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Compositional signatures of ophiolitic rocks from the Dongco massif: Novel insights into the evolution of the central Tibetan Meso-Tethyan oceanic plateau.
- Source :
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Lithos . May2022, Vol. 416, pN.PAG-N.PAG. 1p. - Publication Year :
- 2022
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Abstract
- The role of the Meso-Tethyan oceanic plateau in the growth of the Tibetan Plateau is debated. In this paper, we report coexistence of large-scale mid-ocean ridge basalt (MORB)-like and enormous ocean island basalt (OIB)-type mafic rocks from the Dongco ophiolitic rocks of the Bangong–Nujiang Suture Zone. The MORB-like rocks host tholeiitic geochemical characterizes, and have supra-subduction zone affinity such as enrichments in large ion lithophile elements (LILEs), depletions in high field strength elements, high ε Nd (t) values (+6.5 to +9.5) and low initial 87Sr/86Sr ratios (0.7033–0.7050). The OIB-type rocks have an alkaline affinity and are characterized by enrichments in LILEs and light rare earth elements, strongly negative Sr anomalies, variable ε Nd (t) values of −3.7 to +7.3, and low initial 87Sr/86Sr ratios ranging from 0.7034 to 0.7050. Metamorphic zircons from amphibolites in the sole of the ophiolitic rocks yielded U Pb ages of 104–100 Ma. Detrital zircons from the upper Cretaceous sandstone of the Abushan Formation (K 2 ab) yielded young U Pb ages of 100–86 Ma. Considering the regional geology, we suggest that the Dongco MORB-like rocks were derived from a depleted mantle source and formed from an intra-oceanic subduction-related setting, representing remnants of normal oceanic crust, whereas the OIB-type rocks were derived from an enriched mantle source representing remnants of a Meso-Tethyan oceanic plateau. Our preferred hypothesis is that the Meso-Tethyan oceanic plateau experienced a phase of accretion at 104–100 Ma, which probably increased local subduction erosion of the upper plate and providing provenance for the deposition of the K 2 ab sandstone. The maximum depositional ages of K 2 ab sandstone constraint the minimum ages for closure of the Bangong–Nujiang Tethys Ocean most likely at 100–86 Ma. • Identified a new 104 Ma metamorphic event in the western Bangong–Nujiang Suture • Closure of the Bangong–Nujiang Tethys Ocean most likely occurred during 100–86 Ma • Dongco ophiolitic rocks contain remnants of normal oceanic crust and oceanic plateau [ABSTRACT FROM AUTHOR]
- Subjects :
- *OCEANIC plateaus
*RARE earth metals
*MAFIC rocks
*OCEANIC crust
Subjects
Details
- Language :
- English
- ISSN :
- 00244937
- Volume :
- 416
- Database :
- Academic Search Index
- Journal :
- Lithos
- Publication Type :
- Academic Journal
- Accession number :
- 155994020
- Full Text :
- https://doi.org/10.1016/j.lithos.2022.106660