科普知识学英语 海底火山岩浆与深海碳循环

海量资料下载 免费学习英语 www.englishvip.com/xinlw.htm （申请网址） Scientists from the Smithsonian and the University of Rhode Island have found unsuspected linkages between the oxidation（氧化的） state of iron in volcanic rocks and variations in the chemistry of the deep Earth. Not only do the trends run counter to predictions from recent decades of study, they belie a role for carbon circulating in the deep Earth. The team's research was published May 2 in Science Express.   Elizabeth Cottrell, lead author and research geologist at the Smithsonian's National Museum of Natural History, and Katherine Kelley at the University of Rhode Island's Graduate School of Oceanography measured the oxidation state of iron, which is the amount of iron that has a 3+ versus a 2+ electronic charge, in bits of magma that froze to a glass when they hit the freezing waters and crushing pressures of the sea floor. Due to the high precision afforded by the spectroscopic（光谱的） technique they used, the researchers found very subtle variations in the iron-oxidation state that had been overlooked by previous investigations.   The variations correlate with what Cottrell described as the "fingerprints" of the deep Earth rocks that melted to produce the lavas -- but not in the way previous researchers had predicted. The erupted lavas that have lower concentrations of 3+ iron also have higher concentrations of elements such as barium（钡）, thorium（钍）, rubidium（铷） and lanthanum, that concentrate in the lavas, rather than staying in their deep Earth home. More importantly, the oxidation state of iron also correlates with elements that became enriched in lavas long ago, and now, after billions of years, show elevated ratios of radiogenic isotopes. Because radiogenic isotopic ratios cannot be modified during rock melting and eruption, Cottrell called this "a dead ringer for the source of the melt itself."   Carbon is one of the "geochemical goodies" that tends to become enriched in the lava when rocks melt. "Despite is importance to life on this planet, carbon is a really tricky element to get a handle on in melts from the deep Earth," said Cottrell. "That is because carbon also volatilizes and is lost to the ocean waters such that it can't easily be quantified in the lavas themselves. As humans we are very focused on what we see up here on the surface. Most people probably don't recognize that the vast majority of carbon -- the backbone of all life -- is located in the deep Earth, below the surface -- maybe even 90 percent of it."   The rocks that the team analyzed that were reduced also showed a greater influence of having melted in the presence of carbon than those that were oxidized. "And this makes sense because for every atom of carbon present at depth it has to steal oxygen away from iron as it ascends toward the surface," said Cottrell. This is because carbon is not associated with oxygen at depth, it exists on its own, like in the mineral diamond. But by the time carbon erupts in lava, it is surrounded by oxygen. In this way, concludes Cottrell, "carbon provides both a mechanism to reduce the iron and also a reasonable explanation for why these reduced lavas are enriched in ways we might expect from melting a carbon-bearing rock." 史密森和罗得岛大学的科学家们已经发现了意料之外的联系之间的氧化（氧化的）铁在火山岩石和地球深部化学变化的状态。不仅做趋势背道而驰，从最近数十年的研究预测，但掩饰在地球深部碳循环的作用。该小组的研究，5月2日发在“科学快讯”。   伊丽莎白·科特雷尔，铅作者和研究的地质学家在史密森国家自然史博物馆，并在罗得岛的海洋研究生院大学的凯瑟琳·凯利的氧化状态的铁，这是铁的量，有一个3 +与一个测量2 +电子收费中位，冻结冻结海域海底压力和破碎的玻璃，当他们击中的岩浆。由于所提供的高精度光谱（光谱的）他们使用的技术，研究人员发现了非常微妙的变化，由以前的调查中被忽略了的铁氧化状态。   变化与科特雷尔形容为“指纹”地球深部岩石融化后形成的熔岩-的方式，但不是以前的研究人员曾预言。爆发熔岩有较低的浓度为3 +铁也有较高的浓度，如钡（钡），钍（钍），铷（铷）和镧的元素集中在熔岩，而不是留在地球深部的家。更重要的是，铁的氧化态相关元素变得丰富熔岩不久前，而现在，经过数十亿年，呈现出较高比例的放射性同位素。岩石熔化和喷发过程中，由于放射性的同位素比值，不能修改，科特雷尔称为“酷似融化本身的来源。”   碳是一个“地球化学的好东西”熔岩岩熔融时趋于变得丰富。科特雷尔说：“尽管在这个星球上的生命的重要性，碳熔体中得到处理，从地球深部，是一个非常棘手的元素，”。“那是，因为碳挥发，并失去了对海洋等水域，它不能很容易被量化的熔岩自己。作为人类，我们非常专注于我们所看到的表面上，大多数人可能不承认，绝大多数的碳 - 所有生命骨干 - 位于地球深部，在表面之下 - 也许甚至90％。“   分析该球队也减少，表现出较大的影响比那些被氧化的碳的存在下经熔融的岩石。，“科特雷尔说：”这是有道理的，因为每一个存在的碳原子深度偷铁氧离，因为它向水面上升。这是因为碳与氧在深度不相关，它存在于它自己的，如在矿物钻石。但熔岩碳爆发的时候，它的四周氧气。科特雷尔的结论，通过这种方式，“碳提供一种机制来降低铁，也是一个合理的解释，为什么这些减少的方式，我们可能期望从熔化含碳岩熔岩丰富。” “成千上万人疯狂下载。。。。。。 更多价值连城的绝密英语学习资料， 洛基内部秘密英语，技巧，策略 请在 网上 申请报名” 洛基国际英语 竭诚为您服务