Chronology of ophiolite crystallization, detachment, and emplacement: Evidence from the Brooks Range, Alaska

Journal Article · Wed Jan 01 00:00:00 EST 1992 · Geology; (United States)

DOI:https://doi.org/10.1130/0091-7613(1992)020<0075:COOCDA>2.3.CO;2· OSTI ID:7004040

Wirth, K R; Bird, J M ^[1]

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1. Cornell Univ., Ithaca, NY (United States)

{sup 40}Ar/{sup 39}Ar data from early Middle Jurassic ophiolites (187-184 Ma) in the western Brooks Range, Alaska, indicate that detachment - related metamorphism occurred {approximately}20 m.y. after crystallization and {approximately}20 m.y. before emplacement onto the Arctic Alaska margin. High-temperature metamorphic rocks along the basal surfaces of many ophiolites have ages that are contemporaneous with ophiolite crystallization, suggesting that detachment and thrust faulting occur while the lithosphere is young ({lt}10 Ma) and relatively hot. From these relations it has been generally assumed that detachment and initial overthrusting of oceanic lithosphere occur near the site of generation, such as a marginal basin or mid-ocean ridge. The new data from the Brooks Range ophiolites confirm previous indications that some ophiolites have much longer intervals between crystallization, thrust-related metamorphism, and emplacement. On the basis of these new results and data from other ophiolites, the authors propose that ophiolites originating within large ocean basins will generally have longer crystallization-to-emplacement intervals than the more commonly recognized marginal basin-type ophiolites.

• OSTI ID: 7004040
• Journal Information: Geology; (United States), Vol. 20:1; ISSN 0091-7613
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALASKA
GEOLOGIC FORMATIONS
METAMORPHIC ROCKS
ISOTOPE DATING
PETROGENESIS
ARGON 39
ARGON 40
JURASSIC PERIOD
METAMORPHISM
AGE ESTIMATION
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
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EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
GEOLOGIC AGES
ISOTOPES
LIGHT NUCLEI
MESOZOIC ERA
NORTH AMERICA
NUCLEI
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STABLE ISOTOPES
USA
YEARS LIVING RADIOISOTOPES
580000* - Geosciences