Permo-Triassic arc magmatism in central Tibet: Evidence from zircon U–Pb geochronology, Hf isotopes, rare earth elements, and bulk geochemistry
There is hot debate on whether there is a Paleo -Tethyan suture within Qiangtang and on how the suture extends in central Tibet. In situ Hf and U–Pb isotopes, and rare earth element (REE) analyses of zircons, together with bulk chemistry, have helped us identify a significant, and previously unknown...
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Published in | Chemical geology Vol. 284; no. 3; pp. 270 - 282 |
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Main Authors | , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
24.05.2011
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Subjects | |
Online Access | Get full text |
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Summary: | There is hot debate on whether there is a Paleo
-Tethyan suture within Qiangtang and on how the suture extends in central Tibet.
In situ Hf and U–Pb isotopes, and rare earth element (REE) analyses of zircons, together with bulk chemistry, have helped us identify a significant, and previously unknown stage of subduction-related magmatism along the southern part of the eastern Qiangtang block, north of the Shuanghu suture, central Tibet. SHRIMP and LA-ICP-MS zircon U–Pb data demonstrate that the magmatism started as early as 275
Ma, lasted until 248
Ma, and took place at the same time as blueschist and eclogite were forming in the central Qiangtang high- to ultrahigh-pressure metamorphic belt (QMB). The positive ε
Hf(t) values of the magmatic zircons range from 9.71 to 16.73, and indicate derivation of magma from a relatively uncontaminated, depleted mantle. Variations in ε
Hf(t) values and the REE patterns of magmatic zircons, combined with substantial heterogeneities in the whole
-rock chemistry, suggest that the arc-related magmatism occurred in pulses, and was long-lived. The present data can be interpreted in terms of a history of progressive subduction during the Early Permian and Early Triassic, during which time continental fragments of EQ affinity were tectonically eroded and subducted into the mantle, along with the subducted oceanic slab. The temporal and spatial correlations between the arc-like volcanic belt and the high-pressure metamorphic belt suggest a Late Paleozoic ocean (Paleo-Tethys) existed between the western and eastern Qiangtang blocks, and that the ocean was closed by northwards subduction.
► First report of Early Permian to Early Triassic arc-like volcanism in central Tibet. ► Zircon U/Pb geochronology reveals a long-lived and pulsed volcanism. ► A Paleo-Tethys existed between the western and eastern Qiangtang blocks. ► Built a correlation between nature of subducted slab and arc-volcanics geochemistry. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 0009-2541 1872-6836 |
DOI: | 10.1016/j.chemgeo.2011.03.006 |