Distributed deformation ahead of the Cocos-Nazca Rift at the Galapagos triple junction: DEFORMATION AT THE GALAPAGOS TJ
Distributed deformation ahead of the Cocos-Nazca Rift at the Galapagos triple junction: DEFORMATION AT THE GALAPAGOS TJ
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加拉帕戈斯三重交界处科科斯-纳斯卡裂谷前方的分布式变形：加拉帕戈斯 TJ 处的变形
DOI：
10.1029/2011gc003689
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
Cann, Johnson R.
中科院分区：
文献类型：
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作者：
Smith, Deborah K.;Schouten, Hans;Zhu, Wen-lu;Montési, Laurent G.;Cann, Johnson R.
加拉帕戈斯三重结不是简单的脊-脊-脊(RRR)三重结。科科斯-纳斯卡裂谷(C-N裂谷)尖端与东太平洋隆起(EPR)不符。相反，两个次级裂谷形成了联系：位于2°40‘N的初始裂谷和位于1°10’N的加拉帕戈斯微板块的南部边界迪茨深火山脊，最近收集的水深数据被用于在微板块(∼1.5 Ma)建立之前的区域构造调查。在C-N裂谷以南，一条向东北方向的裂隙带切割了EPR生成的深山。这是之前在C-N裂谷以北发现的同一时代地壳上的一条裂缝带的镜像。在这两个地区，裂缝的西端终止于完整的深海丘陵，这表明每个裂缝都始于EPR扩展中心，并向东切入先前存在的地形。每个裂纹形成一个短暂的三重结，直到它被废弃，一个新的裂纹和三重结在附近萌生。在2.5~1.5 Ma之间，裂纹型式关于C-N裂隙具有显著的对称性，这为裂纹相互作用模型提供了支持，在该模型中，EPR轴处的裂纹萌生由与向西扩展的C-N裂隙尖端相关的应力控制。该模型还表明，EPR轴的偏移量可以解释裂缝不对称的时间。在C-N裂谷以南，在10.5 Ma的海底发现了裂缝，这表明在此期间这个三重结点并不是一个简单的RRR三重结点。
The Galapagos triple junction is not a simple ridge‐ridge‐ridge (RRR) triple junction. The Cocos‐Nazca Rift (C‐N Rift) tip does not meet the East Pacific Rise (EPR). Instead, two secondary rifts form the link: Incipient Rift at 2°40′N and Dietz Deep volcanic ridge, the southern boundary of the Galapagos microplate (GMP), at 1°10′N. Recently collected bathymetry data are used to investigate the regional tectonics prior to the establishment of the GMP (∼1.5 Ma). South of C‐N Rift a band of northeast‐trending cracks cuts EPR‐generated abyssal hills. It is a mirror image of a band of cracks previously identified north of C‐N Rift on the same age crust. In both areas, the western ends of the cracks terminate against intact abyssal hills suggesting that each crack initiated at the EPR spreading center and cut eastward into pre‐existing topography. Each crack formed a short‐lived triple junction until it was abandoned and a new crack and triple junction initiated nearby. Between 2.5 and 1.5 Ma, the pattern of cracking is remarkably symmetric about C‐N Rift providing support for a crack interaction model in which crack initiation at the EPR axis is controlled by stresses associated with the tip of the westward‐propagating C‐N Rift. The model also shows that offsets of the EPR axis may explain times when cracking is not symmetric. South of C‐N Rift, cracks are observed on seafloor as old as 10.5 Ma suggesting that this triple junction has not been a simple RRR triple junction during that time.