Collaborative Research: Constraints on EPR Magmatism Through Studies of the North Orozco Region

墨西哥沿海Orozco转换断层以北的东太平洋隆起(EPR)为我们进一步了解洋壳的起源和上地幔的性质提供了独特的机会。这一地区是EPR北部最浅、最膨胀的部分，将已详细研究的轴向形态范围扩大了两倍，这允许测试一些与岩浆室、火山行为和热液活动有关的轴向形态模型。其次，这一区域可以澄清太平洋上地幔化学特征的性质和来源。从EPR中回收的玄武岩在化学成分分布上与沿中大西洋海脊发现的玄武岩有根本的不同。对于这些差异有两个假设：(1)EPR之下的地幔是由上地幔板块再循环的自然结果--小规模的不均匀作用而无处不在地形成“脉状”的；(2)EPR之下的热点被抹去并混合到上地幔比沿MAR更有效地进行。Orozco异常是EPR附近潜在的小热点轨迹。如果我们发现它是一个热点，并且它的化学特征可以解释沿EPR的MORB富集区，那么第二种模型将被支持。如果不是，那么模型(1)更有可能。

The East Pacific Rise (EPR) north of the Orozco transform fault off the coast of Mexico provides unique opportunities to further our understanding of the origin of the ocean crust and the nature of the upper mantle. This region is the shallowest, most-inflated portion of the northern EPR, and extends the range of axial morphology that has been examined in detail by a factor of two, which allows the test of a number of models relating axial morphology to magma chambers, volcanic behavior, and hydrothermal activity. Second, this region allows a clarification of the nature and origin of the chemical characteristics of the Pacific upper mantle. Basalts recovered from the EPR differ fundamentally in their distribution of chemical compositions from those recovered along the mid-Atlantic Ridge. There are two hypotheses for these differences: (1) that the mantle beneath the EPR is ubiquitously "veined" by small scale heterogeneities that are a natural consequence of plate recirculation in the upper mantle; (2) that hot spots under the EPR are smeared out and mixed in to the upper mantle more efficiently than along the MAR. The Orozco anomaly is a potential small hot spot track near the EPR. If we find that it is a hot spot, and that its chemical characteristics can explain the enriched MORB along the EPR, then the second model will be supported. If not, then model (1) is more likely.