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Age Intrusion Lithology Mineralogy and texture Notes
Carboniferous Dykes Tholeiitic basalt and dolerite (DT) microporphyritic, euhedral olivine and subordinate plagioclase phenocrysts fine-grained or subophitic groundmass Cut Mell Fell Conglomerate; geochemically similar to Cockermouth Lavas
Neck Lapilli-tuff (LZ) clasts of country rock and glassy basalt
Devonian Dykes Lamprophyre (spessartite) (L) acicular brown hornblende, plagioclase and interstitial quartz; augite microphenocrysts Example seen in Haweswater quarry [NY 4947 1526]
Plagioclase-quartz- biotite-phyric microgranite (FG) micropoikilitic feldspar and quartz groundmass; single example with K-feldspar phenocrysts Most are partly cleaved; those within the aureole of the Shap Pluton are not hornfelsed
Shap Pluton Orthoclase-perthite- megaphyric granite (G) up to 30% K-feldspar megacrysts; sparse microdioritic enclaves and veins of aplitic microgranite Contact exposed in Sherry Gill [NY 5384 1012] and Longfell Gill [NY 5613 1009] Radiometric age 397 ± 7 Ma (K-Ar, biotite)
Ordovician Haweswater Intrusions Plugs and dyke-like masses Dolerite (D) and gabbro (E) (including hornblende-gabbro) plagioclase, augite, edenitic amphibole; accessory ilmenite, apatite, biotite, tourmaline; leucrocratic to melanocratic, intergranular and subophitic; in part porphyritic and two-phase Locally with igneous layering. Weaklycleaved. Geochemically very similar to mafic rocks in the Borrowdale Volcanic Group.No isotopic age determination
Plug Microdiorite (HD) plagioclase, clinopyroxene, orthopyroxene; accessory garnet Distinct from others in suite
Marginal dyke-like zone Intrusive breccia fragments of dolerite, gabbro, andesite and felsite in altered feldspathic clastic matrix Marginal zone of Wallow Crag plug and scattered dykes
Dykes Andesite (A), basaltic andesite (AB) and basalt (B) Typically plagioclase-phyric Sporadic, probably related to Borrowdale Volcanic Group
Sills Andesite (A) In Esk Pike Formation only; with chilled margins
Mainly andesite (A); also basaltic andesite (AB) and dacite (RD) Mostly emplaced into volcaniclastic sandstone formations; many with peperitic margins