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Orogenic Volcanism in Eastern Kazakhstan: Composition, Age, and Geodynamic Position
Geotectonics ( IF 1.0 ) Pub Date : 2020-09-22 , DOI: 10.1134/s0016852120040044
S. V. Khromykh , D. V. Semenova , P. D. Kotler , A. V. Gurova , E. I. Mikheev , A. A. Perfilova

Studies of volcanic rocks in orogenic troughs of Eastern Kazakhstan were carried out. The troughs were formed at late-orogenic stages of evolution of Hercynian Altai collision system. Volcanic rocks are represented by basalts, andesites, dacites and rhyolites. Based on geochemical and isotopic data, the basalts and andesites derived from mafic magmas that formed as a result of partial melting of garnet peridotites in the upper mantle under the orogen. U–Pb zircon data prove two volcanic stages: more-scaled Middle Carboniferous (~311 Ma) and less-scaled Early Permian (297–290 Ma). Basalts and andesites in lower parts of the orogenic troughs and independent dacite-rhyolite structures were formed at the Middle Carboniferous stage. Parental mafic magmas were formed as a result of partial melting of mantle substrates in local transtensional zones along large shear faults. The formation of dacites and rhyolites could have been caused by partial melting of crustal substrates under effect of mafic magmas. Transtensional movements in the lithosphere of orogenic belts may indicate the beginning of collapse of orogens. A smaller volume of basalts and andesites formed at the Early Permian stage. Geochemical data prove the independent episode of partial melting in upper mantle. Synchronous basalts and andesites also appeared at wide territory in Tian Shan, Central Kazakhstan, and Central and Southern Mongolia. Early Permian volcanism indicates general extension of the lithosphere at the postorogenic stages. Large-scaled Early Permian mafic and granitoid magmatism in Central Asia has been interpreted in recent years as the Tarim Large Igneous Province caused by Tarim mantle plume activity. Thus, the extension of the lithosphere and associated volcanism in the Early Permian can be an indicator of the onset of the plume–lithosphere interaction process.



中文翻译:

哈萨克斯坦东部造山带火山作用:组成,年龄和地球动力学位置

对哈萨克斯坦东部造山槽中的火山岩进行了研究。该海槽形成于海西阿尔泰碰撞系统演化的造山后期。火山岩以玄武岩,安山岩,菊苣和流纹岩为代表。根据地球化学和同位素数据,玄武岩和安山岩源自镁铁质岩浆,其是造山带下上地幔中石榴石橄榄岩部分熔融的结果。U–Pb锆石数据证明了两个火山爆发阶段:较大规模的中石炭纪(〜311 Ma)和较小规模的早二叠世(297–290 Ma)。造山槽下部的玄武岩和安山岩,在中石炭纪形成了独立的菱镁矿-流纹岩结构。母体镁铁质岩浆是由于沿大剪切断层的局部张性带中地幔底物的部分熔融而形成的。镁铁质岩浆作用下地壳基质的部分熔融可能导致了Dacites和流纹岩的形成。造山带岩石圈中的超张运动可能表明造山带开始坍塌。在二叠纪早期形成了少量的玄武岩和安山岩。地球化学数据证明了上地幔部分熔融的独立过程。同步玄武岩和安山岩也出现在天山,哈萨克斯坦中部以及蒙古中部和南部的广阔地区。二叠纪早期的火山活动表明在造山后阶段岩石圈普遍扩张。近年来,中亚地区大规模的早二叠世铁镁质和花岗岩类岩浆作用被解释为由塔里木地幔羽流活动引起的塔里木大火成岩省。因此,早二叠世的岩石圈和相关火山活动的扩展可以指示羽流与岩圈相互作用过程的开始。

更新日期:2020-09-23
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