TY - JOUR
T1 - Thermal evolution of the Scandian Hinterland, Naver Nappe, Northern Scotland
AU - Mako, Calvin A.
AU - Law, Richard D.
AU - Caddick, Mark J.
AU - Thigpen, J. Ryan
AU - Ashley, Kyle T.
AU - Cottle, John
AU - Kylander-Clark, Andrew
N1 - Publisher Copyright:
© 2019 The Author(s).
PY - 2019
Y1 - 2019
N2 - The Northern Highlands Terrane of Scotland hosts several thrust nappes that were deformed and metamorphosed during the Silurian Scandian orogeny. Quantitative petrological analysis of metamorphic assemblages indicates that the hinterland-positioned Naver nappe experienced decompression heating from 8–9 kbar and 600°C to 6–7 kbar and 700°C. Monazite–xenotime thermometry and geochronology delineate a detailed temperature–time history for the Naver nappe. Monazite often exhibits compositional zoning, which is used to establish multiple temperature–time points in several samples. These data indicate that the Naver nappe experienced relatively fast heating (c. 50°C myr−1) and relatively slow cooling (15–20°C myr−1), with peak temperatures occurring at c. 425 Ma. This temperature–time evolution is compatible with the early Emsian (407–403 Ma) deposition of unmetamorphosed conglomerates that rest on high-grade metamorphic rocks in the Naver nappe, but requires an acceleration in the cooling rate to 40–50°C myr−1 at 420–410 Ma. Geochronological constraints from this study and previous work suggest that deformation and metamorphism in the hinterland of the Scandian orogen in northern mainland Scotland are younger than the c. 430 Ma deformation in the foreland-positioned Moine thrust zone.We postulate that heat from pervasive granitic intrusions in the Naver nappe weakened the crust, allowing deformation to retreat to the hinterland of the orogen. Funding This project was supported by National Science Foundation grant EAR 1220138 to RDL and grants to CAM from the Geological Society of America, Sigma Xi and the Department of Geosciences at Virginia Tech. Scientific editing by Stephen Daly.
AB - The Northern Highlands Terrane of Scotland hosts several thrust nappes that were deformed and metamorphosed during the Silurian Scandian orogeny. Quantitative petrological analysis of metamorphic assemblages indicates that the hinterland-positioned Naver nappe experienced decompression heating from 8–9 kbar and 600°C to 6–7 kbar and 700°C. Monazite–xenotime thermometry and geochronology delineate a detailed temperature–time history for the Naver nappe. Monazite often exhibits compositional zoning, which is used to establish multiple temperature–time points in several samples. These data indicate that the Naver nappe experienced relatively fast heating (c. 50°C myr−1) and relatively slow cooling (15–20°C myr−1), with peak temperatures occurring at c. 425 Ma. This temperature–time evolution is compatible with the early Emsian (407–403 Ma) deposition of unmetamorphosed conglomerates that rest on high-grade metamorphic rocks in the Naver nappe, but requires an acceleration in the cooling rate to 40–50°C myr−1 at 420–410 Ma. Geochronological constraints from this study and previous work suggest that deformation and metamorphism in the hinterland of the Scandian orogen in northern mainland Scotland are younger than the c. 430 Ma deformation in the foreland-positioned Moine thrust zone.We postulate that heat from pervasive granitic intrusions in the Naver nappe weakened the crust, allowing deformation to retreat to the hinterland of the orogen. Funding This project was supported by National Science Foundation grant EAR 1220138 to RDL and grants to CAM from the Geological Society of America, Sigma Xi and the Department of Geosciences at Virginia Tech. Scientific editing by Stephen Daly.
UR - http://www.scopus.com/inward/record.url?scp=85068596231&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85068596231&partnerID=8YFLogxK
U2 - 10.1144/jgs2018-224
DO - 10.1144/jgs2018-224
M3 - Article
AN - SCOPUS:85068596231
SN - 0016-7649
VL - 176
SP - 669
EP - 688
JO - Journal of the Geological Society
JF - Journal of the Geological Society
IS - 4
ER -