Petrochemistry and geochemistry of kimberlites from different provinces of the world Текст научной статьи по специальности «Науки о Земле и смежные экологические науки»

RUSSIAN JOURNAL OF EARTH SCIENCES, VOL. 4, NO. 6, PAGES 433-452, DECEMBER 2002

Petrochemistry and geochemistry of kimberlites from different provinces of the world

I. V. Ilupin and I. A. Roshchina

Central Research Institute for Geological Exploration

Abstract. This paper summarizes the data available on the concentrations of major and trace elements in kimberlites from various provinces of the world. Arithmetic means were calculated for individual kimberlite pipes and dikes, for groups of bodies from individual regions, and for the whole data sample. Some of the most interesting elements and ratios between them are compared and correlation coefficients are offered. Each of the objects of study was found to have its own petrochemical and geochemical characteristics. The kimberlites of the Gondwana group were found to be rich in K, P, La, Th, Zr, and Nb and poor in Ca. Some of the patterns established for the kimberlites of Siberia appeared to be common for all kimberlites, this suggesting some common trend of the deep material evolution during the formation of kimberlite magma and its rise to the ground surface.

Introduction

Kimberlites are of great interest for geologists as the deepest igneous rocks which remove mantle rock xenoliths (nodules) to the ground surface. Most of the papers published on the topic of kimberlites are devoted to the study of these xenoliths including both the rocks as a whole and the minerals composing them. At the same time much less attention is given to kimberlites themselves. This can be accounted for, partly, by the fact that kimberlite pipes are mostly filled with breccias containing an abundant xenogenic material (fragments of intruded rocks), which is hard to remove during the preparation of specimens to be analyzed. At the same time, as mentioned by Fresq et al. [1975], “Particular attention was given to “immobile” incompatible elements such as Ti, P, Nb, Ta, Zr, Hf, Ba, Sr, and the REE which, due to their high abundance in kimberlites and related rocks, must have been least affected by crustal contamination.” At the same time, when dealing with kimberlite breccia samples, one should try to remove foreign fragments as carefully as possible. The most confident analytical results are those that are accompanied by remarks, such as, “Great care was taken

Copyright 2002 by the Russian Journal of Earth Sciences.

Paper number TJE02111.

ISSN: 1681-1208 (online)

The online version of this paper was published 10 December 2002. URL: http://rjes.wdcb.ru/v04/tje02111/tje02111.htm

to remove all xenolithic and extensively altered material, as well as secondary veins.” [Scott Smith et al., 1984].

Until recently, information on the contents of macro-and microcomponents in kimberlites could be derived only from the publications dealing with kimberlites from Siberia, South Africa, India, Greenland, and some single localities in Canada and the USA. When generalizing the data available for a limited number of the objects of study, one of the authors of this paper [Ilupin, 1990] concluded that the kimberlites from the Southern Siberian Province were unique in terms of their low concentrations of barium, REE, thorium, zircon, and phosphorus.

In this paper we report information (collected mainly from publications of 1984-2001) about rock-forming, minor, and rare elements in the kimberlites of Canada, the USA, Greenland, Finland, the northwestern territories of Russia, Siberia, China, India, Australia, South Africa, Zaire, West Africa, and Brazil. Table 1 summarizes information on the contents of major and minor elements in kimberlites for the sites where all most important components (TiO2, P2 O5, Cr, Ni, Sr, Ba, La, Th, Zr, and Nb) were determined, where two or more analyses were made, and where the SiO2/MgO ratio was found to be below 1.7.

The Si to Mg ratio is taken to be the indication of the contamination of ultrabasic kimberlite melt by the crustal material. This characteristic was offered by Ilupin and Lutz [1971] and used by many foreign investigators [Fesq et al., 1975; Paul et al., 1977]. Recently, the ratio of (SiO2 + Al2O3 + Na2O)/(MgO + 2K2O) has been used as the index of contamination. One can agree with the combination of Al

434 ilupin and roshohina: petrochemistry and geochemistry of kimberlites

Table 1. Major and Trace Elements in Kimberlites

Canada, NWT USA Ontario

Somerset Jeiricho Diavik Montana Colorado- Kansas Kentucky Pennsylvania Picton ” Varty

Wyoming Lake”

n=5 n=7 п=6 n=5 n=4 n=2-4 n=2 n=3 n=4 n=3

Major elements in wt.%

SiO2 22.89 2б.89 35.58 33.34 25.54 24.03 33.50 22.94 24.12 28.60

TiO2 1.81 0.б4 0.б4 2.09 1.б7 1.88 2.44 2.71 1.72 3.48

AhO3 212 1.49 2.бб 4.13 2.12 3.38 2.89 2.4б 3.19 4.49

FeOtotal 7.35 б.18 б.89 9.77 8.2б 7.93 8.82 9.41 8.18 13.91

MnO 0.148 0.15б 0.145 0.192 0.188 0.20 0.18 0.203 0.16 0.23

MgO 23.5б 21.99 33.44 23.55 32.21 23.70 31.б9 2б.33 19.72 23.87

CaO 18.00 18.бб б.40 9.52 10.37 14.88 9.50 12.77 18.95 8.93

Na2O 0.12 0.15 0.15 0.09 0.05 0.08 0.88 0.07 0.06 0.77

K2O 0.б2 0.38 0.54 3.02 0.13 0.14 1.24 1.19 0.66 0.99

P2O5 0.78 0.70 0.41 1.19 0.б3 1.05 0.44 0.б4 0.82 1.22

CO2 17.34 13.85 ND 4.67 ND 10.38 3.00 ND 14.70 3.50

LOI 4.01 7.42 11.32 7.08 17.77 10.5б 3.98 19.52 6.72 8.16

Total 98.748 98.50б 98.175 98.642 98.938 98.21 98.5б 98.243 99.00 98.15

Trace elements in ppm

Sc 20.2 ND ND 18.0 ND 15.9 ND ND 22.7 32.4

V 131.б 91.1 ND ND ND ND ND ND 140.0 123.7

Cr 1113 1б29 1б7б 1043 1528 100б 1б08 1353 954 1134

Co б0.8 ND 75.5 81.6 ND б7.8 ND ND 108.2 110.3

Ni 720 1099 1175 967 1230 50б 1304 835 448 293

Rb 39.4 25.9 бб.3 132.6 14.б 14.9 80.2 б9.1 24.5 34.0

Sr 151б 558 б48 1211 1225 1555 530 1117 2458 1310

Ba 2090 3478 1553 2796 21б9 41б4 1524 173б 2327 1167

Y 14.4 10.9 7.7 ND ND ND ND ND 19.5 48.7

La 135.4 1б8.3 83.0 134.8 1б4.2 189.2 85.3 135.3 130.8 385

Th 15.7 22.8 12.2 21.1 27.5 27.4 11.2 17.1 13.0 44.3

U 3.27 ND 2.б 4.46 4.84 б.10 2.18 3.55 4.30 7.17

Zr 1б8.0 87.3 53.5 195.4 14б.8 152.5 127.5 293.3 320 340

Hf 4.02 ND ND 3.86 ND ND ND ND 6.95 9.87

Nb 1б3.8 194.4 144.3 184.2 191.5 277.5 144.5 193.0 200 327

Ta 10.22 ND ND 12.24 ND ND ND ND 9.5 18.3

and Na, but the addition of K to Mg can hardly be justified. The point is that as far as the kimberlites of Siberia are concerned, the K content in the country rocks is higher than in the kimberlites. For instance, the average K2O content in the Lower Paleozoic carbonate-terrigenous rocks from the Malo-Botuoba area (Siberian kimberlite province) is 1.89% (calculated from 214 analyses using Table 60 published in the book [Kimberlite Petrochemistry, 1991, p. 213], whereas the average K2O content for the kimberlites of this region is 0.75%.

Table 2 lists data for the objects represented by single samples, for the objects where not all of the elements concerned were determined (some elements were not determined in all samples), and also for the objects where SiO2/MgO>1.7. This Table also includes data for the com-

positions of the Japecango and Pantano bodies (Brasil). Bizzi et al. [1994] referred to these bodies as mica peri-dotites, whereas McDonald et al. [1995], as kimberlites.

In most cases (Tables 1 and 2) the sums of the macrocomponents are notably lower than 100%. The main cause of this is the sum deficiency in the cited publications. For instance, the sums vary from 95.73 to 98.41% in the case of four kimberlite samples from Orroroo, South Australia [Scott Smith et al., 1984]. Five samples of the Nikos kimberlites (Somerset Island) showed the sums of 98.35 to 98.90% [Schmidberger and Francis, 2001]. Besides, we denote the total iron as FeO, whereas many authors, as Fe2O3(tot) or separately as Fe2O3 and FeO.

Some authors neglect carbon dioxide (CO2) including it in the loss of ignition (LOI).

