| 兴蒙造山带—华北克拉通地球化学走廊带沉积物主成分的含量与空间分布研究 |
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| 引用本文：唐坤,王学求,迟清华.2016.兴蒙造山带—华北克拉通地球化学走廊带沉积物主成分的含量与空间分布研究[J].地球学报,37(6):733-744. |
| DOI：10.3975/cagsb.2016.06.08 |
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| 基金项目:国土资源部公益性行业科研专项课题“地球化学走廊带探测实验与示范”(编号: 201011057) |
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| 中文摘要:选取兴蒙造山带—华北克拉通地球化学走廊带上沉积物的SiO2、Al2O3、CaO、MgO、Na2O、K2O、TFe2O3、FeO、TiO2、MnO、P2O5、CO2、H2O+、pH十四个指标, 研究其在不同二级构造单元、地理景观、土壤类型、降雨量等级下的含量与空间分布特征, 并讨论该地球化学走廊带上化学蚀变指数。结果表明: 在兴蒙造山带—华北克拉通地球化学走廊带上, 作为沉积物主体的SiO2、Al2O3两者含量为明显负相关而空间分布表现出此消彼长的特征; CaO、MgO、CO2高含量分布区则与碳酸盐岩地层或含碳酸盐矿物的土壤有关, 而MgO的高含量还与走廊带上镁铁质基性-超基性岩有一定关系, 表明了这三个指标的高含量受特定岩性或矿物的影响较大; Na2O、K2O含量除了受继承的基岩影响外, 还受到后期的风化作用和气候及自身地球化学性质等复杂因素综合影响, 对Na2O来说尤为如此; TFe2O3、MnO、TiO2、P2O5相对于在地质背景复杂地段, 经过冲积平原的沉积物混匀后, 含量差异更小; 相对干冷的内蒙古半干旱草原的气候条件有利于FeO存在, 使得其相对燕山地区含量差异较TFe2O3要小, 在章丘以南相对温暖湿润地区更易被氧化而导致其含量整体较低; 北方干冷气候条件下, 沉积物H2O+含量普遍较低, 局部高含量位于碳酸盐岩地层或第四系分布区; 走廊带上的pH值反映了沉积物偏碱性的特征, 而在章丘以南的地区随着降雨量的增加, 相对温暖湿润的气候条件, 沉积物pH值表现为中性-偏弱酸性; 兴蒙造山带—华北克拉通地球化学走廊带沉积物的CIA值反映出在寒冷、干燥气候条件下低等的化学风化程度, 兴蒙造山带沉积物平均风化程度相对华北克拉通沉积物的平均风化程度差异变化相对要小, 显示兴蒙造山带的降雨量与温度等风化影响因素变化较小。作为反映元素的地球化学亲和性的量化指标, 离子电位可以更好地帮助理解沉积物元素的含量和空间分布差异。 |
| 中文关键词:地球化学走廊带 兴蒙造山带—华北克拉通 主成分 化学蚀变指数 离子电位 |
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| The Content and Spatial Distribution of Principal Components in Sediments along the Geochemical Transect of the Xingmeng Orogenic Belt and the North China Craton |
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| Abstract:Along the geochemical transect across the Xingmeng Orogenic Belt and the North China Craton, 14 sediments indicators, i.e., SiO2, Al2O3, CaO, MgO, Na2O, K2O, TFe2O3, FeO, TiO2, MnO, P2O5, CO2, H2O+ and pH, were chosen and, on such a basis, statistical analysis was conducted for different secondary tectonic units, geographical landscape units, soil type units and rainfall units so as to obtain an overall knowledge of the transect data. The spatial distribution of the values of these indicators was plotted on the diagram, and the chemical indexes of their alteration were also investigated. Some conclusions have been reached: As the main body elements of sediments, the content and spatial distribution of SiO2 and Al2O3 exhibit a significant negative correlation between the Xingmeng Orogenic Belt and the North China Craton. The high content distribution of CaO, MgO, CO2 is related to carbonate rocks or soil containing carbonate minerals, and MgO high content is also related to mafic basic-ultrabasic rocks, implying that the high values of the three indicators are greatly influenced by the specific lithology or minerals. Not only the inheritance from the bedrock but also the complex combination of factors such as the late weathering, climate or their own geochemical characteristics are affecting the content of Na2O and K2O, especially that of Na2O. Compared with things of the area with complicated geological background, the discrepancy variation of the content of TFe2O3, MnO, TiO2, P2O5 becomes smaller in the alluvial plain area after sediments mixing. Relatively cold and dry weather conditions of semi-arid grasslands of Inner Mongolia are conducive to the presence of FeO, and therefore the discrepancy variation of FeO content is smaller than that of TFe2O3 in the Yanshan area; However, in the south of Zhangqiu County area, relatively warm humid climate conditions are more susceptible to oxidation for FeO, resulting in a lower overall content of FeO. Under the northern dry and cold climate conditions, H2O+ content in sediments is generally low, and the high H2O+ content is in carbonate formation or Quaternary distribution area. The pH values reflect the sediment alkaline characteristics, but in the south of Zhangqiu County area, under the conditions of the increase of rainfall and relatively warm and humid climate, the sediment’s pH value is neutral to weak acid. The CIA values reflect low degree of chemical weathering of sediments under the cold, dry weather condition, and hence the average degree of weathering of discrepancy variation sediments of the Xingmeng orogenic belt is small relative to the North China Cration, suggesting that the weathering factors such as rainfall and temperature in Xingmeng orogenic belt is relatively small. As a quantitative indicator of the geochemical affinity of the elements, the ionic potential can help to understand the difference of the content and spatial distribution of the elements in the sediments. |
| keywords:geochemical transect Xingmeng Orogenic Belt and North China Craton principal components chemical index of alteration ionic potential |
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