The origin of Type II diamonds as inferred from Cullinan mineral inclusions. / Korolev, Nester; Kopylova, Maya; Gurney, John J.; Moore, Andy E.; Davidson, Jim.
In: Mineralogy and Petrology, Vol. 112, 12.2018, p. 275-289.Research output: Contribution to journal › Article › peer-review
}
TY - JOUR
T1 - The origin of Type II diamonds as inferred from Cullinan mineral inclusions
AU - Korolev, Nester
AU - Kopylova, Maya
AU - Gurney, John J.
AU - Moore, Andy E.
AU - Davidson, Jim
PY - 2018/12
Y1 - 2018/12
N2 - We studied a suite of Cullinan diamonds (<0.3 ct) with mineral inclusions, which comprised 266 Type I and 75 blank Type II (<20 ppm N) diamonds, as classified by infrared spectroscopy. More than 90% (n = 68) of Type II diamonds do not luminesce. In contrast, 51.9% (n = 177) of Type I diamonds luminesce, with blue colors of different intensity. Carbon isotopic compositions of Type I and II diamonds are similar, with δ13CVPDB ranging from −2.1 to −7.7‰ for Type I diamonds (n = 25), and from −1.3 to −7.8‰ for Type II diamonds (n = 20). The Type II diamonds are sourced from three parageneses, lithospheric lherzolitic (45%), lithospheric eclogitic (33%), and sublithospheric mafic (22%). The lherzolitic suite contains Cr-pyrope, forsterite, enstatite, clinopyroxene and Cr-spinel formed at 1090–1530 °C and P = 4.6–7.0 GPa. Lithospheric eclogitic diamonds containing garnet, omphacite, kyanite and coesite comprise 33% of Type II diamonds. The sublithospheric mafic paragenesis is mainly represented by Cr-free majorite, various CaSiO3 phases and omphacite equilibrated at 11.6–26 GPa, in the transition zone and the lower mantle. The lherzolitic paragenesis predominates in Type II diamonds, whereas 79% Type I diamonds are sourced from eclogites. The higher incidence of sublithospheric inclusions was found in Type II diamonds, 22% against 6% in Type I diamonds. The similarity of the mineral parageneses and C isotopic compositions in the small Cullinan Type II and Type I diamonds indicate the absence of distinct mantle processes and carbon sources for formation of studied Type II diamonds. The parent rocks and the carbon sources generally vary for Type II diamonds within a kimberlite and between kimberlites.
AB - We studied a suite of Cullinan diamonds (<0.3 ct) with mineral inclusions, which comprised 266 Type I and 75 blank Type II (<20 ppm N) diamonds, as classified by infrared spectroscopy. More than 90% (n = 68) of Type II diamonds do not luminesce. In contrast, 51.9% (n = 177) of Type I diamonds luminesce, with blue colors of different intensity. Carbon isotopic compositions of Type I and II diamonds are similar, with δ13CVPDB ranging from −2.1 to −7.7‰ for Type I diamonds (n = 25), and from −1.3 to −7.8‰ for Type II diamonds (n = 20). The Type II diamonds are sourced from three parageneses, lithospheric lherzolitic (45%), lithospheric eclogitic (33%), and sublithospheric mafic (22%). The lherzolitic suite contains Cr-pyrope, forsterite, enstatite, clinopyroxene and Cr-spinel formed at 1090–1530 °C and P = 4.6–7.0 GPa. Lithospheric eclogitic diamonds containing garnet, omphacite, kyanite and coesite comprise 33% of Type II diamonds. The sublithospheric mafic paragenesis is mainly represented by Cr-free majorite, various CaSiO3 phases and omphacite equilibrated at 11.6–26 GPa, in the transition zone and the lower mantle. The lherzolitic paragenesis predominates in Type II diamonds, whereas 79% Type I diamonds are sourced from eclogites. The higher incidence of sublithospheric inclusions was found in Type II diamonds, 22% against 6% in Type I diamonds. The similarity of the mineral parageneses and C isotopic compositions in the small Cullinan Type II and Type I diamonds indicate the absence of distinct mantle processes and carbon sources for formation of studied Type II diamonds. The parent rocks and the carbon sources generally vary for Type II diamonds within a kimberlite and between kimberlites.
KW - Carbon isotopes
KW - Cullinan kimberlite
KW - Diamond inclusions
KW - Diamond paragenesis
KW - Photoluminescence
KW - Type II diamonds
KW - CARBON ISOTOPES
KW - CALIBRATION
KW - MANTLE PERIDOTITES
KW - KIMBERLITE
KW - NORTHERN SLAVE CRATON
KW - TRANSITION
KW - FINSCH
KW - NITROGEN
KW - GARNET PERIDOTITES
KW - GEOTHERMOBAROMETRY
UR - http://www.scopus.com/inward/record.url?scp=85049155223&partnerID=8YFLogxK
UR - http://www.mendeley.com/research/origin-type-ii-diamonds-inferred-cullinan-mineral-inclusions
U2 - 10.1007/s00710-018-0601-z
DO - 10.1007/s00710-018-0601-z
M3 - Article
AN - SCOPUS:85049155223
VL - 112
SP - 275
EP - 289
JO - Mineralogy and Petrology
JF - Mineralogy and Petrology
SN - 0930-0708
ER -
ID: 36111220