Linhope Spout


Linhope Spout in snow and ice taken in January 2001

Linhope Spout in winter
‘Linn’ means waterfall in Northumbrian.

Map showing the excursion route, locations and igneous rock types in the Linhope area

A map showing the route, locations , and igneous rock types in the area of Linhope Spout

Key

Key for the excursion map

Location 1. Hornfels at Linhope bridge


We park the car with others in the space by the road at NT 97674 16229 just before Hartside Farm. Looking north-east from here, there is a good view towards Dunmoor Hill with Cunyon Crags standing out at the east end and Long Crag towards its west end on the skyline. Cat Crag is visible below Long Crag. Looking south-west, there is a view of the deep cleft of the Breamish valley as it follows the line of the main fault at the southern edge of the Cheviot pluton. We walk the road from Hartside Farm to Linhope and admire the bridge over the burn just before the settlement at NT 96474 16249. There is an outcrop of altered (hornfelsed) andesite here, above the east side of the Linhope Burn. The Burn follows the junction of the lavas and the pluton.


Location 2. Boulder on the path below Ritto Hill


Boulder below Ritto Hill

Boulder below Ritto Hill

With the steep slopes of Ritto Hill on the left and a plantation of conifers on the right, there are frequent boulders on the left-hand side of the path, around NT960163, which show a mixture of pink intrusive rock and dark dioritic rock. These boulders reflect the intermixing of these more and less mafic rock types that we see higher up the Breamish Valley below Low Bleakhope.

Central Belt rock in contact with fine-grained mafic material. Prepared hand specimen in ordinary reflected light.

‘Central Belt’ rock in contact with fine-grained mafic material
Prepared hand specimen in ordinary reflected light.

Central Belt rock in contact with fine-grained mafic material. Thin section viewed in plane polarised light.

A thin section from the same sample viewed in plane polarised light

Central Belt rock in contact with fine-grained mafic material. Thin section viewed with crossed polarising filters.

The same thin section viewed with crossed polarising filters

Location 3. Felsite dyke, Linhope Spout


Felsite dyke at Linhope Spout

Felsite dyke at Linhope Spout
This view, at close range from above and looking directly down, shows the tension jointing that is typical for these dykes.

Linhope Spout at NT 95834 17099 is a small (approx. 10m high) but impressive waterfall.
At its very top, there is a distinctive intrusion of a very fine-grained felsic rock. This is one of the frequent fine-grained granitic dykes classified as aplite or, more commonly, felsite dykes. This one may have hardened the rock locally, increasing its resistance to destructive forces and thereby contributing to the formation of this beautiful waterfall.


Hand specimen from felsite dyke, Linhope Spout.

Hand specimen from felsite dyke, Linhope Spout.

Prepared hand specimen from felsite dyke, Linhope Spout.

Prepared hand specimen from felsite dyke, Linhope Spout.


Thin section of felsite dyke, Linhope Spout viewed in plane polarised light

Thin section of felsite dyke, Linhope Spout viewed in plane polarised light
The green area is chlorite.

Thin section of felsite dyke, Linhope Spout viewed with crossed polarising filters

Thin section of felsite dyke, Linhope Spout viewed with crossed polarising filters


Thin section of felsite dyke with perthitic and micrographic textures, Linhope Spout viewed in plane polarised light

Thin section of felsite dyke with perthitic and micrographic textures, Linhope Spout viewed in plane polarised light

Thin section of felsite dyke with perthitic and micrographic textures, Linhope Spout viewed with crossed polarising filters

The same section viewed with crossed polarising filters


Location 4. ‘Marginal’/’Central Belt’ contact

Thin section of felsite dyke, Linhope Spout viewed with crossed polarising filters

Junction of ‘Central Belt’ and ‘Marginal’ granitic rocks at Linhope Spout

A little bit further back from the top of the Spout some boulders reveal the junction between the ‘Marginal’ (dioritic) and pinker, less mafic ‘Central Belt’ granite.


Hand specimen of medium-grained

Hand specimen of medium-grained ‘Marginal’ quartz monzodiorite from Linhope Spout

Thin-section of medium-grained

Thin-section of medium-grained ‘Marginal’ quartz monzodiorite from Linhope Spout viewed with crossed polarising filters.


Location 5. Quartz & haematite veining


Going further back (south) from this point to NT 95694 17129, the junction between the two types can be traced with occasional quartz veining with haematite.


Location 6. Mica-porphyry dyke


Below the Spout along the path beside the burn in an easterly direction, there is one of the many mica-porphyry dykes in the Cheviots visible if the bracken isn’t tall and thick. The mica-porphyry forms a substantial laccolith near Biddlestone where it is extensively quarried to provide decorative stone and road material. It occurs as dykes frequently in the Cheviot pluton, and forms a more extensive clump on Cold Law.

References

Al-Hafdh N.M. 1985. The Alteration Petrology of the Cheviot Granite. Thesis submitted for PhD. at Newcastle University.

British Geological Survey Online geology map http://mapapps.bgs.ac.uk/geologyofbritain/home.html

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