw/m2 geotherms. At high pres-sures kataforites also vary in thermal conditions. Richterites near the lithosphere base trace both low –and high temperature convective branches. The amphiboles reveal divisions into 9 chemical groups. The melts coexistion with amphiboles have concave patters typical for subduction related melts. LP varieties reveal Eu inflection U, Rb, Ba, Sr peaks and deep troughs in HFSE (except Zr), Pb. The pargasites show high U peaks and relativle less HFSE depressions. Encreasing in pressure for edinites, kataforites and richterise are accompanied byrise in U and Zr peak gentling of depressions in Th, Sr, Nb and Hf and less in Nb,Ta, Hf and peak in Zr and also decrease in LREE and REE. Clinopyroxenes and garnets show variable trace element patterns and divisions in groups with the plume and subduction signatures. The contrasting behaviour of Ta and Nb is regulated by the rutile partition coefficients likely for primary eclogites. Subduction and Na and K (siliceous) types of fluids percolated through the mantle with abundant eclogites possibly was accompanied by amphibolization at the different levels through all the mantle column. The plume melts produced hybridism with the mantle metasomatic assembleges which created more smooth trace element patterns in reacted minerals, clinopyroxene. The new version of monomineral amphibole thermobarometry is suggested

“…In Canada, the oldest diamonds were found in the Archean Ca-alkaline lamprophyres (2.7Ba) in the Wawa district Ontario Superior craton. The other localities in Superior include the Renard kimberlites in Quebec with an age of 654-656 Ma [36,39,40] and the Attawapiskat kimberlites of age ~187-183 Ma [42] and Fort la Corne about 100 Ma [43].…”

Section: North Americamentioning

confidence: 99%

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

Logvinova²,

Spetsius³

et al. 2021

Preprint

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.