Galapagos Hot Spot-Spreading Center System: 1. Spatial petrological and geochemical variations (83°W-101°W)
Galapagos Hot Spot-Spreading Center System: 1. Spatial petrological and geochemical variations (83°W-101°W)
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加拉帕戈斯热点扩散中心系统：1.空间岩石学和地球化学变化（83°W-101°W）
DOI：
10.1029/jb087ib07p05593
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发表时间：
1982
影响因子：
--
通讯作者：
J. Devine
中科院分区：
文献类型：
--
作者：
J. Schilling;R. Kingsley;J. Devine
本文报道了沿加拉帕戈斯扩张中心40—50 km间隔，在83/sup 0/W和101/sup 0/W之间（40个站点）疏浚的玄武岩的岩石学和地球化学。重点研究了“整岩”主要元素、稀土、第一过渡系列微量金属的空间变化，以及斑晶组合的性质及其丰度。这些结果对该地区地幔源非均质性的性质和规模、熔融条件、热场和地壳形成动力学提供了新的约束。我们认为，由于被动的海底扩张，高磁幅带外的脊段处于稳定状态。这些段的玄武岩显然来自于一个相对均匀地失去不相容元素的软流层，这种现象在世界范围内出现。我们拒绝Vogt和DeBoer（1976）的模型，该模型在亚轴向软流层流动的晶体泥流的破裂带中引入了大坝，并在流动线上增加了分数结晶，因为该模型不能解释在加拉帕戈斯地台观测到的稀土元素梯度。我们首选的模型结合了Schilling（1973）的地幔-地幔柱二元混合模型和Hey （1977a）提出的裂谷传播循环概念。我们进一步提出，脉动的地幔柱通量，可能更多地以一串斑点的形式，可能引发新裂缝的发展及其传播。这种新传播裂谷尖端的当前位置定位了这种脉动地幔柱流的波锋。根据Wilson和Hey（1979）的资料，对我们首选的模型进行严格的测试是可能的。«少
We report on the petrology and geochemistry of basalts dredged at 40--50 km intervals along the Galapagos Spreading Center, between 83/sup 0/W and 101/sup 0/W (40 stations). Emphasis is on spatial variations of 'whole rock' major elements, rare earths, trace metals of the first transition series, and the nature of phenocryst assemblages and their abundances. These results provide new constraints on the nature and scale of mantle source heterogeneities, melting conditions, thermal field, and dynamics of crustal formation of the region. We suggest that ridge segments outside the high magnetic amplitude zone are at a steady state as a result of passive seafloor spreading. Basalts from these segments are apparently derived from an asthenosphere relatively uniformally depleted in incompatible elements, which appears of worldwide extent. We reject Vogt and DeBoer's (1976) model invoking damming at fracture zones of subaxial asthenosphere flow of crystal slushes and increasing fractional crystallization down the flow line, because this model would not explain the gradients in REE observed about the Galapagos Platform. Our preferred model combines the mantle-plume binary mixing model of Schilling (1973) with the concept of recurring rift propagation proposed by Hey (1977a). We further propose that pulsating mantle plume flux, perhaps inmore » the form of a chain of blobs, may initiate the development of new rifts and their propagation. The present position of the tips of such new propagating rifts locate the wave fronts of such pulsating mantle plume flow. A two million year period is suggested for the last 4 m.y. from Wilson and Hey's (1979) information Rigorous testing of our preferred model is possible.« less