发掘蓝片岩-地球科学堆栈交换江南电子竞技平台江南体育网页版 最近30从www.hoelymoley.com 2023 - 07 - 09 - t23:00:16z //www.hoelymoley.com/feeds/question/689 https://creativecommons.org/licenses/by-sa/4.0/rdf //www.hoelymoley.com/q/689 11 发掘的蓝片岩 kaberett //www.hoelymoley.com/users/105 2014 - 05 - 01 - t18:38:51z 2014 - 11 - 17 - t12:22:49z < p >蓝片岩等矿物组合,它必须在高压力和低的温度下形成的。因此必须在俯冲板(我相信这与位置有关的发现)。然而,叶子的问题如何< em > < / em >它足够迅速地表面不加热足以reequilibrate和失去矿物组合特征。< / p > < p >当前支持的解释是什么/过程如此快速的从深度发掘? < / p > //www.hoelymoley.com/questions/689/-/728 # 728 4 答案由马克Rovetta蓝片岩的发掘 马克Rovetta //www.hoelymoley.com/users/178 2014 - 05 - 02 - t19:17:23z 2014 - 05 - 02 - t19:17:23z < p >我不知道目前是否喜欢解释,但在加州人提及一些非正式称为< a href = " http://science.kqed.org/quest/2011/05/19/geological-outings-around-the-bay-ring-mountain/ " rel =“nofollow”> < / >西瓜种子理论。大意是,压缩在一个俯冲带设法把这些岩石备份和深度的过程像挤压(射击)湿西瓜种子在手指之间。< / p > //www.hoelymoley.com/questions/689/-/2809 # 2809 6 答案由Gimelist蓝片岩的发掘 Gimelist //www.hoelymoley.com/users/725 2014 - 11 - 15 - t18:03:41z 2014 - 11 - 17 - t12:22:49z < p > <强>快速发掘没有必要保留蓝片岩矿物组合。< / >强这是经典的进积和退化变质作用的区别,它不限于蓝片岩。为什么我们会有榴辉岩在地球表面?麻粒岩呢?角闪岩吗?事实上,为什么我们看到任何变质岩表面上而不是各种粘土及石英吗?< / p > < p >有两个主要原因。< / p >
  1. Prograde metamorphism results in dehydration and loss of water(1). Most of the original water content of the rock was in various hydrous minerals, and as you progress in your metamorphic path you lose more and more water to dehydration reactions. While it is true that in blueschist waster can be retained in minerals such as lawsonite, phengite, epidote and glaucophane, most of it is still lost. If you want to reequilibrate the rock to its previous mineral assemblage, you need to reintroduce the water. This can occur occasionally, for instance in this classic example from Norway:

    rehydration source: http://www.geol.ucsb.edu/faculty/hacker/geo102C/lectures/part11.html
    ...where a granulite was rehydrated along a joint to form eclogite, but it's usually very localised and uncommon.

  2. Most prograde metamorphic reactions are exothermic, i.e. they release heat. Retrograde reactions are usually endothermic. They require heat in order to proceed, but in the event of exhumation, temperatures are decreasing. There is simply not enough heat around to support the retrograde reactions. Furthermore, you have to remember that lower temperature also lowers the reaction kinetics.

This doesn't mean that fast exhumation cannot occur...

There are pieces of evidence that in some cases exhumation can be even faster than the erosion rate(2). This suggest that orogenic events may also result from simple uplift and not only compression and folding. What causes the uplift? This may actually be the result of crustal thinning and extensional stress regimes, as in the examples of Liaodong(3) and Brittany(4). This phenomenon is also known as a core complex, where extensional tectonics result in low angle normal detachment faults that results in rapid unroofing and exposure deep seated rocks. You may be familiar with oceanic core complexes, so this processes is quite similar.



(1) Forgive me for not including the zeolite facies in my definition of metamorphism.

(2) Rubatto, D., & Hermann, J. (2001). Exhumation as fast as subduction?. Geology, 29(1), 3-6. 10.1130/0091-7613(2001)029<0003:EAFAS>2.0.CO;2

(3) Yang, J. H., Wu, F. Y., Chung, S. L., Lo, C. H., Wilde, S. A., & Davis, G. A. (2007). Rapid exhumation and cooling of the Liaonan metamorphic core complex: Inferences from 40Ar/39Ar thermochronology and implications for Late Mesozoic extension in the eastern North China Craton. Geological Society of America Bulletin, 119(11-12), 1405-1414. 10.1130/B26085.1

(4) Brown, M., & Dallmeyer, R. D. (1996). Rapid Variscan exhumation and the role of magma in core complex formation: southern Brittany metamorphic belt, France. Journal of Metamorphic Geology, 14(3), 361-379. 10.1111/j.1525-1314.1996.00361.x

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