东经九十度海岭有效弹性厚度计算及其对构造运动的解释

Effective elastic thickness of Ninetyeast Ridge and its implication for tectonic evolution

有效弹性厚度(Te)表示岩石圈抵抗变形的能力,其大小主要取决于岩石圈内部的温度结构和地壳物质组成。作为全球最长的海岭之一,东经九十度海岭(NER)来源与形成过程一直是国内外科学家研究的热点,然而受到该地区复杂构造活动的影响,研究者对海岭的形成过程仍缺乏清晰认识。本文从Te的角度出发,通过空间褶积方法计算了沿着NER不同位置处Te的空间分布特征。计算结果表明,整个海岭的Te主要在0~35km之间变化,表现为北(8°N^1°N)高(平均值为20km)、中(1°N^15°S)低(平均值在5km以下)、南(15°S^30°S)高(平均值为30km),变化趋势与凯尔盖朗热点的3期岩浆活动相对应。Te的变化反映了NER形成过程中东南印度洋脊与热点的相对位置的调整,说明NER是凯尔盖朗热点、印度洋板块扩张与东南印度洋洋中脊迁移三者共同作用的结果。最后,结合Te的结果与ROYER板块重构的结果,本文提出了NER形成过程的模式。

The effective elastic thickness（Te）which depends on the deep lithospheric temperature structure and crustal compositions,represents the lithospheric ability to resist deformation.The Ninetyeast Ridge（NER）,one of the longest seamount in the world,has been studied by many researchers over its original and process.However,the complicated tectonic activities cause that it is too difficult to uncover the evolution of the NER.Here we investigated the NER in terms of Te with convolution method and obtained its spatial variations of Te.The results show that values vary from 0to 35 km.Teis characterized as high value（averaging20km）in the north section（8°N～1°N）,low value（averaging less than 5km）in the middle part（1°N～15°S）and high value（averaging 30km）in the south section（15°S～30°S）,which are associated with three stages of volcanic activities of Kerguelen hotspot.In addition,the variations of values reflect the adjustment of relative position between Southeast Indian Ridge and hot spot during the evolution of NER and further prove that the NER is influenced and controlled by the Kerguelen hotspot,Indian plate＇s drift and Southeast Indian Ridge＇s jump.Finally,by combining with the evidence of ROYER＇s plate reconstruction,a model was proposed to show the evolution of Ninetyeast Ridge.