Petrogenesis and tectonic implications of the Early Carboniferous to the Late Permian Barleik plutons in the West Junggar (NW China)
| Autor: | Rong Ren, Bo Liu, Zeng-Zhen Wang, Bao-Fu Han, Bo Zheng, Jia-Fu Chen |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
Underplating
Fractional crystallization (geology) Subduction Permian 020209 energy Pluton Geochemistry Geology 02 engineering and technology 010502 geochemistry & geophysics 01 natural sciences Diorite Geochemistry and Petrology Carboniferous 0202 electrical engineering electronic engineering information engineering Petrology 0105 earth and related environmental sciences Petrogenesis |
| Zdroj: | Lithos. :232-248 |
| ISSN: | 0024-4937 |
| DOI: | 10.1016/j.lithos.2016.12.027 |
| Popis: | The Paleozoic accretionary orogenesis and continental crustal growth in Central Asia are thought to have close relationship with the evolution of the Paleo-Asian Ocean (PAO). The well-exposed plutons in the northern Barleik Mountains of the West Junggar region, NW China, may provide essential insights into the evolution of the Junggar Ocean, a branch of the PAO, and mechanism of continental crustal growth. Our work on the Barleik plutons indicates an early suite of 324–320 Ma diorite and a late suite of 314–259 Ma quartz syenite and granitic porphyry. All the plutons are characterized by high-K calc-alkaline to shoshonitic signatures, varying depletion in Nb, Ta, Sr, P, Eu, and Ti, low initial 87Sr/86Sr ratios (0.70241–0.70585), strongly positive eNd(t) values (+ 5.7–+7.7), and young one-stage Nd model ages (390–761 Ma), suggesting that they resulted from different batches of magma that were produced by fractional crystallization of a metasomatized mantle source with minor crustal contamination. The diorite is coeval with the youngest arc magmatic rocks, indicating a subduction-related origin. By contrast, the quartz syenite and granitic porphyry are geochemically similar to A2-type granites, with high Zr, Ga, and FeOT/[FeOT + MgO], and are coeval with the widespread plutons in the West Junggar. This, together with the occurrence of Late Carboniferous fluvial deposits and the lack of < 320 Ma ophiolitic and subduction-related metamorphic lithologies, definitively indicates a post-collisional setting after the closure of the Junggar Ocean. Slab breakoff accompanied by asthenospheric upwelling and basaltic underplating is a possible geodynamic process that is responsible for the post-collisional magmatism and vertical crustal growth in the region. Thus a tectonic switch from subduction to post-collision started at the end of the Early Carboniferous (~ 320 Ma), probably as a result of the final closure of the Junggar Ocean. |
| Databáze: | OpenAIRE |
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