Mesozoic history of the Hawaiian hotspot and Pacific magmatism preserved in Kamchatka

夏威夷热点代表了地球上最强的地幔柱，根据5800公里长的夏威夷-皇帝海山链的记录，它已经活跃了至少85ma。然而，该热点的早期历史已经被俯冲到现在属于堪察加半岛东部的地方。初步研究表明，堪察加东北部中生代堪察加Mys蛇绿岩是旧热点轨迹的增生碎片，因此可能保留了夏威夷热点缺失的早期历史。本课题的主要目标是：1)利用Ar/Ar分步加热和单晶技术确定勘察加东北部蛇绿岩的绝对年龄；2)利用主微量元素、Sr-Nd-Pb-Hf同位素系统和各种矿物熔体包裹体组成表征蛇绿岩的成因和地幔来源。本研究对地幔柱的长期演化、热点的寿命、中生代太平洋海底的演化、东亚活动边缘的地质演化以及堪察加俯冲系统的输入成分等具有重要意义。

The Hawaiian hotspot, representing the strongest mantle plume on Earth, has been active for at least 85 Ma as recorded in the 5800 km long Hawaiian-Emperor Seamount Chain. The earlier history of the hotspot however has been subducted beneath what now belongs to eastern Kamchatka. Preliminary investigations suggest that the Mesozoic Kamchatsky Mys ophiolites in northeastern Kamchatka are accreted fragments of the older hotspot track and therefore may preserve the missing earlier history of the Hawaiian hotspot. The major goals of the proposed project are 1) to determine the absolute ages of the accreted ophiolitic terranes in northeastern Kamchatka using Ar/Ar step-heating and single-crystal techniques, and 2) to characterize their origin and mantle sources using major and trace elements, Sr-Nd-Pb-Hf isotope systematics and the composition of melt inclusions in a variety of minerals. We anticipate that this study could have broad implications for the long-term evolution of mantle plumes, the longevity of hotspots, the evolution of Mesozoic Pacific ocean floor, the geologic evolution of the eastern Asian active margin, and the composition of the input into the Kamchatkan subduction system.