The use of garnet porphyroblasts to resolve the metamorphic pressure-temperature-deformation (P-T-d) path: An example from the Imjingang belts, South Korea

Abstract

S: Quantitative P−T−deformation path determination for metamorphic rocks can be revealed by an approach combined isopleths intersection of zoned garnet compositions with foliation intersection/inflexion axes (FIAs) preserved within the garnet porphyroblast. The method presented here is applied to metapelites in the Jingok Unit of the Imjingang belt, South Korea. Garnet and staurolite FIA trends are E−W to WNW−ESE (90−120°) and NE−SW to ENE−WSW (50−80°), respectively. The FIA data indicate that garnet porphyroblasts have grown under N−S to NNE−SSW bulk shortening. P−T paths for garnet growth in Grt, St and Ky zone in the Jingok Unit, calculated from geothermobarometers and the intersection of isopleths on P−T pseudosections in the MnO−Na 2 O−CaO−K 2 O−FeO−MgO−Al 2 O 3 −SiO 2 −H 2 O (MnNCK-FMASH) system constructed using program THERMOCALC, are compressional heating from 545°C at 5.3 kbar to 610−640°C at 7.9−8.8 kbar. All compositional and microtextural data and thermodynamic modeling indicate that garnet porphyroblasts have formed during compressional heating under N−S crustal shortening, whereas staurolite porphyroblasts have formed dominantly during sub-isothermal decompression with overgrowing NE/ENE FIA. Consequently, the metapelites in the Jingok Unit have experienced clockwise P−T path derived from Barrovian-type metamorphism belong in amphibolites facies.

Occurrence and growth history of texturally sector- and sigmoidal-zoned garnet in the San Lo renzo Schists in the Sierra Nevada de Santa Marta massif (Co lombia)

“…Garnet porphyroblasts in metamorphic rocks provide valuable information on the processes of crystal nucleation and growth for two reasons (Miyashita, 1996): (1) they usually contain internal textural zones and inclusion trails that aid in correlating the timing of garnet growth under specific conditions with deformation and metamorphism (e.g., Hollister, 1966;Andersen, 1984;Rice and Mitchell, 1991;Williams, 1994;Bell et al, 1997;Stallard and Hickey, 2002;Meth and Carlson, 2005;Kim and Jung, 2010;Kiers, 2013), and (2) they have distinct chemical zoning retaining a record of their growth history (e.g., Olimpio and Anderson, 1978;Takasu, 1986;Stallard and Hickey, 2002;Meth and Carlson, 2005;Stowell et al, 2011) and showing some of the greatest variability in terms of solid solution, providing data to constrain the P-T-t evolution of metamorphism in orogenic belts (e.g., Florence and Spear, 1993;Ratner and Cheney, 2002).…”

Metamorphism and Deformation of the Late Paleozoic Pyeongan Supergroup in the Taebaeksan Basin: Reviews on the Permo-Triassic Songrim Orogeny

“…Metamorphic P-T paths of the medium pressure regional metamorphism and thermal metamorphism combined with multiple deformations (D 1 to D 4 ) and relative growth timing of porphyroblasts in the Pyeongan Supergroup are from Kim and Ree (2010), Kim (2011) and . P-T paths for the Okcheon Supergroup and the Imjingang belt are from Cho and Kim (2005), and Cho et al (2007) and Kim and Jung (2010), respectively. Geologic time scale is same as in Fig.…”

“…(Yu et al, 1997;Lee and Sheen, 1998;Ko et al, 1999) (Cluzel et al, 1990;Kim et al, 1994;Kim, 1996;Chough et al, 2000) (Kim et al, 1994;Kim, 1996;Chough et al, 2000) (Cluzel et al, 1990;Cluzel, 1991;Cho and Kim, 2005;Han et al, 2006) 그리고 (3) 쥬라기 중기-백악기 초기 동안의 대보 조산운동 (Cluzel et al, 1990;Cluzel, 1991;Sagong and Kwon, 1998;Han et al, 2006 (Kim et al, 2001;Cheong et al, 2003;Kim et al, 2007)와 변성 온도-압력 조건 (김현철 외, 1995;Min and Cho, 1998;Kim and Cho, 1999;오창환 외, 1999) (Chang, 1988;Cluzel et al, 1990;Koh and Kim, 1995 (Ree et al, 1996;Cho et al, 2007;Kim, 2008;Kown et al, 2009). 임진강 대에 분포하는 데본기 변성이질암은 흑운모, 석류석, 십자석, 남정석 반상변정을 함유하며 바로비안 유형 의 광역 변성작용을 경험하였다 (Kim, 2002;Kim and Jung, 2010). 최고 변성작용은 263-230 Ma 동안 에 발생하였고 (Ree et al, 1996;Jeon and Kwon, 1999;Cho et al, 1996;Cho et al, 2007), 최고 Vol.…”

“…2, 2012 온도-압력 조건은 610-700 o C, 9.0-11.0 kbars이다(Fig. 7; Cho et al, 2007;Kim and Jung, 2010). 기존 연구결과에 의하면, 임진강 변성대는 3회의 변형작용 (D n-1 , D n and D n+1 )을 경험하였다 (Ree et al, 1996;Jung et al, 1999;2002).…”

“…9. Comparison of the late Paleozoic Temperature-time (T-t) paths combined with FIA trends of the late Paleozoic terranes in South Korea (From Kim and Ree, 2012): Taebaeksan basin (Kim and Ree, 2010), the Okcheon basin (Min and Cho, 1995;Cho and Kim, 2005;Lee, 2000), and the Imjingang belt (Kim, 2002;Cho et al, 2007;Kim and Jung, 2010). Although timing of the peak temperature is a little bit different from each terrane, the trend of cooling history is almost identical.…”