Paleomagnetism and geobarometry of the Granite Mountain batholith, Yukon: Minimal geotectonic motion of the Yukon-Tanana Terrane relative to North America

Paleomagnetic and geobarometric results are reported here for the Early Jurassic Granite Mountain batholith, an ~600 km² granodiorite intrusion in the Yukon-Tanana Terrane. Paleomagnetic analyses of 331 specimens from 24 sites yield magnetite-borne characteristic remanent magnetization (ChRM) directions. Eight northerly and westerly sites display a mean direction A (D=337, I=69°; a 95 =7.6°, k=54). Another 11 sites appear to be lightning-struck, or exhibit unstable remanence, and 3 sites in a fault-bounded block to the southeast carry an anomalous northeast upwards ChRM direction B. Two sites in a Cretaceous andesite porphyry dyke and its contact zone give a westerly, steep-down ChRM direction, C. Aluminum-in-hornblende geobarometry at 10 sites defines emplacement depths of ~16 km in the north and west, and ~19 km in the southeast. The batholith has probably not been significantly tilted since its emplacement, but it may be subdivided into two separate intrusive phases or structural blocks that have experienced differential uplift. Ambient temperatures at 16-19 km were too high for magnetite to record an enduring remanence, so the observed ChRMs likely record uplift of the batholith through ~15 km depth, at 180-170 Ma. Both A and C ChRM directions are similar to those expected for Early Jurassic and Late Cretaceous reference poles, respectively, suggesting that the Yukon-Tanana Terrane is not far-traveled with respect to cratonic North America since Early Jurassic time.

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Contact Person {"en": "Yukon Geological Survey", "fr": "Yukon Geological Survey"}
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Open Canada Date Published 2011-04-04 00:00:00
Open Canada Date Modified
Open Canada Subject ["science_and_technology"]
Open Canada Keywords {"en": ["regional-geology", "ygs-import", "ygs-import-20250711", "ygs-publications", "yukon-geological-survey"], "fr-t-en": ["géologie régionale", "importation d'ygs", "ygs-import-20250711", "publications de l'YGS", "enquête géologique du yukon"]}
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