Greenl. Finland Kola Arkhangelsk region

Greenland p.1 “p.2; 3” “p.4; 5; б” “p.9; 10; 14” Zolotitsa other Grib Mela

fields pipe sill

n=8 n=4 n=6 n=4 n=12 n=2-3 n=11-18 n=5-10 n=6 n=2-3

Major elements in wt.%

SiO2 24.21 26.80 32.94 40.72 37.28 30,39 41.55 33.71 37.1б 27.83

TiO2 2.55 1.36 2.22 1.21 2.34 1.24 0.82 2.93 0.88 1.02

AhO3 1.92 3.13 5.42 4.14 4.22 5.08 3.08 3.9б 2.00 3.96

FeOtotal 10.35 9.55 10.2б 7.90 8.98 8.48 6.98 9.92 7.21 10.14

MnO 0.199 0.215 0.292 0.132 0.177 0.236 0.142 0.218 0.14 0.357

MgO 26.53 27.57 21.33 2б.38 2б.77 25.76 29.92 28.29 33.52 22.83

CaO 14.58 14.76 11.04 4.30 5.97 10.26 3.89 4.б5 1.83 13.21

Na2O 0.12 0.115 0.1б 0.14 0.51 0.23 0.96 0.31 0.20 0.18

K2O 1.02 0.90 1.22 0.39 2.25 2.01 1.15 1.22 0.23 0.39

P2O5 0.83 0.52 0.б7 0.24 0.38 1.64 0.42 0.91 0.17 0.96

CO2 13.51 5.50 3.81 1.80 1.01 6.08 1.09 2.б2 1.47 10.26

LOI 3.08 7.25 9.47 13.35 10.0 7.08 8.93 10.47 14.54 7.13

Total 98.899 97.670 98.832 100.702 99.857 98.486 98.932 99.208 99.35 98.267

Trace elements in ppm

Sc 21.0 18.5 20.4 13.б 14.8 18.8 9.1 22.5 б.3 16.0

V 153.9 123.9 184.3 80.7 132.2 99.0 71.1 19б.9 75 99.3

Cr 1152 1320 1057 141б 1234 1387 978 14б2 11б3 1130

Co ND 66.6 5б.5 б8.5 71.4 64.5 75.5 б9.5 95 ND

Ni 821 898 52б 1112 944 878 1192 990 15б7 907

Rb 52.6 58.6 81.4 14.9 97.8 85.3 41.3 54.8 1б 19.4

Sr 1283 1194 809 331 541 1380 453 57б 138 938

Ba 1860 2329 1б27 381 1299 1595 702 1124 2б1 2063

Y 14.5 8.8 14.7 9.0 10.б 14.2 12.0 15.б 4.1 15.3

La 128.2 164.0 137.2 б0.0 101.9 128.1 31.2 123.3 28 99.7

Th 12.75 24.2 18.9 9.4 14.7 10.7 3.45 14.5 2.9 12.5

U ND 3.93 3.8б 1.98 2.97 ND 0.835 4.00 1.1 0.58

Zr 225.8 63.9 9б.4 58.1 7б.3 202.3 106.6 229.3 43 89.0

Hf ND 1.52 2.44 1.б4 2.17 ND 2.87 5.84 0.9 2.00

Nb 192.6 210.2 197.2 87.б 158.0 173.5 40.2 185.2 3б 66.7

Ta ND 12.03 10.95 5.50 10.2б ND 2.53 11.89 3.3 5.10

Kimberlites from Individual Regions (with References)

We begin our description of the Canadian kimberlites from Somerset Island, reporting an average of five samples from the NK3 Pipe of the Nikos Group [Schmidberger and Francis, 2001]. Apparently, the chemical composition of kimberlite from this pipe cannot be taken as representative of the kimberlite from Somerset Island as a whole. The markedly lower contents of TiO2 (0.18%), FeOtot (4.47%), and K2O (0.08%) were reported by Clarke and Mitchell [1975] for a silicate groundmass sample from the Reuyuk C kimberlite body (Somerset Island).

Next we pass to the Slave Craton. Data for aphanite kim-berlite from the Jericho Pipe are reported after [Price et al.,

2000] and those for the Diavik Pipe, after [I. Graham et al., 1999]. Table 2 lists the values averaged over 15 samples from the Slave Craton [Pell, 1997] and the average of three average values for the varieties of the Jericho Pipe [Cookenboo, 1999]. Information for the Sturgeon Lake kimberlite is given after [Hegner et al., 1995].

The bulk of the information for the chemical composition of kimberlites from the USA is given after [Alibert and Albarede, 1988]. The same publication was used to get data for the kimberlites of Crossing Creek (British Columbia) and Bachelor Lake (Quebec). Information of the Montana kim-berlites (Williams 1 and Williams 4 pipes) was borrowed from [Hearn, 1989]. The data reported by Alibert and Albarede [1988], Brookins [1970], and Cullers et al. [1982] were generalized for the kimberlites from Kansas (Riley County). The data listed in Table 2 for the George Creek dike (Col-

Timan Siberia

Vodorazdelnaya M. Nakyn Alakit Daldyn Muna NE NW Kuoyka Kharamay

Botuobiya Sib.prov. Sib.prov.

n=2 n=10-12 n=6 n=31-36 n=22-25 n=9-12 n=34-37 n=28 n=16-24 n=18

Major elements in wt.%

SiO2 36.32 31.31 33.62 28.01 27.91 28.37 27.10 29.23 30.11 27.89

TiO2 2.90 1.26 0.47 1.49 1.94 1.45 3.59 2.94 1.44 2.16

Al2O3 5.24 2.77 2.98 2.23 2.75 2.46 3.14 3.75 2.00 2.62

FeOtotal 9.86 6.67 6.07 6.23 7.21 7.37 9.32 9.78 8.13 9.33

MnO 0.215 0.128 0.142 0.111 0.129 0.145 0.171 0.182 0.173 0.177

MgO 24.95 26.37 27.47 26.79 26.57 30.57 23.32 21.18 27.09 26.20

CaO 4.67 10.54 9.23 12.82 12.44 9.03 12.49 13.62 10.54 12.82

Na2O 0.09 0.25 0.11 0.09 0.12 0.20 0.13 0.25 0.15 0.18

K2O 1.10 0.75 0.58 0.38 0.50 0.76 1.53 1.70 0.66 1.34

P2O5 0.52 0.47 0.58 0.47 0.44 0.68 0.83 0.84 0.41 1.12

CO2 2.56 8.18 6.91 10.27 10.05 8.05 9.28 8.36 10.26 8.02

LOI 10.84 10.47 10.82 10.36 9.49 10.11 7.64 7.16 8.25 7.02

Total 99.265 99.168 98.982 99.251 99.549 99.195 98.541 98.992 99.213 98.877

Trace elements in ppm

Sc 22.5 12.1 9.4 12.2 13.2 14.7 16.7 18.8 12.4 18.3

V 186.0 82.6 47.9 91.2 99.7 96.4 137.1 147.5 ND 165.4

Cr 1084 932 1028 1226 1091 1324 858 836 984 1328

Co 65 71.2 59.0 69.2 64.9 76.0 82.0 75.7 85.2 83.8

Ni 986 1150 1578 1031 884 1098 782 708 1140 1097

Rb 48.5 28.4 16.9 23.5 27.8 53.8 87.6 62.1 35.2 50.3

Sr 452 692 477 476 434 568 1002 816 794 821

Ba 834 656 498 861 612 1542 1571 1132 744 1081

Y 20.0 10.7 10.0 10.2 9.8 14.6 22.2 21.2 15.3 21.4

La 102.6 86.6 14.5 89.0 84.0 127.9 137.4 152.2 86.2 177.0

Th 12.1 9.4 1.47 9.81 9.41 14.2 16.5 15.4 11.6 21.0

U 3.05 2.02 0.58 2.14 2.05 3.01 3.67 3.95 2.45 6.41

Zr 321.0 131.4 61.6 113.8 112.9 189.9 266.0 268.4 116.7 384.6

Hf 6.75 2.93 1.54 3.04 2.97 4.57 6.53 6.65 2.91 8.86

Nb 143.5 106.0 26.3 155.5 161.4 170.4 218.6 188.1 171.8 220.8

Ta 6.0 6.17 1.46 8.04 9.58 9.51 11.0 10.14 7.01 11.04

orado) were borrowed from Carlson and Marsh [1986] and those for the Blue Ball kimberlite (Scott County, Arkansas), from Salpas et al. [1986]. The composition of the Radichal kimberlite (Iron Mountain, Wyoming) was borrowed from [Alibert and Albarede, 1988]. We did not combine this sample with the other Colorado-Wyoming kimberlites (see Table 1 for the average), because it is notably low in Ba, REE, Th, Nb, and Zr. Later, when we combined the sample sites into geographical groups, we added the sample from British Columbia to the US kimberlites, and the sample from Quebec, to the Ontario kimberlites.

Information for the kimberlites from the Picton and Varty Lake dikes was derived from the paper by Arima and Ker-rich [1988]. These dikes are described separately because they differ greatly from one another (primarily in terms of the Ti and Fe contents). The compositions of kimberlites

from Ontario listed in Table 2 are given after [Meyer et al., 1994] for the Kirkland Lake sample, and after [Reed and Sinclair, 1991] for the James Bay sample. The data published for the Kirkland Lake kimberlite seem to contain a misprint: phosphorus is omitted, and the sum of the components is lower than that given in the table. We calculated the P2O5 content (1.18%) using a difference, therefore this value should be treated with caution.

The chemical composition of the West Greenland kimberlites is given after [Larsen and Rex, 1992]. When calculating the average contents, we discarded the samples where not all of the components concerned had been determined.

The evidence of the kimberlites from Finland is reported after [O’Brian and Tyni, 1999]. The samples described in this paper were divided into four groups: (1) Pipe 1,

(2) Pipes 2 and 3, (3) Pipes 4, 5, and 6, and (4) Pipes 9, 10,

China Southern Africa

Mengyin-1 Mengyin-2 Fuxian-3 Fuxian-4 Finsch Bellsbank Sover Newlands Star “Kimberley area”

n=5 n=5 n=5 n=12 n=30 n=35 n=31 n=19 n=8 n=11

Major elements in wt.%

SiO2 33.74 27.38 25.60 27.93 37.53 33.02 35.09 33.52 34.01 34.03

TiO2 1.44 1.89 1.18 1.16 0.88 0.74 1.06 0.62 1.27 1.52

A12O3 2.02 2.22 3.30 2.64 3.34 1.64 2.55 1.71 2.79 3.37

FeOtotal 7.15 6.94 7.10 6.19 7.19 6.99 7.00 6.62 7.73 7.90

MnO 0.126 0.166 0.172 0.195 0.17 0.16 0.15 0.14 0.26 0.16

MgO 32.28 21.68 18.81 19.08 28.18 31.40 29.02 34.08 25.34 25.39

CaO 6.31 17.62 18.71 18.91 6.54 6.61 6.49 6.12 7.92 9.45

Na2O 0.03 0.02 0.04 0.02 0.21 0.12 0.18 0.11 0.17 0.48

K2O 0.48 0.28 0.72 0.48 3.14 1.72 2.91 1.02 2.95 1.60

P2O5 0.83 0.98 1.39 0.59 0.61 1.41 0.68 1.13 0.82 1.12

CO2 ND ND ND ND ND ND ND ND ND 5.08

LOI 14.18 19.57 21.12 21.48 9.90 12.99 11.76 12.42 12.89 8.25

Total 98.586 98.746 98.142 98.675 97.69 96.80 96.89 97.49 96.15 98.35

Trace elements in ppm

Sc 15.6 17.3 25.4 14.9 17 22 16 22 23 16.4

V 91.2 73.2 108.8 90.8 132 73 82 48 ND 98

Cr 1601 980 1229 1071 1765 1670 1852 1891 2156 1380

Co 76.6 67.0 65.5 60.2 71 96 80 71 78 87

Ni 1204 882 712 714 1214 1396 1253 1450 1207 1160

Rb 60.2 21.4 75.4 28.9 ND ND ND ND ND 58

Sr 574 542 822 516 738 1414 1127 1261 1808 632

Ba 1592 564 4381 1178 1467 3439 2442 3351 4370 808

Y 11.8 9.8 19.0 11.2 ND ND ND ND ND 13

La 168.0 188.4 360.4 126.6 62 252 168 203 192 129

Th 26.4 24.5 71.9 23.9 9 45 30 33 28 16.5

U 2.0 ND 7.64 4.17 3 7 3 5 ND 3.7

Zr 226.0 277.0 242.4 194.7 184 291 214 193 194 240

Hf 4.08 4.10 5.50 4.42 5 8 5 4 7 5.38

Nb 183.2 166.0 287.0 124.2 51 168 97 139 134 110

Ta 4.46 3.58 8.60 4.02 3 14 9 9 10 7.9

and 14. Group (2) is distinguished by the highest concentrations of Al and Fe, Group 3, by the lowest contents of P, Ba, and La. The kimberlites of Group 4 are also relatively low in P and La, though in contrast to the samples of Group 3, they are notably higher in Ti, K, and Ba.

