New Identity of the Kimberlite Melt: Constraints from Unaltered Diamondiferous Udachnaya – East Pipe Kimberlite, Russia - Advances in Data, Methods, Models and Their Applications in Geoscience - page 197

b

a

P

ol

P

ac

ol phl

P

phl

mtc

ol

mtc

P

P

P

s

P

phl

h

mtc

d

c

phl

phl

ol

P

phl

phl ac

P

phl

ac

P

P

P

ol

phl

ol

ol

P

Fig. 12. Backscattered electron images of polished surfaces of the Udachnaya-East
kimberlites (a — host kimberlite; b-d — perovskite- and phlogopite-rich clast), showing
typical groundmass assemblage of co-crystallised chlorides, halite (h) and sylvite (s), alkali
carbonates (ac), perovskite (P), phlogopite (phl), monticellite (mtc) and olivine (ol).

Perovskite is particularly abundant (10%) in sample UV31k-05 (Fig. 12 b-d), an ultramafic
(31 wt% MgO), spherical clast (“nucleated autholith” after Mitchell, 1986) found at ~500 m
depth in the pipe (Kamenetsky et al., 2009c). Accumulation of perovskite in kimberlite
magmas is not unusual and has been reported in other kimberlites (Dawson & Hawthorne,
1973; Mitchell, 1986). The autolith and its host kimberlite are broadly similar in composition,
and have the same groundmass assemblage, including interstitial carbonates, chlorides and
perovskite (Fig. 2, 12a). Importantly, perovskite is interstitial to phlogopite crystals (Fig. 2b),
and thus appears to be later than phlogopite in crystallisation sequence. On the other hand,
textural relationships between perovskite and alkali carbonates and chlorides (Fig. 12a, c, d)
suggest their co-precipitation from the melt. The melt that crystallised olivine and