非傳統穩定鍶同位素在陸地風化過程中所產生的同位素分化作用

• Main Author: 游鎮烽
• Other Authors: 地球科學系
• Format: Report
• Language: Chinese; English
• Published: 2012
• Subjects: 非傳統穩定同位素; 陸地風化作用; 鍶同位素; Non-traditional stable isotope; continental weathering; Sr isotopes; Greenland
• Online Access: http://ir.lib.ncku.edu.tw/handle/987654321/129082

計畫編號:NSC101-2116-M006-007 執行機構:國立成功大學地球科學系 研究期間:2012-08~2013-07 全球氣候變遷與陸地風化作用的聯結為一種複雜的因果回饋系統。相較於傳統同位素應用(如放射性同位素Sr, U, Pb和Nd等)，非傳統穩定同位素研究可提供嶄新機會，更進一步瞭解生物地球化學反應外部過程和追蹤風化來源或沉積物源區鑑定。三元鍶同位素作圖(87Sr/86Sr* vs. δ88Sr)已被應用於評估陸地風化鍶循環的角色，提供關於來源(區分矽酸岩或碳酸岩風化)和低溫生地化反應同位素分化的資訊。但是，目前對δ88Sr在自然環境分布變化、遷移過程造成同位素分化關鍵機制及可能控制因子等，仍然了解甚為有限。為最佳利用本實驗室甫創立精確δ88Sr測量新MC-ICPMC技術(Liu et al.,2011), 此計畫擬仔細評估可能影響自然界穩定鍶同位素分化的重要機制，利用控制實驗系統性評估δ88Sr地球化學行為，擬執行包括(1)無機碳酸鈣沉澱實驗、(2)奈米顆粒吸附/脫附實驗、(3)珊瑚養殖箱及(4)現代洞穴碳酸鈣野外現址校正 (橫跨中國南-北20緯度)等；另一方面，也將評估利用87Sr/86Sr*和 δ88Sr成為海水水團指標可能性(Huang et al., 2011)，並分析台灣河流87Sr/86Sr*和 δ88S在溶解相、懸浮顆粒及河床底泥組成，以深入瞭解高山型河川化學風化過程和鍶同位素分布情形，分析SJ3石筍自上次最大間冰期到末次最大冰期以來溫度的變化記錄(格凌蘭超過10℃變化)。我們初步無機沉澱實驗結果顯示δ88Sr是良好溫度指標；此計畫將對全球氣候變遷與陸地風化作用聯結，貢獻關鍵資訊並對鍶同位素地球化學循環有全面新認識。 The linkage of global climatic change and continental weathering is a complex cause-consequence feedback system. Compared to the conventional isotope systems, i.e. radiogenic Sr, U, Pb, Nd isotopes, non-traditional stable isotopes offer a new potential opportunity for a better understanding of biogeochemical reactions in exogenic processes and/or to trace weathering sources or provenance identification. The triple Sr isotopic plot (87Sr/86Sr* vs. δ88Sr) has been utilized efficiently to evaluate the Sr cycle in continental weathering, providing critical combined information on weathering sources (to discriminate sources from carbonate or silicate) and stable isotope fractionation during low-temperature biogeochemical reactions. But, our knowledge on stable Sr isotope fractionation in natural environments and the controlling factors to cause Sr isotope fractionation during mobilization is still very limited. To make the best utilization our newly established MC-ICPMS technique for precise δ88Sr determination (Liu et al., 2011), this proposal is aimed to evaluate in detail of mechanisms that may affect importantly of stable Sr isotope fractionation in nature. We will conduct laboratory experiments, including (1) inorganic carbonate precipitation, (2) Sr sorption/desorption processes, (3) coral culture tanks, and (4) field calibration with modern cave carbonates formation, to delineate effects of temperature and pH on Sr isotopic fractionation, surface exchange and biological processes. In addition, we will put efforts to evaluate the potential of δ88Sr as a new water mass tracer in the ocean (Huang et al., 2011) and to study stable Sr isotopes in dissolved load, suspended particles and bed-load sediments to gain insights into elemental and isotopic systematic of Sr in mountainous rivers during continental weathering, as well as to examine temperature variability in SJ3 speleothem from the last glacial maximum to the last deglacial period, covering the last major climate shift when temperature in Greenland may change by more than 10ºC. Our pilot study has shown promising results for a new δ88Sr thermometry in carbonates. This project will contribute crucial background information for interpreting the link between continental weathering and the climatic evolution in the past.