Data for the kimberlites of the Kola Peninsula were reported by Kalinkin et al. [1993] and Beard et al. [1998]. Some analyses were made by the authors of this paper. Table 1 presents the average value derived from these three sources.

For the Arkhangelsk region we combined data from three publications [Beard et al., 2000; Bogatikov et al., 2001; Ma-hotkin et al., 2000]. We calculated the average values using these values for the Zolotitskii field, for the other fields, and for the kimberlites of the Mel Sill. For the Grib pipe average data are reported by [Verichev et al., 1999]. As far

as the Middle Timan kimberlites are concerned, we used the data available only for the Vodorazdelnaya Pipe, because the kimberlite from the Umba Pipe contains abundant xenogenic material [Kononova et al., 2000].

The compositions of the Siberian kimberlites are reported here using mainly our own data. Data for the Nakyn field (Botuoba Pipe) were the courtesy of Yu. Yu. Golubeva. We discuss separately five kimberlite fields in the Southern (di-amondiferous) part of the Siberian Province. The Malo-Botuoba and Nakyn fields are markedly distant from each other and from the other fields. The neighboring Alakit and Daldyn fields are different markedly in terms of their average Ti, Al, and Fe contents. Compared to the kimberlites from the other southern fields of the province, the kimberlites of the Upper Mun field are enriched in P, La, Th, and Zr. In the northern (poorly diamondiferous) part of the province, we

Southern Africa Sierra Leone Liberia Brazil

IA+IB Benfontein Venetia dikes pipes “Sample Tr.Ranch., Alto Paranatinga

Creek” Limeira Paranaiba

n=17 n=4 n=13 n=13 n=2-5 n=14 n=2 n=5 n=11

Major elements in wt.%

SiO2 29.10 21.81 31.61 30.87 31.69 30.42 32.10 30.06 41.32

T1Ü2 2.71 3.81 1.10 2.02 1.59 5.32 1.83 2.21 2.03

AI2O3 2.40 3.23 2.73 2.08 2.39 1.24 2.21 2.99 3.36

FeOtotal 9.70 13.44 7.47 10.14 9.28 14.04 10.40 9.30 9.09

MnO 0.198 0.27 0.197 0.182 0.158 0.221 0.23 0.190 0.154

MgO 28.44 24.38 28.34 29.48 28.50 30.38 30.75 27.57 28.13

CaO 9.52 15.03 9.60 7.06 8.21 0.90 7.74 8.71 3.69

Na2O 0.10 0.43 0.43 0.03 0.29 0.10 0.06 0.74 0.07

K2O 1.06 0.18 1.11 1.37 1.36 0.10 0.99 1.97 0.22

P2O5 1.18 2.64 0.86 0.42 0.73 0.31 1.89 1.09 0.15

CO2 6.04 ND ND 4.97 4.44 0.94 ND ND ND

LOI 8.66 12.52 15.01 9.41 9.06 13.55 11.22 14.23 10.81

Total 99.108 97.74 98.457 98.032 97.698 97.521 99.42 99.06 99.024

Trace elements in ppm

Sc 18.3 25.2 12.6 14.3 14.0 ND 21.4 ND 12.0

V 115.8 220.2 79.2 74.2 69.8 163.7 79.4 111.0 142.7

Cr 1202 1019 1532 1479 1252 1803 1536 860 938

Co 90.8 ND 64.1 ND ND ND 97.0 ND 77.9

Ni 1170 549 1321 1251 1209 1694 1568 1055 1238

Rb 56.7 16.5 69.2 68.9 66.4 5.8 87.0 97.3 13.6

Sr 858 1594 985 548 653 75.0 2328 1825 154

Ba 1024 2746 1784 1477 1912 356 2978 2716 374

Y 19.4 27.0 6.8 8.7 11.6 3.9 28.0 24.5 8.0

La 129.2 282.2 151.6 162 205 50.1 276.0 152.8 20.85

Th 27.8 50.7 34.1 25.8 25.7 20.1 32.5 23.8* 4.18

U 5.68 10.5 12.6 3.76 4.75 ND 5.40 ND 0.92

Zr 283 661 102.6 143 208 340 457.5 511.6 55.5

Hf ND 14.68 ND 5.42 7.6 ND ND 6.70 1.41

Nb 218 300 209.2 219 270 342 256.0 186.8 63.2

Ta ND 29.9 ND 16.0 18.8 ND ND ND 5.44

Note: ND — No data (here and in other tables).

distinguished the Kuoi field as an independent site, where the kimberlites resemble, in terms of several factors, the kimberlites from the southern part of the province [Ilupin, 1990]. We describe separately the data for the northeastern and northwestern groups of the fields [Ilupin and Genshaft, 1994]. The kimberlites of the Kharamai field differ from the kimberlites of the other fields of the Siberian Province by their enrichment in P, Zr, and Hf [Ilupin, 1999].

The kimberlites of China are described here after [Tompkins et al., 1999]. We classified them into four groups: Group 1 comprising pipe 701 (1) and Group 2 with pipes 6 and 28 (2) in the Mengyin area; Group 3 including pipe 1 and dikes 2, 3, 10, and 11; Group 4 including pipes 30, 42, 50, 51, and 110 and dikes 52, 75, and 104 in the Fuxian area. Groups 1 and 2 differ in the contents of Ti, K, Cr, Ni, Ba,

and Zr. The samples of Group 3 are distinguished by their high Ba, La, Th, and Nb concentrations. Their Th contents are higher than in any other sites described in this paper. Note that the contents of the trace elements are high in all five samples included in Group 3: 262 to 401 ppm La, 53.7 to 82.9 ppm Th, and 216 to 347 ppm Nb. Table 2 lists data of kimberlites from North China reported by [Zhang and, Liu, 1983].

The data for the kimberlites of India and Australia are listed in Table 2. The average data for the kimberlites of Southern India are given after [Middlemost and Paul, 1984]. The value averaged over 5 kimberlite samples from the Wa-jrakarur area was calculated using the data reported by [Nagabhushanam and Venkatanarayana, 1985]. The composition of the Chelima micaceous kimberlite dike is given

Table 2. Single Samples, Kimberlites with SiO2/MgO>1.7 and Samles with Incomplete Set of Elements in Question

NWT Saskat. Br.Col. USA Quebec Ontario

Slave Jericho Sturgeon Crossing “Wyom., “Col., Ark., Blue Bachelor Kirkland James

craton Lake Creek Radichal” George Cr.” Ball Lake Lake Bay

n=15 n=3 av. n=1 n=1 n=1 n=1 n=2 n=1 n=1 n=25

r Ma elements in wt.%

SiO2 38.13 33.93 28.72 32.47 29.93 21.70 ND 20.91 35.15 32.37

TiO2 0.52 0.84 0.52 1.46 2.56 2.43 ND 2.6 3.13 1.44

Al2O3 3.97 2.14 0.79 2.07 2.88 2.45 ND 3.8 3.03 3.31

FeOtotal 6.75 7.17 6.63 6.28 9.85 9.50 8.86 11.01 9.14 8.73

MnO 0.147 0.143 0.14 0.14 0.18 0.24 ND 0.3 0.15 0.21

MgO 28.03 33.87 27.29 23.82 27.67 15.73 ND 14.58 27.64 27.11

CaO 5.57 6.63 17.00 12.51 9.12 23.65 12.05 22.49 6.54 9.28

Na2O 0.26 0.13 0.09 0.08 0.07 0.03 0.04 0.12 0.32 0.20

K2O 1.17 0.32 0.20 1.37 1.05 0.51 3.27 2.22 2.16 1.39

P2O5 0.41 0.32 0.14 0.87 0.43 0.72 ND 1.7 1.18* 0.65

CO2 ND ND ND 9.05 4.86 ND ND ND 1.77 ND

LOI 13.16 12.82 17.20 8.02 9.20 20.38 ND 19.12 6.96 12.96

Total 98.117 98.313 98.72 98.14 97.80 97.34 24.22 98.85 95.99 97.65

Trace elements in ppm

Sc ND ND ND ND ND ND 19.9 ND ND ND

V ND ND 27 ND ND ND ND ND ND 131

Cr 1213 1847 944 1411 1369 583 1411 585 1916 1302

Co 61.5 ND ND ND ND 57 69.05 ND 64 ND

Ni 1142 1395 1472 1142 1209 711 665 220 1100 931

Rb 70.7 40.7 10.2 68.6 66.7 24 157.5 111 105 ND

Sr 613 424 281 975 516 759 915 1685 360 631

Ba 1299 1235 332 2200 992 921 1860 2232 1164 1376

Y 8.5 7.3 3 ND ND 18 ND ND ND ND

La ND ND ND 134* 88* 144 64.8 236* 47 129

Th ND ND 11.7 20.8 11.2 14 5.37 28.3 5 ND

U ND ND 1.24 4.1 2.21 ND 0.86 6.27 ND ND

Zr 100.7 58.3 33 257 98 234 87.5 329 145 220

Hf ND ND ND ND ND ND 2.13 ND ND ND

Nb 140.7 116.0 61 152 132 205 ND 240 140 137

Ta ND ND ND ND ND 17 7.25 ND 20 ND

after [Rao, 1976], and the content of thorium in this dike, after [Paul et al., 1977].

