THEORY OF LIQUID IMMISCIBILITY OF KIMBERLITE MAGMA.

Igor Kryvoshlyk. Toronto, Canada. (416) 359-7809.

My first presentation of my theory of liquid immiscibility of kimberlite magma I made in December 1973 when I worked for Diamond Laboratory of the Central Research Institute of Non-ferrous & Noble Metals (now – YaGEER&D CNIGRI, ALROSA Company Ltd), city of Mirny, Yakutia, Russia. It took three long years to publish it in 1976 (my article was accepted for publication in April 1975).

The basic statements of this theory are:

  1. There are two main genetically different types of kimberlite rocks: massive kimberlites and autolithic kimberlites. Autolithic kimberlites consist of autoliths and matrix. Massive kimberlites represent autolithic material for 100 % [1, 7].
  2. Autoliths = “lapilli”, “inclusions of kimberlite in kimberlite”, etc. Autoliths are solidified drops of subalkaline picritic melt. The matrix of autolithic kimberlites is an immiscible carbonatitic material with its own typomorphic minerals – baddeleyite and pyrochlore. Autolithic kimberlites = kimberlite “tuffs” are igneous (not a pyroclastic) rocks [1, 7].
  3. The coalescence of drops of picritic melt produced the autoliths and blocks of massive kimberlites. Small fragments of carbonatitic material within such blocks look like xenoliths of limestones or like veins of postmagmatic carbonates. [1, 6].
  4. Kimberlite pipes were filled up by just one sole injection of kimberlite magma. Consequent differentiation between both melts produced all possible kimberlite rocks.
  5. The cavity of diatremes was created by series of water hammers generated in the head of ascending magma. Solidified autoliths along with xenoliths gathered into cumulates, which periodically plugged originally elongated dyke-like channel of eruption. Water hammers transformed it into more and more isometric pipe-like one. In some cases, weakened water hammers produced “blind” diatremes, which never had an exit to the earth’s surface. When magma met the plug, water hammer struck in all possible directions making a lot of specific grooves or striae (after mechanical abrasion of the pipe walls by intruded kimberlite) not just vertical, but also inclined and even horizontal (A. Du Toit, 1906) [11].
  6. Deep overcooling of magma followed the moment of liquid immiscibility. This idea has its confirmation in number of experiments. Therefore, it is easy to see, why thermal effect on xenoliths and wall rocks was so low. Sharp overcooling crushed hot mantle xeno- and phenocrysts (in approximately equal proportion, independently of their own hardness). If any outer mechanical forces would crush such a super-hard mineral as diamond is, so these forces must to grind to powder all other kimberlitic minerals, however, they survived.
  7. Serpophit is a volcanic glass of kimberlite rocks [3, 4, 5].
  8. Kimberlites are rich for titanium, potassium, phosphorus, hydrogen, boron, fluorine, etc. that are catalysts of liquid immiscibility in experimental systems.
  9. The word “Kimberlite” has to be used as an economic (not petrographical) term for diamondiferous variety of the wide range of ultrabasic subalkaline hypabyssal rocks rich for olivine and also for carbonate, mica, clinopyroxene, melilite, monticellite, potassium feldspar, etc. Petrologically it has to be a mechanically blended rock-mixture between carbonatites and group of ultrabasic silicate rocks [2].
  10. At least some of diamonds could be generated by kimberlite magma itself during eruption. A long, well known list of undoubtedly crustal minerals among inclusions in diamonds (staurolite, quartz, hornblende, feldspar, plagioclase, etc) cannot be explained on the traditional basis. In addition, this idea can explain the numerous discoveries of diamonds in crustal xenoliths and wall rock made by Botkunov A.A. (1964).

Below is a one of logical explanations. Using classic hydrodynamic formula (8, p.377):

Q = 8.34 * [{dP / (Dm * L)} ^ (4 / 7)] * [(C ^ (19 / 7))/ (B ^ (1 / 7))]

we can receive the volume speed of eruption (Q cub. m / sec).

dP – pressure overfall on the opposite sides of channel of eruption; for kimberlite magma dP = 45 kbar = 4.5 * 10 ^ 9 Pa,

Dm – magma’ density, at least 2.5 * 10 ^ 3 kg / cub. m

L - vertical length of the channel, 150 km = 1.5 * 10 ^ 5 m

C – hydraulic diameter; for dyke:

C = (2 * X * Y) / (X + Y)

where: X – width of dyke, Y – length of dyke (horizontal).

B – kinematic index of viscosity. According to (10, p. 444):

B = A / Dm

where: A – viscosity, Pa / sec; if A = 1 (just for water-rich carbonatitic liquid, which was a transporting agent for kimberlite magma), so B = 4 * 10 ^ (-4) sq. m / sec.

