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首页> 外文期刊>The Journal of Geology: a semi-quarterly magazine of geology and related sciences >Material Sources,Chemical Weathering,and Physical Denudation in the Chubut River Basin(Patagonia,Argentina): Implications for Andean Rivers
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Material Sources,Chemical Weathering,and Physical Denudation in the Chubut River Basin(Patagonia,Argentina): Implications for Andean Rivers

机译：丘布特河流域（阿根廷巴塔哥尼亚）的物质来源，化学风化作用和物理剥蚀作用：对安第斯河的启示

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摘要

The Chubut is a medium-size(42,000 km~2)river basin that drains the arid-to-semiarid Patagonian seaboard and pours its waters into the southwestern Atlantic Ocean(ca.lat 43deg 20'S,long 65deg 04'W).The materials eroded from the continent and deposited in the sea are scarcely affected by chemical weathering(the chemical index of alteration of riverbed sediments is ~55)and bear a typical chemical and mineralogical signature characteristic of volcanic arcs.Clearly,flowing toward a passive margin,the river carries the mineralogical and chemical signature of an active margin.Physically weathered andesites and basalts occupy only about 25% of the drainage area,and therefore most exported material must be supplied by outcropping sedimentary beds of variable age.The Chubut River headwaters are placed in a tectonically active region,soil formation is incipient("weathering-limited regime"),and the rate of denudation(24.6 t km~(-2)yr~(-1))is much lower than the rates exhibited by similar rivers in other parts of the world.The depleted dissolved and particulate load is determined by scarce atmospheric precipitations(i.e.,the drainage basin is in the Andean rain shadow)and by the protective effect of Cenozoic lava flows that often shield sedimentary formations from denudation.Although the index of chemical variability suggests that materials exported are products of the first denudational cycle,the geological history supports the view that most materials may have passed two or even three times through the exogenous cycle without acquiring a chemical or mineralogical signature indicative of repeated weathering.This is probably also true for other basins in temperate Andean climates.
机译：丘布特河是中型河流盆地（42,000 km〜2），排水流干至半干旱的巴塔哥尼亚沿海，并将其水倒入西南大西洋（ca.lat 43deg 20'S，long 65deg 04'W）。从大陆侵蚀并沉积在海中几乎不受化学风化的影响（河床沉积物变化的化学指数为〜55），并具有典型的火山弧化学和矿物学特征。显然，流向被动边缘时，河流具有活跃边缘的矿物学和化学特征。物理风化的安山岩和玄武岩仅占流域的25％，因此，大部分出口物料必须通过露出不同年龄的沉积床来提供。丘布特河源头位于一个构造活跃的区域，土壤形成较早（“风化限制制度”），剥蚀速率（24.6 t km〜（-2）yr〜（-1））远低于相似河流的速率。稀疏的溶解和颗粒物负荷是由稀少的大气降水（即流域位于安第斯雨影中）和新生代熔岩流的保护作用（通常使沉积物地层不被剥蚀）决定的。化学变异性指数表明，出口的材料是第一个剥蚀循环的产物，地质历史支持这样一种观点，即大多数材料可能在未通过外生循环的情况下经过了两次甚至三遍，而没有获得表明反复风化的化学或矿物学特征。在安第斯温带气候下的其他盆地也可能如此。

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