Exhumation of an Ultrahigh-Pressure Slice From the Upper Plate of the Caledonian Orogen—A Record From Titanite in North-East Greenland

Jane A Gilotti; William C McClelland; Wentao Cao; Matthew A Coble

doi:10.1029/2023TC007810

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Exhumation of an Ultrahigh-Pressure Slice From the Upper Plate of the Caledonian Orogen—A Record From Titanite in North-East Greenland

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Exhumation of an Ultrahigh-Pressure Slice From the Upper Plate of the Caledonian Orogen—A Record From Titanite in North-East Greenland

Jane A Gilotti, William C McClelland, Wentao Cao and Matthew A Coble

Tectonics, Vol.43(1), e2023TC007810

01/2024

DOI: 10.1029/2023TC007810

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Abstract

Ultrahigh-pressure (UHP) rocks in North-East Greenland lie within a larger region of high-pressure Laurentian crust formed in the overthickened upper plate of the collision with Baltica. Coesite-bearing zircon dates UHP metamorphism to 365–350 Ma, which formed at the end of the Caledonian collision as a result of intracontinental subduction facilitated by strike-slip faults that broke the lithosphere. Rutile is the stable Ti-bearing phase at UHP, while titanite forms on the retrograde path. Trace elements and U-Pb in titanite were analyzed for six UHP gneisses. Zr-in-titanite temperatures range from 764 to 803°C and lie on the isobaric part of the pressure-temperature path at 1.2 GPa, which fits Ti-phase stability determined by thermodynamic modeling. Large (>600 μm), zoned titanite preserves three distinct trace element patterns that are due to metamorphism, melting and garnet breakdown. Weighted mean 206Pb/238U ages range from 347 ± 5 Ma to 320 ± 11 Ma, but age variation as a function of trace element domain for individual samples is not resolvable within uncertainty. Titanite records a prolonged period of exhumation that is also seen in the zircon record, where phengite decompression melting started at ca. 347 Ma, leucosome emplacement accompanied retrograde metamorphism from 350 to 330 Ma; and titanite grew during isobaric cooling from 345 to 320 Ma when the UHP rocks stalled at lower crustal levels. The same transforms that originally break the lithosphere play a significant role in channeling the UHP rocks back to the lower crust via buoyancy driven exhumation, after which time titanite formed.

titanite

U-Pb geochronology

Greenland Caledonides

UHP terrane

exhumation

strike-slip

UIOWA OA Agreement

Details

Title: Subtitle: Exhumation of an Ultrahigh-Pressure Slice From the Upper Plate of the Caledonian Orogen—A Record From Titanite in North-East Greenland
Creators: Jane A Gilotti - University of Iowa, Earth and Environmental Sciences
William C McClelland - University of Iowa, Earth and Environmental Sciences
Wentao Cao - SUNY Fredonia
Matthew A Coble - GNS Science
Resource Type: Journal article
Publication Details: Tectonics, Vol.43(1), e2023TC007810
DOI: 10.1029/2023TC007810
ISSN: 0278-7407
eISSN: 1944-9194
Publisher: Wiley
Grant note: National Science Foundation. Grant Numbers: EAR 0208158, EAR 0208236, EAR 1049433 Fulbright US Scholar Program
Language: English
Date published: 01/2024
Academic Unit: Earth and Environmental Sciences
Record Identifier: 9984546951302771

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