Experimental Studies on K-Rich Rocks - Origin of Potassium-rich Silica-deficient Igneous Rocks - page 394

Ol þ Phl

þ Ol þ Opx þ Liq þ Vap ! Phl þ Ap þ Ol þ Opx þ Liq þ Vap ! Phl þ Chr
þ

Lig þ Vap ! Phl þ Ol þ Liq þ Vap !

Ol þ Opx þ Ap þ Liq þ Vap ! Phl þ Ap þ Opx þ Chr

þ Ol þ Cb þ Liq þ Vap ! Phl þ Opx
þ Ol þ Ap þ Chr þ Carb þ Vap
High pressure-low temperature assemblage in case of Mohanpur lamproite is
also an apatite- and phlogopite-bearing harzburgite containing minor amount of
priderite and carbonates. The La (0.41) and Ce (0.64) contents of apatites crys-
tallized from the Mohanpur sample at 975 C and 2.5 GPa are also high. Apatite

may therefore, be host mineral for these elements in the mantle rocks. Foley et al.
(1994) studied the stability of priderite and concluded that it is stable up to 5 GPa
and 1,500

°

C; however, in this particular case priderite appears to be a low pressure
phase at 1.0 GPa. It is possible that the P-T

°

T stability of priderite is restricted to a
lower pressure in presence of various phases in lamproite.

-

13.2.6.3 High P-T T Study on a Satyanarayanpur Lamproite

-

The phase equilibria study of the lamproite sample from Satyanarayanpur is sum-
marized in Fig. 13.11 , which shows that with the decrease of temperature following
assemblages appear:

2.5

Satyanarayanpur lamproite

2.0

ol
+
phl
+
opx
+
apat
+
chr
+
rut
+
carb
+
vap

liq
+
vap

1.5

1.0

0.5

600 700 800 900 1000 1100 1200 1300

T o

Fig. 13.11 Phase relations of a lamproite from Satyanarayanpur (Raniganj Basin) (after Gupta
et al. 2002). For abbreviations, see Fig. 13.7 . rut: rutile