The data for Australia were collected from the kimberlites of the Northern Territory (Timber and Merlin), South Australia (Orroroo), and Western Australia (the remaining sites). Data for the Timber Creek kimberlites are given after [Berryman et al., 1999] for the least altered kimberlite. Data for the macrocomponents were obtained by way of a reverse calculation for the water-bearing material (because the authors of the cited paper carried out their calculations for the anhydrous material). The Merlin kimberlites are described here after [Lee et al., 1997]. Cited here is the average for two samples. Analyses for Sc, Co, and Th had been made using one sample, and the ratios including these elements had been calculated only for this sample. The composition of the kimberlite from the Aries Pipe is given here after [Ed-

wards et al., 1992], and the compositions of kimberlites from the Earaheedy Basin are given here after [S. Graham et al., 1999]. The Skerring and Bow Hill kimberlites are reported here after [Atkinson et al., 1984], and the composition of the Orroroo kimberlites, after [Scott Smith et al., 1984].

The chemical compositions of kimberlites from several areas in South Africa, namely, from Finsch, Bellshank, Sover, Newlands, Star (Table 1), and Swartruggens (Table 2), are given here after [Mitchell, 1995]. The mean values for the Finsch Pipe reported by this author are close to the means calculated for 16 samples by [Fraser and Hawkesworth, 1992], namely: 0.88 and 0.92% TiO2, 3.14 and 3.20% K2O, and 0.61 and 0.64% P2O5, respectively. The kimberlites from the Kimberley area are known from the data reported by [Muramatsu, 1983] and [Muramatsu and Wedepohl, 1985]. The arithmetic means for kimberlites of groups IA and IB

China India Australia

North South Wajrak. Chelima Timber Merlin Aries Earaheedy Skerring Bow Orroroo

China India area Creek Hill

n=1-4 average n=5 n=4 n=1 n=1-2 n=2 n=3 n=1 n=1 n=4

Major elements in wt.%

SiO2 29.32 35.57 36.27 32.85 15.87 29.05 40.58 43.92 54.3 32.4 30.36

TiO2 1.21 1.75 2.57 4.65 3.19 0.48 1.21 3.00 2.9 1.2 1.33

A12O3 1.93 5.25 5.84 4.15 6.83 3.97 4.26 6.50 2.2 5.7 2.88

FeOtotal 7.37 8.48 8.90 9.18 5.94 7.98 9.90 7.65 9.53 9.17 8.03

MnO 0.165 0.17 0.178 0.26 0.10 0.125 0.17 0.107 ND ND 0.152

MgO 30.59 23.23 23.27 18.13 23.28 18.43 22.26 23.24 19.3 26.0 25.34

CaO 9.84 13.25 10.95 9.78 19.61 17.16 6.76 3.68 1.8 9.0 10.59

Na2O 0.12 0.25 0.81 0.105 <0.02 0.12 0.66 0.52 0.40 0.04 0.07

K2O 0.42 0.99 1.39 2.44 0.11 2.38 2.39 2.11 0.15 0.10 1.40

P2O5 0.53 0.71 0.73 1.65 1.74 0.50 0.28 0.99 0.39 0.13 0.66

CO2 ND 1.95 ND ND ND ND 4.19 ND ND ND 7.27

LOI 17.68 7.86 8.79 15.49 22.66 18.78 9.25 6.77 ND ND 8.12

Total 99.175 99.46 99.698 98.685 99.33 98.975 101.91 98.487 90.97 83.74 96.202

Trace elements in ppm

Sc 14.2 ND ND ND ND 12* 24.5 12.6 ND ND ND

V 90.2 ND ND 60.0 196.1 69.5 86.5 187.7 ND ND 112.8

Cr 1395 ND 889 632 1552 1069 2106 910 1600 870 1411

Co 94.2 ND 70.6 95 24? 66 ND 51.0 75 90 93.2

Ni 1247 ND 834 548 394 743 1292 546 835 765 1366

Rb 7 2 123 148.0 105.0 7.3 242.0 171.5 110.0 ND ND 100.5

Sr 564 766 873 1280 345 1175 428 368 260 220 828

Ba 1175 3158 1657 2050 3008 2805 1914 1466 430 120 ND

Y 9.5 ND ND 45.0 67.7? 10.5 15.5 19.0 ND 10 14.0

La 165.2 98 ND 360 222 220.5 251 135.3 ND ND ND

Th ND 21.8 ND 38.2* 22.3 51* 51.9 39.3 ND ND ND

U ND 2.93 ND 3.93* 4.9 ND 3.9 6.84 ND ND ND

Zr 198 404 ND 560 553 59.5 96.0 399 340 140 167.0

Hf ND 3.9 ND ND ND ND 1.85 10.2 ND ND ND

Nb 180* ND ND 315 286 214.0 436 135.7 120 150 195.5

Ta 17* 11.0 ND ND ND ND 27.8 7.81 ND ND ND

have been calculated using the data reported by [Smith et al., 1985]. The average of four samples from the Benfontein Sill is used here after [Pearson and Taylor, 1996]. The average value was calculated using 13 samples from the Venetia kimberlite cluster by [Seggie et al., 1999]. The compositions of the other kimberlites from South Africa are listed in Table 2. The average compositions of the kimberlites from the Premier Mine are given after [Fesq et al., 1975] and [Kable et al., 1975]. Data for the compositions of kimberlites from the Kuruman Province are given after [Shee et al., 1989]. Average values were calculated separately for the Bathlaros and Elston 01 kimberlites differing distinctly in terms of Ti, P, and other elements. The composition of the kimberlites from East Griqualand are given after [Nixon et al., 1983], who found Co and Nb only in three samples (out of the total eight), V in five samples, Y in six samples, and Zr in

seven samples. Data for kimberlites from the Prieska area are given after [Skinner et al., 1994].

The composition of kimberlites from Zaire was computed using data from [Fieremans et al., 1984]. When calculating the average values, we discarded the samples for which no carbon dioxide had been calculated, and also the Mbuji-Mayi samples in which SiO2 predominated over MgO (SiO2 > 60%; SiO2/MgO > 9.0). As to the most interesting components, no Ni, Zr, and Nb had been determined. Unfortunately, it was difficult to estimate the Zr content after Hf and the Nb content after Ta, because, judging by the data from the literature, the ratios of these elements varied rather widely: 26.4 to 103.6 for Zr/Hf and 7.0 to 46.4 for Nb/Ta. Naturally, it cannot be ruled out that the extreme values of the ratios between the elements had been caused by analytical errors.

Southern Africa

Swartruggens Premier Bathlaros Elston 01 East Griqualand Prieska area

n=15-21 n=15 n=8 n=2 n=3-8 n=17

Major elements in wt.%

SiO2 36.44 44.33 31.94 30.65 25.74 34.59

TiO2 1.58 1.82 2.63 0.70 2.61 2.04

Al2O3 4.02 3.95 2.50 1.10 3.42 4.05

FeOtotal 7.34 7.91 9.31 6.12 11.26 8.94

MnO 0.16 0.143 0.213 ND 0.21 0.182

MgO 21.25 23.97 30.00 35.90 22.55 25.04

CaO 8.39 6.10 6.91 7.07 15.76 7.87

Na2O 0.24 0.68 0.29 0.14 0.18 0.19

K2O 4.65 1.24 1.39 0.46 0.53 2.66

P2O5 1.34 0.26 0.56 1.94 0.79 1.21

CO2 ND 0.47 3.82 4.68 9.46 ND

LOI 10.45 7.70 8.83 9.92 7.36 12.07

Total 95.86 98.573 98.393 98.68 99.87 98.842

Trace elements in ppm

Sc 20 10.2 ND ND ND ND

V 131 ND ND 14.0 186 157.1

Cr 1207 1020 1060 1180 1172 1382

Co 73 75.9 138.8 117.5 52 90.6

Ni 1034 969 1069 1700 752 1034

Rb ND 103.0 72.5 10 ND 119.8

Sr 1139 367 771 1140 970 1158

Ba 5183 565 2926 775 698 2297

Y ND 8.1 14.2 14.0 30.3 22.9

La 218 33.7 ND ND 105.8 ND

Th 26 6.17 ND ND ND ND

U 7 1.07 ND ND ND ND

Zr 401 106.7 323.1 317.5 350 268.8

Hf 10 2.52 ND ND ND ND

Nb 143 68.2 452.8 203.5 144 138.3

Ta 8 9.52 ND ND ND ND

Evidence for the kimberlites of West Africa (Sierra Leone and Liberia) was derived from [Taylor et al., 1994] and used in Tables 1 and 2. As far as the kimberlites of Sierra Leone (Koidu kimberlites) are concerned, the cited authors had calculated separately the average data for the dikes and pipes and also discarded several samples, because they believed them to have been altered or contaminated. They also discarded the samples in which not all elements of interest had been determined. In the case of the cited average value for the Sierra Leone pipes, Sc, U, Hf, and Ta had been determined in two cases out of five. Calcite kimber-lites are reported separately. In the case of Liberia, these authors calculated an average value using 14 samples having the “Sample Creek” index, whereas listed in Table 2 are data for three samples, the L-4 and BJC samples being characterized as relatively unaltered and uncontaminated.

The geochemical features of the Sample Creek kimberlites are classified as typical of the first phase of kimberlite alteration [Taylor et al., 1994]. This statement is not quite clear. Using the results of studying the kimberlites of Siberia, it was found that the alteration of kimberlites leads to the growth of the Si/Mg ratio and to the removal of Mg and Ni. At the same time, compared to the unaltered L-4 and BJC samples, the Sample Creek samples showed the lower SiO2/MgO ratio (1.00 against 1.19 and 1.15), the higher Ni content (1694 against 970 and 858 ppm), and even the higher Ni(ppm)/MgO(wt.%) ratio (55.8 against 39.1 and 34.2, respectively).

