High-pressure garnet amphibolite from the Funaokayama unit, western Kii Peninsula and the extent of eclogite facies metamorphism in the Sanbagawa belt

被引:8
|
作者
Endo, Shunsuke [1 ,3 ]
Nowak, Izabella [2 ,3 ]
Wallis, Simon R. [3 ]
机构
[1] Natl Inst Adv Ind Sci & Technol, Inst Geol & Geoinformat, Tsukuba, Ibaraki 3058567, Japan
[2] Polish Acad Sci INGPAN, Inst Geol Sci, PL-50449 Wroclaw, Poland
[3] Nagoya Univ, Dept Earth & Planetary Sci, Chikusa Ku, Nagoya, Aichi 4648602, Japan
关键词
Eclogite facies; Funaokayama unit; Garnet amphibolite; P-T path; Sanbagawa belt; PHASE-EQUILIBRIUM EXPERIMENTS; THERMODYNAMIC MODEL; MIXING PROPERTIES; CENTRAL SHIKOKU; SW JAPAN; BEARING; SUBDUCTION; HISTORY; SCHISTS; QUARTZ;
D O I
10.2465/jmps.121125
中图分类号
P57 [矿物学];
学科分类号
070901 ;
摘要
Quantitative analyses of garnet-bearing epidote amphibolite (hereafter garnet amphibolite) from the Funaokayama unit, western Kii Peninsula of the Sanbagawa belt reveal a previously unrecognized high-grade part of the Sanbagawa metamorphism. Petrographic observations suggest that the garnet amphibolite underwent three stages of metamorphism (M1, M2 and M3). Records of M1 are preserved as syn-tectonic prograde-zoned garnet and its inclusions. Pseudosection modeling reproduces the observed M1 assemblage garnet + amphibolite + epidote + phengite + quartz and the growth zoning of garnet records the pressure (P)-temperature (7) evolution from 0.8 GPa, 570 degrees C to 1.3 GPa, 590 degrees C. Therefore, this garnet growth and associated deformation (D1) took place during subduction up to eclogite facies conditions. The garnet rim compositions and inclusions of epidote, titanite, rutile and quartz (5titanite + 2clinozoisite = 5rutile + 3grossular + 2quartz + H2O) give consistent peak-P estimates of 1.3-1.9 GPa. The garnet contains quartz inclusions retaining residual pressures of up to similar to 0.7 GPa, which is as high as the values reported in well-characterized eclogite samples in central Shikoku. The inferred peak-P conditions in the eclogite facies is further supported by the occurrence of aragonite in associated pelitic schist. The assemblage hornblende + epidote + titanite + quartz + albite in the matrix and its equilibrium conditions of similar to 0.8 GPa, 580 degrees C suggest decompression to the epidote-amphibolite facies (M2). The M2 minerals locally show replacement by the mineral assemblage actinolite + epidote + chlorite + titanite + calcite + quartz + albite, suggesting a partial re-equilibration in the greenschist facies (M3). M2 and M3 are synchronous with the main phase of ductile deformation during exhumation (D2). Despite the absence of the omphacite + quartz assemblage, it is likely that eclogite facies metamorphism in the Sanbagawa belt can be extended to western Kii Peninsula.
引用
收藏
页码:189 / 200
页数:12
相关论文
共 50 条