Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska
Thermobarometric data from amphibolite-facies metamorphic rocks west of the Coast Mountains batholith provide important constraints on the structural evolution of the mid-Cretaceous Sumdum–Fanshaw fault system and Late Cretaceous – Paleocene Le Conte Bay shear zone in central southeastern Alaska. Du...
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crcansciencepubl:10.1139/e91-083 2023-12-17T10:51:35+01:00 Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska McClelland, William C. Anovitz, Lawrence M. Gehrels, George E. 1991 http://dx.doi.org/10.1139/e91-083 http://www.nrcresearchpress.com/doi/pdf/10.1139/e91-083 en eng Canadian Science Publishing http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining Canadian Journal of Earth Sciences volume 28, issue 6, page 912-928 ISSN 0008-4077 1480-3313 General Earth and Planetary Sciences journal-article 1991 crcansciencepubl https://doi.org/10.1139/e91-083 2023-11-19T13:39:31Z Thermobarometric data from amphibolite-facies metamorphic rocks west of the Coast Mountains batholith provide important constraints on the structural evolution of the mid-Cretaceous Sumdum–Fanshaw fault system and Late Cretaceous – Paleocene Le Conte Bay shear zone in central southeastern Alaska. Ductile structures that make up the Sumdum–Fanshaw fault system record the east-directed underthrusting of the Alexander terrane and Gravina belt beneath the Ruth assemblage (Yukon–Tanana terrane) and Taku terrane. These structures are truncated to the east by the Le Conte Bay shear zone. Temperature and pressure estimates calculated from the garnet–biotite geothermometer and garnet–rutile–ilmenite–plagioclase–quartz geobarometer suggest juxtaposition of the Gravina belt and Yukon–Tanana terrane at relatively deep levels (>7 kbar) during mid-Cretaceous time. Rocks west of the Le Conte Bay shear zone yield thermobarometric estimates of 465–890 ± 50 °C and 7.1–11.8 ± 1 kbar (1 kbar = 100 MPa). Late Cretaceous and Paleocene metamorphism associated with the Le Conte Bay shear zone reflects synkinematic emplacement of tonalitic intrusions along the western margin of the Coast Mountains batholith. Thermobarometric results from samples adjacent to the tonalite bodies record uplift and retrogression and suggest tonalite emplacement at 7.5–7.7 ± 1 kbar. An eastward increase in thermobarometric estimates observed in Thomas and Le Conte bays is inferred to record uplift and east-side-up tilting of rocks west of and within the Le Conte Bay shear zone during Late Cretaceous and Paleocene time. Rocks within the Le Conte Bay shear zone were apparently rapidly (1.5–2 mm/a) uplifted to shallow crustal levels prior to mid-Eocene time. Thermobarometric results for the Petersburg region are similar to those previously reported along the western flank of the northern Coast Mountains batholith. Article in Journal/Newspaper Alaska Yukon Canadian Science Publishing (via Crossref) Yukon Tilting ENVELOPE(-54.065,-54.065,49.700,49.700) Taku ENVELOPE(-133.854,-133.854,59.633,59.633) Canadian Journal of Earth Sciences 28 6 912 928 |
institution |
Open Polar |
collection |
Canadian Science Publishing (via Crossref) |
op_collection_id |
crcansciencepubl |
language |
English |
topic |
General Earth and Planetary Sciences |
spellingShingle |
General Earth and Planetary Sciences McClelland, William C. Anovitz, Lawrence M. Gehrels, George E. Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska |
topic_facet |
General Earth and Planetary Sciences |
description |
Thermobarometric data from amphibolite-facies metamorphic rocks west of the Coast Mountains batholith provide important constraints on the structural evolution of the mid-Cretaceous Sumdum–Fanshaw fault system and Late Cretaceous – Paleocene Le Conte Bay shear zone in central southeastern Alaska. Ductile structures that make up the Sumdum–Fanshaw fault system record the east-directed underthrusting of the Alexander terrane and Gravina belt beneath the Ruth assemblage (Yukon–Tanana terrane) and Taku terrane. These structures are truncated to the east by the Le Conte Bay shear zone. Temperature and pressure estimates calculated from the garnet–biotite geothermometer and garnet–rutile–ilmenite–plagioclase–quartz geobarometer suggest juxtaposition of the Gravina belt and Yukon–Tanana terrane at relatively deep levels (>7 kbar) during mid-Cretaceous time. Rocks west of the Le Conte Bay shear zone yield thermobarometric estimates of 465–890 ± 50 °C and 7.1–11.8 ± 1 kbar (1 kbar = 100 MPa). Late Cretaceous and Paleocene metamorphism associated with the Le Conte Bay shear zone reflects synkinematic emplacement of tonalitic intrusions along the western margin of the Coast Mountains batholith. Thermobarometric results from samples adjacent to the tonalite bodies record uplift and retrogression and suggest tonalite emplacement at 7.5–7.7 ± 1 kbar. An eastward increase in thermobarometric estimates observed in Thomas and Le Conte bays is inferred to record uplift and east-side-up tilting of rocks west of and within the Le Conte Bay shear zone during Late Cretaceous and Paleocene time. Rocks within the Le Conte Bay shear zone were apparently rapidly (1.5–2 mm/a) uplifted to shallow crustal levels prior to mid-Eocene time. Thermobarometric results for the Petersburg region are similar to those previously reported along the western flank of the northern Coast Mountains batholith. |
format |
Article in Journal/Newspaper |
author |
McClelland, William C. Anovitz, Lawrence M. Gehrels, George E. |
author_facet |
McClelland, William C. Anovitz, Lawrence M. Gehrels, George E. |
author_sort |
McClelland, William C. |
title |
Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska |
title_short |
Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska |
title_full |
Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska |
title_fullStr |
Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska |
title_full_unstemmed |
Thermobarometric constraints on the structural evolution of the Coast Mountains batholith, central southeastern Alaska |
title_sort |
thermobarometric constraints on the structural evolution of the coast mountains batholith, central southeastern alaska |
publisher |
Canadian Science Publishing |
publishDate |
1991 |
url |
http://dx.doi.org/10.1139/e91-083 http://www.nrcresearchpress.com/doi/pdf/10.1139/e91-083 |
long_lat |
ENVELOPE(-54.065,-54.065,49.700,49.700) ENVELOPE(-133.854,-133.854,59.633,59.633) |
geographic |
Yukon Tilting Taku |
geographic_facet |
Yukon Tilting Taku |
genre |
Alaska Yukon |
genre_facet |
Alaska Yukon |
op_source |
Canadian Journal of Earth Sciences volume 28, issue 6, page 912-928 ISSN 0008-4077 1480-3313 |
op_rights |
http://www.nrcresearchpress.com/page/about/CorporateTextAndDataMining |
op_doi |
https://doi.org/10.1139/e91-083 |
container_title |
Canadian Journal of Earth Sciences |
container_volume |
28 |
container_issue |
6 |
container_start_page |
912 |
op_container_end_page |
928 |
_version_ |
1785576892435267584 |