The compositions of the Brazilan kimberlites (Tables 1 and 2) were borrowed from [Araujo et al., 2001; Bizzi et al., 1994; Greenwood et al., 1999]. Because Th was not reported from the Alto Paranaiba kimberlites, we derived its

Zaire Sierra-Leone Liberia Brazil

Mbuji-Mayi Kundelungu Calcite kimb. “B.R.G.M. Bomojaha Wusea Batovi Japecanga,

L-4” BJC WSA Pantano

n=6 n=4 n=2 n=1 n=1 n=1 n=1 n=3

Major elements in wt.%

SiO2 35.61 30.68 14.97 29.45 28.76 49.49 32.06 33.24

TiO2 1.46 2.26 1.46 3.06 4.21 2.71 2.69 3.29

A12O3 4.24 2.64 2.86 2.20 2.87 2.86 3.20 1.33

FeOtotal 6.96 9.91 4.65 10.22 13.39 9.34 10.10 13.58

MnO 0.138 0.215 0.34 0.14 0.42 0.12 0.17 0.203

MgO 14.27 32.56 7.40 24.80 25.08 23.74 31.54 29.06

CaO 13.93 7.00 36.22 10.55 7.46 2.78 4.31 5.40

Na2O 0.156 0.14 <0.05 0.30 0.08 0.14 0.71 0.05

K2O 0.58 0.20 0.80 1.00 0.73 0.36 0.27 0.94

P2O5 1.13 0.55 1.26 0.72 0.65 0.99 0.62 0.43

CO2 10.98 2.72 26.74 7.15 3.08 0.17 ND ND

LOI 9.46 10.11 2.19 8.80 10.45 6.23 14.63 12.04

Total 98.914 98.985 98.89 98.39 97.18 98.93 100.30 99.563

Trace elements in ppm

Sc 12.3 14.2 13.4 ND ND ND 15.8 18.0

V ND ND 74.5 227 111 128 254 152.7

Cr 1703 1540 1605 1070 1225 2083 1175 1031

Co 56.3 92.0 ND ND ND ND 91 116.7

Ni ND ND 1023 970 858 1936 1076 1890

Rb 33.2 20.0 43.5 ND 43 17 26.3 69.0

Sr 747 421 2165 735 566 132 433 924

Ba 578 912 1728 885 916 1063 2308 1212

Y ND ND 32.0 34 23 13 12.9 13.4

La 79.0 113.8 188.0 ND 173 93 113 89.3

Th 16.9 15.95 25.8 ND 18 25 16.2 16.2

U 2.43 4.05 6.35 ND ND ND 2.91 6.67

Zr ND ND 238.0 ND 273 244 119 709.7

Hf 4.65 2.93 7.05 ND ND ND 2.67 ND

Nb ND ND 306.5 ND 305 307 179 215.7

Ta 15.5 13.9 16.3 ND ND ND 10.9 ND

concentration from the data available for the contents of La, Ni, and P and the ratios of these elements with Th in some other areas of Brazil (proceeding from the strong positive Th-La, Th-Nb, and Th-P correlations). The Paranatinga kimberlites are classified as altered and contaminated with crustal material: the SiO2 /MgO ratio is 1.47 for the average of eleven samples, the contamination index varying from 1.25 to 1.97 for some samples. As mentioned by Greenwood et al. [1999], “neither this contamination, nor the degree of alteration of the samples (estimated visually) appears to have a major effect on the ratios of incompatible trace-elements.” Like in the case of the Liberian kimberlites, we would note that the Paranatinga kimberlites are richer in nickel than the Batovi kimberlites, discussed in the same paper: 1238 against 1076 ppm, the Ni/MgO ratio being higher, too, 44.0 against 34.1.

Kimberlite Peculiarity

When examining the data listed in Tables 1 and 2, one notes the peculiarity of the chemical composition of kimber-lites from each region concerned. The idea that the compositions of all known kimberlite bodies are unique was offered by Kryuchkov and Khar’kiv [1989]: “Each body of these rocks is a unique geologic object having no complete analog in nature in terms of its mineralogy, petrochemistry, texture, and structure.”

We calculated the arithmetic means for the contents of major and trace elements in kimberlites using the data listed in Tables 1 and 2. The number of source data for each element varied from 71 to 84. The mean values thus obtained are generally close to the values cited in [Muramatsu,

1983]; notably higher were only our mean values for Ba (1665 against 1000 ppm), Th (21.1 against 16 ppm), and Nb (183 against 110 ppm); slightly higher was the mean value for Cr (1286 against 1100 ppm).

We combined these objects into larger groups: the Slave Craton kimberlites in the northwest of Canada; the USA kimberlites, this group including a kimberlite sample from British Columbia, Canada; kimberlites from Ontario and Quebec (Southeast Canada); kimberlites from Finland; kimberlites from the Northeast of Russia (Arkhangelsk Province, Kola Peninsula, and Middle Timan); kimberlites from the southern (diamondiferous) part of the Siberian Province; kimberlites from the northern (poorly diamondiferous) part of the Siberian Province; kimberlites from China, India, Australia, South Africa, Zaire, West Africa, and Brazil. For each of these groups we computed the arithmetic means of the components (using data from Tables 1 and 2). These arithmetic means, as well as the data for the Nikos kimber-lite (Somerset Island), for the Western Greenland kimberlite (Table 1), and for the Sturgeon Lake (Saskatchewan) kimberlite (Table 2) are listed in Table 3. Each value is supplemented with an “accumulation factor” obtained as a result of the division of this value by the average content of this component in kimberlites. The coefficients higher than 1.2 are given in bold, the values lower than 0.8, in italics. Table 3 lists also the mean values of the components we computed in the kimberlites and the mean values for ultrabasic rocks borrowed from [Wedepohl and Muramatsu, 1979].

The individual kimberlite bodies or their groups, listed in Table 3 as “objects”, may differ notably from one another. At the same time each object (as a whole) shows its own undoubtful peculiarity. Described below are the peculiarities of the chemical compositions of some kimberlite pipes and dikes, groups of pipes, and kimberlite provinces.

One of the most unique pipes is the Aries Pipe in West Australia. The unique character of its kimberlites was demonstrated, for example, by [Taylor et al., 1994]. Compared to the other well known pipes, Aries stands out because of its high ratios of La(ppm)/P2Og (wt.%) (896) and Th(ppm)/P2Og (wt.%) (185.4). As to the other objects of study, high values were shown by the Merlin kimberlites (Australia): 441 and 104.1, respectively.

With the great diversity of kimberlites in Australia, we would note insignificant Sr contents at five sites out of the seven discussed: 220 to 428 ppm. The exceptions are 828 ppm in the Orroroo kimberlite and 1175 ppm in the Merlin kimberlite. The Zr(ppm)/TiO2 (%) ratio varies from 11б.7 to 133 over a limited range (again in 5 cases out of 7), the exceptions being Aries (79.3) and Timber (173.4). Thorium was found only at four sites, its values ranging from 22.3 to 51.9 ppm, the maximum average value being

41.1 ppm (shown in Table 3). Rubidium was determined in four areas, the K/Rb ratio being almost equal (116-125) in three areas (Timber, Aries, and Orroroo), 82 in the Merlin kimberlite, and 159 in the Earaheedy kimberlite.

Very low contents of Sr, Ba, REE, Zr, and Nb were found in the kimberlites of Sturgeon Lake (Saskatchewan), in the Grib pipe (Arkhangelsk Province), and in the Nakyn Field (Siberia). Although this analogy is not complete beginning with the contents of TiO2 (0.52, 0.88, and 0.47%), Al2O3

(0.79, 2.00. 2.98%), and P2O5 (0.14, 0.17, and 0.58%).

The kimberlites of Sierra-Leone differ from those of Liberia in their TiO2 contents (1.46-2.02 against 2.715.32%) and in the Ba contents (1477-1912 against 3561063 ppm), both showing the high concentrations of niobium (219-342 ppm) and the similar ratios of Zr/Nb (0.65-0.99) and K/Rb (141-176). The kimberlites of Sierra-Leone (dikes and pipes) showed very low Zr/Hf ratios: 26.4 and 27.4, respectively. A roughly similar value (27.7) was found for the Star Pipe (South Africa). This value was found to be not lower than 33 in the other kimberlites.

The kimberlites of Liberia are most rich in titanium. The average TiO2 content in the Sample Creek specimens was found to be 5.32% with variations of 1.57 to 11.40%. Similarly high Ti concentrations were found in the Mayeng kimberlite sill complex (South Africa) [Apter et al., 1984]. This author reported the values of 4.7, 5.12, and 5.42% TiO2 for three samples. Because he reported only the macrocomponents, we did not include the Mayeng samples in our review. Among the other areas concerned, the highest TiO2 content was found in the Chelima dike, India (4.65%), this being followed by the value of 4.21% in the BJC sample (Liberia). The kimberlites of the Benfontein Sill (South Africa), known for their abundance of metallic minerals, are slightly lower in titanium: the value of 3.81%, included in our Table 1, is an average of 4 samples. The value of 4.08% TiO2 was reported by [Yoshida and Aoki, 1986] as an average of two samples.

The highest Zr/Hf value (103.6) was found for the kim-berlites of India [Middlemost and Paul, 1984]. As far as the other objects are concerned, the highest ratio (76.4) was found in the kimberlites of the Alto Paranaiba area (Brazil).

As follows from [Tompkins et al., 1999], the kimberlites of China show high Nb/Ta values: 31-33 ppm for the Fux-ian area and 41-46 for Mengyin. The high values for the other kimberlites discussed are 23.9 (Middle Timan, NW Russia) and 23.8 (Kuoika, Siberia). It should be emphasized that the extreme values of some factors (component contents and, especially, ratios between elements) may be associated with analytical errors. Note that the Nb/Ta value of 10.6 for North China was found to be most common [Zhang and Liu, 1983]. The lowest Nb/Ta values were found for the Kirkland Lake kimberlite, Ontario (7.0), and for the Premier kimberlite, South Africa (7.2).

The Slave Craton kimberlites are distinguished by the fairly narrow variation ranges of TiO2 (0.52-0.84%), Zr (53.5-100.7 ppm), Sr (424-648 ppm), and Zr/Nb ratio (0.370.72). The P2Og content is slightly higher in the aphanite kimberlite of the Jericho Pipe (0.70%). The three other areas concerned showed this ratio to be rather low: 0.32 to 0.41%. The hypabyssal kimberlite of the Leslie Pipe from the same region (two samples) [Berg et al., 1998] showed similar values for Ti and P: 0.52 and 0.66% TiO2 and 0.26 and 0.40% P2Og. Because merely main components are reported for the Leslie pipe, it was not included in our review, similar to the Mayeng Complex.

