學術資源整合系統-相關推薦
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| 作者 | Tseng, Chien-Yuan*, Zuo, Guo-Chao, Yang, Huai-Jen, Yang, Houng-Yi, Tung, Kuo-An, Liu, Dun-Yi, Wu, Han-Quan |
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| 出版日期 | 2009 |
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| 著作名稱 | Occurrence of Alaskan-type mafic-ultramafic intrusions in the North Qulian Mountains, NW China: Evidence of Cambrian arc magmatism on the Qilian Block.
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| 卷 | 18: 526-549(SCI) |
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| 摘要 | Field relationships, mineralogy and petrology, whole-rock chemistry, and age of the Zhamashi mafic–ultramafic intrusion in the North Qilian Mountains, northwest China, have been studied in the present work. The Zhamashi intrusive body consists of ultramafic, gabbroic, and dioritic rocks in a crudely concentrically zoned structure. The ultramafic rocks are layered cumulates with rock types varying continuously from dunite through wehrlite and olivine clinopyroxenite to clinopyroxenite. The gabbroic and dioritic rocks are
also layered or massive cumulates with rock types varying continuously from noritic gabbro through hornblende gabbro to diorite. The ultramafic and adjoining gabbroic rocks are discontinuous in lithology and discordant in structure across the interface. The interface
is steep, sharp, and fractured. Contact metamorphic zones are well developed between the Zhamashi intrusive body and the country rock. The concentrically zoned structure of the intrusive body and the intrusion into the continental crust are the two main pieces of evidence for considering that the Zhamashi intrusion is Alaskan-type. The mineral chemistry
of the chromian spinels (Cr-spinels) and clinopyroxenes, and the variation trend of the whole-rock compositional plot in the (Na2O K2O)–FeO–MgO (AFM) diagram are also supportive of this consideration. The age of the Zhamashi intrusive body, determined with
sensitive high mass-resolution ion microprobe on the zircon grains, is 513.0±4.5 Ma. Parental magma of the Zhamashi intrusion is compositionally close to the primitive magma
produced by partial melting of the mantle peridotite. It was differentiated by fractional
crystallization at low total pressure and under H2O-rich conditions in an arc environment
to form all the major rock types. The concentrically zoned structure of the Zhamashi intrusive body was constructed in two stages: formation of a stratiform-type layered sequence, followed by diapiric re-emplacement. The occurrence of the Alaskan-type intrusion
suggests an active continental margin and Cambrian arc magmatism for the northern margin of the Qilian Block. |
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| 全文 |  |
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| 系統號 | NO000003521 |
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