Evolution and modification of lithospheric mantle within deeply continental subduction zone: Insights from two contrasting orogenic garnet peridotites in South Altun–North Qaidam belt
Deciphering the geodynamic evolution and compositions of the Earth's mantle is crucial for understanding the origin and evolution of the Earth, however, the original geodynamic setting and significance of tectonically emplaced mantle in ancient orogens is always ambiguous. Orogenic garnet perid...
| Main Authors: | , , , , |
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| Format: | Journal article |
| Language: | English |
| Published: |
Elsevier
2023
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| Summary: | Deciphering the geodynamic evolution and compositions of the Earth's mantle is crucial for understanding the origin and evolution of the Earth, however, the original geodynamic setting and significance of tectonically emplaced mantle in ancient orogens is always ambiguous. Orogenic garnet peridotites can shed light on the understanding of upper mantle petrology and the tectonic processes that operate at convergent plate boundaries. Petrographical evidence and P-T conditions of two contrasting types of orogenic garnet peridotites in the South Altun–North Qaidam (SAT–NQD) HP/UHP metamorphic belt suggest that they experienced a notably different geological history. Geochemical characteristics show that the garnet peridotites in the Bashiwake unit represent ultramafic complexes emplaced into the continental crust before subduction, while those in the Luliangshan unit originate from the mantle wedge above a deep subduction zone. Sr[sbnd]Nd isotopes for the two contrasting ultramafic rocks indicate that both have been modified either by mantle metasomatism or crustal contamination. The distinct petrochemical and isotopic characteristics of these contrasting orogenic garnet peridotite types demonstrate spatio-temporal variation in the tectonothermal-evolution of the SAT–NQD HP/UHP orogen. |
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