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| Titel |
Mineral inclusions in zircons of S-type granite: implications for high pressure metamorphism history of meta-sedimentary rocks in the Huai’an terrain, North China Craton |
| VerfasserIn |
Haozheng Wang, Huafeng Zhang, Mingguo Zhai, Xiahong Cui |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250122865
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| Publikation (Nr.) |
 EGU/EGU2016-2000.pdf |
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| Zusammenfassung |
| The Paleoproterozoic evolution of North China Craton (NCC) arises many argument as
geologists have different viewpoints on the distribution and metamorphic history of mafic
granulites and granulite facies meta-sedimentary rocks. To provide more evidence of
constraining the metamorphic history of granulite facies meta-sedimentary rocks, we select
granulite facies meta-sedimentary rocks and co-existing S-type granite in the Huai’an terrain
to make a deep research. Magmatic zircons derived from the S-type granite reveal the
magmatic age of ∼1.95 Ga and metamorphic age of ∼1.85 Ga with ɛHf(t) value
of -4.5 – -0.5. The ɛHf(t) value of S-type granite and relict of garnet-sillimanite
gneiss suggest that the S-type granite is generated by melting of meta-sedimentary
rocks. Zircons with ages of ∼1.95 Ga and ∼1.85 Ga have the mineral inclusions
of Ky + Qz + Ru + Pl and these mineral inclusions are determined by method of
Laser-Raman. The ∼1.95 Ga magmatic zircons with inclusions of Ky + Qz + Ru + Pl
suggest that meta-sedimentary rocks have mineral assemblages Ky + Qz + Ru + Pl.
However, previous studies in the Huai’an terrain showed that almost granulite facies
metamorphic condition of meta-sedimentary rocks were regarded as medium pressure by
considering the Sill + Grt + Bt + Pl + Qz + Ru + Kf. Presence of kyanite instructs that
meta-sedimentary rocks may experience high pressure granulite facies metamorphism.
According to pseudosection calculation by using effective bulk composition of
garnet-sillimanite gneiss, mineral assemblage of Grt + Ky + Pl + Bt + Qz + Ru
+ Kf is regarded as the peak stage of high pressure metamorphism. This mineral
assemblage is occurred at field of 1033 – 1123 K and 9 – 15 Kbar and the peak
pressure is around 11 – 13 Kbar, determined by the XMg and XCa isopleths of
garnet. This P-T result is consistent with peak condition of high pressure mafic
granulite. Considering the ∼1.95 Ga magmatic age of S-type granite generated by
decompression partial melting of meta-sedimentary rocks, we propose that the
high pressure granulite facies metamorphism on meta-sedimentary rocks before or
around 1.95 Ga. Integrating 1.95 Ga metamorphic age recorded in the high pressure
mafic granulite occurred in Huai’an terrain, we deduce that mafic granulite and
meta-sedimentary experience the similar granulite facies metamorphism since ∼1.95 Ga.
Additionally, inclusions of kyanite occurred in ∼1.95 Ga and ∼1.85 Ga zircons
may be a robust evidence that ∼1.85 Ga zircons are recrystallized from ∼1.95 Ga
magmatic zircons. Based on these results and deduction and related previous data, we
suggest that Huai ’an terrain experienced the continental collision since ∼1.95
Ga.
This research is supported by Open Research Fund of Key Laboratory of Mineral
Resources, Chinese Academy of Sciences (KLMR2015-15), Natural Sciences Foundation of
China (41530208 and 41210003) and 973 project (2012CB4166006). |
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