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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Probing the Pacific's oldest MORB glass: mantle chemistry and melting conditions during the birth of the Pacific Plate
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Probing the Pacific's oldest MORB glass: mantle chemistry and melting conditions during the birth of the Pacific Plate

机译：探测太平洋最古老的MORB玻璃：太平洋板块诞生期间的地幔化学和融化条件

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摘要

Major element chemistry of basalt from the southern East Pacific Rise (EPR) is different from that of the EPR at the time of the formation of the Pacific Plate at 170 Ma. Glass recovered from Jurassic age (170 Ma) Pacific ocean crust [Bartolini and Larson, Geology 29 (2001) 735-738] at Ocean Drilling Program Hole 801C records higher Fe_8 (10.77 wt%) and marginally lower Na_8 (2.21 wt%) compared to the modern EPR, suggesting deeper melting and a temperature of initial melting that was 60 ℃ hotter than today. Trace element ratios such as La/Sm and Zr/Y, on the other hand, show remarkable similarities to the modern southern EPR, indicating that Site 801 was not generated on a hotspot-influenced ridge and that mantle composition has changed little in the Pacific over the past 170 Ma. Our results are consistent with the observation that mid-ocean ridge basalts (MORBs) older than 80 Ma were derived by higher temperature melting than are modern MORBs [Humler et al., Earth Planet. Sci. Lett. 173 (1999) 7-23], which may have been a consequence of the Cretaceous superplume event in the Pacific. Site 801 predates the formation of Pacific oceanic plateaus and 801C basalt chemistry indicates that higher temperatures of mantle melting beneath Pacific ridges preceded the initiation of the superplume.
机译：东太平洋上升带（EPR）南部的玄武岩的主要元素化学与太平洋板块在170 Ma形成时的EPR不同。在海洋钻探计划（Ocean Drilling Program Hole）801C钻孔中从侏罗纪时期（170 Ma）太平洋地壳中回收的玻璃[Bartolini and Larson，Geology 29（2001）735-738]记录到的Fe_8（10.77 wt％）较高，而Na_8（2.21 wt％）较低。对现代EPR而言，这表明它的融化更深，初始融化温度比今天高60℃。另一方面，诸如La / Sm和Zr / Y之类的微量元素比率与现代南部EPR表现出显着相似之处，这表明Site 801不是在受热点影响的山脊上产生的，而地幔组成在太平洋地区几乎没有变化过去170 Ma我们的结果与以下观察结果一致：80 Ma以上的中海脊玄武岩（MORB）是通过比现代MORB更高的温度融化而获得的[Humler等，Earth Planet。科学来吧173（1999）7-23]，这可能是太平洋白垩纪超褶积事件的结果。站点801早于太平洋高原的形成，而801C玄武岩化学表明，在太平洋洋洋脊下方的地幔融化温度较高。

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