Research output: Contribution to journal › Article › peer-review
Paragenesis and complex zoning of olivine macrocrysts from unaltered kimberlite of the Udachnaya-East pipe, Yakutia : Relationship with the kimberlite formation conditions and evolution. / Sobolev, N. V.; Sobolev, A. V.; Tomilenko, A. A. et al.
In: Russian Geology and Geophysics, Vol. 56, No. 1-2, 01.01.2015, p. 260-279.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Paragenesis and complex zoning of olivine macrocrysts from unaltered kimberlite of the Udachnaya-East pipe, Yakutia
T2 - Relationship with the kimberlite formation conditions and evolution
AU - Sobolev, N. V.
AU - Sobolev, A. V.
AU - Tomilenko, A. A.
AU - Kovyazin, S. V.
AU - Batanova, V. G.
AU - Kuz'min, D. V.
PY - 2015/1/1
Y1 - 2015/1/1
N2 - Unaltered Mg-olivine (Fo=85-94) is a predominant mineral of the kimberlite block (serpentine-free) of the Udachnaya-East pipe, and it prevails in peridotite xenoliths and as inclusions in diamonds. The kimberlite of this pipe, like a series of hypabyssal kimberlites in other regions, contains two main types of olivine macrocrysts according to their size and morphology: those rounded or irregularly shaped (olivine I) and euhedral phenocrysts (olivine II), which are usually no larger than 0.5mm and very seldom reach 1mm in size. This study was focused on several thousand olivine samples assigned both to olivines I and to olivines II, with a gradual transition between them. Particular attention was paid to the search for mineral inclusions in olivine and for phenocrysts with a clear zoning. In the phenocryst cores of homogeneous composition, we have revealed orthopyroxene inclusions as well as clinopyroxene (chrome-diopside and chrome-omphacite) inclusions with wide variations in the Na2O and Cr2O3 contents, significantly higher than the previously established ones: up to 6.00wt.% Na2O and 4.23wt.% Cr2O3. Convincing evidence for the high-pressure origin of the olivine macrocryst cores is the presence of pyrope inclusions with 1.41-9.14wt.% &2O3, 4.64-6.61wt.% CaO, and Mg#=75.6-83.7 in six samples, which testifies to the high-pressure lherzolite paragenesis of the phenocrysts cores. The cores of the studied olivine phenocrysts are identical in the contents of Ni, Co, Ca, Cr, and Mn to olivines from diamonds and peridotite xenoliths. However, they differ significantly in the steady elevated Ti content, equal to 100-300ppm for the majority of the phenocrysts, including those containing pyroxene and pyrope inclusions.
AB - Unaltered Mg-olivine (Fo=85-94) is a predominant mineral of the kimberlite block (serpentine-free) of the Udachnaya-East pipe, and it prevails in peridotite xenoliths and as inclusions in diamonds. The kimberlite of this pipe, like a series of hypabyssal kimberlites in other regions, contains two main types of olivine macrocrysts according to their size and morphology: those rounded or irregularly shaped (olivine I) and euhedral phenocrysts (olivine II), which are usually no larger than 0.5mm and very seldom reach 1mm in size. This study was focused on several thousand olivine samples assigned both to olivines I and to olivines II, with a gradual transition between them. Particular attention was paid to the search for mineral inclusions in olivine and for phenocrysts with a clear zoning. In the phenocryst cores of homogeneous composition, we have revealed orthopyroxene inclusions as well as clinopyroxene (chrome-diopside and chrome-omphacite) inclusions with wide variations in the Na2O and Cr2O3 contents, significantly higher than the previously established ones: up to 6.00wt.% Na2O and 4.23wt.% Cr2O3. Convincing evidence for the high-pressure origin of the olivine macrocryst cores is the presence of pyrope inclusions with 1.41-9.14wt.% &2O3, 4.64-6.61wt.% CaO, and Mg#=75.6-83.7 in six samples, which testifies to the high-pressure lherzolite paragenesis of the phenocrysts cores. The cores of the studied olivine phenocrysts are identical in the contents of Ni, Co, Ca, Cr, and Mn to olivines from diamonds and peridotite xenoliths. However, they differ significantly in the steady elevated Ti content, equal to 100-300ppm for the majority of the phenocrysts, including those containing pyroxene and pyrope inclusions.
KW - Clinopyroxene
KW - Diamond
KW - Kimberlite
KW - Olivine
KW - Paragenesis
KW - Pyrope
KW - Trace elements
UR - http://www.scopus.com/inward/record.url?scp=84925305849&partnerID=8YFLogxK
U2 - 10.1016/j.rgg.2015.01.019
DO - 10.1016/j.rgg.2015.01.019
M3 - Article
AN - SCOPUS:84925305849
VL - 56
SP - 260
EP - 279
JO - Russian Geology and Geophysics
JF - Russian Geology and Geophysics
SN - 1068-7971
IS - 1-2
ER -
ID: 25763909