[지구시스템] [지구사랑세미나] 박문재 교수 (충북대학교 지구환경과학과)
일시 : 2026-04-10(금) 11:30 ~ 12:30
연사 : 박문재 교수
소속 : 충북대학교 지구환경과학과
문의 : 심세나(senasim@snu.ac.kr)
장소 : 25-1동 304호 지구사랑 Hall
Title: Tracking Deformation in the Earth's Lithosphere
[Abstract]
Understanding how deformation is recorded at the crystal scale and how it relates to large-scale tectonic processes is fundamental to deciphering the evolution of Earth's lithosphere. This study presents a synthesis of microstructural and petrofabric analyses of mafic and ultramafic rocks from four distinct tectonic settings, linking crystal-scale deformation to plate-scale tectonics.
In the Rio Grande Rift (RGR), USA, olivine lattice preferred orientations (LPOs) in spinel peridotite xenoliths reveal contrasting deformation conditions between the rift axis and rift shoulder: A-type LPO under dry conditions at the rift axis and C-type LPO under hydrous conditions at the rift shoulder, reflecting localized mantle metasomatism related to dehydration of the subducted Farallon plate (Park et al., 2014). Complementary fluid-inclusion analysis of the same peridotites documents two distinct fluid percolation events (CO₂–N₂ and CO₂–H₂O), providing direct evidence for the complexity of mantle fluids and multi-stage metasomatism beneath the RGR (Park et al., 2017).
In the Gyeonggi Massif, Korean Peninsula, well-preserved transitional microstructures in the Yugu peridotite body record a continuous olivine fabric evolution within a mantle shear zone: A-type (proto-mylonite) → D-type (mylonite) → E-type (ultra-mylonite), reflecting progressive increases in shear strain and water activity under decreasing temperature conditions (Park & Jung, 2017). Deformation mechanism maps indicate a transition from dislocation creep to dislocation accommodated grain boundary sliding and ultimately to a combination of dislocation and diffusion creep. Spinel peridotite xenoliths beneath the Baekdusan volcano, NE Asia, exhibit two distinct olivine fabrics — A-type in coarse-granular and D-type in fine-granular harzburgites — reflecting a compositionally and texturally heterogeneous vertical mantle section (Park et al., 2020). The A-type LPO is interpreted as a preserved Archean cratonic mantle fabric formed under high-temperature and low-stress conditions, whereas the D-type LPO likely originated from later localized deformation after a high degree of partial melting.
Finally, phengite eclogites from the Yuka terrane, North Qaidam UHP metamorphic belt, NW China, demonstrate that mineral assemblage exerts a first-order control on the seismic properties of subducting oceanic crust (Park & Jung, 2019). Phengite-bearing eclogites produce seismic anisotropy at least three times higher than bimineralic eclogites, suggesting that phengite plays a critical role in generating trench-parallel seismic anisotropy in subduction zones.
Collectively, these results demonstrate that crystal-scale fabric analysis of mafic and ultramafic rocks provides powerful constraints on lithospheric deformation processes across diverse tectonic environments, from continental rifting and mantle shear zones to cratonic mantle and subduction zones, ultimately bridging the gap between microstructural observations and plate-scale tectonics.
[Abstract]
Understanding how deformation is recorded at the crystal scale and how it relates to large-scale tectonic processes is fundamental to deciphering the evolution of Earth's lithosphere. This study presents a synthesis of microstructural and petrofabric analyses of mafic and ultramafic rocks from four distinct tectonic settings, linking crystal-scale deformation to plate-scale tectonics.
In the Rio Grande Rift (RGR), USA, olivine lattice preferred orientations (LPOs) in spinel peridotite xenoliths reveal contrasting deformation conditions between the rift axis and rift shoulder: A-type LPO under dry conditions at the rift axis and C-type LPO under hydrous conditions at the rift shoulder, reflecting localized mantle metasomatism related to dehydration of the subducted Farallon plate (Park et al., 2014). Complementary fluid-inclusion analysis of the same peridotites documents two distinct fluid percolation events (CO₂–N₂ and CO₂–H₂O), providing direct evidence for the complexity of mantle fluids and multi-stage metasomatism beneath the RGR (Park et al., 2017).
In the Gyeonggi Massif, Korean Peninsula, well-preserved transitional microstructures in the Yugu peridotite body record a continuous olivine fabric evolution within a mantle shear zone: A-type (proto-mylonite) → D-type (mylonite) → E-type (ultra-mylonite), reflecting progressive increases in shear strain and water activity under decreasing temperature conditions (Park & Jung, 2017). Deformation mechanism maps indicate a transition from dislocation creep to dislocation accommodated grain boundary sliding and ultimately to a combination of dislocation and diffusion creep. Spinel peridotite xenoliths beneath the Baekdusan volcano, NE Asia, exhibit two distinct olivine fabrics — A-type in coarse-granular and D-type in fine-granular harzburgites — reflecting a compositionally and texturally heterogeneous vertical mantle section (Park et al., 2020). The A-type LPO is interpreted as a preserved Archean cratonic mantle fabric formed under high-temperature and low-stress conditions, whereas the D-type LPO likely originated from later localized deformation after a high degree of partial melting.
Finally, phengite eclogites from the Yuka terrane, North Qaidam UHP metamorphic belt, NW China, demonstrate that mineral assemblage exerts a first-order control on the seismic properties of subducting oceanic crust (Park & Jung, 2019). Phengite-bearing eclogites produce seismic anisotropy at least three times higher than bimineralic eclogites, suggesting that phengite plays a critical role in generating trench-parallel seismic anisotropy in subduction zones.
Collectively, these results demonstrate that crystal-scale fabric analysis of mafic and ultramafic rocks provides powerful constraints on lithospheric deformation processes across diverse tectonic environments, from continental rifting and mantle shear zones to cratonic mantle and subduction zones, ultimately bridging the gap between microstructural observations and plate-scale tectonics.
첨부파일 (1개)
- 지구사랑세미나_초록_박문재교수님.pdf (67 KB, download:17)
