The effects of cooling rate on texture and pyroxene chemistry in DSDP Leg 34 basalt: A microprobe study
The effects of cooling rate on texture and pyroxene chemistry in DSDP Leg 34 basalt: A microprobe study
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冷却速率对 DSDP Leg 34 玄武岩结构和辉石化学的影响：微探针研究
DOI：
10.1016/0012-821x(79)90048-7
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发表时间：
1979
影响因子：
5.3
通讯作者：
L. Taylor
中科院分区：
文献类型：
--
作者：
R. Coish;L. Taylor
为了确定液体的凝固速度对所产生的织构和矿物学的影响，对来自DSDP支腿34的15.6m冷却单元进行了研究。从冷却单元的顶部和底部边缘向内到中心的详细采样显示了系统的结构和矿物学变化，这是不同冷却速度的结果。质地从冷却边缘的球晶-夹杂结构向流动内部的亚蛇绿/蛇绿结构转变。斜长石宽度随距流缘距离的增加而增大，长宽比随距离的增加而减小(因此随冷却速率的减小而减小)。冷却边缘辉石中钛和铝的含量高于内陆辉石，但常量元素含量没有系统性变化。因此，正如在月球岩石系统[4，33]中的实验所表明的那样，辉石中的钛和铝含量随着冷却速度的增加而增加。根据传导热流方程计算的冷却速度范围从冷却单元边缘的>；100℃/小时到内部(距离边缘3米)的<；0.1℃/小时。当人们试图通过比较辉石成分来将粗粒辉长岩和火山岩与共同母体联系起来时，必须考虑到辉石的微量元素含量因冷却速度的变化而发生的变化。
A 15.6-m cooling unit from DSDP Leg 34 is investigated to determine the effects of the rate of solidification of a liquid on the resulting textures and mineralogy. A detailed sampling from the top and bottom margins of the cooling unit inward to the center has revealed systematic textural and mineralogical variations that are the result of different cooling rates. Textures change from spherulitic-intersertal in the chilled margins through intergranular to subophitic/ophitic in the interior of the flow. Plagioclase width increases and the length/width ratio decreases with distance from the flow margins (and hence with decreasing cooling rate). Titanium and Al contents are higher in pyroxenes from the chilled margins than in those from the interior regions although there is no systematic change in major element concentrations. Thus, as has been shown by experiments in lunar rock systems [4,33], Ti and Al contents in pyroxene increase with increasing cooling rate. Cooling rates calculated from conductive heat flow equations range from >100°C/hr in the margins of the cooling unit to <0.1°C/hr in the interior (>3 m from the margin). The variations in minor element content of pyroxene due to cooling rate must be taken into account when one attempts to relate coarse-grained gabbros and volcanic rocks to a common parent by comparing their pyroxene compositions.