Episodic ages of Greenstones: A key to mantle dynamics?
Episodic ages of Greenstones: A key to mantle dynamics?
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DOI：
10.1029/95gl01804
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发表时间：
1995-08
影响因子：
5.2
通讯作者：
K. Condie
中科院分区：
文献类型：
--
作者：
K. Condie
在2.5-2.2 Ga和1.65-1.35 Ga的两个绿岩年龄最小值可能与年龄的超大陆时，更大比例的绿岩被回收到地幔俯冲。根据绿岩和新生陆壳的年龄分布，地球历史可划分为3个阶段：I）> 2.8Ga，绿岩和微大陆不断形成并碰撞，但可能直到3Ga左右才形成超大陆;（2）2.8- 1.3Ga，绿岩喷发和碰撞时代具有明显的幕式性，其中两个绿岩年龄极小值与超大陆的年龄一致; III）<1.3 Ga，此时绿岩和大陆似乎已经形成并不断碰撞，这可能是对超大陆分散和聚集时间的重大重叠的反应。绿石年龄峰值2.7，1.9和1.3 Ga可能反映灾难性的地幔翻转开始的情节下沉的冷岩石圈板块通过660公里的不连续性的D层启动一个情节的主要地幔柱活动。在过去的1.3戈伊中，绿岩的连续生产和保存与地震层析成像数据一致，这表明板块稳定地下沉到下地幔。
Two greenstone age minima at 2.5-2.2 Ga and 1.65-1.35 Ga may correlate with ages of supercontinents when a greater proportion of greenstones were recycled into the mantle by subduction. From the age distributions of greenstones and juvenile continental crust, earth history can be divided into three stages : I) >2.8 Ga, when greenstones and microcontinents formed and collided continuously, although probably not forming a supercontinent until about 3 Ga ; II) 2.8-1.3 Ga, where a clear episodisity is apparent in greenstone eruption and collision ages, and where two greenstone age minima coincide in age with supercontinents ; and III) <1.3 Ga, when greenstones and continents appear to have formed and collided continuously, perhaps in response to significant overlap in the times of dispersal and assembly of supercontinents. Greenstone age peaks 2.7, 1.9 and 1.3 Ga may reflect catastrophic overturn of the mantle initiated by episodes of sinking of cold lithospheric slabs through the 660-km discontinuity to the D layer initiating an episode of major mantle plume activity. Continuous production and preservation of greenstones in the last 1.3 Gy is consistent with seismic tomography data, which suggest a steady sinking of slabs into the lower mantle.