海洋Sr同位素的变化主要是由陆地河流注入的Sr同位素的变化所引起。在全球河流中，流经喜马拉雅山地河流（恒河—布拉马普特拉河）表现出与世界上其它河流明显不同的特点，具有高87 Sr / 86 Sr、高［Sr］的特征。恒河—布拉马普特拉河是世界上第四大河流，是当今世界海洋Sr的重要来源。国际上，目前人们对造成喜马拉雅河流Sr异常的原因（来源）的认识，仍存较大分歧。归纳起来，主要有3 种认识：一是认为来源于硅酸盐岩；二是认为来源于碳酸盐岩的风化；三是认为来源于碳酸盐岩和硅酸盐岩的风化。近年来，作者对高喜马拉雅中央结晶岩系河流Sr同位素异常及其源岩进行的研究表明，高喜马拉雅河流Sr 同位素受流域地质作用的强烈影响，呈现出高87 Sr /86Sr、低［Sr］的特点。对岩石和单矿物的研究表明，中央结晶岩系变质岩（片岩、片麻岩）和花岗岩黑云母中的87 Sr / 86 Sr与［Rb］成正比并具有高87 Sr / 86 Sr、低［Sr］的特征。黑云母矿物具有的易风化性，为高喜马拉雅河流放射性87Sr提供了主要来源。恒河—布拉马普特拉河的Sr异常（高⁸⁷ Sr / 8 6Sr和高［Sr］）则可能是反映了流经整个喜马拉雅造山带河流Sr混合平衡后的特征。

The variation ofthe m arine Srisotope is large ly caused with the inputofthe river Srisotope . In the global rivers ， the rivers draining through the Him alayan （ Ganga- Brahm aputra rivers ） possess the typical Sr isotope
character ， i. e . high 8 7 Sr / 8 6 Srratio and high ［Sr］ concentration ， which obviously differentiates from other ri vers.
The Ganga- Brahm aputra ， the fourth largest river in the world ， is im portantsource for the m arine Sr. Current ly，it is stillcontroversial for the source rock res ulting in the Srisotope anom aly in the Ganga- B rahm aputra rivers. Basi-cally ， there appearthree opinions for the source roc k， the first opinion advocates thatthe source ro ck is the silicate rock ， the second the carbonate ， and the third both the silicate and carbonate. In the recentyears ， ourresearch has disclosed thatthe Sr in the High Him alayan riv ers possesses the feature of the high 87 Sr / 86 Sr ratio and low ［Sr］
concentration ， which is intensely affected by the specific ge ology in the drainage. The study on the m etam or phic rocks （ schist ， gneiss ） and the granites and the m inerals indicates th atin the biotite in the Central Crystal Series ，the 8 7 Sr / 8 6 Sr has the positive relationship with ［Rb］， and that the biotite also has the high 8 7 Sr / 8 6 Sr ratio and low［Sr］ concentration. The biotite is readily weathe red and should be the prim ary source to the radi oactive 87 Sr oftheHigh Him alayan rivers. The Sr anom aly （ high 8 7 Sr / 86 Srratio and high ［Sr］） in the Ganga- Brahm aputra is possi-bly attributed to the m ixing balance ofthe riv ers draining through the whole Him alayan.