The average dimensions for Siberian kimberlite dykes (9) are: X = 2 – 3 m, Y = 500 – 800 m, so C = 4.98 m.

So, Q = 8,236 cub. m / sec.

Linear speed of magma V = Q / Sd, where Sc – the size of the cross-section; for Siberian dykes Sd = 1,625 sq. m, so:

V = 5.1 m / sec.

The loss of the quantity of movement [dK] during single water hammer is:

dK = Mk * dV

where Mk – mass of magmatic column, dV – loss of the speed during the water hammer.

Mk = Dm * L * Sc= 6.09 * 10 ^ 11 kg.

If to accept dV = 2.55 m / sec (just 50 % of its original speed),

dK = 1.55 * 10 ^ 12 kgm / sec.

If the duration of the loss of speed (dT) was 5 min, so the power of single water hammer was:

F = dK / dT = 5.17 * 10 ^ 9 N

During water hammers in the front of the magmatic column, the pressure 40 kbar (necessary for diamond growth) could be reached in the sphere with the surface of:

Ss = F / P = [5.17 * 10 ^ 9] / [4 * 10 ^ 9] = 1.29 sq. m

and the diameter:

D = (Ss / π) ^ 0.5 = 64 cm

Each water hammer could create a cavity:

U = F / (g * Dr)

Where: U –volume of wall rocks,

F – power of single water hammer, 5.17 * 10 ^ 9 N

g = 9.81 m / sq. sec

Dr – wall rock’s density, 2.6 * 10 ^ 3 kg / cub. m [12]

So, U = 2.027 * 10 ^ 5 cub. m

An average kimberlite pipe has a volume about 505 * 10 ^ 5 cub. m [12]. Therefore, to create this size diatreme, the number of water hammers around 250 will be necessary.

If to accept that the duration of single water hammer was 1 hour (5 min to loose the speed and 55 min to gather it back), time about 10 days will be enough to create average kimberlite pipe. It also looks big enough for diamonds growth. It is not a secret, that the greater number of natural diamonds has intensively dislocated inner structure, possibly, under water hammers influence as well.

Major Publications:

  1. KryvoshlykI. 1976. The Peculiarities of Morphology and Some Questions of Genesis of Autoliths in Kimberlite Breccias. Geology and Geophysics, # 7. 1976. Novosibirsk, (in Russian).
  2. KryvoshlykI. 1978a. About The Term of “The Kimberlite”. 1978. Deposited Manuscript # 859-78. Moscow, (in Russian).
  3. KryvoshlykI. 1978b. To the Question of Studying of Autoliths in Kimberlite Rocks. 1978. Deposited Manuscript # 2115-78. Moscow, (in Russian).
  4. KryvoshlykI. 1979. To the Question of Possibility of Liquid Immiscibility in Kimberlite Pipes. 1979. Deposited Manuscript # 2440-79. Moscow, (in Russian).
  5. KryvoshlykI. 1980. Autoliths and Some Conclusions of the Hypothesis of Liquid Immiscibility. 1980. Transactions of the Academy of Science of the USSR. V. 252, # 1. Moscow, (in Russian).
  6. KryvoshlykI. 1981. The Globules of Immiscible Carbonatites in Kimberlite Rocks. 1981. Transactions of the Academy of Sciences of the USSR. V. 260, # 4. Moscow, (in Russian).
  7. KryvoshlykI. 1983. Genesis of Autoliths of Kimberlite Rocks.. PhD thesis. MoscowUniversity.
  8. KryvoshlykI. 1998. Brief Review of the Theory of Liquid Immiscibility of Kimberlite Magma. 1998. 7th International Kimberlite Conference. Cape Town. Extended Abstracts, pp. 473-474.

Also:

  1. Povh I.L. 1964. Hydrodynamics., (in Russian).
  2. Kovalsky V.V. 1963. Kimberlite Rocks of Yakutia. Academy of Sciences of the USSR. Moscow. (in Russian).
  3. Loytsyansky L.G. 1970. Fluid and Gas Mechanics. Nauka (Science) Publication. Moscow. (in Russian).
  4. Clement C.R., Harris J.W., Robinson D.N., and Hawthorne J.B. 1986. The De Beers Kimberlite Pipe – A Historic South African Diamond Mine. Mineral Deposits of Southern Africa. pp. 2193-2214.
  5. Milashev V.A. 1984. Pipes of Explosion. Nedra. (in Russian).

IMPORTANT NOTE.

This theory was ignored for many years. At the present time it became a classic point of view. The impressive list of publications and even PhD dissertations by those “scientists” who used to use somebody else’s ideas confirms a justice of my theory. Should I be thankful to these plagiarists? Should I attach their list?