矿物演化反应地球的化学变化历史
文章来源:未知 文章作者:enread 发布时间:2013-03-01 06:54 字体: [ ]  进入论坛
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Mineral evolution is a new way to look at our planet's history. It's the study of the increasing diversity and characteristics of Earth's near-surface minerals, from the dozen that arrived on interstellar(星际的) dust particles when the Solar System was formed to the more than 4,700 types existing today. New research on a mineral called molybdenite(辉钼矿) by a team led by Robert Hazen at Carnegie's Geophysical Laboratory provides important new insights about the changing chemistry of our planet as a result of geological and biological processes. The work is published by Earth and Planetary Science Letters.
 
Mineral evolution is an approach to understanding Earth's changing near-surface geochemistry. All chemical elements were present from the start of our Solar System, but at first they formed comparatively few minerals -- perhaps no more than 500 different species in the first billion years. As time passed on the planet, novel combinations of elements led to new minerals.
 
Molybdenite is the most common ore mineral of the critical metallic1 element molybdenum. Hazen and his team, which includes fellow Geophysical Laboratory scientists Dimitri Sverjensky and John Armstrong, analyzed2 442 molybdenite samples from 135 locations and ages ranging from 2.91 billion years old to 6.3 million years old. They specifically looked for trace contamination of the element rhenium(铼) in the molybdenite, because rhenium can be used to use to gauge3 historical chemical reactions with oxygen from the environment.
 
They found that concentrations of rhenium, a trace element that is sensitive to oxidation reactions, increased significantly -- by a factor of eight -- over the past three billion years. The team suggests that this change reflects the increasing near-surface oxidation conditions from the Archean Eon more than 2.5 billion years ago to the Phanerozoic Eon less than 542 million years ago. This oxygen increase was a consequence of what's called the Great Oxidation Event, when Earth's atmospheric4 oxygen levels skyrocketed as a consequence of oxygen-producing photosynthetic5 microbes.
 
In addition, they found that the distribution of molybdenite deposits through time roughly correlates with five periods of supercontinent formation, the assemblies of Kenorland, Nuna, Rodinia, Pannotia, and Pangea. This correlation6 supports previous findings from Hazen and his colleagues that mineral formation increases markedly during episodes of continental7 convergence and supercontinent assembly and that a dearth8 of mineral deposits form during periods of tectonic stability.
 
"Our work continues to demonstrate that a major driving force for mineral evolution is hydrothermal(地热的) activity associated with colliding continents and the increasing oxygen content of the atmosphere caused by the rise of life on Earth," Hazen said.
 
Hazen's other co-authors were Joshua Golden, Melissa McMillan, Robert T. Downs, Grethe Hystad, and Ian Goldstein of the University of Arizona; and Holly9 J. Stein and Aaron Zimmerman of Colorado State University (the former also of the Geological Survey of Norway).


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1 metallic LCuxO     
adj.金属的;金属制的;含金属的;产金属的;像金属的
参考例句:
  • A sharp metallic note coming from the outside frightened me.外面传来尖锐铿锵的声音吓了我一跳。
  • He picked up a metallic ring last night.昨夜他捡了一个金属戒指。
2 analyzed 483f1acae53789fbee273a644fdcda80     
v.分析( analyze的过去式和过去分词 );分解;解释;对…进行心理分析
参考例句:
  • The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
  • The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程,因为对他来说,爱是个不可分析的迷。 来自《简明英汉词典》
3 gauge 2gMxz     
v.精确计量;估计;n.标准度量;计量器
参考例句:
  • Can you gauge what her reaction is likely to be?你能揣测她的反应可能是什么吗?
  • It's difficult to gauge one's character.要判断一个人的品格是很困难的。
4 atmospheric 6eayR     
adj.大气的,空气的;大气层的;大气所引起的
参考例句:
  • Sea surface temperatures and atmospheric circulation are strongly coupled.海洋表面温度与大气环流是密切相关的。
  • Clouds return radiant energy to the surface primarily via the atmospheric window.云主要通过大气窗区向地表辐射能量。
5 photosynthetic 1f9a8b17a4e53d9a4fd0ed5147e2f5bd     
adj.光合的,促进光合作用的
参考例句:
  • In some plants photosynthetic products are stored in the form polyfructosans. 在有些植物中,光合作用产物是以多聚果糖的形式储藏。
  • Chlorotic or necrotic lesions were evidence of decreased photosynthetic tissues. 缺绿的或坏死的侵蚀斑便是减少了光合组织的证据。
6 correlation Rogzg     
n.相互关系,相关,关连
参考例句:
  • The second group of measurements had a high correlation with the first.第二组测量数据与第一组高度相关。
  • A high correlation exists in America between education and economic position.教育和经济地位在美国有极密切的关系。
7 continental Zazyk     
adj.大陆的,大陆性的,欧洲大陆的
参考例句:
  • A continental climate is different from an insular one.大陆性气候不同于岛屿气候。
  • The most ancient parts of the continental crust are 4000 million years old.大陆地壳最古老的部分有40亿年历史。
8 dearth dYOzS     
n.缺乏,粮食不足,饥谨
参考例句:
  • There is a dearth of good children's plays.目前缺少优秀的儿童剧。
  • Many people in that country died because of dearth of food.那个国家有许多人因为缺少粮食而死。
9 holly hrdzTt     
n.[植]冬青属灌木
参考例句:
  • I recently acquired some wood from a holly tree.最近我从一棵冬青树上弄了些木料。
  • People often decorate their houses with holly at Christmas.人们总是在圣诞节时用冬青来装饰房屋。
TAG标签: earth evolution mineral
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