Composition of primary kimberlite magma : constraints from melting and diamond dissolution experiments. / Sokol, A. G.; Khokhryakov, A. F.; Palyanov, Yu N.
In: Contributions to Mineralogy and Petrology, Vol. 170, No. 3, 26, 01.10.2015.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Composition of primary kimberlite magma
T2 - constraints from melting and diamond dissolution experiments
AU - Sokol, A. G.
AU - Khokhryakov, A. F.
AU - Palyanov, Yu N.
PY - 2015/10/1
Y1 - 2015/10/1
N2 - Experiments are applied to constrain the composition of primary kimberlitic magmas which were in equilibrium with lithospheric peridotite and could resorb the entrained diamond to form typical dissolution features. The experiments are run on samples of a model carbonatite and a melt of the Udachnaya kimberlite at 6.3 GPa and 1400 °C, and at unbuffered or Re–ReO2-buffered oxygen fugacity (1–2 log units above Ni–NiO). Near-liquidus dry Fe3+-free carbonatitic melt (derived from carbonated harzburgite) is saturated with the Ol–Grt–Opx–Mgs assemblage and is almost inert to diamond. Carbonatitic melts that bear 4.6–6.8 wt% Fe2O3 or 1.5 wt% H2O are in equilibrium only with Mgs ± Ol near the liquidus. Dissolution of diamond by these melts produces surface textures uncommon (corrosion sculptures) or common (negative-oriented trigons, shield-shaped laminae and elongate hillocks) to kimberlitic diamonds. The near-liquidus melt of the Udachnaya kimberlite (Yakutia) with 10–12 wt% H2O is saturated with the Ol–Grt–Cpx assemblage and may result from melting of carbonated garnet-bearing wehrlite. Hydrous kimberlitic melt likewise resorbs diamonds forming typical negative-oriented trigons, shield-shaped laminae and elongate hillocks on their surfaces. Therefore, the melts that could originate in the thermal conditions of subcratonic lithosphere, entrain diamond and dissolve it to produce dissolution features on crystal surfaces, were compositionally close to kimberlite (16–19 wt% SiO2) and rich in H2O. Dry Fe3+-bearing carbonatites with fO2 controlled by the ferric/ferrous equilibrium slightly above the Ni–NiO buffer cannot be diamond carriers.
AB - Experiments are applied to constrain the composition of primary kimberlitic magmas which were in equilibrium with lithospheric peridotite and could resorb the entrained diamond to form typical dissolution features. The experiments are run on samples of a model carbonatite and a melt of the Udachnaya kimberlite at 6.3 GPa and 1400 °C, and at unbuffered or Re–ReO2-buffered oxygen fugacity (1–2 log units above Ni–NiO). Near-liquidus dry Fe3+-free carbonatitic melt (derived from carbonated harzburgite) is saturated with the Ol–Grt–Opx–Mgs assemblage and is almost inert to diamond. Carbonatitic melts that bear 4.6–6.8 wt% Fe2O3 or 1.5 wt% H2O are in equilibrium only with Mgs ± Ol near the liquidus. Dissolution of diamond by these melts produces surface textures uncommon (corrosion sculptures) or common (negative-oriented trigons, shield-shaped laminae and elongate hillocks) to kimberlitic diamonds. The near-liquidus melt of the Udachnaya kimberlite (Yakutia) with 10–12 wt% H2O is saturated with the Ol–Grt–Cpx assemblage and may result from melting of carbonated garnet-bearing wehrlite. Hydrous kimberlitic melt likewise resorbs diamonds forming typical negative-oriented trigons, shield-shaped laminae and elongate hillocks on their surfaces. Therefore, the melts that could originate in the thermal conditions of subcratonic lithosphere, entrain diamond and dissolve it to produce dissolution features on crystal surfaces, were compositionally close to kimberlite (16–19 wt% SiO2) and rich in H2O. Dry Fe3+-bearing carbonatites with fO2 controlled by the ferric/ferrous equilibrium slightly above the Ni–NiO buffer cannot be diamond carriers.
KW - Diamond dissolution
KW - Etch forms
KW - Experiment
KW - Fluid
KW - Kimberlite
KW - Magma
KW - Mantle
KW - Water
UR - http://www.scopus.com/inward/record.url?scp=84940526279&partnerID=8YFLogxK
U2 - 10.1007/s00410-015-1182-z
DO - 10.1007/s00410-015-1182-z
M3 - Article
AN - SCOPUS:84940526279
VL - 170
JO - Contributions to Mineralogy and Petrology
JF - Contributions to Mineralogy and Petrology
SN - 0010-7999
IS - 3
M1 - 26
ER -
ID: 25726539