BASIC DYKES. 



133 



A chemical analysis of the Kawa dyke (specimen No. fifa) has 



been kindly made by Dr. Christie in the 



Chemical composition, y^^^y of the Geological Survey. It is us 



follows : — 



Specific (liavity 



Sid 9 

 Ala 0, . 



\-v, 0, • 



FeO 



MgO . 



CaO 



Na e O . 



K,() 



H,o (below 108° C) 



11 ,() (above 108° C) 



TiO, . 



ZnOa • 



co 2 



P,0 8 . . 



80s (total S as) 



Or,O a . 



MnO . 



BaO 



SrO 



3*00 



60' -2[i 



16-51 



3-83 



8*26 



.")• 8 

 9-53 

 2*07 

 104 



•us 

 •83 



1-41 



t race 



t race 

 ■31 



•23 



•01 

 •14 



•02 



trace 



99-78 



Of the remaining basic dykes, there is only one, namely that at 



Bodi, 5 2 /\) (12500), where the material is suffi- 



Bodi dyke. ciently preserved to be recognisable. The dyke 



is about G feet wide and imperfectly exposed on the pathway to 



Paliapar, intruding the biotite schist of that area (sec p. 62). 



It appears as a fine-grained, black rock. In thin section the plagio- 



clase is in long lath-shaped forms arranged in beautiful cruciform 



or star-shaped clusters, and is probably labradorite. The augitc 



is of a dull brownish yellow colour and is present as hypidiomorphic 



granules and patches. There is no quartz, a fair amount of iron- 



Sre, no residual glassy base that can be detected, no porphyritic 



elements and no ophitic structure. The dyke is bordered by a 



still finer-grained selvage No. £ft (12501, PI. 16, fig. <1), which 



has a particularly beautiful appearance in thin section. 



A number of other, and very probably similar, basic dykes, 

 appeal anion-' nearly all of the Bamanvada 



Bamanvada dykes. ^ { ^-^^-^ ,/ roups of Aravalli TOCks, 



in a perfectly irregular and indescribable way, impossible of mapping— 



