胡云,何梦颖,许欢,等. 两种重矿物分析方法在青藏高原东南缘伊洛瓦底江沉积物物源分析中的应用[J]. 海洋地质与第四纪地质,2022,42(4): 181-193. doi: 10.16562/j.cnki.0256-1492.2021112901
引用本文: 胡云,何梦颖,许欢,等. 两种重矿物分析方法在青藏高原东南缘伊洛瓦底江沉积物物源分析中的应用[J]. 海洋地质与第四纪地质,2022,42(4): 181-193. doi: 10.16562/j.cnki.0256-1492.2021112901
HU Yun,HE Mengying,XU Huan,et al. Application of two heavy mineral analysis methods in the provenance study of Irrawaddy River sediments on the southeastern margin of Tibetan Plateau[J]. Marine Geology & Quaternary Geology,2022,42(4):181-193. doi: 10.16562/j.cnki.0256-1492.2021112901
Citation: HU Yun,HE Mengying,XU Huan,et al. Application of two heavy mineral analysis methods in the provenance study of Irrawaddy River sediments on the southeastern margin of Tibetan Plateau[J]. Marine Geology & Quaternary Geology,2022,42(4):181-193. doi: 10.16562/j.cnki.0256-1492.2021112901

两种重矿物分析方法在青藏高原东南缘伊洛瓦底江沉积物物源分析中的应用

Application of two heavy mineral analysis methods in the provenance study of Irrawaddy River sediments on the southeastern margin of Tibetan Plateau

  • 摘要: 伊洛瓦底江是亚洲大型河流之一,其沉积物记录了青藏高原周缘造山带的剥蚀风化信息,对该流域沉积物的溯源研究是探究高原隆升对水系演化影响的重要课题。沉积物的重矿物种类与源岩联系紧密,是物源分析的重要手段之一。重矿物鉴定分析手段层出不穷,但不同鉴定手段之间缺乏对比分析。采用自动矿物分析系统TIMA与光学显微镜鉴定(optical microscope, OM)两种方法对伊洛瓦底江沉积物重矿物进行了鉴定分析,结果表明:伊洛瓦底江上游主要重矿物是角闪石-石榴子石-赤/磁铁矿、钛铁矿;伊洛瓦底江下游主要重矿物是赤/磁铁矿、钛铁矿-石榴子石-黝帘石-角闪石;支流钦敦江主要重矿物组合是黝帘石-角闪石-石榴子石。两种方法的结果都指示了伊洛瓦底江沉积物主要来自上游流经的缅甸北部构造单元的变质岩以及中/基性岩,太公-密支那带对伊洛瓦底江沉积物贡献量最大,钦敦江流域对伊洛瓦底江下游沉积物贡献量有限。但是两种方法对重矿物种类以及单个重矿物含量鉴定结果有着明显差异:TIMA方法的鉴定种类更加丰富,且其分析结果与伊洛瓦底江流域地质岩性分布的耦合程度更高,但TIMA无法区分化学性质相同的矿物;OM法对光学性质相近的矿物鉴定结果不准确。因此建议对重矿物分类程度或精确性要求更高的研究使用TIMA进行精确分析,同时辅助OM法区分化学性质相同的矿物。

     

    Abstract: The Irrawaddy River is one of the large rivers in Asia, and its sediments record the denudation and weathering information of the orogenic belt around the Tibetan Plateau. Tracing the sediments in this basin is an important topic to explore the impact of plateau uplift on the evolution of river system. The types of heavy minerals in sediments are closely related to source rocks, which is one of the important means for provenance analysis. There are a variety of methods to identify and analyze heavy minerals, but there is a lack of comparative analysis among different methods. This paper adopted TESCAN Integrated Mineral Analyzer (TIMA) and Optical Microscope (OM) to identify and analyze heavy minerals of Irrawaddy River sediments. The main heavy minerals in the upper reaches of the Irrawaddy are amphibole-garnet- hematite/magnetite, ilmenite. The main heavy minerals in the lower reaches of the Irrawaddy are hematite/magnetite, ilmenite-garnet-zoisite-hornblende. The main heavy mineral combination of the tributary Chindwin River is zoisite-hornblende-garnet. The results of both methods indicate that the Irrawaddy sediments are mainly derived from metamorphic and intermediate or mafic rocks of tectonic units in northern Myanmar, with the Tagaung-Myitkyina Belt contributing the most to the Irrawaddy sediments and the Chindwin River basin contributing a limited amount to the lower reaches of the Irrawaddy sediments. However, there are significant differences in the identification results of heavy mineral species and individual heavy mineral contents between the two methods. The identification species of TIMA method are more abundant, and its analysis results are more coupled with the geological lithological distribution of Irrawaddy River basin. It’s also found that TIMA cannot distinguish the minerals with the same chemical properties, and OM method is not accurate in identifying the minerals with similar optical properties. Therefore, it is promoted in this paper that TIMA should be used for accurate analysis in studies requiring more precise and accurate classification of heavy minerals, while the OM method should be supplemented to distinguish minerals with the same chemical properties.

     

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