Chamba State

· 1904 · Public domain (published pre-1930) · archive.org ↗

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2Oxamea Stare. | Gneissose-granite. (Parr A.

3slates. ‘The granite had partially consolidated before it was moved CHAP I A.

4into place: large porphyritic cry stals of felspar end numerous micas Physical

5and quartz-praims hd formed : the semi-plastic mas: was subjected to Aspects.

6enormous pressure : the mica was crumpled, the erystals of felspar Caneeof the

7were sometimes cracked and ruptured : and so much of the micaceous folietion,

8silicious materials as remained unconsolidated were forced into the

9rents made in the already formed materials. The final consolida-

10tion took place under conditions of continued strain.

11The possibility thet the foliation and other structura] pecu- Tangential

12Vjarities seen in the Dalhousie granite were produced by tangential per esis

13pressure and shearing, after the complete consolidation of the

14granite, has been carefully considered and rejected, and my reasons

15for discarding this hypothesis are briefly stated as follows :-—

161. The effect of comparatively soft rocks being crushed Bese ae

17against a hard consolidated granite would have been felt in the

18sedimentary rocks rather than in the hard granite, whereas one

19finds the dark carbonaceous limestones and hypo-metamorpbie

20black slates”, in contact with the outer band of intensely foliated

21and platey granite, show extiemely little metamorphism.

22The limestones are never more than sub-crystelline, and the

23carbonaceous material has not been converted into graphite. More-

24over the idea that tangential pressure should be so great as to

25cause the formation of poly-synthetic quartz and cerypto-crystalline |

26mica throughout a solid mass of consolidated granite, ranging

27from six to eleven miles in width, passes belief,

289. The foliation observed in the intruded granite is not

29always visible along the margin of the rock in contact with the

30slates. In places the eranite, though porphyritic, is granitic in

31structure and is not foliated. Had the foliation observable in the

32porphyritic granite been the result of the shearing of a solid rock,

33the granitic portions next the slutes could net have escaped being

34affected by the movement, and the sharply rectangular porphyritic

35crystals of felspars, which orient in all directions, would have been

36drawn out into strings. The partial foliation, observed in portions

37of the rock, is obviously due to the uniformity in direction imposed

38on the flakes of mica, by pressure on an imperfectly consolidated,

39viscous rock.

40§. ‘The fact that the granite passes capriciously from afoliated =”

41to an unfoliated rock in parts away from the margin, and that long

42splinters of schists are met with half a mile or more from the

43margin of the sedimentary series, shows that the foliation observed

44in places cannot be due to the shearing of a consolidated rock.

45Had such shearing taken place the granite would have been uni-

46formly foliated, and the embedded fragments of Schist would heve

47been ground down to wafers.

48A glance at the photograph of a transverse section of one of

49,hese splinters, given at page 179, Vol. XVI, of the Records, Geol.