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The North Pennine Batholith, also known as the Weardale Granite is a
10.1144/pygs.58.1.273
/ref> The batholith consists of five plutons, the Tynehead, Scordale, Rowlands Gill, Cornsay and Weardale plutons. The Weardale Granite pluton is the largest and the only one that has been proved (sampled), after the Rookhope Borehole confirmed Martin Bott's hypothesis that a large negative
In 1934, Kingsley Dunham published a paper proposing that ore deposits in the Alston Block were formed due to a granite intrusion beneath Weardale. This was later tested by a gravity survey, which found a large negative gravity anomaly, supporting the hypothesis.
In the early 1960s, a borehole was drilled at Rookhope by Durham University, and proved the existence of the intrusion at a depth of 390 m. The intrusion was found to have a weathered top, so couldn't account for the mineralisation that was the basis of the hypothesis that first suggested its existence.
In 2004, a second borehole was drilled in Eastgate, and the granite was reached at 270 m below the surfaceManning D.A.C., P.L. Younger, F.W. Smith, J.M. Jones, D.J. Dufton and S. Diskin (2007), 'A deep geothermal exploration well at Eastgate, Weardale, UK: a novel exploration concept for low-enthalpy resources', ''Journal of the Geological Society, London''
164, 371–382; do
10.1144/0016-76492006-015
/ref>
granitic
A granitoid is a generic term for a diverse category of coarse-grained igneous rocks that consist predominantly of quartz, plagioclase, and alkali feldspar. Granitoids range from plagioclase-rich tonalites to alkali-rich syenites and from quartz- ...
batholith lying under northeast England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
, emplaced around 400 million years ago in the early Devonian.Kimbell, G.S., B. Young, D. Millward and Q. G. Crowley (2010). 'The North Pennine batholith (Weardale Granite) of northern England: new data on its age and form', ''Proceedings of the Yorkshire Geological Society'' 58, 107-128; do10.1144/pygs.58.1.273
/ref> The batholith consists of five plutons, the Tynehead, Scordale, Rowlands Gill, Cornsay and Weardale plutons. The Weardale Granite pluton is the largest and the only one that has been proved (sampled), after the Rookhope Borehole confirmed Martin Bott's hypothesis that a large negative
gravity anomaly
The gravity anomaly at a location on the Earth's surface is the difference between the observed value of gravity and the value predicted by a theoretical model. If the Earth were an ideal oblate spheroid of uniform density, then the gravity meas ...
under Weardale
Weardale is a dale, or valley, on the east side of the Pennines in County Durham, England. Large parts of Weardale fall within the North Pennines Area of Outstanding Natural Beauty (AONB) – the second-largest AONB in England and Wales. Th ...
represented a low-density igneous intrusion
In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
.
History of Study
In 1934, Kingsley Dunham published a paper proposing that ore deposits in the Alston Block were formed due to a granite intrusion beneath Weardale. This was later tested by a gravity survey, which found a large negative gravity anomaly, supporting the hypothesis.
In the early 1960s, a borehole was drilled at Rookhope by Durham University, and proved the existence of the intrusion at a depth of 390 m. The intrusion was found to have a weathered top, so couldn't account for the mineralisation that was the basis of the hypothesis that first suggested its existence.
In 2004, a second borehole was drilled in Eastgate, and the granite was reached at 270 m below the surfaceManning D.A.C., P.L. Younger, F.W. Smith, J.M. Jones, D.J. Dufton and S. Diskin (2007), 'A deep geothermal exploration well at Eastgate, Weardale, UK: a novel exploration concept for low-enthalpy resources', ''Journal of the Geological Society, London''
164, 371–382; do10.1144/0016-76492006-015
/ref>
See also
*Whin Sill
The Whin Sill or Great Whin Sill is a tabular layer of the igneous rock dolerite in County Durham, Northumberland and Cumbria in the northeast of England. It lies partly in the North Pennines Area of Outstanding Natural Beauty and partly in Nort ...
, another large igneous intrusion in northeast England.
References
{{reflist Geology of the Pennines Batholiths of Europe Devonian magmatism