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为了评估青藏高原化学风化对海水Sr同位素比值变化的影响,系统采集了中国境内源自青藏高原的7条主要河流(金沙江、澜沧江、怒江、黄河、雅砻江、岷江与大渡河)的河水及河床沉积物样品,分析它们的Sr含量及同位素比值.结合其他学者研究的青藏高原南部的恒河、布拉马普特拉河、印度河及伊洛瓦底江数据,此11条大河搬运的总Sr通量为3.47×109mol·a-1,占全球河流搬运入海总通量的10.2%;加权平均87Sr/86Sr为0.71694,高于全球河流平均值.中国境内7条大河的87Srex通量(超过海水87Sr/86Sr部分的87Sr通量)为1.55×106mol·a-1,仅占青藏高原区域11条大河的6%,而恒河-布拉马普特拉河联合贡献了86%.假设40Ma以来全球其他河流输送入海的Sr通量保持常量,而青藏高原区域的11条河流所贡献的Sr通量从40Ma前的0线性增加到现在的值,那么与构造抬升相对应的这一Sr通量的增加能够解释同一时期海水87Sr/86Sr增长量的69%,剩下的31%可能由其他因素所引起.
In order to evaluate the influence of chemical weathering on the Sr isotope ratio of the seawater in the Qinghai-Tibet Plateau, the river system of seven major rivers (Jinsha River, Lancang River, Nujiang River, Yellow River, Yalong River, Minjiang River and Dadu River) originating from the Qinghai-Tibet Plateau was collected And riverbed sediments, and analyze their Sr content and isotopic ratio.Combined with the data of Ganges, Brahmaputra, Indus and Irrawaddy in the southern Tibetan Plateau studied by other scholars, the total Sr Which is 3.47 × 109mol · a-1, accounting for 10.2% of the total volume of the global river transports into the sea; the weighted average 87Sr / 86Sr is 0.71694, which is higher than the average of the global rivers. The 87Srex flux of seven major rivers in China (exceeding 87Sr / 86Sr part of the 87Sr flux) of 1.55 × 106mol · a-1, accounting for only 6% of the 11 major rivers in the Tibetan Plateau region, while the Ganges-Brahmaputra combined contribution of 86%. Assuming 40Ma since the global The Sr fluxes entering the sea from other rivers remained constant, while the Sr flux contributed by 11 rivers in the Tibetan Plateau increased linearly from 0 before 40Ma to the present value. Then the Sr flux corresponding to tectonic uplift Increase can explain the same Seawater 87Sr / 69% 86Sr increase the amount of the remaining 31% may be caused by other factors.