湖北宜昌峡口剖面二叠系－三叠系（P/T）界线高分辨硼同位素组成及其对海洋酸化事件的指示

The Permian-Triassic mass extinction was the most severe biodiversity crisis in the Phanerozoic. Ocean acidification, which plays an important role in the chain reaction of extinction, can affect creature directly. However, due to lack of effective markers, the previous studies on ocean acidification mainly based on speculation. Boron isotopic compositions of marine carbonates in recent years have been proved to be a useful record of ocean acidity. Because the large-scale extinctions usually took place in short time, high spatial resolution methods are needed for the research on the event stratigraphy in order to reveal catastrophic events happened within a short geological time. Our project of in situ analysis of boron isotope in carbonate strata by LA-MC-ICPMS will establish the high spatial resolution evolution curve of Boron isotopic composition against the time in Permian-Triassic (P/T) transitional sections at Xiakou (Yichang, Hubei Province). Through this high spatial resolution information of isotope geochemistry that has not been reported yet, the ocean acidification event at P/T boundary can be further discussed and provide new insights for the P/T boundary extinction event.

二叠纪－三叠纪（P/T）之交发生了显生宙最大的生物灭绝事件，海洋酸化是大灭绝连锁反应中的重要一环，是直接影响生物生存的重要环境条件，但由于缺少有效的标识物，以往对海洋酸化事件的研究多源于推测。海洋碳酸盐的硼同位素组成近年来被证明是海洋酸度的有效记录。由于大灭绝通常发生在短暂的地质时间内，对事件地层的研究需要高空间分辨率的研究手段，以揭示小时间尺度下突发的地质事件。本项目通过LA-MC-ICPMS对碳酸盐岩地层硼同位素的微区原位分析，将建立湖北宜昌峡口剖面P/T界线高空间分辨率硼同位素组成随时间的演化曲线，通过这种尚未报导过的高空间分辨率的同位素地球化学信息深入探讨P/T之交海洋酸化事件，并为P/T界线生物灭绝事件提供新的认识。

本项目主要目的是对湖北宜昌峡口剖面二叠系－三叠系（P/T）界线地层开展微米级硼同位素组成研究，这是对高分辨率化学地层学研究手段极大的创新，有可能为P/T界线生物灭绝事件提供以前无法获得的极短时间尺度的古海洋环境信息，为认识P/T界线生物灭绝事件提供新的认识。为实现本目的，本研究设计了激光剥蚀信号在线平滑装置和开放式激光剥蚀系统样品引入装置，并分别建立了开放式纳秒和飞秒激光剥蚀ICP-MS分析方法，分析数据准确。成功的实现了在完全敞开的环境下对大尺寸样品（陶瓷、地层样品）进行微区原位主微量元素分析。结合团队成员开发的激光原位硼同位素分析方法，现已完成对峡口剖面P/T界线的微米级硼同位素与其他地球化学特征参数提取，更多的微米级地球化学特征的解释与对古海洋环境的反映还需要进一步讨论。