68 HAYDEN : GEOLOGY OF THE PROVINCES OF TSANG AND 0. 
any younger beds that may have overlain the shale have been cut out 
by a fault which brings the upper Cretaceous over the Tertiary. The 
table of strata facing PI. 3 shows the sequence of the Cretaceous and 
Tertiary beds of the Kampa series. 
6. Basic igneous rocks, including dolerite and serpentine, occur 
as dykes in the Jurassic slates near Gyantse and 
Igneous rocks. 
along the shores of Yamdrok Tso. Granite is 
found in the valleys of the Tsangpoand Kyi Chu and also at Lhasa, 
where it is used as a building stone. The Kyi Chu granite is a fairly 
coarse-grained, hornblende granite, containing oligoclase, biotite and 
sphene, and differs markedly from the typical biotite-granite of the 
Himalaya. The difference, however, consists chiefly in the large 
quantity of lime and lime-sihcates occurring in the former rock and 
may be due to the absorption by it of lime from the! sedimentary 
beds into which it was intruded. Pebbles of dacite and allied volcanic 
rocks occur in the gravels of the Tsangpo near Chaksam, and are 
apparently derived from the hills between Shigatse and Kampa-partsi. 
A bed of amygdaloidal trap was found among the slates believed 
to be of Jurassic age in the hills to the north-east of Gyantse. If 
truly contemporaneous, this bed is of some interest as being the first 
indication of Jurassic lava flows yet observed in the Himalaya. 
7. Few minerals of economic value were found in situ ; gohl occurs 
in very small quantity in the Tsangpo gravels, 
Economic geology. , ra j 1 1 f j- 
and an efiiorescence, composed largely 01 sodmm 
carbonate, is found at Utsi, 6 miles north-west of Kampa dzong. 
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