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The Igneous Rocks Of North-east England Essay, Research Paper The area of north-east England, east of the Pennines and between the Scottish border to the north and Teesside to the south has a variety of igneous rocks of different ages, and in this essay I will try to describe the major types that are found, concentrating on the Whin Sill, the Cheviots, and the Weardale Granite in particular, but also commenting on other igneous rocks of the region.
I have included a map of the area to show the main bands of igneous rock. The main igneous rock of the north-east is the Great Whin Sill, the largest hypabyssal intrusion in Britain which was intruded approximately million years ago.
As the name suggests, it is an example of a common concordant intrusion known as a sill, and the whole Whin Sill complex is a number of lenses of differing thicknesses linked together at depth.
The Farne Islands are part of the sill, as are the crags at Bamburgh, which are home to the castle. The coastline between Dunstanburgh and Cullernose Point, as well as the rock that leads to High Force waterfall in Co.
Durham are also parts of the Whin Sill.
The Whin Sill has a total area of at least square kilometres. Eastwood, As the sill is made up of a number of lenses, the number varying with location 5 lenses were found in certain parts of Northumberlandthe thickness varies accordingly, although the common thickness is about ft.
The greatest depth discovered was at the Burtree Pasture Lead Mine in Weardale, which had a thickness of ft. The sill itself is made up of a variety of rock types, the most abundant being a dark coloured, blue-grey quartz-dolerite which has a fine to medium grain size of 0.
The rock structure is of an interlocking network of plagioclase laths which show a sub-ophitic texture, and there are also granular aggregates of augite. Phenocrysts of both strongly zoned plagioclase and pyroxene are frequently found, in lengths up to and over 2mm.
Closer examination found a finer grained rock of basaltic composition, and they are commonly found to be made up of phenocrysts of pyroxene and of plagioclase or aggregates of iron ore and serpentine.
The sill is also intruded by fine grained veins of basalt of varying widths Smythe,and despite their age being younger than that of the sill, their chilled facies resemble the Whin Sill.
There are many other less common rocks found in certain parts of the sill, and they include dolerite-pegmatites found in Teesside and the South Tyne region and a variety of acid rocks, the most abundant being pink-red apilitic veins up to 20mm wide which intrude into the sill.
Vesicles up to 0. The Whin Sill also has an associated dyke suite across the region, especially in four distinct areas, with a generally north-easterly trend. South of the Cheviot mass is the left handed dyke-echelon trending eastwards towards Holy Island called the High Green dyke-echelon.
Oswalds Chapel dyke-echelon starts near Haltwhistle and heads out to sea to a distance of around 6. The Hett dyke system is the most southerly, and although the width is only about 10m at maximum, it can be traced for 32kms across South Durham, the longest unbroken line of outcrop.
The Cheviot complex is the remnant of an old volcano which is deeply dissected, and has been intruded by a mass of granite and traversed by numerous dykes, and an overall age is Lower Devonian.
After an initial phase of vulcanicity, there was a mass outpouring of lavas, which today still covers an area of square kilometres. Two major types of lava can be distinguished, the first of these to reach the surface are known as biotite lavas or mica-felsites, and they are porphyritic rhyolites, reddish in colour.
One variety of this lava is found in the Borders and it forms many of the high peaks in the area, including Windy Gale. There are large, abundant phenocrysts of biotite and much-altered feldspar in a groundmass of quartz and feldspar.
The other variety is composed of only a few flows, and it weathers purple or grey, and it has phenocrysts of biotite. They are porphyritic lavas generally coloured from very dark to light grey and purple, often flecked with white spots where feldspars have been altered to a clay like substance.
These lavas, found throughout the Cheviot region are well jointed and usually much altered, and they have phenocrysts of andesine-labradorite. These pitchstone-andesites are grey to black, with plagioclase laths and unaltered phenocrysts of rhombic pyroxene and augite, set in a groundmass of glass and fresh feldspar.
It is cut by thin red veins and is weathered by exfoliation. Oligoclase trachytes are only found at the head of the River Alwin. They can be recognised by their platy structure in hand specimen, and also by their groundmass of oligoclase and altered pyroxene under the microscope.
Around million years ago, granite was intruded into the andesites in the east of the Cheviot region, and this granite now forms the highest points in the Cheviot Hills. The granite, which has a significant metamorphic aureole around it, is thought to have a surface area up to 70 square kilometres. The granite contains three essential minerals, all visible in hand specimen, namely quartz, feldspar, and mica.
Jhingren described three variations in the composition, the marginal, the standrop and the granophyric varieties. The first of these is fine grained and dark grey, and contains quartz, feldspar, diopside, biotite and iron ore.
The other two are coarser grained and differ as they are richer in quartz and orthoclase feldspar, although the granophyric variety contains very little pyroxene.
In the south of the Cheviots, there are a set of dykes, which have been classified as mica-porphyrites, quartz-porphyrites, felsites and pyroxene-porphyrites, then former of these being the most common. All the dykes have a groundmass of acid feldspar and quartz, but the phenocrysts differ, and they may be made up of plagioclase feldspar and biotite, or quartz.The oldest sedimentary rocks and some igneous rocks (in isolated hills of granite) Plateaus of limestone, gritstone, and carboniferous strata are associated with major and the coal-mining, metalworking, and engineering centres of the Midlands and the North East.
England has large tracts of derelict areas, scarred by the spoil heaps of. UK rocks by region. Updated Wednesday 27th September North England Central England South East England South West England Wales Ireland.
Highlands The Scottish Highlands have spectacular mountains made of old igneous and metamorphic rocks. The oldest rocks are gneiss in the Outer Hebrides and the extreme north west . Jan 25, · Description The Second Edition of this unique pocket field guide has been thoroughly revised and updated to include advances in physical volcanology, emplacement of magmas and interpreting structures and textures in igneous rocks.
The book integrates new field based techniques (AMS and geophysical studies of pluton Format: Paperback.
Learn more about the major types of igneous rock, which include plutonic, intrusive and extrusive igneous rocks.
Rock Identification Tips First, decide whether your rock is igneous, sedimentary or metamorphic. Igneous rocks such as granite or lava are tough, frozen melts with little texture or layering. Home» Rocks. Rocks: Igneous, Metamorphic and Sedimentary Rocks hold the history of the earth and the materials that will be used to build its future. The oldest sedimentary rocks and some igneous rocks (in isolated hills of granite) Plateaus of limestone, gritstone, and carboniferous strata are associated with major and the coal-mining, metalworking, and engineering centres of the Midlands and the North East. England has large tracts of derelict areas, scarred by the spoil heaps of.
Learn more about the major types of igneous rock, which include plutonic, intrusive and extrusive igneous rocks. Tuff is so closely associated with volcanism that it is usually discussed along with types of igneous rocks. The geology of England is mainly urbanagricultureinitiative.com youngest rocks are in the south east around London, progressing in age in a north westerly direction.
The Tees-Exe line marks the division between younger, softer and low-lying rocks in the south east and the generally older and harder rocks of the north and west which give rise to higher relief . Similar to those in North America, Jurassic rocks in the rest of the world can be divided into three types: igneous rocks associated with continental rifting and seafloor spreading, sedimentary rocks associated with epicontinental seaways and terrestrial systems, and deformed deposits associated with subduction and mountain-building (orogenic.