In terms of their low Zr contents (58.1-96.4 ppm) the kim-berlites of Finland are similar to those of the Slave Craton. Also similar are the average values of P, La, Th, and Nb. Yet, the kimberlites of Finland are more enriched in TiO2, (av-

Table 3. Average Concentration, and Enrichment Coefficients

Objects TiO2 Fe°tot MnO Al2O3 K2O CaO P2O5 Cr Ni Sr Ba La Th Zr Nb

kimb. (n=71-84) 1.94 8.63 0.184 3.12 1.14 10.39 0.81 1286 1037 842 1665 152.2 21.1 223.6 183

ultrabasites, av. 0.13 8.34 0.134 2.70 0.05 3.81 0.05 3090 1450 22 20 0.92 0.07 16 1.3

Somerset Island 1.81 7.35 0.148 2.12 0.62 18.00 0.78 1113 720 1516 2090 135.4 15.7 168 163.8

coeff 0.93 0.85 0.80 0.68 0.54 1.73 0.96 0.87 0.69 1.80 1.26 0.89 0.74 0.75 0.90

Slave craton 0.66 6.75 0.148 2.56 0.60 9.32 0.46 1591 1203 561 1891 125.6 17.5 75.0 148.8

coeff. 0.34 0.78 0.80 0.82 0.53 0.90 0.57 1.24 1.16 0.67 1.14 0.82 0.83 0.34 0.81

Sturgeon Lake 0.52 6.63 0.14 0.79 0.20 17.00 0.14 944 1472 281 332 ND 11.7 33 61

coeff. 0.27 0.77 0.76 0.25 0.18 1.64 0.17 0.73 1.42 0.33 0.20 0.55 0.15 0.33

USA 2.16 8.74 0.190 2.80 1.32 12.71 0.75 1257 952 978 2040 131.1 17.3 176.9 185.0

coeff. 1.11 1.01 1.03 0.90 1.16 1.22 0.93 0.98 0.92 1.16 1.23 0.86 0.82 0.79 1.01

Ontario + Quebec 2.47 10.19 0.210 3.56 1.48 13.24 1.11 1178 598 1289 1653 185.6 22.6 270.8 208.8

coeff. 1.27 1.18 1.14 1.14 1.30 1.27 1.37 0.92 0.58 1.53 0.99 1.22 1.07 1.21 1.14

E.Greenland 2.55 10.35 0.199 1.92 1.02 14.58 0.83 1152 821 1283 1860 128.2 12.8 225.8 192.6

coeff. 1.31 1.20 1.08 0.62 0.89 1.40 1.02 0.90 0.79 1.52 1.12 0.84 0.61 1.01 1.05

Finland 1.78 9.17 0.204 4.23 1.19 9.02 0.45 1257 870 719 1409 115.8 16.8 73.7 163.2

coeff. 0.92 1.06 1.11 1.36 1.04 0.87 0.56 0.98 0.84 0.85 0.85 0.76 0.80 0.33 0.89

Arkh.+Kola+Timan 1.63 8.76 0.218 3.89 1.02 6.42 0.77 1201 1087 656 1096 85.5 9.4 165.2 107.5

coeff. 0.84 1.02 1.18 1.25 0.89 0.62 0.95 0.93 1.05 0.78 0.66 0.56 0.44 0.74 0.59

Siberia-south 1.32 6.71 0.131 2.64 0.59 10.81 0.53 1120 1148 529 834 80.4 8.9 121.9 123.9

coeff. 0.68 0.78 0.71 0.85 0.52 1.04 0.65 0.87 1.11 0.63 0.50 0.53 0.42 0.54 0.68

Siberia-north 2.53 9.14 0.176 2.88 1.31 12.37 0.80 1002 932 858 1132 138.2 16.1 259.0 199.9

coeff. 1.30 1.06 0.96 0.92 1.15 1.19 0.99 0.78 0.90 1.02 0.68 0.91 0.76 1.16 1.09

China 1.38 6.95 0.165 2.42 0.48 14.28 0.86 1255 952 604 1778 201.7 36.7 227.6 188.1

coeff. 0.71 0.80 0.90 0.78 0.42 1.37 1.06 0.98 0.92 0.72 1.07 1.32 1.74 1.02 1.03

India 2.99 8.85 0.203 5.08 1.61 11.33 1.03 760 691 973 2288 229.0 30.0 482.0 315

coeff. 1.54 1.02 1.10 1.63 1.41 1.09 1.27 0.59 0.67 1.16 1.37 1.50 1.42 2.16 1.72

Australia 1.90 8.31 0.131 4.62 1.23 9.80 0.67 1360 849 518 1624 207.2 41.1 250.6 219.6

coeff. 0.98 0.96 0.71 1.48 1.08 0.94 0.83 1.06 0.82 0.62 0.98 1.36 1.95 1.12 1.20

Southern Africa 1.67 8.33 0.187 2.85 1.77 8.63 1.10 1432 1152 1064 2258 160.5 27.8 275.3 171.7

coeff. 0.86 0.96 1.02 0.91 1.55 0.83 1.36 1.11 1.11 1.26 1.36 1.05 1.32 1.23 0.94

Zaire 1.86 8.44 0.176 3.44 0.39 10.46 0.84 1622 ND 584 745 96.4 16.4 ND ND

coeff. 0.96 0.98 0,96 1.10 0.34 1.01 1.04 1.26 0.69 0.45 0.63 0.78

West Africa 2.91 10.15 0.226 2.36 0.82 10.45 0.73 1502 1277 696 1191 145.2 23.4 241.0 291.6

coeff. 1.50 1.18 1.23 0.76 0.72 1.01 0.90 1.17 1.23 0.83 0.72 0.95 1.11 1.08 1.59

Brazil 2.41 10.49 0.189 2.62 0.88 5.97 0.84 1108 1365 1133 1918 245.4 18.6 370.7 180.1

coeff. 1.24 1.21 1.03 0.84 0.77 0.57 1.04 0.86 1.32 1.35 1.15 1.61 0.88 1.66 0.98

Note: Bold font means coefficient > 1.2. Italic font means coefficient < 0.8.

eragely 1.78 against 0.66%), in FeOtot (9.17 against 6.75%), and in Al2O3 (4.23 against 2.56%) compared to the samples of the Slave Craton.

The kimberlites of South Africa show high variations

in all petrochemical and geochemical data. Four objects (Benfontein, Bellsbank, Venetia Cluster, and Newlands) showed high Th contents (33 to 50.7 ppm). Extremely high Zr(ppm)/TiO2 (%) values were found for Newlands (311),

Table 4. Selected components in Kurkhan diatreme and in kimberlites, poor in lithophile rare elements (from pipes of Siberia, Canada and Arkhangel’sk region)

0bject Ti02 % Al 2 0 CO % P to 0 cn % Sr ppm Ba ppm La ppm Th ppm Zr ppm Nb ppm Ta ppm

Kurkhan diatreme 0.04 0.42 0.16 3.41 7.73 0.69 0.29 4.83 1.24 0.01—0.02

Ruslovaya pipe 0.12 1.55 0.23 630 100 45 4.6 28 ND 1.2

Muza pipe 0.065 0.78 0.18 490 150 42 4.2 49 ND 1.8

Sturgeon Lake 0.52 0.79 0.14 281 332 ND 11.7 33 61 ND

Grib pipe 0.88 2.00 0.17 138 261 28 2.9 43 36 3.3

Botuobinskaya 0.47 2.98 0.58 477 498 14.5 1.47 61.6 26.3 1.46

Bellsbank (393), and Elston 01 (454). As to the remaining study areas, the maximum values of this ratio were found to be 254 (Swartruggens, South Africa) and 250 (Tres Ranchos-Limeria Group in Brazil).

The kimberlites of Zaire are (averagely) low in Ba (745 ppm, the lower value (332 ppm) having been found only in the Sturgeon Lake sample) and are rich in Cr (1622 ppm) which is similar to the value of 1591 found in the kimberlite of the Slave Craton.

The kimberlites from the southern part of the Siberian Province are averagely low in La and Th (80.4 and 8.9 ppm). Very similar values were found for the kimberlites from the northwestern province of Russia (85.5 and 9.4 ppm). Yet, the latter are notably richer in Ti, Fe, Mn, K, and P, compared to the south of the Siberian Province. Judging by the contents of Nb and Sm, the lowest concentration of La (about 30 ppm) was found in a Sturgeon Lake sample (Saskatchewan).

Kimberlites from different bodies vary in the absolute MnO content. The maximum values were found in the kim-berlite of the Mell Sill (Arkhangelsk Province) (0.357%) and in the calcite kimberlites of Sierra Leone (0.34%). Varying widely is the 100xMn0/Fe0tot value: from 1.28 and 1.37 in WSA and L-4 samples (Liberia) to 7.31 in calcite kimberlite (Sierra Leone). Relatively low 100xMn0/Fe0 values were found in the kimberlites of Australia (1.40-1.89), in the samples of the Paranatinga-Batovi Group (Brazil) (1.68-1.69), and in the kimberlites from most of the studied fragments in the Siberian Province (1.78-1.97), except for the Kuoi Field (2.13) and the Nakyn Field (2.34). This ratio is somewhat higher in the kimberlites of the Slave Craton (1.99-2.18) and in the Jericho aphanite kimberlite (2.52). Most of the South African kimberlites (10 out of 14) showed this value to be

2.01 to 2.36. Lower values were found in the Premier (1.81) and East Griqualand (1.86) kimberlites; the highest - in the Venetia Cluster (2.64) and in the Star Pipe (3.36).

The fairly high 100xMn0/Fe0tot value (2.76) was found in the kimberlites of the Kola Peninsula with a fairly good agreement between the values obtained from the results of three laboratories (2.48, 2.78, and 3.09). In this connection it is pertinent to mention the conclusion of Shcherbina et al. [1971] about the varying Mn content of the rocks from different regions. They mentioned, in particular, that “...the Lovozero alkaline massif shows a higher Mn content com-

pared to SW Greenland.” It cannot be ruled out that the Mn-rich region includes the fragment of the Kola Peninsula, where kimberlites have been found. This ratio is markedly lower (1.92) in the kimberlites of Western Greenland.

Bogatikov et al. [2001] emphasized differences between the kimberlites and lamproites from the Northern continents (Laurasia Group) and those from the southern continents (Gondwana Group), this reflecting the global geochemical heterogeneity of the mantle. The data we collected in this study illustrate these differences. The kimberlites of the southern continents are averagely enriched in P, La, Th, Zr, Nb, and less distinctly in Ti, being low in Ca (Table 3).

Mentioning the wide variations of trace and rare elements in kimberlites, it should be emphasized that even the minimum concentrations reported in literature are notably higher than the average values known for common ultraba-sic rocks [Wedepohl and Muramatsu, 1979]. In this connection the rocks of the Kurkhan diatreme (Far East, Russia) can hardly be classified as kimberlites. Reporting the very low content of Ti in the studied samples of this diatreme, Sakhno et al. [1997, 2001] compared their samples with the kimberlite of the Ruslovaya Pipe. Indeed, the Ruslovaya Pipe, like the Muza Pipe (both located in the Kuoi Field, Siberian Province), is very low in Ti and low in Al and P. Table 4 compares the contents of these components, and also of some minor and trace elements, in the Kurkhan di-atreme, in the Ruslovaya and Muza pipes, and also in the pipes reported here, which are the poorest in lithophile trace elements: Sturgeon Lake Pipe (Saskatchewan), Grib Pipe (Arkhangelsk Province), and Botuoba Pipe (Nakyn Field). As far as the Kurkhan diatreme is concerned, Sakhno et al. [1997] calculated its Ti, Al, and P contents as averages for 8 samples; they also calculated trace and rare earth elements as averages of three samples [Sakhno et al., 2001]. This showed that the contents of Sr, Ba, La, Th, Zr, Nb, and Ta were one to two orders of magnitude lower in the samples from the Kurkhan diatreme than in our pipes.

