Oceanic crustal accretion at mid-ocean ridges is a function of spreading rate, mantle temperature, and composition, which are intertwined in affecting melt production and oceanic crustal thickness. Sparse and irregular seismic and geochemical observations on a global scale showed no correlation between crustal thickness and spreading rate along slow to fast-spreading centers. Here, we compile a global oceanic crustal thickness model from gravity data to revisit this issue at a high resolution. Gravity-observed melt volume shows a positive correlation with spreading rate globally, implying that spreading rate is the dominant factor in melt production. However, oceanic crustal thickness is negatively correlated with spreading rate from slow to fast-spreading centers, and this trend is further consolidated by the increase in Curie point depth (a geothermal proxy) and ridge depth with increasing spreading rate. Thus, a decreasing near-ridge temperature probably contributes to crustal thinning from slow to fast-spreading centers. Inferred low melt volume anomalies beneath fast-spreading centers are consistent with a 20 °C temperature drop in the near-ridge mantle, likely caused by efficient hydrothermal cooling.

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全球重力观测显示的大洋地壳厚度，熔体体积和扩散速率之间的关系

大洋中脊的海洋地壳增生是扩散速率，地幔温度和成分的函数，它们相互影响，影响熔体产量和海洋地壳厚度。在全球范围内，稀疏和不规则的地震和地球化学观测表明，地壳厚度与沿慢速到快速扩展中心的扩展速率之间没有关联。在这里，我们根据重力数据编制了一个全球海洋地壳厚度模型，以高分辨率重新探讨了这个问题。重力观察到的熔体体积与全球扩散速率呈正相关，这表明扩散速率是熔体生产的主导因素。但是，海洋地壳厚度与从慢速扩散中心到快速扩散中心的扩散率呈负相关，随着居里点深度（地热代理）和山脊深度随扩散率的增加而增加，这一趋势得到进一步巩固。因此，近洋脊温度的降低可能导致地壳从缓慢扩展到快速扩展的中心变薄。推断快散中心下方的低熔体体积异常与近岭地幔中的20°C温度下降相一致，这可能是由有效的水热冷却引起的。