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华北北部洪水庄组黑色页岩是中元古代的富有机质沉积,它可能记录了当时重要的地球化学信息。通过对洪水庄组页岩中的常量和微量元素特征的分析,研究了洪水庄组的物源及其风化作用。高Th/Sc、Al2O3/TiO2、La/Sc、La/Cr、La/Co、Th/Cr和Th/Co值,低Cr/Zr和TiO2/Zr比值,Euan值、Co/Y-Ti/Zr关系和La-Th-Sc组成表明洪水庄组页岩物源主要为上地壳中的长英质花岗闪长岩。洪水庄组页岩的Al、Ca、Na和K组成表明其具有较高的化学蚀变指数(CIA),同时,元素组成的化学风化作用轨迹反映了洪水庄组页岩受到钾交代作用的影响,可能导致CIA值被低估,其原始CIA值应在90以上。高的原始CIA、化学风化指数(CIW)和斜长石蚀变指数(PIA)表明洪水庄组物源区经历了强烈的化学风化作用。化学风化作用强度以及微量元素组成特征揭示了中元古代洪水庄组沉积时期可能处于温暖潮湿的气候条件,这与中元古代时期大气高CO2浓度以及华北板块古大陆当时位于低纬度地区重建的结果不谋而合。
The black shale of the Hongshuangzhuang Formation in northern North China is a Mesoproterozoic organic-rich sediment that may have undergone important geochemical information at that time. Based on the analysis of the constants and trace elements in the shale of Hongshuizhuang Formation, the source and weathering of Hongshuizhuang Formation are studied. High Th / Sc, Al2O3 / TiO2, La / Sc, La / Cr, La / Co, Th / Cr and Th / Co, low Cr / Zr and TiO2 / Zr ratios, The relationship and La-Th-Sc composition indicate that the shale source of the Hongshuangzhuang Formation is predominantly feldspar granitic diorite in the upper crust. The composition of Al, Ca, Na and K in the Hongshuang Formation shale shows that it has a high chemical alteration index (CIA). At the same time, the trace of chemical weathering of the elemental composition reflects the influence of potassium metasomatism on the shale of Hongshuizhuang Formation , May lead to CIA values are underestimated, the original CIA value should be 90 or more. The high original CIA, CIW and PIA indicate that the Hongshuangzhuang source area experienced strong chemical weathering. The intensity of chemical weathering and the trace element composition reveal that the Neoproterozoic Hongshuizhuang Formation may be in a warm and humid climate during the depositional period. This is consistent with the high atmospheric CO2 concentration in the Mesoproterozoic and the reconstruction of the ancient continent in the North China Plateau at that time Coincide