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为什么一个俯冲带产生蛇纹石化底辟而不是火山活动?

在塞浦路斯的经典Troodos蛇绿岩由“蛇纹石化事件”一直在上升。上地幔橄榄岩()使蛇纹石化创造一个活跃的底辟。这已经上升的海洋地壳足够推力在大陆地壳(潜在的大陆地壳从重力调查推断)。

最后一个句子的抽象“三级提升的历史Troodos地块、塞浦路斯”,AHF罗伯逊说:

涉及的主要驱动力可能解放向北俯冲带的水浸在塞浦路斯。

这是有道理的——蛇纹石化橄榄石- >蛇形的改造过程中存在的水。正如我们所知,俯冲板释放液体(主要是水)进入上覆地幔楔。

这些液体通常促进局部融化导致安山岩弧火山活动。然而,塞浦路斯这个巨大的蛇纹岩底辟而不是火山活动。为什么?

是什么原因导致的液体俯冲板偶尔导致蛇纹石化的地幔楔而不是部分融化?

回答

首先,你的声明意味着火山活动没有发生在Troodos。这是不正确的。Troodos甚至被称为“Troodos火山”一旦Miyashiro 1973对Troodos[文章][1]。塞浦路斯地质地图清楚地表明,大部分的蛇绿岩由熔岩(火山)和堤坝(次火山):!(塞浦路斯的地质图)[2]<一口>([源][3])< /一口>注意红、棕色和粉红色的颜色。这不过不是弧火山活动你是指而是海底火山活动传播中心设置。至于你的问题,为什么没有在Troodos弧火山活动,答案很简单:它不够热。让我们把水从哪里来的问题放在一边,和专注于当水遇到一个超镁铁的岩石,这正是地幔岩石。!(变质超基性的岩石)[4]<一口>([源][5])< /一口>你可以看到蛇是稳定在温度低于600°C,甚至更低(更多有关我们的情况下)低压力。在更高的温度下蛇形不再稳定,稳定的矿物是橄榄石(造岩矿物的二辉橄榄岩和方辉橄榄岩)。橄榄石是一种干燥的矿物质,所以所有的水会发生什么变化? The water acts to lower the temperature needed to melt the mantle rocks. You can see the dry versus the wet solidus (the temperature in which a rock begins to melt) in the following diagram. ![Solidi][6] So to sum it up, serpentinite forms when water reacts with ultramafic rocks at low temperature, for example when seawater infiltrates the mantle rocks, or when fluids from the subducted dehydrated slab reach the colder shallow mantle rocks. Melting and consequently arc volcanism occurs for example when fluids from the subducted dehydrated slab rise to deep and hot mantle rocks and suppress the melting temperature to below the ambient temperature. There are several reasons that the mantle rocks in Troodos were "cold" enough for this to occur. First of all, you are talking about very shallow rocks, very close to the plutonic section of the ophiolite. ![Isotherms][7] <sup>([source][8])</sup> You can see that shallow mantle rocks are in the 300-500°C range. The arc volcanoes that you see in that figure are situated above the areas where fluids from the subducting slab can infiltrate hot (1000ish°C) mantle rocks. So you can use the Japan Sea as an analogue for Troodos in this case. Now, it is true that temperatures were likely higher because magmatic activity *did occur* in Troodos, but as Troodos was a slow-spreading center, the magmatic activity was rather sporadic and localized. The Nuriel et al. (2009) paper that Lanzafame refers to actually advocates the idea that Troodos was a core-complex. That is, the mantle rocks were directly exposed to seawater due to faulting, which both cooled them considerably and facilitated serpentinization. The Troodos ophiolite is indeed a supra-subduction zone ophiolite. And it is reasonable to think that arc volcanism occurred somewhere, but the record is absent from the Troodos ophiolite itself. If you are interested, look up "a h f robertson" on Google Scholar and read some of his newer work. The article you cited is from the 70s and much research has been conducted since then. [1]: http://dx.doi.org/10.1016/0012-821X(73)90118-0 [2]: http://i.stack.imgur.com/RWUEn.jpg [3]: http://www.moa.gov.cy/moa/gsd/gsd.nsf/dmlGeoMap_en/dmlGeoMap_en [4]: http://i.stack.imgur.com/CMnjY.jpg [5]: http://www.geol.ucsb.edu/faculty/hacker/geo102C/lectures/part5.html [6]: http://i.stack.imgur.com/b8ST1.gif [7]: http://i.stack.imgur.com/pnLDz.gif [8]: http://specialpapers.gsapubs.org/content/403/147

编辑总结

取消

\ begingroup美元是的,海底火山活动是传播——比侵位。温度的控制因素是有道理的,但然后问题就来了:为什么这部分冷? \ endgroup美元
- - - - - -winwaed
2014年10月6日在二二21
\ begingroup美元我编辑的答案来解决你的问题。 \ endgroup美元
- - - - - -Gimelist
2014年10月6日22:36
\ begingroup美元我想我还没有完全满足,听起来仍有一些争议,但这似乎是最完整的答案- - - - - - -我的标记。 \ endgroup美元
- - - - - -winwaed
2014年10月7日在12:57
\ begingroup美元肯定还是有一些争论。研究生在我前集团是致力于serpentinisation Troodos时刻,我知道更多的人在其他团体也在做着同样的事情。文章与新见解Troodos(和蛇绿岩)和出版。 \ endgroup美元
- - - - - -Gimelist
2014年10月8日11:13

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