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首页> 外文学位 >Spatial and temporal variations in the petrology, morphology and tectonics of a migrating spreading center: The Endeavour Segment, Juan de Fuca Ridge.
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Spatial and temporal variations in the petrology, morphology and tectonics of a migrating spreading center: The Endeavour Segment, Juan de Fuca Ridge.

机译：迁移中心的岩石学，形态学和构造的时空变化：奋进段，胡安·德富卡岭。

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摘要

The tectonic and volcanic consequences of ridge crest migration have been investigated at the Juan de Fuca Ridge, which migrates northwestward over the mesosphere rapidly compared with its spreading rate. The detailed morphology and neo-tectonics of the Endeavour Segment have been analyzed using Seabeam bathymetry, Sea MARC II images, magnetics data, seismic reflection records and deep-tow photographs. The ridge axis, a narrow ({dollar}<{dollar}1 km) rift valley, is segmented at a small (15-20 km) scale, and incised into a variety of structures along-strike. Lavas recovered from the region have been analysed with electron microprobe and X-ray fluorescence techniques. Samples from the axial valley and flanking ridges have enriched incompatible element signatures, whereas depleted n-MORB's comprise the adjacent seamounts.; Morphological variations are interpreted to reflect spatial and temporal variations in magma supply. The elongate, shallow Endeavour Ridge, built during a high magma supply period, is segmented. Magmas delivered to each segment appear to have been derived from an axially-discontinuous or poorly mixed magma chamber which has been resupplied from the mantle through a de-centralized geometry. The chaotic, deeper North and South Endeavour Valleys and West Valley result from lower over magma supply. Flanking ridges parallel to the axis show progressive lengthening to the south, indicating temporal variations in the amplitude of magma supply.; Ridge axis and seamount lavas can be derived by melting a source which varies between a depleted and enriched endmember, with superimposed fractional crystallization. The degree of enrichment has increased over the 2 million year period observed. Local trace element patterns require significant small scale heterogeneity in the mantle.; Spatial and temporal variations observed are explained with a model in which the Endeavour Segment axis has migrated toward and overridden the Heckle melting anomaly. Off-axis seamount volcanism results from preferential melting within heterogeneities embedded in the mantle ascending in advance of the migrating ridge axis. Eventually, melting anomaly products become incorporated in the ridge axis magmatic system, dominating the geochemical signature of ridge axis lavas. Corresponding increases in magma supply at the axis have triggered reversals in rift propagation direction at the Cobb Offset.
机译：在胡安·德富卡山脊已经研究了脊顶迁移的构造和火山后果，与蔓延速率相比，它在中层迅速向西北迁移。已使用Seabeam测深法，Sea MARC II图像，磁学数据，地震反射记录和深拖照片分析了Endeavor段的详细形态和新构造。脊轴是一个狭窄的（{dollar} <{dollar} 1 km）裂谷，以小规模（15-20 km）被分割，并沿走向切割成各种结构。从该地区回收的熔岩已经用电子探针和X射线荧光技术进行了分析。轴向谷和侧脊的样品富含不相容的元素特征，而耗尽的n-MORB则构成了相邻的海山​​。解释形态变化以反映岩浆供应的时空变化。在岩浆供应旺盛的时期建造的细长浅层奋进岭被分段。输送到每个段的岩浆似乎来自轴向不连续或混合不良的岩浆室，岩浆室通过分散的几何结构从地幔中重新供应。北部和南部奋进谷和西部谷更混乱，更深是由于岩浆供应量较低。平行于轴线的侧翼脊向南逐渐延伸，表明岩浆供应振幅随时间变化。脊轴和海山熔岩可以通过熔化在贫化和富化的端构件之间变化的源与叠加的分步结晶来获得。在观察到的200万年中，浓缩程度有所提高。局部痕量元素模式要求地幔中存在明显的小尺度异质性。用模型解释了观察到的时空变化，其中“奋进段”轴已移向并覆盖了Heckle融化异常。离轴海山火山活动是由于地幔中非均质性的优先融化所致，而该非均质性则在迁移脊轴之前上升。最终，融化的异常产物被整合到脊轴岩浆系统中，主导了脊轴熔岩的地球化学特征。轴上岩浆供应量的相应增加触发了柯布偏移处裂谷传播方向的逆转。

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  • 作者

    Karsten, Jill Leslie.;

  • 作者单位

    University of Washington.;

  • 授予单位 University of Washington.;
  • 学科 Physical Oceanography.; Geology.
  • 学位 Ph.D.
  • 年度 1988
  • 页码 374 p.
  • 总页数 374
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 海洋物理学;地质学;
  • 关键词

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