The peculiarity (uniqueness) of the chemical compositions of kimberlites from individual provinces, fields, and groups of pipes agrees with the data on the compositions of trace elements in diamonds. Watling et al. [1995] reported the results of studying diamonds in Russia, China, Australia, South Africa, and Zaire, unfortunately without mentioning

Figure 1. Selected ternary distribution diagrams for element associations in diamonds from five deposits: solid square - Russia; open square - China; triangle - Australia; solid circle - South Africa; open circle - Zaire.

their more exact locations. Their triangular diagrams showing relationships among Ga, Rb, Y, Zr, Mo, Sn, Ba, Ce, W, and Pb, show that the data points for the samples from different regions are grouped to independent, not overlapping fields (Figure 1). Diamonds from Russia are relatively enriched in tungsten, those from South Africa, in lead, and those from Australia, in zirconium.

Classification of Kimberlites into Groups

Smith et al. [1985] suggested that kimberlites can be classified into Group 1 (basaltic) and Group 2 (micaceous). The attributes distinguishing these varieties include a 87Sr/86Sr ratio of 0.703-0.705 for Group 1 and of 0.7075-0.710 for

Group 2. They also mentioned some mineralogical differences, although with the reservation that “these are generalized trends only,” and also some mineralogical differences, namely: the kimberlites of Group 1 are poor in phlogopite and contain zircon and ilmenite, while those of Group 2 are rich in phlogopite with zircon and ilmenite being absent. It should be emphasized that the first paragraph of this paper includes an important reservation: “Isotopic studies have provided unambiguous evidence that the source rocks of these two varieties of kimberlite must be distinctive, at least in southern Africa” (italics ours - I.I. and I.R.). We will also remind that in his well-known monograph, ?.?. Mitchell [1986] repeated (pp. 125, 235, 394) that the regularities found for kimberlites of some region cannot be applied to kimberlites as a whole. For instance, in Section 5.3 (Tectonic controls on the distribution of kimberlites), he states: ”...it is inappropriate to apply hypotheses developed for any given province to another region.”

Nevertheless, the authors of many recent publications dealing with kimberlite compositions often compare their study objects with kimberlites of Groups 1 and 2 after C. B. Smith. It should be recognized that this kimberlite classification cannot always be used unconditionally.

Taylor et al. [1994] emphasized the peculiarity of the Koidu kimberlite (Sierra-Leone). As follows from a number of their geochemical characteristics, these kimberlites differ from the kimberlites of Groups 1 and 2 and show some similarity with the peculiar kimberlites of the Aries Pipe (Australia).

Beard et al. [2000] stated that the kimberlites from the Arkhangelsk region occupy the intermediate position between the kimberlites of Group 1, the kimberlites of Group 2, and lamproites. The term “transitional kimberlite magma types” was used in the heading of this paper.

Kornilova and Safronov [1995] advanced their view against the subdivision of the Yakutian kimberlites into Groups 1 and 2: “No division into Groups 1 and 2, like in South Africa, can be made. Yakutian kimberlites show wide variations of their geochemical and chemical compositions, without any distinct grouping. The initial 87Sr/86Sr ratio of the Yakutian kimberlites varies from 0.7034 to 0.7127, being the highest in micaceous-carbonate kimberlites and kimberlite breccias with both high and low TiO2 concentrations.”

The classification of the Siberian kimberlites into Groups 1 and 2 is doubtful also because the Siberian Province is known to include kimberlite bodies containing abundant macro-crysts of both phlogopite and ilmenite (in contrast to the criteria suggested by C. B. Smith). Examples are the well known Iskorka Pipe in the Alakit Field, the micaceous variety of the Druzhba Pipe in the Chomurdakh Field, the “Anomaly 62n” Pipe in the West-Ulukit Field, the Sister-

1 Pipe in the Upper-Motorchun Field, Kubanskaya Pipe in the East-Ulukit Field, the Flogopite Pipe in the Merchimden Field, and the Slyudyanka and Pyatnitsa pipes in the Kuoi Field.

It is advisable to classify kimberlites into types (varieties) using the classifications developed by many authors, which are based on their textures, structures, and mineralogy. In particular, the following varieties are known: massive kim-berlites, kimberlite breccias, tuff breccias, and tuffs; kimber-

lites containing abundant and scarce autoliths; kimberlites rich and poor in mica; kimberlites containing and devoid of pyrope (“picrite porphyry” after V. A. Milashev); and, finally, kimberlites differing in the predominant size of magmatic minerals. The classification of kimberlites using these bases (applicable in the field) will be more important, both in terms of theory and practice, than the attempts of the artificial classification into Groups 1 and 2.

Carbonate Matter in Kimberlites

Of particular importance is the information on the content of carbonate matter in kimberlites. Because until recently the best known kimberlites (as indicated by the number foreign publications) were those from South Africa, the comparison of the Siberian kimberlites with them has revealed the unusual enrichment of the Siberian kimberlites in CaO and CO2. The common view was to associate these features with the composition of the host rocks. The Lower Paleozoic substantially carbonate rocks intruded by kimberlite pipes and dikes in the Siberian Province are found as xeno-liths in the kimberlite breccias. While preparing specimens for analyses, these fragments were not always removed carefully enough. Very small fragments measuring fractions of a millimeter can hardly be removed at all. Moreover, some amounts of carbonate matter might have been removed by solutions from the host rocks in the course of the secondary transformations of kimberlites. At the same time, a positive correlation between the CaO and CO2 contents, on the one hand, and between the contents of P and REE, on the other, was discovered for the kimberlites of Siberia. Using the kim-berlites of Siberia as an example, Ilupin [1970] proved that the addition of carbonate material from the country rocks caused the growth of the CaO/P2Og ratio.

The average CaO contents in the kimberlites of the southern and northern Siberian Provinces are 10.81 and 12.37%, respectively (Table 3). Some kimberlites from our list showed higher CaO contents (%): 18.00 (Somerset I.), 17.00 (Sturgeon Lake, Saskatchewan), 14.58 (Greenland), 14.28 (China), 13.24 (Ontario + Quebec), and 12.71 (USA). The high contents of calcium and carbon dioxide in the kimberlites are believed by the authors of the cited papers to have been associated with mantle material. For instance, Schmidberger and Francis [2001] wrote in their paper devoted to the Nikos kimberlite (Somerset I.): “The kimberlite whole-rock analyses are extremely high in CaCO3 (27-39 wt.%), indicating liquid compositions intermediate between kimberlite and carbon-atite... ”

The attitude toward carbonate matter (and water) in kim-berlite composition was clearly formulated by Smith et al. [1985]: “Kimberlite analyses have not been normalized to volatile-free composition simply because the H2O+ and CO2 contents are unquestionably an integral part of the rock.”

