Reports and Proceedings — Geological Society of London. 



191 



They form bands witli outcrops from a few feet to over a quarter of 

 a mile in width, interbedded with the granulites. The limestones 

 themselves have a banded structure (foliation) parallel to that of the 

 granulites and to the boundaries. This foliation of the limestone 

 depends on variations in structure, amount of accessory minerals, 

 and relative proportion of calcite and dolomite. The grain is coarse, 

 sometimes exceedingly so. Parallel and graphic intergrowths of 

 calcite and dolomite are very characteristic. The most abundant 

 accessory minerals are olivine, phlogopite, pink or violet spinel, 

 diopside, pyrite, and blue apatite ; less common are amphiboles, 

 clinohumite, green spinel, etc. The most characteristic contact- 

 minerals are diopside, amphibole, green spinel, and greenish micas ; 

 and, rather in the granulite than the limestone, scapolite, phlogopite, 

 diopside, sphene. There occur also in the limestones, nodular 

 mineral aggregates composed of characteristic minerals such as 

 diopside, phlogopite, blue apatite, and spinel. 



There are often transitions between the limestones and granulites. 

 In some other cases a zone of green rocks (with diopside, dark mica, 

 amphibole, and green spinel) intervenes. Bands (sills) of granulite 

 of various width, down to less than a foot, may occur in the 

 limestone, and are parallel to the foliation and general strike. 

 These show peripheral transitions to the limestone by incoming of 

 original calcite and the appearance of lime-silicates, or are separated 

 from it by a zone a few inches wide, in which the minerals diopside, 

 amphibole^ and green spinel are characteristic. 



Some interrupted sills are described, and compared with the 

 interrupted dykes of nepheline-syenite in the crystalline limestones 

 of Alno, described by Professor Hcigbom. A sill may thus be 

 continued along the strike as a series of lenticles. Elsewhere quite 

 isolated masses of pyroxene-granulite occur as inclusions in the 

 limestone. 



Although the relation of the granulites to the limestones is on the 

 whole intrusive, the two rocks in their present condition are 

 essentially contemporaneous, and seem alike to have consolidated 

 from a molten magma. The calcite occurring in the granulites near 

 the contact has all the appearance of an original mineral. The 

 foliation of the limestone is regarded as a sort of flow-structure, and 

 corresponds with that of the granulites to which it is always parallel. 

 That the foliation does not result from the action of earth-movements 

 on a solid rock is shown by this, that the very minerals whose 

 variable distribution is one of its chief causes, have certainly not 

 been affected by deforming earth-movements, nor ai'e they such as to 

 have been produced by these ; moreover, in this respect a distinction 

 cannot be made between the limestones and granulites, which would 

 necessarily have suffered alike had they been subjected to deforming 

 strains since the consolidation of the latter. The original nature of 

 the limestones is less evident : they may have been sedimentary or 

 tufaceous, and, if so, subsequently softened and metamorphosed ; 

 or possibly ah initio truly igneous rocks, and related to the 

 charnockite-magma. Eeasons for and against these views are 2;iven. 



