TheNipissing sills, also called theNipissing diabase, is a large 2217– to 2210–million year old group ofsills in theSuperior craton of theCanadian Shield inOntario,Canada,[2] which intrude theHuronian Supergroup.[3] Nipissing sills intrude all the Huronian sediments and older basement rocks in the northern margin of theSudbury Basin;[4]: 25, 67 they were emplaced after thefaulting andfolding of Huronian rocks, and arehornblendegabbro oftholeiitic basalt composition.[4]: 25 In theSudbury–Elliot Lake area the Nipissing diabase is deformed; outcrops are parallel to the fold axes of the Huronian sedimentary rocks.[3] Nipissing diabase intrusions are east-northeast trending and are no wider than 460 m (1,510 ft).[5]: 972
The Nipissing sills in the Southern Province of the Superior craton are thought to originate from a radiatingdike swarm area 1,300 km (810 mi) to the northeast.[6]: 3 The mantle source for the Nipissing sills did not come from the mantle beneath the Southern Province that had generated the 2500– to 2450–million year oldMatachewan dike swarm.[6]: 3 The 2217– to 2210–million year oldUngava magmatic event – located under theLabrador Trough – fed the Nipissing sills;[6]: 3, 5 evidence shows the sills were laterally fed from amantle plume center 1,500 km (930 mi) away via the 2216–million year old Senneterre dikes which form part of the radiating dike swarm.[7]
In 1911, Willett G. Miller named the Nipissing diabase type area atCobalt, Ontario.[1][8]
^abPalmer, H. C.; Ernst, R. E.; Buchan, K. L. (April 1, 2007). "Magnetic Fabric Studies of the Nipissing sill province and Senneterre dykes, Canadian shield, and Implications for Emplacement".Canadian Journal of Earth Sciences.44 (4). NRC Research Press:507–528.Bibcode:2007CaJES..44..507P.doi:10.1139/E06-096.
^Palmer, H.C.; Ernst, R.E.; Buchan, K.L. (2004). "Mapping Flow Patterns in Nipissing sills of the Southern Province, Canadian shield: a Magnetic Fabric Study".AGU Spring Meeting Abstracts.2004. American Geophysical Union, Spring Meeting 2004, abstract #GP34A-04: GP34A–04.Bibcode:2004AGUSMGP34A..04P.
