@article{554009514cc54bcabfe2fc3cbd80778d,
title = "Dating deformation using sheared leucogranite: temporal constraints by 40Ar/39Ar thermochronology for the Mae Ping shear zone, NW Thailand",
abstract = "The Mae Ping shear zone (MPSZ) is one of the major ductile strike-slip systems associated with the Cenozoic extrusion tectonics in Southeast Asia. However, its sinistral shear lacks a robust temporal constraint. This study attempts to acquire the deformation timing by applying 40Ar/39Ar thermochronology on a sheared pegmatitic leucogranite showing sinistral S–C fabrics with a thrust component. The contact of the leucogranite sub-paralleling to the major foliation in host gneiss indicates it could be a pre- to syn-shearing intrusion. Most minerals, including garnet, muscovite, K-feldspar, albite, and quartz, exhibit ductile to brittle deformation. Mineral microstructural analysis suggests a retrograde sinistral shear from > 600 to 250 °C. In situ 40Ar/39Ar dating on muscovite yield ages mainly within 42–38 Ma with calculated closure temperatures of 435–330 °C. Fine-grained muscovite aggregates are slightly older than fish, implying that grain size reduction may not always reset 40Ar/39Ar ages. The K-feldspar 40Ar/39Ar step heating age spectrum with two segments of contiguous steps at 24.5 and 35.4 Ma may reflect the coexistence of high-T porphyroclast and low-T K-rich fine-grain recrystallizing at pressure shadows. The reconstructed cooling path and inferred deformation temperatures constrain a shear duration of 42–30 Ma for the MPSZ. The activation of the MPSZ before 42 Ma could be linked to the Eocene metamorphism within a transpressional regime triggering crustal thickening that may further induce the leucogranitic melt. This study also shows leucogranite can be a nice thermal history recorder for a shear zone regarding its petrogenesis and suitable mineral assemblage for thermochronology.",
keywords = "In situ muscovite Ar/Ar dating, K-feldspar Ar/Ar step heating, Lan Sang gneisses, Leucogranite, Mae Ping shear zone, Thermochronology",
author = "Lin, {Yu Ling} and Lee, {Tung Yi} and Lo, {Ching Hua} and Sherlock, {Sarah C.} and Yoshiyuki Iizuka and Tadashi Usuki and Quek, {Long Xiang} and Punya Charusiri",
note = "Funding Information: This research was supported by funding provided by Ministry of Science and Technology to TYL (MOST 108-2116-M-003-007-MY3). The authors gratefully acknowledge Meng-Wan Yeh for field works, sample collection, laboratory equipment, and discussions. Special thanks to Chieh-Yu Wu, Michael J. Kunk and Ryan J. McAleer for instructions in mineral separation, Ar/Ar experiments, and data reduction. Chin-Ho Tsai is thanked for the use of SEM facility in the National Dong Hwa University. Thorough review and constructive comments by Sebasti{\'a}n Oriolo and Willis E. Hames are gratefully acknowledged, and Timothy L. Grove is thanked for editorial handling. 40 39 Funding Information: This research was supported by funding provided by Ministry of Science and Technology to TYL (MOST 108-2116-M-003-007-MY3). The authors gratefully acknowledge Meng-Wan Yeh for field works, sample collection, laboratory equipment, and discussions. Special thanks to Chieh-Yu Wu, Michael J. Kunk and Ryan J. McAleer for instructions in mineral separation,40Ar/39Ar experiments, and data reduction. Chin-Ho Tsai is thanked for the use of SEM facility in the National Dong Hwa University. Thorough review and constructive comments by Sebasti?n Oriolo and Willis E. Hames are gratefully acknowledged, and Timothy L. Grove is thanked for editorial handling. Funding Information: This research was supported by funding to Tung-Yi Lee, provided by Ministry of Science and Technology, Taiwan (MOST 108-2116-M-003-007-MY3). Publisher Copyright: {\textcopyright} 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.",
year = "2021",
month = sep,
doi = "10.1007/s00410-021-01822-4",
language = "English",
volume = "176",
journal = "Contributions to Mineralogy and Petrology",
issn = "0010-7999",
publisher = "Springer Verlag",
number = "9",
}