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| Titel |
Paleomagnetic constraints on the Mesozoic drift of the Lhasa terrane (Tibet) from Gondwana to Eurasia |
| VerfasserIn |
Zhenyu Li, Peter Lippert, Lin Ding, Peiping Song, Yahui Yue, Douwe van Hinsbergen |
| 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 |
250127170
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| Publikation (Nr.) |
 EGU/EGU2016-7012.pdf |
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| Zusammenfassung |
| The Mesozoic plate tectonic history of Gondwana-derived crustal blocks of the Tibetan
Plateau is hotly debated, but so far, paleomagnetic constraints quantifying their
paleolatitudinal drift history remain sparse. Here, we compile existing data published mainly
in Chinese literature and provide a new, high-quality, well-dated paleomagnetic pole from the
∼180 Ma Sangri Group volcanics of the Lhasa terrane. Our Sangri Group pole is calculated
from pre-folding characteristic remanent magnetizations carried by thermoremanent
magnetizations in low-Ti titanomagnetite and titanohematite in basalts and basaltic andesites
that we have dated using zircon U-Pb geochronology. Forty-two lava sites (68%) meet our
quality criteria and provide an average direction of D±ΔD = 341.9±3.4˚ , I±ΔI =
-13.3±6.5˚ , A95 = 3.4, K = 42.9, n=42, corresponding to a paleolatitude of ∼6˚ S. The A95
value falls within the n-dependent confidence envelope of Deenen et al. (2011) (A95min=2.7;
A95max=7.8), indicating that the data scatter can be straightforwardly explained by
paleosecular variation of the paleomagnetic field alone. In addition, positive fold tests
are consistent with a pre-folding remanence acquisition. Our new pole confirms a
trend in existing data of variable quality that suggests the Lhasa terrane rifted from
Gondwana in Late Triassic rather than Permian time, as widely perceived. A total
northward drift of ∼ 4500 km between ∼220 and ∼130 Ma yields a reasonable average
paleolatitudinal plate motion rate of 5 cm/yr. Our results are consistent with both an
Indian or an Australian original position of the Lhasa terrane and cannot directly
discriminate between these two interpretations. Nonetheless, we show that paleomagnetic
data can provide a strong constraint on Mesozoic plate kinematics of the Tethyan
realm. Our study also underscores the need for new, high-quality and well-dated
paleomagnetic poles from the Paleozoic and Mesozoic of the Tibetan terranes. |
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