Introduction - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 9

Table 1.1 (continued)
Sl. Locality Rock types Age

34. Kaindy, former U.S.S.R. K-rich volcanics Middle to early

Permian

35. Yakokut, former U.S.S.R. K-rich volcanics Quaternary

36. Andriyanovka, former U.S.S.R. K-rich volcanics 20 + 3 Ma.

37. Elpinskii, former U.S.S.R. K-rich volcanics 14.5 Ma

38. Anomaly Pipe, former U.S.S.R. K-rich volcanics Upper Mesozoic

39. Molobo, former U.S.S.R. Lamproite 122 92 Ma

-

40. Rododendron, former U.S.S.R. Shonkinite 166 + 5Ma

41. Kamchatka, former U.S.S.R. Trachybasalt, tephrite 20 + 3Ma

42. Tommot, former U.S.S.R. Leucitetephrite 167 125 Ma

-

43. Omolon, former U.S.S.R. Leucitelamproite Palaeocene

44. Damodar Valley, Eastern India Leucitelamproite and

Olivine lamproite

105 Ma

45. West Kimberley, Australia Lamproite 24 17 Ma

-

46. New South Walse, Australia Leucitite 14 10 Ma

-

Navon and Stolper is feasible? Numerous field-oriented studies of Alpine massif,

ophiolites and xenoliths show that a common mode of transport in the upper mantle
is through the conduits formed by hydraulic fracturing. Does the method of

uid

migration related to the presence of non-percolating fluid, increase pore pressure

approaching the lithostatic pressure? Do the isolated pockets of fluid nucleate mi-

crocracks? With the increase in strain, do the microcracks interact to produce
enechelon of crack arrays? Does the array of cracks extend and coalesce further to
form fracture systems? These are the questions to be addressed, when one considers
the methods of large-scale mantle metasomatism.
Phlogopite, K-richterite and apatite found in the mantle xenoliths within the
K-rich lavas, are enriched in fluorine (Edgar et al. 1996). The study of Vukadinovic
and Edgar (1993) on hydroxy-

uor-phlogopite, hydroxy- uor K-richterite and

uor apatite however, showed that Df crystal/liquid is usually >1. Fluorine
therefore appears to be a compatible element in the mantle. Why then the K-rich
partial melts of ultrama

hydroxy-

c mantle (containing these minerals) are enriched in

fluorine, when they should have been retained in the mantle phases? The K-rich
melts are also quite high in the TiO 2 contents. What is the mechanism for Ti-
enrichment in such melts?
The upper atmosphere is dominated by the presence of nitrogen. It is also an
essential constituent of many biological components particularly protein and their
degradation products (Hall 1999), and it is therefore present in soils and sediments.
Igneous and metamorphic rocks are in general poorer in nitrogen than most
sediments.
The ammonium ion is very similar in its properties to the potassium ion, which is
substituted readily by NH 4 + as the ionic radius of K + (1.46 A o ) is close to NH 4 +
(1.61 A o ). Besides, their coordination number is similar. Like Rb + and Cs + ,NH 4 +