Along Hudson Bay shore there is a strip of similar rocks, and a long row of small islands of the same age, with great sheets of trap or diabase forming the tops of the hills.
All the volcanic rocks of these islands are submarine stratified tuffs which are penetrated here and there by andesite or diabase dikes.
In the western portion of Mainland, in Northmavine, -there is a considerable tract of rocks of this age which are formed largely of intrusive diabase-porphyrite; similar volcanic rocks occur in Papa Stour.
Sheets of diabase, apparently volcanic flows, and numerous dykes interfere with the regularity of the stratification.
This consists largely of rocks of igneous origin, of which the amygdaloidal diabase of Klipriversberg forms the type.
The basis of the islands consist of granite, syenite, diorite, diabase and related kinds of rock, porphyry appearing comparatively seldonr.
Along with these, similarly, hornblende and diabase occur in the Pelew Islands and gneiss and mica 1 These are dependencies of New Zealand, as are also the following islands and groups which lie apart from the main Polynesian clusters, nearer New Zealand itself: Antipodes Islands, Auckland Islands, Bounty Islands, Campbell Islands, Chatham Islands, Kermadec Islands.
Blackrock diabase (cones and dikes) -
Near Haco's Ness in Shapinsay there is a small exposure of amygdaloidal diabase which is of course older than that in Hoy.
Here prevailing granite and diabase give rise to a complicated mountain system through which the rivers cleave their way in a curved and irregular course.
They are accompanied by intrusions of diabase and gabbro, and they are sometimes folded, sometimes but little disturbed.
At Inverell in New South Wales a diamond (1906) has been found embedded in a hornblende diabase which is described as a dyke intersecting the granite.
Curacao consists of eruptive rocks, chiefly diorite and diabase, and is surrounded by coral reefs.
Quartz porphyry, diabase and diorite appear in the Ardennes.
The great igneous masses of Troodos, &c., consisting of diabase, basalt and serpentine, are of later date.
South of Lake Vener they are capped by thick beds of eruptive diabase (called trapp).
Slates, schists, quartzites and limestones form the greater part of the hills, but the Brocken and Victorshohe are masses of intrusive granite, and diabases and diabase tuffs are interstratified with the sedimentary deposits.
The most conspicuous member of the Mesozoic group is the sheet of diabase and dolerite, made up of laccolites and sills, which covers most of the central plateau of Tasmania.
This sheet of diabase has been regarded as Carboniferous; but, according to W.
There occur also quartz-porphyry (Sierra Morena, Pyrenees, &c), diorite, porphyrite, diabase (well developed in the north of Andalusia, where it plays a great part in the structure of the Sierra Morena), ophite (Pyrenees, Cadiz), serpentine (forming an enormous mass in the Serrania de Ronda), trachyte, liparite, andesite, basalt.
Igneous rocks are not extensively developed; in Wales they form an important feature and occur in considerable thickness; they are represented by lavas of olivine-diabase and by contemporaneous tuffs which are traversed by later granite and quartz felsite.
The cobalt silver ores are found mainly in Huronian conglomerate, but also in older Keewatin rocks and younger diabase, and the silverbearing region, which at first included only a few square miles, is found to extend 25 m.