Important deposits may be expected at or about the line of unconformability where slates, shales, quartzites, sandstones, limestones, schists and other sedimentary deposits are pierced by intrusive masses of igneous rocks.
Curiously enough large masses of true igneous rock rarely contain valuable deposits of mineral, but where such intrusive masses cut dikes or walls of porphyry, or diorite, the region is worthy of careful investigation.
The eruptive rocks have burst through them in places, changed their character, divided them byintrusive masses, and generally enriched them with mineral deposits.
In South Africa a chain of pools usually follows the course of a line fault, which in its turn marks where an intrusive lode carrying mineral separates two different formations.
But I fear our venerable friend derived little pleasure or comfort from these almost intrusive visits.
And I think now of this girl as of a damsel of romance, a Sleeping Beauty in the wood of time, secluded from intrusive elements of fact, and folded in the love and faith of her own simple worshippers.
Joseph, the eldest, who, though placed by his brother in an obnoxious situation, as intrusive King of Spain, held the reputation of a good and moderate man.
For truth is seldom so intrusive as to need avoiding.
Mr. Green leapt back, with a scream of pain, hands to his eyes, and quite unconsciously set himself to play to the life the part of the intrusive old fellow in the comedy.
D'ye recall a ruse of Sir Harry Wildairs to rid himself of the company of an intrusive old fool who was not wanted?
He resented the clergyman's intrusive presence more and more.
He says: 'Slowly we have learned to understand the phenomena, but we cannot control them, and the child is still cruelly embarrassed by intrusive tappings and cracklings as she visits her friends or as she sits in her seat in school.
She might have borne also in patience, or repelled with scorn, the bitter taunts and occasional violence of her brother, Colonel Douglas Ashton, and the impertinent and intrusive interference of other friends and relations.
But some intrusive footstep awakes him from his slumbers.
A thousand dreadful visions haunted his imagination all night, and in the morning he was awaked from a feverish slumber, by the only circumstance which could have added to his distress,--the visit of an intrusive ass.
He had even the delicacy to withdraw to the farthest corner of the room, so as to render his official attendance upon them as little intrusive as possible, when Effie was composed enough again to resume her conference with her sister.
They monopolise us unless we resist the intrusive appeals that they make to us.
Paul is generalising his own experience when he speaks of the condemnation of an intrusive alien force that holds unregenerate human nature in bondage.
The rite, just because it is a rite, is the prophecy of a time when the need for it, arising from weak flesh and an intrusive world, shall cease.
The attempt to separate them chronologically into a Lower and Upper division was premature, as shewn by the fact that many of them, upon detailed study, prove to be intrusive igneous rocks.
We are obliged to root up with ceaseless toil these intrusive competitors, if we wish to enjoy the kindly fruits of the earth in due season.
Are you leagued with him, O agile and intrusive Harlequin, to steal away my peace of mind?
In this vale are two small lakes, the higher of which is the only Welsh lake which has any pretensions to compare with our own; and it has one great advantage over them, that it remains wholly free from intrusive objects.
We must indicate in a summary way the stage which the Reformation had reached in England when Puritanism, in its various forms, made itself intrusive and obnoxious in demanding further changes.
Among these comparatively minor incidents, must be reckoned the attempt made by the British Government to rescue the Calabrian dominions of the Neapolitan Bourbons from the intrusive government of Joseph Buonaparte.
The tidings of insurrection, imperfectly heard and reluctantly listened to, on the northern side of the Pyrenees, were renewed with astounding and overpowering reiteration, as the intrusive King approached the scene of his proposed usurpation.
The headquarters at Vittoria, honoured with the residence of the intrusive King, was soon more illustrious by the arrival of Buonaparte himself, a week before the British army had commenced its march from Portugal or Corunna.
He opened a communication with Oporto, and soon learned the important news of the defeat of Dupont, and the flight of the intrusive King from Madrid.
Those that have solidified beneath the surface are known as intrusive rocks, or if the cooling has taken place slowly at great depth, as plutonic rocks, e.
Perhaps the most noteworthy example is the great layer of such intrusive igneous rock, part of which outcrops for seventy miles mostly as a bold cliff forming the famous Palisades of the Hudson, near New York City.
Near the base of the volcanic seriesintrusive igneous rocks of Carboniferous age appear in the form of sills and bosses, as, for instance, the oval mass of olivine-basalt on Suidhe Hill.
In the days of Copperfield, Two Coaches ran between Great Yarmouth and London—“The Blue” and “The Royal Mail.
The whimsical description of the central church—ST.
Cuesta de Los Hornos, a crooked range of mountains formed of intrusive rocks of the same nature with the above described hillocks.
In this space, the number and bulk of the intrusive masses of differently coloured porphyries, injected one into another and intersected by dikes, is truly extraordinary.
Lower down the valley, the mountains are almost exclusively composed of porphyries, many of them of intrusive origin and non-stratified, others stratified, but with the stratification seldom distinguishable except in the upper parts.
This great pile of strata has been broken up in several places by intrusivehillocks of purple claystone porphyry, and by dikes of porphyritic greenstone: it is said that a few poor metalliferous veins have been discovered here.
I nowhere observed mica in this formation, and rarely hornblende; where the latter mineral did occur, I was generally in doubt whether the mass really belonged to this formation, or was of intrusive origin.
The peculiar, abruptly conical form of the hills in this neighbourhood, would have led any one at first to have supposed that they had been formed of injected or intrusive rocks.
This in itself does not seem improbable; for where the earth's crust has once yielded, it would be liable to yield again, though the liquified intrusive matter might not be any longer enabled to reach the submarine surface and flow as lava.
John had not lowered his eyes before the intrusive gaze, but he felt now as if he had been subjected to an electric current.
It has squeezed into fissures forming dikes; it has burrowed among the strata as intrusive sheets; it has melted the rocks away or lifted the overlying strata, filling the chambers which it has made with intrusive masses.
The rock of the intrusive masses is coarsely crystalline, and no doubt solidified slowly under the pressure of vast thicknesses of overlying rock, now mostly removed by erosion.
Where intrusive masses open communication with the surface, volcanoes are established or fissure eruptions occur such as those of Iceland.
Intrusions give rise to fissures, dikes, and intrusive sheets, and these dislocations cannot fail to produce earthquakes.
The source of the intrusive sheet may often be traced to some dike (known therefore as the feeding dike), or to some mass of igneous rock.
Intrusive sheets are usually harder than the strata in which they lie and are therefore often left in relief after long denudation of the region (Fig.
From the main granite dikes or veins often run out into the surrounding rocks, thus proving that the granite is intrusive and has forced its way upwards by splitting apart the strata among which it lies.
It is now believed, however, that they are comparatively recent and include sedimentary rocks, partly of Palaeozoic age, and intrusive masses which may be nearly massive or may have gneissose, flaser or granulitic structures.
