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首页> 外文期刊>Geochemistry, geophysics, geosystems >Magnetic minerals in three Asian rivers draining into the South China Sea: Pearl, Red, and Mekong Rivers
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Magnetic minerals in three Asian rivers draining into the South China Sea: Pearl, Red, and Mekong Rivers

机译：流入南中国海的三条亚洲河流中的磁性矿物：珍珠河，红河和湄公河

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摘要

The use of the marine sedimentary magnetic properties, as tracers for changes in precipitation rate and in oceanic water masses transport and exchanges, implies to identify and to characterize the different sources of the detrital fraction. This is of particular importance in closed and/or marginal seas such as the South China Sea. We report on the magnetic properties of sedimentary samples collected in three main Asian rivers draining into the South China Sea: the Pearl, Red, and Mekong Rivers. The geological formations as well as the present climatic conditions are different from one catchment to another. The entire set of performed magnetic analyses (low-field magnetic susceptibility, ARM acquisition and decay, IRM acquisition and decay, back-field acquisition, thermal demagnetization of three-axes IRM, hysteresis parameters, FORC diagrams, and low-temperature magnetic measurements) allow us to identify the magnetic mineralogy and the grain-size distribution when magnetite is dominant. Some degree of variability is observed in each basin, illustrating different parent rocks and degree of weathering. On average it appears that the Pearl River is rich in magnetite along the main stream while the Mekong River is rich in hematite. The Red River is a mixture of the two. Compared to clay mineral assemblages and major element contents previously determined on the same samples, these new findings indicate that the magnetic fraction brings complementary information of great interest for environmental reconstructions based on marine sediments from the South China Sea.
机译：使用海洋沉积磁学性质作为示踪剂，以监测降水率的变化以及海洋水团的运输和交换，意味着确定并表征碎屑组分的不同来源。这在诸如南中国海这样的封闭和/或边缘海中尤其重要。我们报告了在流入南中国海的三个主要亚洲河流（珠江，红河和湄公河）中收集的沉积物样品的磁性。一个集水区到另一个集水区的地质构造和当前的气候条件是不同的。整套执行的磁分析（低场磁化率，ARM采集和衰减，IRM采集和衰减，后场采集，三轴IRM的热消磁，磁滞参数，FORC图和低温磁测量）使我们能够确定磁铁矿占主导地位时的磁性矿物学和粒度分布。在每个盆地中观察到一定程度的变化，说明了不同的母岩和风化程度。平均而言，珠江沿干流富含磁铁矿，而湄公河则富含赤铁矿。红河是两者的混合物。与先前在相同样品上确定的粘土矿物组合和主要元素含量相比，这些新发现表明，磁性组分为基于南中国海沉积物的环境重建带来了令人感兴趣的补充信息。

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