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首页> 外文期刊>Sedimentary geology >Geochemistry of Jurassic to earliest Cretaceous deposits in the Nagato Basin, S W Japan: implication of factor analysis to sorting effects and provenance signatures
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Geochemistry of Jurassic to earliest Cretaceous deposits in the Nagato Basin, S W Japan: implication of factor analysis to sorting effects and provenance signatures

机译：日本西南部长门盆地侏罗纪至最早的白垩纪沉积物的地球化学：因子分析对分选效果和物源特征的影响

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摘要

One of the intractable problems in provenance analysis is the hydraulic sorting effect and resultant mineralogical heterogeneity in coarse- and fine-grained sediments which conceals provenance characteristics. The present study uses factor analysis to address geochemical responses to the sorting effect and provenance of Late Mesozoic sediments in the Nagato Basin, SW Japan. Factor analysis has proven useful for comprehending geochemical gradients between coarse- and fine-grained sediments. In the present example, compositional differences are based on varying proportions of quartz, plagioclase, chrome spinel, authigenic minerals and phyllosilicates. The contrasting behaviors of these minerals during the depositional stage resulted in the systematic fractionation of SiO_2/Al_2O_3, Na_2O/K_2O and Cr/Ba. Sandstones and mudstones exhibit an array of compositions in SiO_2/Al_2O_3-Na_2O/K_2O and SiO_2/Al_2O_3-Cr/Ba diagrams, the ranges of which reflect compositional variations due to the sorting effect. Sediments of different provenance exhibit distinctive mineral arrays and can be discriminated simply by reading the gradients of the continua. Therefore, this kind of data management concurrently quantifies the sorting effect and allows an estimation of the original source material. The SiO_2/Al_2O_3-Na_2O/ K_2O diagram is particularly useful for scrutinizing igneous and mature continental provenances, while the SiO_2/Al_2O_3-Cr/ Ba diagram ascertains contributions from mafic sources. This investigative approach delineates a systematic provenance transition within the Nagato Basin: a serpentinite melange provenance in the early Early Jurassic, a magmatic arc in the late Early to middle Middle Jurassic and a continental interior in the latest Jurassic to earliest Cretaceous. The provenance changed by the direct input of mature continental material into the Nagato Basin, which resulted from dissection of the volcanic arc.
机译：物源分析中难以解决的问题之一是水力分选效应以及在粗粒和细粒沉积物中产生的矿物异质性，这些特征掩盖了物源特征。本研究使用因子分析来解决地球化学对日本长门盆地晚中生代沉积物的分类效应和物源的反应。事实证明，因子分析对于理解粗粒和细粒沉积物之间的地球化学梯度很有用。在本实例中，组成差异是基于石英，斜长石，铬尖晶石，自生矿物和页硅酸盐的不同比例。这些矿物在沉积阶段的对比行为导致了SiO_2 / Al_2O_3，Na_2O / K_2O和Cr / Ba的系统分馏。砂岩和泥岩在SiO_2 / Al_2O_3-Na_2O / K_2O和SiO_2 / Al_2O_3-Cr / Ba图中显示出一系列的成分，其范围反映了由于分选效应而引起的成分变化。不同出处的沉积物表现出独特的矿物排列，可以通过读取连续体的坡度简单地区分。因此，这种数据管理可以同时量化排序效果，并可以估算原始原始资料。 SiO_2 / Al_2O_3-Na_2O / K_2O图对于仔细检查火成岩和成熟陆源特别有用，而SiO_2 / Al_2O_3-Cr / Ba图则可确定铁镁质来源。这种调查方法描绘了长门盆地内一个系统的物源过渡：侏罗纪早期的蛇纹岩混杂物起源，侏罗纪中晚期到中晚期的岩浆弧，以及侏罗纪最新到最早的白垩纪的大陆内部。由于火山弧的剥离，成熟的大陆材料直接输入长门盆地而改变了物源。

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