The Evolution of Seafloor Spreading Behind the Tip of the Westward Propagating Cocos‐Nazca Spreading Center
The Evolution of Seafloor Spreading Behind the Tip of the Westward Propagating Cocos‐Nazca Spreading Center
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向西传播的科科斯-纳斯卡扩张中心尖端后面海底扩张的演化
DOI：
10.1029/2020gc008957
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发表时间：
2020
期刊：
影响因子：
3.7
通讯作者：
S. Curry
中科院分区：
文献类型：
--
作者：
Deborah K. Smith;H. Schouten;R. Parnell‐Turner;E. Klein;J. Cann;C. Dunham;G. Alodia;I. Blasco;B. Wernette;D. Zawadzki;E. Latypova;S. Afshar;S. Curry
在赤道太平洋的加拉帕戈斯三重连接处，科科斯-纳斯卡扩张中心并不与东太平洋隆起（EPR）相接，而是在EPR侧翼分裂成40万年前的岩石圈。科科斯-纳斯卡向向西扩展形成了V形的加拉帕戈斯戈尔。自~1.4 Ma以来，在活动的戈尔尖端开口一直在科科斯加拉帕戈斯微板块扩展制度。在本文中，水深测量，磁，重力数据收集的第一个400公里以东的戈尔尖被用来检查年轻的岩石圈裂谷和过渡到岩浆扩张段。从一开始，该轴显示了由裂陷盆地组成的构造分段，裂陷盆地的边界断层最终标志着戈尔的边缘。裂谷作用在前三段（s1-s3）发展为岩浆扩张，这三段在可可加拉帕戈斯微板块之间以目前约19-29毫米/年的缓慢速度打开。s4-s9段起源于更快扩张（~48毫米/年）的Cocos-Nazca体系，明确的磁异常和靠近戈尔边缘的深海丘陵组构表明，向完全岩浆扩张的过渡比现在更快。磁线理显示，在1.1 Ma之后，Cocos-Nazca扩张速率增加了20%。近轴地幔布格重力异常向东减小，变得更圆，这表明地幔上涌，温度升高，并可能发展到一个发达的熔体供应下段。个别Cocos-Nazca段的向西传播是常见的，速率范围在12和54 mm/年之间。段长度和段之间的横向偏移通常随着距戈尔尖端的距离而增加。
At the Galapagos triple junction in the equatorial Pacific Ocean, the Cocos‐Nazca spreading center does not meet the East Pacific Rise (EPR) but, instead, rifts into 0.4 Myr‐old lithosphere on the EPR flank. Westward propagation of Cocos‐Nazca spreading forms the V‐shaped Galapagos gore. Since ~1.4 Ma, opening at the active gore tip has been within the Cocos‐Galapagos microplate spreading regime. In this paper, bathymetry, magnetic, and gravity data collected over the first 400 km east of the gore tip are used to examine rifting of young lithosphere and transition to magmatic spreading segments. From inception, the axis shows structural segmentation consisting of rifted basins whose bounding faults eventually mark the gore edges. Rifting progresses to magmatic spreading over the first three segments (s1–s3), which open between Cocos‐Galapagos microplate at the presently slow rates of ~19–29 mm/year. Segments s4–s9 originated in the faster‐spreading (~48 mm/year) Cocos‐Nazca regime, and well‐defined magnetic anomalies and abyssal hill fabric close to the gore edges show the transition to full magmatic spreading was more rapid than at present time. Magnetic lineations show a 20% increase in the Cocos‐Nazca spreading rate after 1.1 Ma. The near‐axis Mantle Bouguer gravity anomaly decreases eastward and becomes more circular, suggesting mantle upwelling, increasing temperatures, and perhaps progression to a developed melt supply beneath segments. Westward propagation of individual Cocos‐Nazca segments is common with rates ranging between 12 and 54 mm/year. Segment lengths and lateral offsets between segments increase, in general, with distance from the tip of the gore.
太平洋板块上保存的加拉帕戈斯三重交界点的近代历史
影响因子：
5.3
作者：
Smith, Deborah K.;Schouten, Hans;Montési, Laurent;Zhu, Wenlu
通讯作者：
Zhu, Wenlu