Metamorphic rates in collisional orogeny from in situ allanite and monazite dating

Emilie Janots; Martin Engi; Daniela Rubatto; Alfons Berger; Courtney Gregory; Meinert Rahn

doi:10.1130/G25192A.1

Metamorphic rates in collisional orogeny from in situ allanite and monazite dating

Emilie Janots^*, Martin Engi, Daniela Rubatto, Alfons Berger, Courtney Gregory, Meinert Rahn

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

142 Citations (Scopus)

Abstract

The prograde sequence of rare earth minerals recorded in metapelites during regional metamorphism reveals a series of irreversible reactions among silicates and phosphates. In individual samples from the northern Lepontine (Central Alps), allanite is partly replaced by monazite at 560-580 °C. Relic allanite retains its characteristic growth zoning acquired at greenschist facies conditions (430-450 °C). Coexisting monazite and allanite were dated in situ to delimit in time successive stages of the Barrovian metamorphism. In situ sensitive high-resolution ion microprobe (SHRIMP) U-Th-Pb dating of allanite (31.5 ± 1.3 and 29.2 ± 1.0 Ma) and monazite (18.0 ± 0.3 and 19.1 ± 0.3 Ma) constrains the time elapsed between 430-450 °C and 560-580 °C, which implies an average heating rate of 8-15 °C /m.y. Combined with new fi ssion track ages (zircon, 10-9 Ma; apatite, 7.5-6.5 Ma), metamorphic rates of the entire orogenic cycle, from prograde to fi nal cooling, can be reconstructed.

Original language	English
Pages (from-to)	11-14
Number of pages	4
Journal	Geology
Volume	37
Issue number	1
DOIs	https://doi.org/10.1130/G25192A.1
Publication status	Published - 2009

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title = "Metamorphic rates in collisional orogeny from in situ allanite and monazite dating",

abstract = "The prograde sequence of rare earth minerals recorded in metapelites during regional metamorphism reveals a series of irreversible reactions among silicates and phosphates. In individual samples from the northern Lepontine (Central Alps), allanite is partly replaced by monazite at 560-580 °C. Relic allanite retains its characteristic growth zoning acquired at greenschist facies conditions (430-450 °C). Coexisting monazite and allanite were dated in situ to delimit in time successive stages of the Barrovian metamorphism. In situ sensitive high-resolution ion microprobe (SHRIMP) U-Th-Pb dating of allanite (31.5 ± 1.3 and 29.2 ± 1.0 Ma) and monazite (18.0 ± 0.3 and 19.1 ± 0.3 Ma) constrains the time elapsed between 430-450 °C and 560-580 °C, which implies an average heating rate of 8-15 °C /m.y. Combined with new fi ssion track ages (zircon, 10-9 Ma; apatite, 7.5-6.5 Ma), metamorphic rates of the entire orogenic cycle, from prograde to fi nal cooling, can be reconstructed.",

author = "Emilie Janots and Martin Engi and Daniela Rubatto and Alfons Berger and Courtney Gregory and Meinert Rahn",

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doi = "10.1130/G25192A.1",

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T1 - Metamorphic rates in collisional orogeny from in situ allanite and monazite dating

AU - Janots, Emilie

AU - Engi, Martin

AU - Rubatto, Daniela

AU - Berger, Alfons

AU - Gregory, Courtney

AU - Rahn, Meinert

PY - 2009

Y1 - 2009

N2 - The prograde sequence of rare earth minerals recorded in metapelites during regional metamorphism reveals a series of irreversible reactions among silicates and phosphates. In individual samples from the northern Lepontine (Central Alps), allanite is partly replaced by monazite at 560-580 °C. Relic allanite retains its characteristic growth zoning acquired at greenschist facies conditions (430-450 °C). Coexisting monazite and allanite were dated in situ to delimit in time successive stages of the Barrovian metamorphism. In situ sensitive high-resolution ion microprobe (SHRIMP) U-Th-Pb dating of allanite (31.5 ± 1.3 and 29.2 ± 1.0 Ma) and monazite (18.0 ± 0.3 and 19.1 ± 0.3 Ma) constrains the time elapsed between 430-450 °C and 560-580 °C, which implies an average heating rate of 8-15 °C /m.y. Combined with new fi ssion track ages (zircon, 10-9 Ma; apatite, 7.5-6.5 Ma), metamorphic rates of the entire orogenic cycle, from prograde to fi nal cooling, can be reconstructed.

AB - The prograde sequence of rare earth minerals recorded in metapelites during regional metamorphism reveals a series of irreversible reactions among silicates and phosphates. In individual samples from the northern Lepontine (Central Alps), allanite is partly replaced by monazite at 560-580 °C. Relic allanite retains its characteristic growth zoning acquired at greenschist facies conditions (430-450 °C). Coexisting monazite and allanite were dated in situ to delimit in time successive stages of the Barrovian metamorphism. In situ sensitive high-resolution ion microprobe (SHRIMP) U-Th-Pb dating of allanite (31.5 ± 1.3 and 29.2 ± 1.0 Ma) and monazite (18.0 ± 0.3 and 19.1 ± 0.3 Ma) constrains the time elapsed between 430-450 °C and 560-580 °C, which implies an average heating rate of 8-15 °C /m.y. Combined with new fi ssion track ages (zircon, 10-9 Ma; apatite, 7.5-6.5 Ma), metamorphic rates of the entire orogenic cycle, from prograde to fi nal cooling, can be reconstructed.

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DO - 10.1130/G25192A.1

M3 - Article

SN - 0091-7613

VL - 37

SP - 11

EP - 14

JO - Geology

JF - Geology

IS - 1

ER -

Metamorphic rates in collisional orogeny from in situ allanite and monazite dating

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