Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean

The origin and tectonic implication of Early–Middle Devonian magmatism in the northern margin of YB (Yili Block) remain enigmatic and are important for understanding Late Paleozoic evolution of the Junggar Ocean and southern Kazakhstan Orocline. Here, we present the systematic study of whole-rock ge...

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Autores principales:	Youxin Chen, Shengqiang Zhu, Xianzhi Pei, Lei He, Jun Zhao, Bate Bulong, Meng Wang, Shaowei Zhao, Hai Zhou
Formato:	article
Lenguaje:	EN
Publicado:	MDPI AG 2021
Materias:	Central Asian Orogenic Belt northern margin of Yili Block the Early Devonian volcanic rocks subduction Mineralogy QE351-399.2
Acceso en línea:	https://doaj.org/article/e244a74f5ef44cef83372891c8f6478f
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spelling	oai:doaj.org-article:e244a74f5ef44cef83372891c8f6478f2021-11-25T18:26:35ZEarly Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean10.3390/min111112482075-163Xhttps://doaj.org/article/e244a74f5ef44cef83372891c8f6478f2021-11-01T00:00:00Zhttps://www.mdpi.com/2075-163X/11/11/1248https://doaj.org/toc/2075-163XThe origin and tectonic implication of Early–Middle Devonian magmatism in the northern margin of YB (Yili Block) remain enigmatic and are important for understanding Late Paleozoic evolution of the Junggar Ocean and southern Kazakhstan Orocline. Here, we present the systematic study of whole-rock geochemical and Sr–Nd isotope features as well as U–Pb–Hf isotope characteristics of zircon crystals for newly identified Early Devonian volcanic rocks from the northern margin of YB. The volcanic rocks are composed of rhyolite, rhyolite porphyry, and rhyolitic tuff. Zircon U-Pb age dating indicates they were formed at ca. 407~418 Ma. They have high SiO<sub>2</sub> (70.16–77.52 wt.%) and alkali (5.10–9.56 wt.%) contents, and high Zr + Nb + Ce + Y content (~456 ppm), indicative of A-type magma. Their relative depletion of Nb, Ta, and Ti, and enrichment of LILEs show arc affinity. Their low initial <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.699708–0.709822) and negative <i>ε</i><sub>Nd</sub>(t) values (−1.8 to −4.0) indicate a mainly continental magma source and their positive <i>ε</i><sub>Hf</sub>(t)values (+6.13 to +14.81) are possibly due to the garnet effect. All these above reveal that volcanic rocks were generated by re-melting of lower crust under a high temperature condition, which was induced by long-lived heat accumulation with no or minimal basalt flux. Combined with active continental margin inference evidenced by contemporaneous sedimentary rocks, we attribute the generation of the volcanic rocks to a continental arc setting related to the southward subduction of Junggar oceanic crust. Thus, we infer the Early–Middle Devonian arc-related magmatic rocks in the northern margin of YB are eastward counterparts of the southern limb of the Devonian Volcanic Belt, which resulted from a relatively steady-state southward subduction.Youxin ChenShengqiang ZhuXianzhi PeiLei HeJun ZhaoBate BulongMeng WangShaowei ZhaoHai ZhouMDPI AGarticleCentral Asian Orogenic Beltnorthern margin of Yili Blockthe Early Devonianvolcanic rockssubductionMineralogyQE351-399.2ENMinerals, Vol 11, Iss 1248, p 1248 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Central Asian Orogenic Belt northern margin of Yili Block the Early Devonian volcanic rocks subduction Mineralogy QE351-399.2
spellingShingle	Central Asian Orogenic Belt northern margin of Yili Block the Early Devonian volcanic rocks subduction Mineralogy QE351-399.2 Youxin Chen Shengqiang Zhu Xianzhi Pei Lei He Jun Zhao Bate Bulong Meng Wang Shaowei Zhao Hai Zhou Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean
description	The origin and tectonic implication of Early–Middle Devonian magmatism in the northern margin of YB (Yili Block) remain enigmatic and are important for understanding Late Paleozoic evolution of the Junggar Ocean and southern Kazakhstan Orocline. Here, we present the systematic study of whole-rock geochemical and Sr–Nd isotope features as well as U–Pb–Hf isotope characteristics of zircon crystals for newly identified Early Devonian volcanic rocks from the northern margin of YB. The volcanic rocks are composed of rhyolite, rhyolite porphyry, and rhyolitic tuff. Zircon U-Pb age dating indicates they were formed at ca. 407~418 Ma. They have high SiO<sub>2</sub> (70.16–77.52 wt.%) and alkali (5.10–9.56 wt.%) contents, and high Zr + Nb + Ce + Y content (~456 ppm), indicative of A-type magma. Their relative depletion of Nb, Ta, and Ti, and enrichment of LILEs show arc affinity. Their low initial <sup>87</sup>Sr/<sup>86</sup>Sr ratios (0.699708–0.709822) and negative <i>ε</i><sub>Nd</sub>(t) values (−1.8 to −4.0) indicate a mainly continental magma source and their positive <i>ε</i><sub>Hf</sub>(t)values (+6.13 to +14.81) are possibly due to the garnet effect. All these above reveal that volcanic rocks were generated by re-melting of lower crust under a high temperature condition, which was induced by long-lived heat accumulation with no or minimal basalt flux. Combined with active continental margin inference evidenced by contemporaneous sedimentary rocks, we attribute the generation of the volcanic rocks to a continental arc setting related to the southward subduction of Junggar oceanic crust. Thus, we infer the Early–Middle Devonian arc-related magmatic rocks in the northern margin of YB are eastward counterparts of the southern limb of the Devonian Volcanic Belt, which resulted from a relatively steady-state southward subduction.
format	article
author	Youxin Chen Shengqiang Zhu Xianzhi Pei Lei He Jun Zhao Bate Bulong Meng Wang Shaowei Zhao Hai Zhou
author_facet	Youxin Chen Shengqiang Zhu Xianzhi Pei Lei He Jun Zhao Bate Bulong Meng Wang Shaowei Zhao Hai Zhou
author_sort	Youxin Chen
title	Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean
title_short	Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean
title_full	Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean
title_fullStr	Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean
title_full_unstemmed	Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean
title_sort	early devonian arc-related volcanic rocks in the haerdaban, north margin of the yili block: constraint on the southward subduction of the junggar ocean
publisher	MDPI AG
publishDate	2021
url	https://doaj.org/article/e244a74f5ef44cef83372891c8f6478f
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Early Devonian Arc-Related Volcanic Rocks in the Haerdaban, North Margin of the Yili Block: Constraint on the Southward Subduction of the Junggar Ocean

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