摘要
Pelitic granulite from the Khondalite Belt,North China Craton,is composed of garnet,sillimanite,perthite,biotite and quartz.Oriented rutile needles in garnet are reported for the first time from the granulite.The rutile needles have been identified by optical microscopy and confirmed by in situ Raman spectroscopy,where they show the characteristic bands at 446–448 and 610 cm-1.Because of their very strong shape preferred orientation in3–4 easily observable directions,these rutile needles are interpreted to have formed by precipitation during exhumation and cooling following peak metamorphism.The ternary feldspar geothermometer gives a peak metamorphic temperature of*980°C at 10 kbar.The presence of oriented rutile needles in garnet is suggested to be a valuable indicator of ultrahigh-temperature(UHT)metamorphism in the Khondalite Belt and therefore likely in other UHT terrains.
Pelitic granulite from the Khondalite Belt, North China Craton, is composed of garnet, sillimanite, perthite, biotite and quartz. Oriented rutile needles in gar- net are reported for the first time from the granulite. The rutile needles have been identified by optical microscopy and confirmed by in situ Raman spectroscopy, where they show the characteristic bands at 446-448 and 610 cm-1. Because of their very strong shape preferred orientation in 3-4 easily observable directions, these futile needles are interpreted to have formed by precipitation during exhu- mation and cooling following peak metamorphism. The ternary feldspar geothermometer gives a peak metamorphic temperature of ,- 980 ℃ at 10 kbar. The presence of oriented rutile needles in garnet is suggested to be a valuable indicator of ultrahigh-temperature （UHT） metamorphism in the Khondalite Belt and therefore likely in other UHT terrains.
基金
supported by the National Basic Research Program of China(2012CB416606)
MOST Special Fund from the State Key Laboratory of Continental Dynamics
the Natural Science(NJ13032)
Start-up Research(PR12104)Foundations of Northwest University
Natural Science Foundation of Education Department of Shaanxi Provincial Government(14JK1733)
关键词
中国北方
金红石
石榴石
克拉通
麻粒岩
岩带
泥质
矽线石
Oriented rutile needles in garnet
Precipitation
UHT metamorphism ； Khondalite Belt
North China Craton
