山西五台群变质砂岩的物源和构造环境
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P588.21+2.3

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国家重点研发计划(2016YFC0600106,2018YFC0603702)


Provenance and tectonic setting of metamorphosed sandstones of the Wutai Group of Shanxi Province, China
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    摘要:

    华北克拉通中北部五台杂岩中出露一套变质砂岩,归属于上太古界五台群,其物质来源和构造环境分析对理解本区新太古代末期的地壳演化具有重要意义。该变质砂岩主要由石英、长石和粘土质胶结物组成,岩相学特征显示为杂砂岩,利用主量、微量元素判别的结果与岩相学观察一致。岩石地球化学分析结果显示,样品的SiO2含量变化较大(64.51%~71.80%),成熟度较低(SiO2/Al2O3=3.98~4.73)。化学蚀变指数(CIA)、风化指数(CIW)和斜长石蚀变指数(PIA)分别为60~76、63~91、61~89,反映该套砂岩是由近源风化的碎屑物质经过快速搬运沉积而成。与区域潜在源区物质的不活动元素比值(Th/La、Sm/La、Zr/Hf、Y/Ho)进行对比分析,结果显示该套砂岩的物源可能主要来自于区内的酸性火山岩。这一特征与大陆边缘弧的沉积物质主要来自酸性火山岩的特性相吻合。同时,多种微量元素构造环境判别结果也都显示该砂岩与大陆边缘弧的砂岩特征相似。因此,认为华北克拉通五台群变质砂岩形成于新太古代末大陆边缘弧的构造环境。

    Abstract:

    A suit of metamorphosed sandstones of the Wutai Group in the Wutai Complex, North Central North China Craton was recognized recently. Their provenance and tectonic setting are vital for further understanding on the Late Neoarchean crust evolution in this area. The metamorphosed sandstones are mainly composed of quartz, feldspar and clay cement. The petrographic characteristics show that they are greywackes, which is consistent with the result distinguished by their major and trace elements compositions. The geochemical features show that they have relatively large variation of SiO2 content (64.51%~71.80%), and relatively low maturity (SiO2/Al2O3=3.98~4.73). Their chemical index of alteration (CIA), chemical index of weathering (CIW) and plagioclase index of alteration (PIA) are 60~76, 63~91 and 61~89, respectively, which indicate that the protolith of the metamorphosed sandstones was formed by rapid transportation and deposition of near-source weathered clasts. Compared with ratios of immobile elements (such as Th/La, Sm/La, Zr/Hf, Y/Ho) of the potential source rocks, the provenances of metamorphosed sandstones are mainly from acidic volcanic rocks. This result is highly similar to those of sedimentary materials of the continental island arc which were mainly derived from acidic volcanic rocks. The discrimination results of trace elements on tectonic setting also show that the characteristics of the sandstones assemble those of the continental island arc. Consequently, we consider that the metamorphosed sandstones of the Wutai Group, North China Craton, were formed in a continental island arc setting in the Late Neoarchean.

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沙启舟,张华锋,孙继超,等, 2022. 山西五台群变质砂岩的物源和构造环境[J]. 岩石矿物学杂志, 41(1):61~74.
SHA Qi-zhou, ZHANG Hua-feng, SUN Ji-chao, et al, 2022. Provenance and tectonic setting of metamorphosed sandstones of the Wutai Group of Shanxi Province, China[J]. Acta Petrologica et Mineralogica, 41(1): 61~74.

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  • 收稿日期:2020-11-14
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  • 在线发布日期: 2022-01-21
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