An ongoing challenge in studies of the oceanic upper mantle is how intraplate hotspots impact the thermal structure of the lithosphere. To address this issue at the Hawaiian hotspot, we analyze mineral compositions for a petrographically diverse suite of garnet pyroxenite xenoliths from the Salt Lake Crater (SLC) rejuvenation stage, volcanic tuff ring in Honolulu. Garnet‐clinopyroxene geobarometry and two‐pyroxene geothermometry indicate equilibrium pressures of 13–18 kbar and temperatures of 1000°C–1100°C. These pressures place the xenoliths at mid‐lithospheric depths of 45–55 km, with temperatures 200°C–300°C hotter than expected for normal 90‐Myr‐old oceanic lithosphere. Garnet and clinopyroxene occur as discrete primary grains, as well as exsolution blebs and lamellae, with lateral dimensions up to several hundred microns. Compositions within garnet and pyroxene grains are remarkably uniform and display no systematic variation with distance to grain boundaries. Together, these observations indicate that the calculated pressures and temperatures reflect the thermal state of the lithosphere under which the xenoliths last equilibrated. We attribute the elevated lithospheric temperatures under Honolulu primarily to the heating by magma as it penetrated the lithosphere during rejuvenation magmatism and the voluminous shield magmatic stage. We anticipate such magmatic heating to be common among all Hawaiian volcanoes, supporting conclusions of a recent study of earthquakes beneath Hawai‘i Island. This local lithospheric thermal anomaly may also contribute to the enigmatically weak flexural response of the lithosphere due to volcano loading along the Hawaiian hotspot chain.

中文翻译：

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盐湖火山口地幔异种岩推断的夏威夷群岛下岩石圈的广泛岩浆加热

海洋上地幔研究中的一个持续挑战是板内热点如何影响岩石圈的热结构。为了解决夏威夷热点地区的这个问题，我们分析了盐湖火山口（SLC）复兴阶段，火奴鲁鲁的火山凝灰岩环中的一组石榴石辉石形异岩的矿物组成。石榴石—斜柏岩地热法和双吡咯岩体地热法表明平衡压力为13–18 kbar，温度为1000°C–1100°C。这些压力将异种岩层置于岩圈中层深度为45-55 km，温度比正常的90-Myr大洋岩石圈预期的温度高200°C-300°C。石榴石和次氯环己烯以离散的初生晶粒形式存在，以及析出泡和薄片，其横向尺寸高达几百微米。石榴石和辉石晶粒内的成分非常均匀，并且与晶界的距离没有系统的变化。这些观察结果一起表明，计算出的压力和温度反映了异物最后平衡的岩石圈的热状态。我们将檀香山下岩石圈温度升高的主要原因归因于在回春岩浆活动和大体积盾构岩浆形成阶段，岩浆加热穿透了岩石圈。我们预计这种岩浆加热将在所有夏威夷火山中普遍存在，从而支持最近对夏威夷岛以下地震研究的结论。