Table 5. Inter-element Correlation of Elements in Kimberlites

Correlation TiO2 Al2O3 FeO MnO MgO CaO K2O P2O5 Si/Mg Mg/Fe Fe/Ti

TiO2 1 0.144 0.832 0.346 -0.159 -0.059 -0.065 0.164 -0.147 -0.709 -0.778

AI2O3 0.157 1 0.269 0.431 -0.429 -0.050 0.282 0.109 0.616 -0.467 -0.153

FeO 0.862 0.222 1 0.627 -0.082 -0.149 -0.003 0,324 -0.133 -0.776 -0.497

MnO 0.522 0.304 0.687 1 -0.309 0.113 0.100 0.411 0.056 -0.660 -0.119

MgO -0.173 -0.370 -0.037 -0.207 1 -0.729 -0.005 -0.206 -0.475 0.656 0.287

CaO -0.049 -0.085 -0.169 0.065 -0.736 1 -0.222 0.303 -0.114 -0.329 -0.148

K2O -0.083 0.324 0.010 0.214 -0.020 -0.214 1 0.120 0.296 -0.046 -0.001

P2O5 0.174 0.130 0.331 0.529 -0.216 0.302 0.129 1 -0.221 -0.327 -0.067

Si/Mg -0.167 0.570 -0.190 -0.100 -0.441 -0.134 0.311 -0.221 1 -0.192 0.065

Mg/Fe -0.755 -0.409 -0.768 -0.668 0.629 -0.319 -0.067 -0.343 -0.132 1 0.610

Fe/Ti -0.779 -0.198 -0.552 -0.336 0.340 -0.180 0.036 -0.086 0.077 0.698 1

Cr -0.220 -0.317 -0.101 0.109 0.498 -0.363 0.287 -0,017 -0.179 0.383 0.351

Ni -0.277 -0.462 -0.213 -0.252 0.743 -0.661 0.057 -0.290 -0.084 0.592 0.458

Sr 0.007 0.036 0.175 0.446 -0.190 0.356 0.252 0.622 -0.289 -0.264 -0.053

Ba -0.199 -0.121 -0.073 0.315 -0.155 0.338 0.254 0.512 -0.190 -0.048 0.169

La 0.127 0.014 0.304 0.417 -0.269 0.362 0.066 0.713 -0.197 -0.354 -0.124

Th 0.101 -0.105 0.238 0.381 -0.193 0.280 0.021 0.651 -0.178 -0.257 -0.052

Zr 0.554 0.048 0.587 0.544 -0.207 0.156 0.096 0.747 -0.221 -0.544 -0.419

Nb 0.609 -0.069 0.659 0.530 -0.232 0.302 -0.177 0.498 -0.420 -0.632 -0.477

Zr/Nb -0.032 0.130 -0.021 0.082 -0.024 -0.141 0.399 0,271 0.206 0.036 0.122

K/Ba -0.031 0.492 -0.029 -0.095 0.004 -0.383 0.609 -0.199 0.520 -0.006 0.014

Mn/Fe -0.413 0.052 -0.390 0.385 -0.259 0.307 0.224 0.203 0.158 0.117 0.303

Correlation Cr Ni Sr Ba La Th Zr Nb Zr/Nb K/Ba Mn/Fe

TiO2 -0.213 -0.272 0.004 -0.204 0.134 0.110 0.549 0.618 -0.042 -0.010 -0.390

AI2O3 -0.340 -0.511 0.023 -0.108 -0.004 -0.118 -0.027 -0.077 0.054 0.413 0.210

FeO -0.122 -0.244 0.169 -0.068 0.287 0.220 0.534 0.612 -0.041 -0.049 -0.233

MnO 0.001 -0.308 0.332 0.259 0.268 0.232 0.286 0.292 0.007 -0.165 0.594

MgO 0.511 0.755 -0.179 -0.154 -0.244 -0.168 -0.149 -0.196 0.011 0.031 -0.335

CaO -0.368 -0.650 0.353 0.340 0.351 0.268 0.135 0.273 -0.142 -0.392 0.312

K2O 0.289 0.056 0.248 0.245 0.075 0.031 0.108 -0.143 0.384 0.617 0.133

P2O5 -0.015 -0.272 0.622 0.513 0.706 0.644 0.731 0.473 0.275 -0.204 0.182

Si/Mg -0.205 -0.153 -0.284 -0.183 -0.194 -0.179 -0.252 -0.387 0.145 0.480 0.223

Mg/Fe 0.402 0.614 -0.249 -0.052 -0.322 -0.226 -0.462 -0.564 0.068 0.026 -0.043

Fe/Ti 0.321 0.423 -0.047 0.175 -0.140 -0.072 -0.425 -0.508 0.128 -0.031 0.358

Cr 1 0.527 0.032 0.326 0.122 0.219 -0.086 -0.001 -0.022 -0.077 0.176

Ni 0.516 1 -0.319 -0.173 -0.377 -0.207 -0.205 -0.350 0.138 0.126 -0.126

Sr 0.030 -0.337 1 0.668 0.534 0.389 0.508 0.342 0.176 -0.302 0.233

Ba 0.331 -0.179 0.668 1 0.631 0.654 0.237 0.349 -0.048 -0.470 0.412

La 0.116 -0.399 0.536 0.638 1 0.902 0.546 0.678 -0.054 -0.360 0.085

Th 0.213 -0.226 0.391 0.661 0.901 1 0.489 0.641 -0.061 -0.419 0.127

Zr -0.113 -0.259 0.514 0.246 0.545 0.485 1 0.552 0.487 -0.106 -0.158

Nb -0.012 -0.373 0.353 0.368 0.679 0.641 0.552 1 -0.342 -0.430 -0.206

Zr/Nb -0.040 0.102 0.174 -0.051 -0.056 -0.065 0.482 -0.346 1 0.448 0.063

K/Ba -0.093 0.119 -0.305 -0.470 -0.380 -0.443 -0.134 -0.484 0.461 1 -0.173

Mn/Fe 0.286 -0.041 0.281 0.467 0.150 0.208 -0.074 -0.141 0.121 -0.111 1

Note: Figures above diagonal represent the inter-element correlation in all objects from Table 1 “Figures below diagonal represent the inter-element correlation in the same collection without two objects (Finland — p. 2—3; Arkhangel’sk — Mela sill)”.

General Reqularities in the Chemical 1978] turned out to be common for the kimberlites of all

Compositions of Kimberlites regions discussed.

Pair correlation coefficients were calculated for all regions Some regularities discovered in the compositions of the listed in Table 1. The coefficients for the most interesting Siberian kimberlites [Ilupin, 1997, 1999, 2000; Ilupin et al., components are listed in Table 5, separately for the whole

data array and for the array without two regions (Group 2 for Finland and the Mell Sill from the Arkhangelsk Province), which showed anomalous relationships of manganese with trace elements.

A direct correlation was found between the Al2O3 contents and the SiO2/MgO ratio (0.616); this relationship for the kimberlites of Siberia is shown graphically in the book by [Ilupin et al., 1978, p. 85]. Closely related are Ti with Fe (0.832) and Mg with Ni (0.755). A distinct negative correlation exists between Mg and Ca (-0.729), reflecting a variable relationship between the “silicate” and “carbonate” constituents of the kimberlites.

A direct relationship (r=0.610) was found between the MgO/FeOtot and FeOtot/TiO2 ratios. Using the Siberian Province as an example, it was shown that the elevated values of both ratios were typical of diamond-bearing kimberlite bodies. The Fe/Ti ratio is the most important constituent of a “potential diamond content factor (PDCF)” offered by Milashev [1965].

The trace and rare elements concerned (Sr, Ba, La, Th, Zr, and Nb) were found to correlate with one another. The strongest correlation exists between Th and La (0.902). Only one (Ba-Zr) correlation (0.237) was found to be below the critical value. Also poorly correlated are Sr-Th (0.389), Sr-Nb (0.342), and Ba-Nb (0.349). All of these six elements have a positive correlation with P, the correlation coefficients varying from 0.473 (Nb) to 0.731 (Zr). Zr and Nb also correlate with Ti and Fe, the respective coefficients varying from

0.534 to 0.618.

Information on the CO2 content in the samples is not reported by all researchers. We examined the relations of CaO with the other components (keeping in mind that kim-berlites contain Ca not only in the form of carbonate, but also in the forms of perovskite, apatite, and other minerals). We found that Ca showed a low (yet significant) correlation with P (0.303), Sr (0.353), Ba (0.340), and La (0.351).

We found a positive correlation (r=0.461) between the K/Ba and Zr/Nb ratios.

A week but significant correlation (0.307) was found between the Ca content and the Mn/Fe ratio. In the case of Siberian kimberlites this correlation is shown graphically by [Ilupin et al., 1978, p. 202] and [Ilupin, 1997] and is explained by the high Mn/Fe ratio in the carbonate matter. For instance, the kimberlite veins (dikes) of the Malo-Botuoba Field (Siberian Province), most rich in carbonate (30.30-36.06% CO2 and 38.60-46.25% CaO [Ilupin et al., 1978, p. 21] showed a MnO/FeOtot ratio of 2.85 to 9.01, this ratio being 2.13 for the average kimberlite contents obtained in our study.

A direct relationship was found between the concentrations of manganese and LREE [Ilupin, 1997]. In our case, having discarded two “anomalous” areas, we got a significant correlation of manganese with Ti, P, Sr, Ba, La, Th, Zr, and Nb, the correlation of Mn with P2O5, Sr, Ba, La, and Th being stronger than the correlation of these elements with Fe (see Table 5, values below the diagonal).

The comparison of kimberlites from different fields (and groups of pipes) in the Siberian province revealed a direct relationship between the Co(ppm)/MgO(wt%) ratio and the contents of Ti, P, and lithophile trace elements [Ilupin, 1999].

Table 6. Pair correlation coefficients of components with values Co/MgO and Ni/Co (for 45 objects, critical value ro.o5 = 0.292)

MgO Co/MgO Co Ni/Co Ni

TiO2 -0.369 0.517 0.309 -0.638 -0.467

P2O5 -0.210 0.392 0.257 -0.326 -0.202

Sr -0.159 0.480 0.392 -0.322 -0.147

Ba -0.106 0.135 0.042 -0.131 -0.078

La -0.289 0.479 0.281 -0.510 -0.393

Th -0.180 0.247 0.132 -0.353 -0.284

Zr -0.219 0.575 0.509 -0.362 -0.064

Nb -0.306 0.510 0.325 -0.649 -0.483

MgO/FeOt 0.707 -0.649 -0.190 0.696 0.590

To verify this relationship we used samples listed in Table 1 (those found to contain Co) and samples from Table 2, found to contain all components of interest. We calculated correlation coefficients (Table 6) for our data array of 45 objects. We found significant correlations between Co/MgO and TiO2 (0.517), P2O5 (0.392), Sr (0.480), La (0.479), Zr (0.575), and Nb (0.510). Like in the case of the Siberian kimberlites, the correlation coefficient (absolute value) of all listed components with Co/MgO is higher than in the case of the correlation separately with Co and Mg.

A significant inverse correlation was found between the Ni/Co ratio and TiO2 (-0.638), P2O5 (-0.326), Sr (-0.322), La (-0.510), Th (-0.353), Zr (-0.362), and Nb (-0.649). The absolute values of the coefficients were again found to be higher than in the case of the correlation separately with Ni and Mg. As would be expected, a direct correlation was found between MgO/FeOtot and Ni/Co (0.696).

In the overwhelming majority of cases our correlation coefficients for the kimberlite of the whole world are lower (in absolute value) than the coefficients calculated earlier for the Siberian Province. To some extent, this might have been caused by analytical errors. Yet, the main cause seems to be the peculiarity of individual kimberlite provinces, fields, and pipe groups. The ratios between elements can vary notably from region to region. This can be illustrated by the Th(ppm)/P2O5(wt.%) ratio varying from 28.2 to 46.5 for the groups of samples from Finland, from 6.5 to 17.1 for the samples from the neighboring region of the Arkhangelsk Province (including the Kola Peninsula), and being 23.3 in the Vodorazdelnaya Pipe (Middle Timan). The Zr/Nb ratio was found to vary from 0.65 to 0.99. As far as the South African kimberlites are concerned, a similar value (0.71) was found only for the Bathlaros kimberlite, whereas in other

11 cases it varies from 1.30 to 2.21, being even higher in Swartruggens (2.80) and in Finsch (3.61). These differences are bound to impair correlation.

Conclusions

1. In terms of their petro- and geochemical characteristics, kimberlites from all regions (provinces, groups of bodies, and

individual bodies) are peculiar, differing from other objects in some attributes or their combinations (because some attributes may happen to be identical). This peculiarity of all kimberlite occurrences (like the peculiarity of diamonds transported by them) can be explained by the heterogeneity of the upper mantle. The most exact information of the chemical compositions of kimberlites can be obtained if all foreign (epigenetic) materials are removed thoroughly.

2. Compared to the kimberlites of the northern continents (Laurasia group), the kimberlites of the southern continents (Gondwana Group) are more enriched in P, La, Th, Zr, Nb, and Ti and are poor in Ca.

3. The subdivision of kimberlites into Groups 1 and 2, specified for the kimberlites of South Africa, can hardly be used for the kimberlites of all other provinces, keeping in mind a remark offered by [Smith et al., 1985] concerning the applicability of this subdivision “at least in southern Africa.”

4. Similar to water, carbon dioxide is a natural constituent of kimberlite.

5. The common regularities, proved for all known provinces, seem to attest the existence of some common trends in the evolution of a deep-seated material during the generation of kimberlite magma and its movement toward the Earth’s surface.

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(Received 19 November 2002)